@article{liu_miranda_bielicki_ellis_johnson_2024, title={Life Cycle Greenhouse Gas Emissions of CO<sub>2</sub>-Enabled Sedimentary Basin Geothermal}, volume={58}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.3c04006}, abstractNote={The expansion of renewable energy and the large-scale deployment of carbon dioxide (CO2) capture and storage (CCS) can decarbonize the power sector. The use of CO2 to extract geothermal heat from naturally porous and permeable sedimentary basins to generate electricity (CO2-plume geothermal (CPG) system) presents an opportunity to simultaneously generate renewable energy and geologically store CO2. In this study, we estimate the life cycle greenhouse gas (GHG) impacts of CPG systems through 12 scenarios in which CPG systems are combined with one of six CO2 sources (e.g., bioenergy with carbon capture and storage (BECCS) and iron and steel facilities) and operate in two geological settings. We find the life cycle GHG emissions of CPG systems ranging from -0.25 to -6.18 kg CO2eq/kWh. CPG systems can achieve the highest emissions reductions when utilizing the CO2 captured from BECCS. We evaluate uncertainty through a Monte Carlo simulation, demonstrating consistent net reductions in life cycle emissions and a local, one-parameter-at-a-time sensitivity analysis that identifies the CO2 capture capacity as the high-impact parameter of the results. Through the production of electricity, CPG systems can provide additional environmental benefits to the deployment of large-scale CCS.}, number={4}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Liu, Lily and Miranda, Marcos M. and Bielicki, Jeffrey M. and Ellis, Brian R. and Johnson, Jeremiah X.}, year={2024}, month={Jan}, pages={1882–1893} }
 @article{chalendar_keskar_johnson_mathieu_2024, title={Living laboratories can and should play a greater role to unlock flexibility in United States commercial buildings}, volume={8}, ISSN={["2542-4351"]}, DOI={10.1016/j.joule.2023.11.009}, abstractNote={Energy demand flexibility from commercial buildings can play a critical role in the ongoing energy transition. There is an urgent need to redirect more research and deployment efforts toward real-world experimentation. Buildings-sector roadmaps overwhelmingly rely on simulations that imperfectly capture reality. We draw lessons from a review of two decades of literature on real-world flexibility and demand response experiments and from our “Living Laboratory” experiences at three major academic institutions in the United States. While the prevailing method is “model first, experiment second,” there is also strong value in “experiment first, model second” and in improving our understanding of a system through experimentation while modeling it. Commercial building clusters on university and corporate campuses offer valuable and often untapped potential. They are both ideal test beds for research on energy flexibility and a significant source of flexibility. Our research agenda provides practical recommendations for conducting and scaling experimentation in these test beds and leveraging experimental findings to improve modeling.}, number={1}, journal={JOULE}, author={Chalendar, Jacques A. de and Keskar, Aditya and Johnson, Jeremiah X. and Mathieu, Johanna L.}, year={2024}, month={Jan}, pages={13–28} }
 @article{lin_lei_keskar_hiskens_johnson_mathieu_2024, title={The Sub-Metered HVAC Implemented for Demand Response Dataset}, volume={146}, ISSN={["1528-9028"]}, DOI={10.1115/1.4064348}, abstractNote={
 Closed-loop control of commercial building heating, ventilating, and air conditioning (HVAC) for demand response requires measurements used as feedback to the controllers. Demand response effectiveness is usually measured as a power deviation from baseline, but the Building Automation System (BAS) does not usually collect power measurements, and whole-building electric meters typically measure power at intervals of 15 minutes, which may be too slow for some types of demand response. Demand response strategies are sometimes focused on components of building HVAC systems, e.g., the response of supply/return fans to temperature set-point changes, but these components are usually not sub-metered. Fan power can be estimated from physics-based models leveraging BAS data, e.g., airflow measurements; but our ability to effectively close the loop on these estimates is not clear. In this paper, we introduce a massive dataset that contains both sub-metered fan power data and BAS data for several building HVAC systems during typical operation and demand response events. Through a case study we show that models leveraging BAS data alone do not provide accurate estimates of fan power during event transients, making it unlikely that closed-loop control of commercial building HVAC components for demand response would be effective using BAS data alone. This demonstrates the value of sub-metering HVAC components. More broadly, our dataset will enable future research bridging the gap between building control and power systems research.}, number={1}, journal={JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME}, author={Lin, Austin J. and Lei, Shunbo and Keskar, Aditya and Hiskens, Ian and Johnson, Jeremiah X. and Mathieu, Johanna L.}, year={2024}, month={Jan} }
 @article{luo_garcia-menendez_lin_he_johnson_2023, title={Accelerating China's power sector decarbonization can save lives: integrating public health goals into power sector planning decisions}, volume={18}, ISSN={["1748-9326"]}, url={https://doi.org/10.1088/1748-9326/acf84b}, DOI={10.1088/1748-9326/acf84b}, abstractNote={China, the world’s largest greenhouse gas emitter in 2022, aims to achieve carbon neutrality by 2060. The power sector will play a major role in this decarbonization process due to its current reliance on coal. Prior studies have quantified air quality co-benefits from decarbonization or investigated pathways to eliminate greenhouse gas emissions from the power sector. However, few have jointly assessed the potential impacts of accelerating decarbonization on electric power systems and public health. Additionally, most analyses have treated air quality improvements as co-benefits of decarbonization, rather than a target during decarbonization. Here, we explore future energy technology pathways in China under accelerated decarbonization scenarios with a power system planning model that integrates carbon, pollutant, and health impacts. We integrate the health effects of power plant emissions into the power system decision-making process, quantifying the public health impacts of decarbonization under each scenario. We find that compared with a reference decarbonization pathway, a stricter cap (20% lower emissions than the reference pathway in each period) on carbon emissions would yield significant co-benefits to public health, leading to a 22% reduction in power sector health impacts. Although extra capital investment is required to achieve this low emission target, the value of climate and health benefits would exceed the additional costs, leading to $824 billion net benefits from 2021 to 2050. Another accelerated decarbonization pathway that achieves zero emissions five years earlier than the reference case would result in lower net benefits due to higher capital costs during earlier decarbonization periods. Treating air pollution impacts as a target in decarbonization can further mitigate both CO2 emissions and negative health effects. Alternative low-cost solutions also show that small variations in system costs can result in significantly different future energy portfolios, suggesting that diverse decarbonization pathways are viable.}, number={10}, journal={ENVIRONMENTAL RESEARCH LETTERS}, author={Luo, Qian and Garcia-Menendez, Fernando and Lin, Jiang and He, Gang and Johnson, Jeremiah X.}, year={2023}, month={Oct} }
 @article{jain_kumar ch_sonti_keskar_johnson_ghosh_patel_2023, title={High-Performance Hybrid MPPT Algorithm Based Single-Stage Solar PV Fed Induction Motor Drive for Standalone Pump Application}, volume={59}, ISSN={["1939-9367"]}, DOI={10.1109/TIA.2023.3310490}, abstractNote={The article presents a high-performance hybrid sample-based perturb and observe (P&O) maximum power point tracking (MPPT) algorithm for a single-stage solar photovoltaic (SPV) fed open-end winding induction motor (OEWIM) driven standalone pumping system. Traditionally, the P&O algorithm utilizes slow sample-based computation for MPPT to avoid high oscillations near MPP. The slow sample-based algorithm has the drawback of poor tracking speed and loss of MPPT for the environmental change corresponding to the decrement in the PV power (i.e., step decrement in irradiance). Conversely, the algorithm designed for a faster sample rate faces the drawback of poor MPPT performance due to high oscillations near MPP. The proposed algorithm integrates the advantages of both fast and slow sample-based P&O MPPT algorithms. It switches to the fast sample-based MPPT when the PV operating point is away from MPP or there is a change in environmental conditions. It switches back to slow sample-based MPPT algorithms when the operating point reaches near MPP. The complete details of the proposed hybrid sample-based MPPT algorithm for the SPV pump application system are given in the article. Further, a comparative analysis of the proposed algorithm performance with both fast and slow sample-based algorithms is also carried out using MATLAB/Simulink simulation environment. The simulation results demonstrate the superior performance of the proposed algorithm in terms of MPPT speed and accuracy. The enhanced MPP accuracy further improves the pump performance by minimizing torque and speed ripple. The robustness of the proposed strategy is also elucidated experimentally.}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Jain, Sachin and Kumar Ch, S. V. S. Phani and Sonti, Venu and Keskar, Aditya and Johnson, Jeremiah X. and Ghosh, Subhojit and Patel, R. N.}, year={2023}, month={Nov}, pages={7103–7115} }
 @article{keskar_galik_johnson_2023, title={Planning for winter peaking power systems in the United States}, volume={173}, ISSN={0301-4215}, url={http://dx.doi.org/10.1016/j.enpol.2022.113376}, DOI={10.1016/j.enpol.2022.113376}, abstractNote={Most regions in the United States experience peak electricity demand during the summer months. Several regions, however, are dual peaking with distinct summer and winter peaks of roughly equal magnitude. Deep decarbonization of our energy system could lead to greater instances of dual or winter peaking power systems across the country. This seasonal shift has important implications for grid operations. Furthermore, the compounding impacts of decarbonization strategies and climate change could introduce new challenges in ensuring sufficient generator availability during peak demand. This paper provides policy recommendations to plan for a shift to dual or winter peaking power systems. We first analyze the seasonal peak demand trends between 2016 and 2021 at the regional and subregional levels. We provide key examples of how regulators and system operators plan for winter resource adequacy, focusing on the measures undertaken by different stakeholders, post-Winter Storm Uri. We then detail challenges posed by the multilevel regulation framework in planning for winter peaking power systems for both extreme cold events and a gradual shift due to electrification. Finally, we provide our policy recommendations for utilities and regulators on how they can robustly meet the challenges of winter peaking systems.}, journal={Energy Policy}, publisher={Elsevier BV}, author={Keskar, Aditya and Galik, Christopher and Johnson, Jeremiah X.}, year={2023}, month={Feb}, pages={113376} }
 @article{keskar_soni_shukla_jain_ghosh_patel_johnson_2023, title={Tapping the Unused Energy Potential of Solar Water Pumps in India}, volume={57}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.3c02378}, abstractNote={India seeks to deploy millions of solar water pumps to farmers who often lack access to electricity or face an unreliable power supply. Improving the use of this technology can bolster sustainable agriculture and expand clean energy services. We investigate farm-level impacts and opportunities with primary survey data (n = 292 farmers) and a large real-time pump operational data set (n = 1106 pumps). By modeling the potential solar generation of off-grid solar water pumps, we estimate 300-400 kWh/month of unutilized solar energy per pumping system, representing up to 95% of potential generation. While farmers report increased revenues and ease of pump operation, unsolved challenges concerning the lack of panel cleaning and tracking remain. Pump operational data show pump usage in the summer and monsoon seasons and an expansion of irrigation to grow crops in the winter. Relative to emissions associated with the use of diesel pumps, solar pumps that are highly utilized reduced life cycle CO2-eq emissions by 93% on average, while the pumping systems with the lowest use result in a net increase of 26% relative to the diesel alternatives. Based on observed usage rates, approximately 70% of pumps had positive environmental benefits. The high share of unutilized solar energy provides a significant opportunity to use the energy for nonpumping purposes.}, number={38}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Keskar, Aditya and Soni, Vivek and Shukla, Jaya and Jain, Sachin and Ghosh, Subhojit and Patel, Ramnarayan and Johnson, Jeremiah X.}, year={2023}, month={Sep}, pages={14173–14181} }
 @article{luo_garcia-menendez_yang_deshmukh_he_lin_johnson_2023, title={The Health and Climate Benefits of Economic Dispatch in China's Power System}, volume={57}, ISSN={["1520-5851"]}, url={http://dx.doi.org/10.1021/acs.est.2c05663}, DOI={10.1021/acs.est.2c05663}, abstractNote={China’s power system is highly regulated and uses an “equal-share” dispatch approach. However, market mechanisms are being introduced to reduce generation costs and improve system reliability. Here, we quantify the climate and human health impacts brought about by this transition, modeling China’s power system operations under economic dispatch. We find that significant reductions in mortality related to air pollution (11%) and CO2 emissions (3%) from the power sector can be attained by economic dispatch, relative to the equal-share approach, through more efficient coal-powered generation. Additional health and climate benefits can be achieved by incorporating emission externalities in electricity generation costs. However, the benefits of the transition to economic dispatch will be unevenly distributed across China and may lead to increased health damage in some regions. Our results show the potential of dispatch decision-making in electricity generation to mitigate the negative impacts of power plant emissions with existing facilities in China.}, number={7}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, publisher={American Chemical Society (ACS)}, author={Luo, Qian and Garcia-Menendez, Fernando and Yang, Haozhe and Deshmukh, Ranjit and He, Gang and Lin, Jiang and Johnson, Jeremiah X.}, year={2023}, month={Feb} }
 @article{luo_garcia-menendez_yang_deshmukh_he_lin_johnson_2023, title={The Health and Climate Benefits of Economic Dispatch in China?s Power System}, volume={57}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.2c056632898}, number={7}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Luo, Qian and Garcia-Menendez, Fernando and Yang, Haozhe and Deshmukh, Ranjit and He, Gang and Lin, Jiang and Johnson, Jeremiah X.}, year={2023}, month={Feb}, pages={2898–2906} }
 @article{bielicki_leveni_johnson_ellis_2023, title={The promise of coupling geologic CO2 storage with sedimentary basin geothermal power generation}, volume={26}, ISSN={["2589-0042"]}, DOI={10.1016/j.isci.2022.105618}, abstractNote={Achieving ambitious greenhouse gas mitigation targets will require technological advances and cost reductions in dispatchable carbon-free power generation sources that can provide load following flexibility to integrate high penetrations of variable wind and solar power. Several other sectors may be difficult to decarbonize and a net-zero or net-negative carbon economy may require the deployment of geologic carbon dioxide (CO2) storage. Utilizing CO2 as a working fluid for geothermal energy production and energy storage can achieve both goals: isolating CO2 from the atmosphere and providing valuable power system services to enable high penetrations of variable carbon-free electricity production. The use of CO2 as a working fluid facilitates access to low-grade heat in sedimentary basins, which are widely available and could allow for strategic citing near CO2 sources or where power system flexibility is needed. In this perspective piece, we summarize the state of knowledge for sedimentary basin CO2-geothermal, sometimes referred to as CO2 plume geothermal, and explore how it could support decarbonization of the energy sector. We also present the potential for using geologically stored CO2 for bulk energy storage which could provide valuable time-shifting and other services to the power grid. We explore the promise and challenges of these technologies, identify key research gaps, and offer a critical appraisal of the role that policy for a technology at the intersection of renewable energy, energy storage, and geologic CO2 storage may play in achieving broad deployment.}, number={2}, journal={ISCIENCE}, author={Bielicki, Jeffrey M. and Leveni, Martina and Johnson, Jeremiah X. and Ellis, Brian R.}, year={2023}, month={Feb} }
 @article{luo_copeland_garcia-menendez_johnson_2022, title={Diverse Pathways for Power Sector Decarbonization in Texas Yield Health Cobenefits but Fail to Alleviate Air Pollution Exposure Inequities}, ISSN={["1520-5851"]}, url={https://doi.org/10.1021/acs.est.2c00881}, DOI={10.1021/acs.est.2c00881}, abstractNote={Decarbonizing power systems is a critical component of climate change mitigation, which can have public health cobenefits by reducing air pollution. Many studies have examined strategies to decarbonize power grids and quantified their health cobenefits. However, few of them focus on near-term cobenefits at community levels, while comparing various decarbonization pathways. Here, we use a coupled power system and air quality modeling framework to quantify the costs and benefits of decarbonizing the Texas power grid through a carbon tax; replacing coal with natural gas, solar, or wind; and internalizing human health impacts into operations. Our results show that all decarbonization pathways can result in major reductions in CO2 emissions and public health impacts from power sector emissions, leading to large net benefits when considering the costs to implement these strategies. Operational changes with existing infrastructure can serve as a transitional strategy during the process of replacing coal with renewable energy, which offers the largest benefits. However, we also find that Black and lower-income populations receive disproportionately higher air pollution damages and that none of the examined decarbonization strategies mitigate this disparity. These findings suggest that additional interventions are necessary to mitigate environmental inequity while decarbonizing power grids.}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Luo, Qian and Copeland, Brenna and Garcia-Menendez, Fernando and Johnson, Jeremiah X.}, year={2022}, month={Sep} }
 @article{sioshansi_denholm_arteaga_awara_bhattacharjee_botterud_cole_cortes_queiroz_decarolis_et al._2022, title={Energy-Storage Modeling: State-of-the-Art and Future Research Directions}, volume={37}, ISSN={["1558-0679"]}, url={http://dx.doi.org/10.1109/tpwrs.2021.3104768}, DOI={10.1109/TPWRS.2021.3104768}, abstractNote={Given its physical characteristics and the range of services that it can provide, energy storage raises unique modeling challenges. This paper summarizes capabilities that operational, planning, and resource-adequacy models that include energy storage should have and surveys gaps in extant models. Existing models that represent energy storage differ in fidelity of representing the balance of the power system and energy-storage applications. Modeling results are sensitive to these differences. The importance of capturing chronology can raise challenges in energy-storage modeling. Some models ‘decouple’ individual operating periods from one another, allowing for natural decomposition and rendering the models relatively computationally tractable. Energy storage complicates such a modeling approach. Improving the representation of the balance of the system can have major effects in capturing energy-storage costs and benefits.}, number={2}, journal={IEEE TRANSACTIONS ON POWER SYSTEMS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Sioshansi, Ramteen and Denholm, Paul and Arteaga, Juan and Awara, Sarah and Bhattacharjee, Shubhrajit and Botterud, Audun and Cole, Wesley and Cortes, Andres and Queiroz, Anderson de and DeCarolis, Joseph and et al.}, year={2022}, month={Mar}, pages={860–875} }
 @article{mueller_thomas_johnson_decarolis_call_2021, title={Life cycle assessment of salinity gradient energy recovery using reverse electrodialysis}, volume={25}, ISSN={["1530-9290"]}, DOI={10.1111/jiec.13082}, abstractNote={This study is the first comprehensive life cycle assessment (LCA) of reverse electrodialysis (RED), a technology that converts salinity gradient energy into electricity. Our goal is to identify RED system components of environmental concern and provide insights on potential environmental impacts. We conduct an attributional LCA of two RED scenarios: large‐scale energy generation from natural bodies of water and smaller‐scale energy generation from industrial processes. A functional unit of 1 MWh of net electricity production enables comparison to existing renewable energy technologies, including wind and solar photovoltaics. Under theoretical, favorable conditions, environmental impacts from RED are found to be comparable to, and often lower than, established renewable energy technologies. Processes associated with membrane manufacture are primary contributors to six of the nine evaluated impact categories. Under baseline assumptions, impacts are an average of 50% higher for the Natural Water scenario compared to the Concentrated Brine scenario because of the increased power density achieved with concentrated brines. This early‐stage LCA demonstrates that the expected environmental impacts of RED are comparable to existing renewable technologies and a large improvement over fossil‐based generation. However, eutrophication, ecotoxicity, and carcinogenic impacts are larger for RED than other technologies under some assumptions.}, number={5}, journal={JOURNAL OF INDUSTRIAL ECOLOGY}, author={Mueller, Katelyn E. and Thomas, Jeffrey T. and Johnson, Jeremiah X. and DeCarolis, Joseph F. and Call, Douglas F.}, year={2021}, month={Oct}, pages={1194–1206} }
 @article{fell_johnson_2021, title={Regional disparities in emissions reduction and net trade from renewables}, volume={4}, ISSN={["2398-9629"]}, DOI={10.1038/s41893-020-00652-9}, number={4}, journal={NATURE SUSTAINABILITY}, author={Fell, Harrison and Johnson, Jeremiah X.}, year={2021}, month={Apr}, pages={358–365} }
 @article{sodano_decarolis_queiroz_johnson_2021, title={The symbiotic relationship of solar power and energy storage in providing capacity value}, volume={177}, ISSN={["1879-0682"]}, DOI={10.1016/j.renene.2021.05.122}, abstractNote={Ensuring power system reliability under high penetrations of variable renewable energy is a critical task for system operators. In this study, we use a loss of load probability model to estimate the capacity credit of solar photovoltaics and energy storage under increasing penetrations of both technologies, in isolation and in tandem, to offer new understanding on their potential synergistic effects. Increasing penetrations of solar PV alter the net load profile on the grid, shifting the peak net load to hours with little or no solar generation and leading to diminishing capacity credits for each additional increment of solar. However, the presence of solar PV decreases the duration of daily peak demands, thereby allowing energy-limited storage capacity to dispatch electricity during peak demand hours. Thus, solar PV and storage exhibit a symbiotic relationship when used in tandem. We find that solar PV and storage used together make a more significant contribution to system reliability: as much as 40% more of the combined capacity can be counted on during peak demand hours compared to scenarios where the two technologies are deployed separately. Our test case demonstrates the important distinction between winter and summer peaking systems, leading to significantly different seasonal capacity values for solar PV. These findings are timely as utilities replace their aging peaking plants and are taking energy storage into consideration as part of a low carbon pathway.}, journal={RENEWABLE ENERGY}, author={Sodano, Daniel and DeCarolis, Joseph F. and Queiroz, Anderson Rodrigo and Johnson, Jeremiah X.}, year={2021}, month={Nov}, pages={823–832} }
 @article{hollingsworth_ravishankar_o'connor_johnson_decarolis_2020, title={Environmental and economic impacts of solar-powered integrated greenhouses}, volume={24}, ISSN={["1530-9290"]}, DOI={10.1111/jiec.12934}, abstractNote={Greenhouse vegetable production plays a vital role in providing year‐round fresh vegetables to global markets, achieving higher yields, and using less water than open‐field systems, but at the expense of increased energy demand. This study examines the life cycle environmental and economic impacts of integrating semitransparent organic photovoltaics (OPVs) into greenhouse designs. We employ life cycle assessment to analyze six environmental impacts associated with producing greenhouse‐grown tomatoes in a Solar PoweRed INtegrated Greenhouse (SPRING) compared to conventional greenhouses with and without an adjacent solar photovoltaic array, across three distinct locations. The SPRING design produces significant reductions in environmental impacts, particularly in regions with high solar insolation and electricity‐intensive energy demands. For example, in Arizona, global warming potential values for a conventional, adjacent PV and SPRING greenhouse are found to be 3.71, 2.38, and 2.36 kg CO2 eq/kg tomato, respectively. Compared to a conventional greenhouse, the SPRING design may increase life cycle environmental burdens in colder regions because the shading effect of OPV increases heating demands. Our analysis shows that SPRING designs must maintain crop yields at levels similar to conventional greenhouses in order to be economically competitive. Assuming consistent crop yields, uncertainty analysis shows average net present cost of production across Arizona to be $3.43, $3.38, and $3.64 per kg of tomato for the conventional, adjacent PV and SPRING system, respectively.}, number={1}, journal={JOURNAL OF INDUSTRIAL ECOLOGY}, author={Hollingsworth, Joseph A. and Ravishankar, Eshwar and O'Connor, Brendan and Johnson, Jeremiah X. and DeCarolis, Joseph F.}, year={2020}, month={Feb} }
 @article{decarolis_jaramillo_johnson_mccollum_trutnevyte_daniels_akin-olcum_bergerson_cho_choi_et al._2020, title={Leveraging Open-Source Tools for Collaborative Macro-energy System Modeling Efforts}, volume={4}, ISSN={["2542-4351"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85097654384&partnerID=MN8TOARS}, DOI={10.1016/j.joule.2020.11.002}, abstractNote={The authors are founding team members of a new effort to develop an Open Energy Outlook for the United States. The effort aims to apply best practices of policy-focused energy system modeling, ensure transparency, build a networked community, and work toward a common purpose: examining possible US energy system futures to inform energy and climate policy efforts. Individual author biographies can be found on the project website: https://openenergyoutlook.org/. The authors are founding team members of a new effort to develop an Open Energy Outlook for the United States. The effort aims to apply best practices of policy-focused energy system modeling, ensure transparency, build a networked community, and work toward a common purpose: examining possible US energy system futures to inform energy and climate policy efforts. Individual author biographies can be found on the project website: https://openenergyoutlook.org/. Many nations have committed to mitigating climate change by designing and implementing policy solutions that enable deep decarbonization of their energy systems. Due to global reliance on fossil fuels, appropriate action requires fundamental and coordinated changes in the way societies generate and use energy. Policy makers face the monumental challenge of crafting effective energy and climate policy in the face of a highly uncertain future. The stakes are high because energy infrastructure often involves large, up-front investments in long-lived assets. Macro-energy system models, which are distinguished from other energy models by their energetic, temporal, and spatial scales,1Levi P.J. Kurland S.D. Carbajales-Dale M. Weyant J.P. Brandt A.R. Benson S.M. Macro-Energy Systems: Toward a New Discipline.Joule. 2019; 3: 2282-2286Abstract Full Text Full Text PDF Scopus (29) Google Scholar provide a systematic way to examine future decarbonization pathways, evaluate technology choices, test the effects and consequences of proposed policies, and explore decisions under future uncertainty. Analyses using these models yield critical insights that inform energy and climate policymaking around the world and underpin influential reports, including the World Energy Outlook by the International Energy Agency,2International Energy AgencyWorld Energy Outlook 2019.https://www.iea.org/reports/world-energy-outlook-2019Date: 2019Google Scholar the Annual Energy Outlook by the US Energy Information Administration,3US Energy Information AdministrationAnnual Energy Outlook 2020.https://www.eia.gov/outlooks/aeo/Date: 2020Google Scholar the Special Report on Global Warming of 1.5°C by the Intergovernmental Panel on Climate Change,4Hoegh-Guldberg, O., Jacob, D., Bindi, M., Brown, S., Camilloni, I., Diedhiou, A., Djalante, R., Ebi, K., Engelbrecht, F., Guiot, J., and Hijioka, Y. (2018). Impacts of 1.5 C global warming on natural and human systems. Global warming of 1.5°C. An IPCC Special Report. https://www.ipcc.ch/sr15/.Google Scholar and many others. It is an ongoing challenge for macro-energy system modeling teams to meet the universal and unprecedented policy needs associated with climate change mitigation. We envision a paradigm shift in the process of conducting model-based analysis from single-institution modeling teams to distributed, collaborative teams, allowing access to a much wider array of disciplinary and domain expertise to inform a given analysis. While some European efforts are already moving in this direction, the potential for collaborative, model-based analysis has yet to be realized. Energy system models vary considerably in their scope and complexity, and the choice of model should always be based on the research questions driving the analysis.5DeCarolis J. Daly H. Dodds P. Keppo I. Li F. McDowall W. Pye S. Strachan N. Trutnevyte E. Usher W. Winning M. Formalizing best practice for energy system optimization modelling.Appl. Energy. 2017; 194: 184-198Crossref Scopus (159) Google Scholar Here, we focus attention on employing macro-energy system models that cover the whole energy system and are used to inform policy at scales ranging from national to global. In this broadest macro-scale context, the boundaries of the modeled systems present numerous challenges for modeling deep decarbonization pathways. First, many supply- and demand-side technologies at varying stages of development could help decarbonize energy systems. Many of these technologies are novel (e.g., direct air capture and hydrogen-based steel production), have rapidly changing costs (e.g., solar photovoltaics, lithium-ion batteries, and electrolyzers), or have location-specific attributes (e.g., heat pumps and wind farms). These qualities make the projection of technology cost and performance characteristics over the multi-decade timescale of deep decarbonization very challenging. Second, the many decision makers across the energy system, each with their own objectives and preferences, make it difficult to model technology uptake, behavioral change, and public acceptance. Third, there is a need for modeling with high spatiotemporal resolution and multiple years of weather data in order to properly represent high penetrations of renewables with energy storage and other options for flexibility, since the modeled spatial variation in resource availability and temporal variation in supply and demand can have a significant impact on results. Fourth, policy-relevant insights should account for key underlying uncertainties affecting the modeled energy system. Neglecting any of these four challenges can lead to oversimplified model representations of the energy system with misleading conclusions; yet, including them increases model complexity, data requirements, and computational burden. Resolving this tension, given available resources, is difficult. Addressing the technical challenges of modeling decarbonization pathways requires considerable coordination of effort and broad domain expertise. When the effort is centralized at a single institution, institutional and governance structures can limit its effectiveness. Energy system modeling efforts housed within a single research group can suffer from a limited breadth of expertise. At the other extreme, some of the oldest and most established energy system models have been produced by government agencies and intergovernmental organizations that have the scale to draw on deep internal expertise across the energy system, but model-based analyses produced by these organizations can be subject to political considerations that limit the range of technologies or policies they will consider. In addition, commercial modeling efforts often rely on proprietary models and data that are not available to the broader expert community or interested stakeholders and therefore result in outcomes that cannot be easily reproduced and scientifically verified. To help address these shortcomings, distributed modeling teams can utilize existing open-source models, datasets, and tools to conduct collaborative, model-based analysis. Open-source efforts in the macro-energy space have proliferated over the last decade, and the resultant models, tools, and datasets serve as an important foundation for distributed modeling efforts because they enable transparency, accessibility, and replicability among team members and with the broader modeling community. Distributed efforts focused on model-based analysis allow for the flexible arrangement of teams to conduct different macro-energy modeling exercises, with each team configured to meet project-specific research objectives. The flexible arrangement of teams, in turn, means that specific modeling efforts can include participants with different disciplinary backgrounds and domain expertise who contribute to the diversity of ideas that can be explored in the analysis. The collective consideration of those ideas better reflects the system being modeled. For example, participants with a background in public policy, public administration, or economics can assist with the formulation, execution, and interpretation of more realistic policy scenarios, informed by debates and discussions in their respective communities. Modeling teams with collectively broad expertise across a range of issues and disciplines permit a more comprehensive analysis of the technical, social, economic, and policy features of deep decarbonization pathways, which are difficult to encode in models. In fact, all team members need not write code—the purposeful inclusion of non-modelers can lead to new insights and approaches associated with the model-based analysis.6Trutnevyte E. Hirt F.L. Bauer N. Cherp A. Hawkes A. Edelenbosch O.Y. Pedde S. van Vuuren D.P. Societal transformations in models for energy and climate policy: The ambitious next step.One Earth. 2019; 1: 423-433Abstract Full Text Full Text PDF Scopus (52) Google Scholar Diverse teams participating across the full project life cycle—from the formulation of key research questions, to the decision on how to represent a particular concept quantitatively, and then to the interpretation of model results as policy-relevant insights—can more effectively capture and assimilate novel ideas compared to conventional system modeling approaches that seek feedback at the end of the project or at discrete points during the project life cycle. These insights and ideas can range widely and may include the identification and proper use of a new dataset, a new model feature that captures a system dynamic critical to the issue under analysis, or the use of more efficient algorithms or methods that improve computational performance. Modeling teams that lack the appropriate depth and breadth are less able to effectively search, select, and incorporate new ideas from the broader macro-energy idea space into the analysis. Model parsimony should also be a design objective in order to avoid needless complexity,5DeCarolis J. Daly H. Dodds P. Keppo I. Li F. McDowall W. Pye S. Strachan N. Trutnevyte E. Usher W. Winning M. Formalizing best practice for energy system optimization modelling.Appl. Energy. 2017; 194: 184-198Crossref Scopus (159) Google Scholar and thus, distributed modeling teams must judiciously filter new ideas for incorporation into the analysis. Furthermore, the expanding scope enabled by distributed teams must be balanced with limited time, funding, and computational resources. The European Union is already pioneering a distributed and collaborative approach under the €80 billion Horizon 2020 research and innovation program. Projects such as SET-NAV (https://www.set-nav.eu/), openENTRANCE (https://openentrance.eu/), SENTINEL (https://sentinel.energy/), Spine (http://www.spine-model.org/), and EMP-E (http://www.energymodellingplatform.eu/) involve large teams variously working to integrate different models into larger frameworks, solicit input from a wide array of stakeholders, and perform model-based analysis that informs European energy and climate policy. The European Union is uniquely positioned to lead such efforts, given its ambitious energy-climate policy portfolio, well-funded scientific research programs, and ambitions for pan-national integration. While many other nations and regions—including the US—cannot easily replicate the top-down European approach without a significant change in policy priorities, we nonetheless assert that it is possible for researchers to organize similar efforts from the bottom up by leveraging existing resources within the scientific community. While distributed efforts focused on model-based analysis present unique logistical challenges, they also provide the flexibility to organize teams that capture diverse domain expertise and disciplinary approaches. All of the necessary elements exist to coordinate distributed model-based analysis: open-source energy models, well-established software development tools, a wide range of collaborative communication tools, and an increasing number of publicly available datasets on which to build. First, the open energy modeling initiative (“openmod”), an active and vibrant community of energy modelers committed to open-source practices, has cataloged a large array of open-source models7Openmod InitiativeOpen Models.https://wiki.openmod-initiative.org/wiki/Open_ModelsDate: 2020Google Scholar and helped to promulgate best practice standards for model developers that include licensing, documentation, reproducibility, and user support.8DeCarolis J.F. Hunter K. Sreepathi S. The case for repeatable analysis with energy economy optimization models.Energy Econ. 2012; 34: 1845-1853Crossref Scopus (82) Google Scholar, 9Pfenninger S. Hirth L. Schlecht I. Schmid E. Wiese F. Brown T. Davis C. Gidden M. Heinrichs H. Heuberger C. Hilpert S. Opening the black box of energy modelling: Strategies and lessons learned.Energy Strategy Reviews. 2018; 19: 63-71Crossref Scopus (129) Google Scholar, 10Pfenninger S. DeCarolis J. Hirth L. Quoilin S. Staffell I. The importance of open data and software: Is energy research lagging behind?.Energy Policy. 2017; 101: 211-215Crossref Scopus (192) Google Scholar, 11Morrison R. Energy system modeling: Public transparency, scientific reproducibility, and open development.Energy Strategy Reviews. 2018; 20: 49-63Crossref Scopus (52) Google Scholar Second, many energy modelers are using modern software development tools, which enable distributed control of code and data, with changes archived in publicly accessible web repositories. Third, a variety of communication options, including traditional email, cloud-based collaboration platforms, and videoconferencing software, make it possible for distributed teams to collaborate on highly technical issues in near-real time and at low cost. These modes of communication have indeed become an increasingly familiar part of our lives given how the coronavirus disease (COVID-19) pandemic has disrupted normal meeting patterns. In addition, social media represents a particularly effective way to crowdsource new ideas and approaches from the broader stakeholder community. Fourth, the volume of available data to populate energy models has grown over time and can be used to better parameterize models. The challenge, however, is that modelers are not aware of all relevant datasets, particularly those curated outside of the energy modeling community, nor do they always understand the underlying assumptions and limitations. Diversity in expertise among the modeling team can help ensure the proper identification and use of such datasets. In the long run, by using open-source tools and drawing on the expertise of non-modelers who are typically disconnected from the modeling process, distributed modeling teams may counteract the “incumbency advantage” of “long-lived and dominant” energy models12Strachan N. Fais B. Daly H. Reinventing the energy modelling–policy interface.Nat. Energy. 2016; 1: 1-3Crossref Google Scholar by helping redefine the way energy models operate. We view this approach as a critical element in the reinvention of the modeling-policy interface.12Strachan N. Fais B. Daly H. Reinventing the energy modelling–policy interface.Nat. Energy. 2016; 1: 1-3Crossref Google Scholar As with any new approach, there will be attendant challenges. Macro-energy modeling efforts face the same funding and coordination challenges confronted by other large scientific endeavors. Funding challenges are more logistically difficult with teams spanning multiple institutions. There is no single solution: financial arrangements will necessarily be a product of the funding agency, team composition, and objectives of the analysis. While there may be circumstances where funding can be equitably distributed among all participants, there might be other times when one or two lead organization(s) take the bulk of the responsibility, with smaller support grants and in-kind contributions from other members of the distributed team. Furthermore, funding need not always be a requirement for participation: limited but strategic input from a broad constellation of team members delivered at the right time in the process can have a large, positive impact on the direction of the project. While the Stanford Energy Modeling Forum (https://emf.stanford.edu/) is focused on inter-model comparison, its long-term success demonstrates that participants are willing to contribute their time, often without financial compensation, in return for the opportunity to collaborate with others and produce new scholarly research. Another challenge is the incentive structure within academia. It takes significant upfront effort to establish a common language and align project goals among team members from different academic disciplines. In addition, receiving credit for work completed is an important aspect of scholarly work. Credit often takes the form of co-authorship on reports and journal articles, and it is important to track the contributions of team members to ensure their efforts are recognized in an appropriate way, commensurate with their own institutional and disciplinary incentive structures. Furthermore, academic institutions should formally recognize the effort required to develop the open-source models, tools, and datasets that underpin the model-based analysis. The CRediT taxonomy, used by this publisher (https://www.cell.com/pb/assets/raw/shared/guidelines/CRediT-taxonomy.pdf), provides an excellent way to track the various contributions to distributed macro-energy modeling efforts. New modeling efforts that leverage these emerging opportunities can fulfill a unique niche within the global energy modeling community. We have begun to see the benefits of such an approach in our own effort to develop an Open Energy Outlook for the US (https://openenergyoutlook.org/). In addition to using an open-source modeling platform to perform the analysis (https://temoacloud.com/), we have established an interdisciplinary and inter-sectoral team of experts who are working collaboratively on the project with a unified vision. Our international team involves a number of experts drawn from academia, non-profits, and government labs and includes both experienced macro-energy system modelers and domain experts. Funding is distributed across two institutions that have primary responsibility for the deliverables, while participants from the remaining 20+ institutions make in-kind contributions of their time to the effort. Our project has a fraction of the funding associated with the large European efforts referenced above, and thus relies heavily on our collective interest in the project objectives and the opportunity to collaboratively produce scholarly work. Because participants are already working in related areas, they are able to leverage ongoing research activities and resources for this project. Our current team is meant to be a starting point for this long-term effort. Just as open-source tools foster collaborative development, democratization of the team building process can ensure a greater diversity of perspectives and make the effort more adaptable to new challenges. To this end, we are currently working on a formal and open nomination process for team membership. In addition, we are building a broader network of contributors to the project, and have sought input through a variety of online outlets, including social media, virtual workshops, and mailing lists. While still in the early stages, the project has already benefited from the diverse perspectives of the participants. For example, the electricity experts have pushed for a novel approach to increase the model’s temporal resolution while maintaining computational tractability and also identified opportunities to leverage existing open-source tools (https://github.com/gschivley/PowerGenome) and datasets (https://github.com/catalyst-cooperative/pudl). Likewise, the building experts are pushing the project to consider building thermodynamics more explicitly in order to better represent building thermal performance. The value here is bidirectional: systems modelers gain more familiarity with tools and data within particular sectors, while domain experts gain a better understanding of how their expertise can influence long-term energy scenarios. If done well, such an approach allows us to rethink and redefine common modeling approaches, potentially leading to innovative methods that result in new insights that are rigorously grounded by careful consideration of how the energy system—and all its myriad connections and feedbacks—is modeled. We would like to thank the Alfred P. Sloan Foundation for supporting this work. We also thank the two anonymous reviewers whose detailed and insightful feedback significantly strengthened the manuscript. Leveraging Open-Source Tools for Collaborative Macro-energy System Modeling EffortsDeCarolis et al.JouleFebruary 17, 2021In Brief(Joule 4, 2523–2531; December 16, 2020) Full-Text PDF Open Access}, number={12}, journal={JOULE}, publisher={Elsevier BV}, author={DeCarolis, Joseph F. and Jaramillo, Paulina and Johnson, Jeremiah X. and McCollum, David L. and Trutnevyte, Evelina and Daniels, David C. and Akin-Olcum, Gokce and Bergerson, Joule and Cho, Soolyeon and Choi, Joon-Ho and et al.}, year={2020}, month={Dec}, pages={2523–2526} }
 @article{hollingsworth_copeland_johnson_2019, title={Are e-scooters polluters? The environmental impacts of shared dockless electric scooters}, volume={14}, ISSN={["1748-9326"]}, DOI={10.1088/1748-9326/ab2da8}, abstractNote={Shared stand-up electric scooters are now offered in many cities as an option for short-term rental, and marketed for short-distance travel. Using life cycle assessment, we quantify the total environmental impacts of this mobility option associated with global warming, acidification, eutrophication, and respiratory impacts. We find that environmental burdens associated with charging the e-scooter are small relative to materials and manufacturing burdens of the e-scooters and the impacts associated with transporting the scooters to overnight charging stations. The results of a Monte Carlo analysis show an average value of life cycle global warming impacts of 202 g CO2-eq/passenger-mile, driven by materials and manufacturing (50%), followed by daily collection for charging (43% of impact). We illustrate the potential to reduce life cycle global warming impacts through improved scooter collection and charging approaches, including the use of fuel-efficient vehicles for collection (yielding 177 g CO2-eq/passenger-mile), limiting scooter collection to those with a low battery state of charge (164 g CO2-eq/passenger-mile), and reducing the driving distance per scooter for e-scooter collection and distribution (147 g CO2-eq/passenger-mile). The results prove to be highly sensitive to e-scooter lifetime; ensuring that the shared e-scooters are used for two years decreases the average life cycle emissions to 141 g CO2-eq/passenger-mile. Under our Base Case assumptions, we find that the life cycle greenhouse gas emissions associated with e-scooter use is higher in 65% of our Monte Carlo simulations than the suite of modes of transportation that are displaced. This likelihood drops to 35%–50% under our improved and efficient e-scooter collection processes and only 4% when we assume two-year e-scooter lifetimes. When e-scooter usage replaces average personal automobile travel, we nearly universally realize a net reduction in environmental impacts.}, number={8}, journal={ENVIRONMENTAL RESEARCH LETTERS}, author={Hollingsworth, Joseph and Copeland, Brenna and Johnson, Jeremiah X.}, year={2019}, month={Aug} }
 @article{keskar_anderson_johnson_hiskens_mathieu_2019, title={Do commercial buildings become less efficient when they provide grid ancillary services?}, ISSN={1570-646X 1570-6478}, url={http://dx.doi.org/10.1007/S12053-019-09787-X}, DOI={10.1007/S12053-019-09787-X}, journal={Energy Efficiency}, publisher={Springer Science and Business Media LLC}, author={Keskar, Aditya and Anderson, David and Johnson, Jeremiah X. and Hiskens, Ian A. and Mathieu, Johanna L.}, year={2019}, month={Apr} }
 @article{liang_qu_zhao_zhang_daigger_newell_miller_johnson_love_zhang_et al._2019, title={Quantifying the Urban Food-Energy-Water Nexus: The Case of the Detroit Metropolitan Area}, volume={53}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.8b06240}, abstractNote={The efficient provision of food, energy, and water (FEW) resources to cities is challenging around the world. Because of the complex interdependence of urban FEW systems, changing components of one system may lead to ripple effects on other systems. However, the inputs, intersectoral flows, stocks, and outputs of these FEW resources from the perspective of an integrated urban FEW system have not been synthetically characterized. Therefore, a standardized and specific accounting method to describe this system is needed to sustainably manage these FEW resources. Using the Detroit Metropolitan Area (DMA) as a case, this study developed such an accounting method by using material and energy flow analysis to quantify this urban FEW nexus. Our results help identify key processes for improving FEW resource efficiencies of the DMA. These include (1) optimizing the dietary habits of households to improve phosphorus use efficiency, (2) improving effluent-disposal standards for nitrogen removal to reduce nitrogen emission levels, (3) promoting adequate fertilization, and (4) enhancing the maintenance of wastewater collection pipelines. With respect to water use, better efficiency of thermoelectric power plants can help reduce water withdrawals. The method used in this study lays the ground for future urban FEW analyses and modeling.}, number={2}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Liang, Sai and Qu, Shen and Zhao, Qiaoting and Zhang, Xilin and Daigger, Glen T. and Newell, Joshua P. and Miller, Shelie A. and Johnson, Jeremiah X. and Love, Nancy G. and Zhang, Lixiao and et al.}, year={2019}, month={Jan}, pages={779–788} }
 @article{arbabzadeh_sioshansi_johnson_keoleian_2019, title={The role of energy storage in deep decarbonization of electricity production}, volume={10}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-019-11161-5}, abstractNote={Abstract Deep decarbonization of electricity production is a societal challenge that can be achieved with high penetrations of variable renewable energy. We investigate the potential of energy storage technologies to reduce renewable curtailment and CO 2 emissions in California and Texas under varying emissions taxes. We show that without energy storage, adding 60 GW of renewables to California achieves 72% CO 2 reductions (relative to a zero-renewables case) with close to one third of renewables being curtailed. Some energy storage technologies, on the other hand, allow 90% CO 2 reductions from the same renewable penetrations with as little as 9% renewable curtailment. In Texas, the same renewable-deployment level leads to 54% emissions reductions with close to 3% renewable curtailment. Energy storage can allow 57% emissions reductions with as little as 0.3% renewable curtailment. We also find that generator flexibility can reduce curtailment and the amount of energy storage that is needed for renewable integration.}, journal={NATURE COMMUNICATIONS}, author={Arbabzadeh, Maryam and Sioshansi, Ramteen and Johnson, Jeremiah X. and Keoleian, Gregory A.}, year={2019}, month={Jul} }
 @article{arbabzadeh_sioshansi_johnson_keoleian_2019, title={The role of energy storage in deep decarbonization of electricity production (vol 10, 3413, 2019)}, volume={10}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-019-11778-6}, abstractNote={An amendment to this paper has been published and can be accessed via a link at the top of the paper.}, journal={NATURE COMMUNICATIONS}, author={Arbabzadeh, Maryam and Sioshansi, Ramteen and Johnson, Jeremiah X. and Keoleian, Gregory A.}, year={2019}, month={Aug} }
 @article{ryan_johnson_keoleian_lewis_2018, title={Decision Support Algorithm for Evaluating Carbon Dioxide Emissions from Electricity Generation in the United States}, volume={22}, DOI={10.1111/jiec.12708}, abstractNote={This article presents an algorithm to aid practitioners in determining the most appropriate method to estimate carbon dioxide emissions from an electricity load. Applications include sustainability assessments of products, processes, energy efficiency improvements, changes in generation infrastructure, and changes in electricity demand. Currently, there is no consensus on appropriate methods for calculating greenhouse gas emissions resulting from specific electricity loads. Previous research revealed significant differences in emissions when different methods were used, a situation that could result in divergent sustainability or policy recommendations. In this article, we illustrate the distribution of emissions estimates based on method characteristics such as region size, temporal resolution, average or marginal approaches, and time scales. Informed by these findings, a decision support algorithm is presented that uses a load's key features and an analyst's research question to provide recommendations on appropriate method types. We defined four different cases to demonstrate the utility of the algorithm and to illustrate the variability of methods used in previous studies. Prior research often employed simplifying assumptions, which, in some cases, can result in electricity being allocated to the incorrect generating resources and improper calculation of emissions. This algorithm could reduce inappropriate allocation, variability in assumptions, and increase appropriateness of electricity emissions estimates.}, number={6}, journal={Journal of Industrial Ecology}, author={Ryan, N.A. and Johnson, J.X. and Keoleian, G.A. and Lewis, G.}, year={2018}, month={Oct}, pages={1318–1330} }
 @article{ryan_lin_mitchell-ward_mathieu_johnson_2018, title={Use-Phase Drives Lithium-Ion Battery Life Cycle Environmental Impacts When Used for Frequency Regulation}, volume={52}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.8b02171}, abstractNote={Battery storage systems are attractive alternatives to conventional generators for frequency regulation due to their fast response time, high cycle efficiency, flexible scale, and decreasing cost. However, their implementation does not consistently reduce environmental impacts. To assess these impacts, we employed a life cycle assessment (LCA) framework. Our framework couples cradle-to-gate and end-of-life LCA data on lithium-ion batteries with a unit commitment and dispatch model. The model is run on a 9-bus power system with energy storage used for frequency regulation. The addition of energy storage changes generator commitment and dispatch, causing changes in the quantities of each fuel type consumed. This results in increased environmental impacts in most scenarios. The impacts caused by the changes in the power system operation (i.e., use-phase impacts) outweigh upstream and end-of-life impacts in the majority of scenarios analyzed with the magnitude most influenced by electricity mix and fuel price. Of parameters specific to the battery, round trip efficiency has the greatest effect.}, number={17}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Ryan, Nicole A. and Lin, Yashen and Mitchell-Ward, Noah and Mathieu, Johanna L. and Johnson, Jeremiah X.}, year={2018}, month={Sep}, pages={10163–10174} }
 @article{novacheck_johnson_2017, title={Diversifying wind power in real power systems}, volume={106}, ISSN={0960-1481}, url={http://dx.doi.org/10.1016/j.renene.2016.12.100}, DOI={10.1016/j.renene.2016.12.100}, abstractNote={One method to reduce wind variability is to diversify the wind power resource by interconnecting wind resources across a larger geography. This study uses a modified version of mean-variance portfolio optimization (MVP) to assess the potential for diverse wind to reduce the variability of wind. A one year unit commitment and economic dispatch model of the U.S. Midwest is used to understand the value of the reduced variability. The model assesses four different wind portfolios, ranging in diversity, of two wind power penetrations (10% of total system load and 20%). Employing MVP, the variance in the ramp rates decrease by 50% with a 4% increase in capacity in the 20% wind penetration and a 2% increase in the 10% penetration. With a 20% wind penetration, decreasing the ramp rate variance can reduce curtailment from 5% to 0.1%. In the absence of significant curtailment, decreasing the ramp rate variance reduces the proportion of conventional generation required for ramping. However, the impact on total production cost and emissions from conventional generation is complicated by complexities of the power system, including transmission constraints and the time of day of ramping.}, journal={Renewable Energy}, publisher={Elsevier BV}, author={Novacheck, Joshua and Johnson, Jeremiah X.}, year={2017}, month={Jun}, pages={177–185} }
 @article{berry_johnson_mcdevitt_2017, title={Effect of cold temperatures on the behavior and ultimate capacity of GFRP-reinforced concrete beams}, volume={136}, ISSN={0165-232X}, url={http://dx.doi.org/10.1016/J.COLDREGIONS.2017.01.003}, DOI={10.1016/J.COLDREGIONS.2017.01.003}, abstractNote={Abstract This study evaluated the effects of subfreezing temperatures on the behavior and ultimate capacity of GFRP-reinforced concrete beams. Duplicate beam specimens at four temperatures (20 °C, 0 °C, − 20°C, and − 40 °C) were tested in four-point bending until failure, while monitoring applied load and resulting deflection. The ultimate capacity of the beams was observed to increase with decreasing temperature, a result attributed to the effects of temperature on the compressive and tensile capacities of the concrete. Further, the increased tensile capacity of the concrete with decreasing temperature caused a noted difference in the post-cracking response of the beams: an increase in magnitude of drops in the force-deflection response associated with cracking. The method proposed by ACI 440 (2006) for calculating the ultimate capacity of GFRP reinforced beams accurately predicted the capacity of the beams in this investigation, with an average measured to predicted ratio 1.00 using the measured concrete properties and 1.03 using the design concrete properties.}, journal={Cold Regions Science and Technology}, publisher={Elsevier BV}, author={Berry, Michael and Johnson, Jeremiah and McDevitt, Kate}, year={2017}, month={Apr}, pages={9–16} }
 @article{lin_mathieu_johnson_hiskens_backhaus_2017, title={Explaining inefficiencies in commercial buildings providing power system ancillary services}, volume={152}, ISSN={0378-7788}, url={http://dx.doi.org/10.1016/j.enbuild.2017.07.042}, DOI={10.1016/j.enbuild.2017.07.042}, abstractNote={Ancillary services are required to balance supply and demand in electric power systems. Demand response may provide attractive options for these services, through means such as varying the power consumption of commercial building HVAC systems. However, experimental results from a 30,000 m2 office building suggest that when a building provides ancillary services it consumes more energy than when it is operated normally. This translates to additional costs and environmental impacts. This paper investigates potential causes for building inefficiency associated with ancillary services provision. We develop a physics-based simulation model that captures heat exchange processes and fan and air duct dynamics. During an ancillary service event, we vary the fan power consumption, and then compute the difference between the baseline and actual energy consumption to determine the efficiency of the actions. We explore the impact of building parameters, control design, and baseline model accuracy on the efficiency. In simulation, we find that shorter duration power changes and less aggressive controllers result in less change in energy consumption. We also find that baseline error has outsized effects on the efficiency calculations. These results offer new understanding of the mechanisms underlying inefficiency and point to opportunities to reduce associated costs and environmental burdens.}, journal={Energy and Buildings}, publisher={Elsevier BV}, author={Lin, Yashen and Mathieu, Johanna L. and Johnson, Jeremiah X. and Hiskens, Ian A. and Backhaus, Scott}, year={2017}, month={Oct}, pages={216–226} }
 @article{alfaro_miller_johnson_riolo_2017, title={Improving rural electricity system planning: An agent-based model for stakeholder engagement and decision making}, volume={101}, ISSN={0301-4215}, url={http://dx.doi.org/10.1016/j.enpol.2016.10.020}, DOI={10.1016/j.enpol.2016.10.020}, abstractNote={Energy planners in regions with low rates of electrification face complex and high-risk challenges in selecting appropriate generating technologies and grid centralization. To better inform such processes, we present an Agent-Based Model (ABM) that facilitates engagement with stakeholders. This approach evaluates long-term plans using the cost of delivered electricity, resource mix, jobs and economic stimulus created within communities, and decentralized generation mix of the system, with results provided in a spatially-resolved format. This approach complements existing electricity planning methods (e.g., Integrated Resource Planning) by offering novel evaluation criteria based on typical stakeholder preferences. We demonstrate the utility of this approach with a case study based on a “blank-slate” scenario, which begins without generation or transmission infrastructure, for the long-term rural renewable energy plans of Liberia, West Africa. We consider five electrification strategies: prioritizing larger populations, deploying large resources, creating jobs, providing economic stimulus, and step-wise cost minimization. Through the case study we demonstrate how this approach can be used to engage stakeholders, supplement more established energy planning tools, and illustrate the effects of stakeholder decisions and preferences on the performance of the system.}, journal={Energy Policy}, publisher={Elsevier BV}, author={Alfaro, Jose F. and Miller, Shelie and Johnson, Jeremiah X. and Riolo, Rick R.}, year={2017}, month={Feb}, pages={317–331} }
 @inproceedings{ryan_lin_mitchell-ward_mathieu_johnson_2017, title={Life Cycle Environmental Impacts of using Lithium Ion Batteries for Power System Reserves and Strategies for Mitigation}, number={#214}, booktitle={Proceedings of 2017 AEESP Research and Education Conference}, author={Ryan, N.A. and Lin, Y. and Mitchell-Ward, N. and Mathieu, J.L. and Johnson, J.X.}, year={2017} }
 @article{johnson_2017, title={Location or insolation: the importance of siting in emissions mitigation from solar photovoltaics}, volume={6}, ISSN={2041-8396}, url={http://dx.doi.org/10.1002/wene.249}, DOI={10.1002/wene.249}, abstractNote={Achieving environmental benefits is often a primary motivation for integrating renewable energy into the grid. The magnitude of generation from a solar power project is influenced by the solar resource quality, but locations with high insolation do not necessarily yield the greatest emission reduction benefits. This study simulates the power system response to 10 identical solar projects in different regions across the United States, selected to represent a wide range of solar resource quality and power grid configurations. The power grid mix is often a key determinant in offsetting CO2 , SO2 , and NOx emissions, illustrating how lower‐quality solar resources can be more effective than sunnier sites at emissions mitigation when one considers characteristics of the power grid. The analysis shows a strong relationship between emissions mitigation and the share of offset generation that is coal‐fired. The strongest correlation is shown for CO2 ; the presence or absence of emissions control equipment and the sulfur content of the coal complicates the relationship of SO2 and NOx . The emissions intensity of offset generation is insensitive to whether the solar project is fixed tilt or single‐axis tracking. When seeking to mitigate power sector emissions, the impacts of solar design considerations on the temporal profile of generation are less important than the overall amount of generation and the location of interconnection. Public policies that target only the magnitude of generation from renewables (e.g., many Renewable Portfolio Standards) or the installed cost (e.g., the Investment Tax Credit) will likely lead to suboptimal emissions mitigation. WIREs Energy Environ 2017, 6:e249. doi: 10.1002/wene.249}, number={5}, journal={Wiley Interdisciplinary Reviews: Energy and Environment}, publisher={Wiley}, author={Johnson, Jeremiah X.}, year={2017}, month={Apr}, pages={e249} }
 @article{arbabzadeh_johnson_keoleian_2017, title={Parameters driving environmental performance of energy storage systems across grid applications}, volume={12}, ISSN={2352-152X}, url={http://dx.doi.org/10.1016/j.est.2017.03.011}, DOI={10.1016/j.est.2017.03.011}, abstractNote={Large-scale energy storage may effectively meet the needs of several grid applications. However, understanding the environmental impact of energy storage for these grid applications is challenging due to diversity in loads, grid mixes, and energy storage systems. Comprehensive sustainability assessments are necessary to yield the best environmental outcomes for grid-scale energy storage systems. To achieve this, we first developed fundamental principles for green energy storage, addressing key issues such as material sustainability, round-trip efficiency, service life, and degradation. In the current study, we couple the principles with a sustainability assessment model to investigate the impact of design and operational parameters on environmental outcomes of utilizing energy storage for grid applications. This model takes into account the service that the energy storage would provide (e.g., bulk energy time-shifting) as well as the energy storage parameters and grid application parameters that influence environmental outcomes. Parameters examined include energy storage round-trip efficiency, degradation, service life, upstream production burden, and heat rates of charging and displaced generation technologies. Environmental sustainability performance is evaluated using a universal set of equations that incorporates all the mentioned parameters. The relationships between these parameters are investigated to determine their influence on environmental performance of energy storage for three grid applications: energy time-shifting, frequency regulation, and power reliability. This model guides the design and operation of new and existing technologies, targeting audiences from energy storage designers to energy storage operators and power utilities.}, journal={Journal of Energy Storage}, publisher={Elsevier BV}, author={Arbabzadeh, Maryam and Johnson, Jeremiah X. and Keoleian, Gregory A.}, year={2017}, month={Aug}, pages={11–28} }
 @article{forrester_zaman_mathieu_johnson_2017, title={Policy and market barriers to energy storage providing multiple services}, volume={30}, ISSN={1040-6190}, url={http://dx.doi.org/10.1016/J.TEJ.2017.10.001}, DOI={10.1016/J.TEJ.2017.10.001}, abstractNote={Policy and market conditions remain the primary barriers to stacking energy storage services, reducing its cost-competitiveness with traditional technologies. This article explores two cases that show how treating energy storage as a traditional asset class providing either market-remunerated or regulated services limits its profitability, and how changing market rules creates regulatory risk that could be mitigated through stacking services.}, number={9}, journal={The Electricity Journal}, publisher={Elsevier BV}, author={Forrester, Sydney P. and Zaman, Ansha and Mathieu, Johanna L. and Johnson, Jeremiah X.}, year={2017}, month={Nov}, pages={50–56} }
 @article{ryan_johnson_keoleian_2016, title={Comparative Assessment of Models and Methods To Calculate Grid Electricity Emissions}, volume={50}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/acs.est.5b05216}, DOI={10.1021/acs.est.5b05216}, abstractNote={Due to the complexity of power systems, tracking emissions attributable to a specific electrical load is a daunting challenge but essential for many environmental impact studies. Currently, no consensus exists on appropriate methods for quantifying emissions from particular electricity loads. This paper reviews a wide range of the existing methods, detailing their functionality, tractability, and appropriate use. We identified and reviewed 32 methods and models and classified them into two distinct categories: empirical data and relationship models and power system optimization models. To illustrate the impact of method selection, we calculate the CO2 combustion emissions factors associated with electric-vehicle charging using 10 methods at nine charging station locations around the United States. Across the methods, we found an up to 68% difference from the mean CO2 emissions factor for a given charging site among both marginal and average emissions factors and up to a 63% difference from the average across average emissions factors. Our results underscore the importance of method selection and the need for a consensus on approaches appropriate for particular loads and research questions being addressed in order to achieve results that are more consistent across studies and allow for soundly supported policy decisions. The paper addresses this issue by offering a set of recommendations for determining an appropriate model type on the basis of the load characteristics and study objectives.}, number={17}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Ryan, Nicole A. and Johnson, Jeremiah X. and Keoleian, Gregory A.}, year={2016}, month={Aug}, pages={8937–8953} }
 @article{lin_johnson_mathieu_2016, title={Emissions impacts of using energy storage for power system reserves}, volume={168}, ISSN={0306-2619}, url={http://dx.doi.org/10.1016/j.apenergy.2016.01.061}, DOI={10.1016/j.apenergy.2016.01.061}, abstractNote={Energy storage devices, such as batteries and flywheels, are promising options for providing operating reserves due to their fast response and low emissions during operation. However, because of the complex nature of power systems, adding energy storage-based reserves to the power system may not necessarily benefit the environment. In this paper, we analyze these impacts in a test system and identify important drivers that affect the environmental outcomes. Dispatch results are obtained by solving an optimal power flow (OPF) problem and are used to determine emissions. We find that the impacts of adding energy storage are highly case-dependent. In systems with high renewable penetration levels and significant renewable curtailment, adding energy storage reduces emissions; in other systems, the impacts on emissions could be positive, neutral, or negative. The analyses presented in this paper show that policies to procure energy storage as a means to reduce emissions may actually lead to increased system-wide emissions if current dispatch algorithms are used. We also explore the impacts of modifying the dispatch algorithm to ensure system emissions with energy storage are no worse than system emissions without energy storage.}, journal={Applied Energy}, publisher={Elsevier BV}, author={Lin, Yashen and Johnson, Jeremiah X. and Mathieu, Johanna L.}, year={2016}, month={Apr}, pages={444–456} }
 @article{chiang_moore_johnson_keoleian_2016, title={Emissions reduction benefits of siting an offshore wind farm: A temporal and spatial analysis of Lake Michigan}, volume={130}, ISSN={0921-8009}, url={http://dx.doi.org/10.1016/j.ecolecon.2016.07.010}, DOI={10.1016/j.ecolecon.2016.07.010}, abstractNote={Siting decisions of offshore wind farms influence the magnitude of emissions reduction benefits. This paper calculates electricity generation and emissions reduction of CO2, NOx, and SO2, and values these reductions to determine the impact of the siting location for a 300 MW offshore wind farm in Lake Michigan. The most important patterns for emissions reduction were the monthly trends, where January, March, and December consistently had the highest electricity generation and emissions reduction benefits. Summer months such as July and August had the lowest emissions reduction benefits. The intra-day trends showed higher emissions reduction benefits during off-peak hours, due to a higher likelihood of coal units being the marginal generator. These diurnal differences were smaller in magnitude than the seasonal differences. Two benefit valuation scenarios were analyzed for a 20-year time period, one using marginal damages of pollution and another using market prices for pollution allowances. The first scenario resulted in emissions reduction benefits ranging from $1827/kW to $2690/kW ($2508/kW averaged) throughout the Lake Michigan region for the 20-year period (applying a 3% discount rate). This equates to approximately $33/MWh in all lake locations since the emissions reduction benefits are primarily a function of electricity generation. The market price scenario resulted in a much lower range of $820/kW to $1060/kW ($987/kW average or 39% of the pollution damage costs). In scenario 1, the major component of emissions reduction benefits was CO2 reduction (86% of benefits), and 83% of these CO2 benefits were from offsetting coal plant emissions. A sensitivity analysis on size and region of emission reduction location showed that the NOx and SO2 benefits vary significantly (unlike CO2 benefits), but this variation had minimal effects on the total emissions reduction benefits. In comparison with economic investment costs, the scenario 1 emissions reduction benefits equal 49% of the total investment cost (in 2014 $million) on average. Spatial maps and heat maps are generated to illustrate the spatial and temporal variations in the emissions reduction benefits.}, journal={Ecological Economics}, publisher={Elsevier BV}, author={Chiang, Amy C. and Moore, Michael R. and Johnson, Jeremiah X. and Keoleian, Gregory A.}, year={2016}, month={Oct}, pages={263–276} }
 @article{good_johnson_2016, title={Impact of inverter loading ratio on solar photovoltaic system performance}, volume={177}, ISSN={0306-2619}, url={http://dx.doi.org/10.1016/j.apenergy.2016.05.134}, DOI={10.1016/j.apenergy.2016.05.134}, abstractNote={Due to decreasing solar module prices, some solar developers are increasing their projects’ inverter loading ratio (ILR), defined as the ratio of DC module capacity to AC inverter capacity. In this study, we examine the operational impacts of this trend. Using minute-level solar data, we examine the relationship between inverter induced clipping losses and AC generation. We find minimal clipping losses at an ILR of 1.25; at an ILR of 2.0, we observe that 16% of potential annual generation is lost. Minute-level data prove to be essential in determining the generation lost to clipping, as hourly data mask key clipping and ramping events. Higher ILRs lead to a greater frequency of time spent at maximum generation, but also a greater frequency and magnitude of large solar ramping events. Module degradation can attenuate the impacts of inverter clipping over time. We observe that the effective degradation rate (net of any changes to inverter clipping losses) can be as little as half the actual degradation rate for projects with high ILRs. The diurnal and seasonal trends in clipping correspond with solar insolation patterns, with the highest clipping occurring around noon. For fixed tilt installations with tilt angles at latitude, we observe the highest clipping near the autumnal and vernal equinoxes. Increasing the tilt angle leads to more winter clipping, while lower tilt angles shifts the clipping to summer months. Shifting from fixed tilt to north–south single axis tracking increases the generation lost to clipping significantly. At an ILR of 1.25, annual clipping approximately doubles to 1% compared to fixed tilt at latitude, while clipping under an ILR of 2.0 increases to 22%, compared to 16% for the fixed configuration. As expected, more clipping occurs during the hours preceding and following noon when using single axis tracking.}, journal={Applied Energy}, publisher={Elsevier BV}, author={Good, Jeremy and Johnson, Jeremiah X.}, year={2016}, month={Sep}, pages={475–486} }
 @article{johnson_novacheck_2015, title={Emissions Reductions from Expanding State-Level Renewable Portfolio Standards}, volume={49}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es506123e}, DOI={10.1021/es506123e}, abstractNote={In the United States, state-level Renewable Portfolio Standards (RPS) have served as key drivers for the development of new renewable energy. This research presents a method to evaluate emissions reductions and costs attributable to new or expanded RPS programs by integrating a comprehensive economic dispatch model and a renewable project selection model. The latter model minimizes incremental RPS costs, accounting for renewable power purchase agreements (PPAs), displaced generation and capacity costs, and net changes to a state's imports and exports. We test this method on potential expansions to Michigan's RPS, evaluating target renewable penetrations of 10% (business as usual or BAU), 20%, 25%, and 40%, with varying times to completion. Relative to the BAU case, these expanded RPS policies reduce the CO2 intensity of generation by 13%, 18%, and 33% by 2035, respectively. SO2 emissions intensity decreased by 13%, 20%, and 34% for each of the three scenarios, while NOx reductions totaled 12%, 17%, and 31%, relative to the BAU case. For CO2 and NOx, absolute reductions in emissions intensity were not as large due to an increasing trend in emissions intensity in the BAU case driven by load growth. Over the study period (2015 to 2035), the absolute CO2 emissions intensity increased by 1% in the 20% RPS case and decreased by 6% and 22% for the 25% and 40% cases, respectively. Between 26% and 31% of the CO2, SO2, and NOx emissions reductions attributable to the expanded RPS occur in neighboring states, underscoring the challenges quantifying local emissions reductions from state-level energy policies with an interconnected grid. Without federal subsidies, the cost of CO2 mitigation using an RPS in Michigan is between $28 and $34/t CO2 when RPS targets are met. The optimal renewable build plan is sensitive to the capacity credit for solar but insensitive to the value for wind power.}, number={9}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Johnson, Jeremiah X. and Novacheck, Joshua}, year={2015}, month={Apr}, pages={5318–5325} }
 @article{johnson_novacheck_2015, title={Environmental Benefits of Renewable Portfolio Standards in an Age of Coal Plant Retirements}, volume={28}, ISSN={1040-6190}, url={http://dx.doi.org/10.1016/j.tej.2015.09.007}, DOI={10.1016/j.tej.2015.09.007}, abstractNote={An examination of the environmental benefits of an expanded RPS in Michigan find that, with higher coal retirements, significantly more natural gas is displaced by the expanded RPS, thereby reducing the emissions mitigation potential. This illustrates how the environmental benefits of renewable energy are dependent on the system into which it is integrated.}, number={8}, journal={The Electricity Journal}, publisher={Elsevier BV}, author={Johnson, Jeremiah X. and Novacheck, Joshua}, year={2015}, month={Oct}, pages={59–68} }
 @article{novacheck_johnson_2015, title={The environmental and cost implications of solar energy preferences in Renewable Portfolio Standards}, volume={86}, ISSN={0301-4215}, url={http://dx.doi.org/10.1016/j.enpol.2015.06.039}, DOI={10.1016/j.enpol.2015.06.039}, abstractNote={Many state-level Renewable Portfolio Standards (RPS) include preferences for solar generation, with goals of increasing the generation diversity, reducing solar costs, and encouraging local solar industries. Depending on their policy design, these preferences can impact the RPS program costs and emissions reduction. This study evaluates the impact of these policies on costs and emissions, coupling an economic dispatch model with optimized renewable site selection. Three policy designs of an increased RPS in Michigan are investigated: (1) 20% Solar Carve-Out, (2) 5% Distributed Generation Solar Carve-Out, and (3) 3× Solar Multiplier. The 20% Solar Carve-Out scenario was found to increase RPS costs 28%, while the 5% Distributed Generation Solar Carve-Out increased costs by 34%. Both of these solar preferences had minimal impact on total emissions. The 3× Solar Multiplier decreases total RPS program costs by 39%, but adds less than half of the total renewable generation of the other cases, significantly increasing emissions of CO2, NOx, and SO2 relative to an RPS without the solar credit multiplier. Sensitivity analysis of the installed cost of solar and the natural gas price finds small changes in the results of the Carve-Out cases, with a larger impact on the 3× Solar Multiplier.}, journal={Energy Policy}, publisher={Elsevier BV}, author={Novacheck, Joshua and Johnson, Jeremiah X.}, year={2015}, month={Nov}, pages={250–261} }
 @article{arbabzadeh_johnson_keoleian_rasmussen_thompson_2015, title={Twelve Principles for Green Energy Storage in Grid Applications}, volume={50}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/acs.est.5b03867}, DOI={10.1021/acs.est.5b03867}, abstractNote={The introduction of energy storage technologies to the grid could enable greater integration of renewables, improve system resilience and reliability, and offer cost effective alternatives to transmission and distribution upgrades. The integration of energy storage systems into the electrical grid can lead to different environmental outcomes based on the grid application, the existing generation mix, and the demand. Given this complexity, a framework is needed to systematically inform design and technology selection about the environmental impacts that emerge when considering energy storage options to improve sustainability performance of the grid. To achieve this, 12 fundamental principles specific to the design and grid application of energy storage systems are developed to inform policy makers, designers, and operators. The principles are grouped into three categories: (1) system integration for grid applications, (2) the maintenance and operation of energy storage, and (3) the design of energy storage systems. We illustrate the application of each principle through examples published in the academic literature, illustrative calculations, and a case study with an off-grid application of vanadium redox flow batteries (VRFBs). In addition, trade-offs that can emerge between principles are highlighted.}, number={2}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Arbabzadeh, Maryam and Johnson, Jeremiah X. and Keoleian, Gregory A. and Rasmussen, Paul G. and Thompson, Levi T.}, year={2015}, month={Dec}, pages={1046–1055} }
 @article{arbabzadeh_johnson_de kleine_keoleian_2015, title={Vanadium redox flow batteries to reach greenhouse gas emissions targets in an off-grid configuration}, volume={146}, ISSN={0306-2619}, url={http://dx.doi.org/10.1016/j.apenergy.2015.02.005}, DOI={10.1016/j.apenergy.2015.02.005}, abstractNote={Energy storage may serve as a solution to the integration challenges of high penetrations of wind, helping to reduce curtailment, provide system balancing services, and reduce emissions. This study determines the minimum cost configuration of vanadium redox flow batteries (VRFB), wind turbines, and natural gas reciprocating engines in an off-grid model. A life cycle assessment (LCA) model is developed to determine the system configuration needed to achieve a variety of CO2-eq emissions targets. The relationship between total system costs and life cycle emissions are used to optimize the generation mixes to achieve emissions targets at the least cost and determine when VRFBs are preferable over wind curtailment. Different greenhouse gas (GHG) emissions targets are defined for the off-grid system and the minimum cost resource configuration is determined to meet those targets. This approach determines when the use of VRFBs is more cost effective than wind curtailment in reaching GHG emissions targets. The research demonstrates that while incorporating energy storage consistently reduces life cycle carbon emissions, it is not cost effective to reduce curtailment except under very low emission targets (190 g of CO2-eq/kW h and less for the examined system). This suggests that “overbuilding” wind is a more viable option to reduce life cycle emissions for all but the most ambitious carbon mitigation targets. The findings show that adding VRFB as energy storage could be economically preferable only when wind curtailment exceeds 66% for the examined system. The results were most sensitive to VRFB costs, natural gas upstream emissions (e.g. methane leakage), and wind capital cost.}, journal={Applied Energy}, publisher={Elsevier BV}, author={Arbabzadeh, Maryam and Johnson, Jeremiah X. and De Kleine, Robert and Keoleian, Gregory A.}, year={2015}, month={May}, pages={397–408} }
 @article{johnson_de kleine_keoleian_2014, title={Assessment of energy storage for transmission-constrained wind}, volume={124}, ISSN={0306-2619}, url={http://dx.doi.org/10.1016/j.apenergy.2014.03.006}, DOI={10.1016/j.apenergy.2014.03.006}, abstractNote={Grid-scale energy storage is one option to reduce curtailment and increase deliverability of transmission-constrained wind. This study examines four hypothetical wind and transmission projects in the United States to quantify the reduction in curtailment under various energy storage configurations and determine the cost targets that energy storage must achieve to become a viable solution for use with remote wind. The delivered cost of wind is determined using a power purchase agreement approach and six AC transmission voltage classes are considered. The findings show that curtailment reduction can be achieved with energy storage costs as high as $780/kW with ten hours of storage capacity, a value that is 50–85% lower than current cost estimates for redox and sodium sulfur batteries. Batteries with higher power ratings result in greater curtailment reduction, but also lower maximum viable costs. Sizing the battery to reduce a small portion of curtailment allows for higher utilization of the storage and supports higher cost batteries. Using energy storage to increase wind installed capacity can also be economically viable, but at costs lower than those for curtailment reduction. The results were most sensitive to the elimination of wind subsidies, the installed cost of transmission, battery efficiency degradation, and battery cycle life. The study did not show economic viability for the use of energy storage to reduce transmission voltage class.}, journal={Applied Energy}, publisher={Elsevier BV}, author={Johnson, Jeremiah X. and De Kleine, Robert and Keoleian, Gregory A.}, year={2014}, month={Jul}, pages={377–388} }
 @article{johnson_mcmillan_keoleian_2013, title={Evaluation of Life Cycle Assessment Recycling Allocation Methods}, ISSN={1088-1980}, url={http://dx.doi.org/10.1111/jiec.12050}, DOI={10.1111/jiec.12050}, abstractNote={Life cycle assessment practitioners struggle to accurately allocate environmental burdens of metals recycling, including the temporal dimension of environmental impacts. We analyze four approaches for calculating aluminum greenhouse gas emissions: the recycled content (RC) or cut‐off approach, which assumes that demand for recycled content displaces primary production; end‐of‐life recycling (EOLR), which assumes that postuse recycling displaces primary production; market‐based (MB) approaches, which estimate changes in supply and demand using price elasticities; and value‐corrected substitution (VCS), which allocates impact based on price differences between primary and recycled material. Our analysis suggests that applications of the VCS approach do not adequately account for the changing scrap to virgin material price ratio over time, whereas MB approaches do not address stock accumulation and depletion. The EOLR and RC approaches were analyzed using two case studies: U.S. aluminum beverage cans and vehicle engine blocks. These approaches produced similar results for beverage cans, which have a closed material loop system and a short product life. With longer product lifetimes, as noted with the engine blocks, the magnitude and timing of the emissions differs greatly between the RC and EOLR approaches. The EOLR approach indicates increased impacts at the time of production, offset by negative impacts in future years, whereas the RC approach assumes benefits to increased recycled content at the time of production. For vehicle engine blocks, emissions using EOLR are 140% higher than with RC. Results are highly sensitive to recycled content and future recycling rates, and the choice of allocation methods can have significant implications for life cycle studies.}, journal={Journal of Industrial Ecology}, publisher={Wiley}, author={Johnson, Jeremiah X. and McMillan, Colin A. and Keoleian, Gregory A.}, year={2013}, month={Sep}, pages={n/a-n/a} }
 @article{claramunt_muir_johnson_sutton_2010, title={Spatio-temporal trends in the food habits of age-0 lake whitefish}, volume={36}, ISSN={0380-1330}, url={http://dx.doi.org/10.1016/j.jglr.2010.01.002}, DOI={10.1016/j.jglr.2010.01.002}, abstractNote={We compared diets of juvenile lake whitefish among six sites in Lake Michigan and one in Lake Superior during 2005 and 2006 to assess spatial and temporal patterns in food habits and evaluate if ontogenetic diet shifts occur that may influence growth and survival. A total of 262 and 496 juveniles were captured in 2005 and 2006, the majority of which were captured during June and July. Sites in southern Lake Michigan tended to have larger juveniles, and the smallest juveniles were observed at Naubinway, northern Lake Michigan, and Whitefish Point, Lake Superior. The mean number of prey items per stomach differed among sampling sites and years. Copepods were the most prevalent prey item, and were present in greater than 70% of juvenile stomachs from most sites. However, the percent by number of copepods decreased during July as chironomids and other benthic macroinvertebrates increased in number. There was a significant positive relationship between percent of benthic prey items and mean length of juvenile lake whitefish. A substantial increase in the percent of benthic prey consumed after 40 mm (total length) was observed and likely resulted from juvenile lake whitefish crossing a size threshold for benthic feeding relating to morphological changes (i.e., transition of mouth opening from terminal to sub-terminal) in addition to a potential increase in the availability of emergent macroinvertebrates. Timing of the transition to benthic feeding is likely regulated by the number of prey per juvenile and the overlap with peak emergence of important benthic aquatic invertebrates such as chironomids. A better understanding of these factors will increase our understanding of juvenile lake whitefish growth and survival, which are necessary for improving year-class strength predictions.}, number={Supplement 1}, journal={Journal of Great Lakes Research}, publisher={Elsevier BV}, author={Claramunt, Randall M. and Muir, Andrew M. and Johnson, Jeremiah and Sutton, Trent M.}, year={2010}, month={Jan}, pages={66–72} }
 @article{johnson_chertow_2009, title={Climate Stabilization Wedges in Action: A Systems Approach to Energy Sustainability for Hawaii Island}, volume={43}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es801700a}, DOI={10.1021/es801700a}, abstractNote={Pacala and Socolow developed a framework to stabilize global greenhouse gas levels for the next fifty years using wedges of constant size representing an increasing use of existing technologies and approaches for energy efficiency, carbon free generation, renewables, and carbon storage. The research presented here applies their approach to Hawaii Island, with modifications to support local scale analysis and employing a "bottom-up" methodology that allows for wedges of various sizes. A discretely bounded spatial unit offers a testing ground for a holistic approach to improving the energy sector with the identification of local options and limitations to the implementation of a comprehensive energy strategy. Nearly 80% of total primary energy demand across all sectors for Hawaii Island is currently met using petroleum-based fuels.The Sustainable Energy Plan scenario included here presents an internally consistent set of recommendations bounded by local constraints in areas such as transportation efficiency, centralized renewable generation (e.g., geothermal, wind), reduction in transmission losses, and improved building efficiency. This scenario shows thatthe demand for primary energy in 2030 could be reduced by 23% through efficiency measures while 46% could be met by renewable generation, resulting in only 31% of the projected demand being met by fossil fuels. In 2030, the annual releases of greenhouse gases would be 3.2 Mt CO2-eq/year under the Baseline scenario, while the Sustainable Energy Plan would reduce this to 1.2 Mt CO2-eq/year--an annual emissions rate 40% below 2006 levels and 10% below 1990 levels. The total for greenhouse gas emissions during the 24-year study period (2007 to 2030) is 59.9 Mt CO2-eq under the Baseline scenario and 32.5 Mt CO2-eq under the Sustainable Energy Plan scenario. Numerous combinations of efficiency and renewable energy options can be employed in a manner that stabilizes the greenhouse gas emissions of Hawaii Island.}, number={7}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Johnson, Jeremiah and Chertow, Marian}, year={2009}, month={Apr}, pages={2234–2240} }
 @article{wang_mao_johnson_reck_graedel_2008, title={Anthropogenic metal cycles in China}, volume={10}, ISSN={1438-4957 1611-8227}, url={http://dx.doi.org/10.1007/s10163-008-0203-7}, DOI={10.1007/s10163-008-0203-7}, number={2}, journal={Journal of Material Cycles and Waste Management}, publisher={Springer Science and Business Media LLC}, author={Wang, Tao and Mao, Jiansu and Johnson, Jeremiah and Reck, Barbara K. and Graedel, Thomas E.}, year={2008}, month={Sep}, pages={188–197} }
 @article{johnson_reck_wang_graedel_2008, title={The energy benefit of stainless steel recycling}, volume={36}, ISSN={0301-4215}, url={http://dx.doi.org/10.1016/j.enpol.2007.08.028}, DOI={10.1016/j.enpol.2007.08.028}, abstractNote={The energy used to produce austenitic stainless steel was quantified throughout its entire life cycle for three scenarios: (1) current global operations, (2) 100% recycling, and (3) use of only virgin materials. Data are representative of global average operations in the early 2000s. The primary energy requirements to produce 1 metric ton of austenitic stainless steel (with assumed metals concentrations of 18% Cr, 8% Ni, and 74% Fe) is (1) 53 GJ, (2) 26 GJ, and (3) 79 GJ for each scenario, with CO2 releases totaling (1) 3.6 metric tons CO2, (2) 1.6 metric tons CO2, and (3) 5.3 metric tons CO2. Thus, the production of 17 million metric tons of austenitic stainless steel in 2004 used approximately 9.0×1017 J of primary energy and released 61 million metric tons of CO2. Current recycling operations reduce energy use by 33% (4.4×1017 J) and CO2 emissions by 32% (29 million tons). If austenitic stainless steel were to be produced solely from scrap, which is currently not possible on a global level due to limited availability, energy use would be 67% less than virgin-based production and CO2 emissions would be cut by 70%. The calculation of the total energy is most sensitive to the amount and type of scrap fed into the electric arc furnace, the unit energy of the electric arc furnace, the unit energy of ferrochromium production, and the form of primary nickel.}, number={1}, journal={Energy Policy}, publisher={Elsevier BV}, author={Johnson, Jeremiah and Reck, B.K. and Wang, T. and Graedel, T.E.}, year={2008}, month={Jan}, pages={181–192} }
 @article{johnson_graedel_2008, title={The “Hidden” Trade of Metals in the United States}, volume={12}, ISSN={1088-1980}, url={http://dx.doi.org/10.1111/j.1530-9290.2008.00092.x}, DOI={10.1111/j.1530-9290.2008.00092.x}, abstractNote={The transport of ore and refined metals into and from countries has long been quantified, both because of its financial implications and because of the relative ease of tracking those flows. This information says little, however, about the net trade of metal in all its forms, particularly “semiproducts,” such as sheet and wire, and metal in traded products (MTP). A comprehensive analysis for the United States for copper, lead, zinc, chromium, and silver, in which all trade flows are included, demonstrates that MTP flows can often be a large factor in determining a country's import/export dependence, accounting for between 13% (zinc) and 57% (silver) of traded metal in all forms. A methodology was created to calculate the end user net import reliance, which is the net import of metal contained in ore, concentrate, refined forms, and semi‐manufactured and finished products, plus any releases of metal from government or producer stocks, as a function of the flow of metal into end use by consumers. For all five metals, this calculation showed a higher reliance on imports than calculations that solely examine ore, concentrate, and refined metals. This suggests that the metal contained in semi‐manufactured and finished products increases U.S. material import vulnerability. However, the in‐use stocks of these metals contained in products may serve as a potential resource, serving to mitigate this vulnerability. Graphical representations of metal trade in all forms by geographical origin and destination are provided to characterize the nature of the trade and provide information that would be useful in characterizing U.S. import vulnerability.}, number={5-6}, journal={Journal of Industrial Ecology}, publisher={Wiley}, author={Johnson, Jeremiah and Graedel, T. E.}, year={2008}, month={Oct}, pages={739–753} }
 @article{johnson_harper_lifset_graedel_2007, title={Dining at the Periodic Table:  Metals Concentrations as They Relate to Recycling}, volume={41}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es060736h}, DOI={10.1021/es060736h}, abstractNote={A correlation between the prices of a variety of substances and their dilutions in their initial matrices was shown in 1959 by T.K. Sherwood. The research presented here shows that the relationship holds for engineering metals today, which we termed the metals-specific Sherwood plot. The concentrations of metals in products (e.g., printed wiring boards and automobiles) and waste streams (e.g., municipal solid waste, and construction and demolition debris) were plotted with this correlation. In addition, for the products and waste streams that undergo disassembly at end-of-life, the metals concentrations of the disassembled components were also plotted. It was found that most of the metals that are currently targeted for recycling have post-disassembly concentrations that lie above the metals-specific Sherwood plot (i.e., have concentrations that are more enriched than minimum profitable ore grades). This suggests that material concentration plays a role in the viability of recycling at end-of-life. As products grow in complexity and the variety of materials used, analyses such as this one provide insight for policymakers and those interested in material sustainability into macro-level trends of material use and future recycling practices.}, number={5}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Johnson, Jeremiah and Harper, E. M. and Lifset, Reid and Graedel, T. E.}, year={2007}, month={Mar}, pages={1759–1765} }
 @misc{johnson_2007, title={Transforming sustainability strategy into action: The chemical industry}, volume={61}, ISSN={0921-8009}, url={http://dx.doi.org/10.1016/j.ecolecon.2006.03.023}, DOI={10.1016/j.ecolecon.2006.03.023}, abstractNote={Key parameters of OECD biodegradation screening tests were analyzed for impact on the assessment of biodegradation potential of selected fragrance compounds.Comparison of official Japanese OECD 301C test results for 48 predominantly readily biodegradable chemicals with recent OECD 301F screening data demonstrated a significantly higher occurrence of false negatives potentially attributable to inoculum limitations for the former, while for the latter, restriction to 28 days was frequently limiting.Influence of test concentration was studied for two groups of quaternary carbon-containing compounds under high (OECD 301F) and low (OECD 301D) concentrations and extended incubations. Ionones were generally ultimately biodegradable within 28 days or readily biodegradable, whereas damascones reached ultimate biodegradation in OECD 301D tests only and required extended incubations.Predictions from Biowin and Catalogic models were analyzed for ionones, damascones and other selected structural groups of fragrance compounds. Comparison with previously published experimental data revealed significant differences in results between OECD screening tests, thus illustrating the shortcomings of currently available data collections and the potential risk of training prediction models with false negative results, particularly if used for models that are primarily based on data from one specific test. In addition, the analysis revealed specific limitations for prediction models that cannot take into account positioning of fragments within a structure. As a result, it appears that the presence of more than one unfavorable fragment usually does not allow reaching currently accepted threshold scores that would identify a given compound as biodegradable.The outcome of the analyses of this study underlines the need to take into account results from OECD screening tests that are best adapted to physico-chemical properties of fragrances (hydrophobicity, volatility and inhibition potential at high test concentration) and conducted at reduced stringency compared to OECD guidelines (extended incubation owing to reduced bioavailability). Negative MITI database results should be critically reviewed, particularly for quaternary carbon-containing compounds. For future efforts aimed at designing more environmentally benign chemicals, the apparent underestimations will have to be overcome by providing more realistic experimental data that should subsequently be used to improve current biodegradation prediction models for better guidance.}, number={1}, journal={Ecological Economics}, publisher={Elsevier BV}, author={Johnson, Jeremiah}, year={2007}, month={Feb}, pages={194–195} }
 @article{harper_johnson_graedel_2006, title={Making Metals Count: Applications of Material Flow Analysis}, volume={23}, ISSN={1092-8758 1557-9018}, url={http://dx.doi.org/10.1089/ees.2006.23.493}, DOI={10.1089/ees.2006.23.493}, abstractNote={Industrial ecology is frequently regarded as the organizing framework for studying interactions of technological societies with the environment. A theme central to industrial ecology is the way that materials are used which, in turn, relates to environmental and resource availability concerns. The material fluxes seen between the production of raw materials, the manufacture and use of products, and their fate at their end of life are quantified using material flow analysis, the record keeping of atoms mobilized by humans within a bounded system. The Stocks and Flows project at Yale University examines the full life cycle of anthropogenically mobilized material on a variety of spatial levels, including city-, country-, regional-, and global-level cycles. Different temporal levels are also examined, with research conducted on historical studies, contemporary studies, and scenario development. Material cycles have been completed for copper, zinc, and silver, with current work including iron and steel, chromi...}, number={3}, journal={Environmental Engineering Science}, publisher={Mary Ann Liebert Inc}, author={Harper, Ermelinda M. and Johnson, Jeremiah and Graedel, Thomas E.}, year={2006}, month={May}, pages={493–506} }
 @article{johnson_gordon_graedel_2006, title={Silver cycles: The stocks and flows project, part 3}, volume={58}, ISSN={1047-4838 1543-1851}, url={http://dx.doi.org/10.1007/s11837-006-0006-z}, DOI={10.1007/s11837-006-0006-z}, number={2}, journal={JOM}, publisher={Springer Science and Business Media LLC}, author={Johnson, Jeremiah and Gordon, Robert and Graedel, Thomas}, year={2006}, month={Feb}, pages={34–38} }
 @article{johnson_schewel_graedel_2006, title={The Contemporary Anthropogenic Chromium Cycle}, volume={40}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es060061i}, DOI={10.1021/es060061i}, abstractNote={Chromium is an essential engineering metal used in stainless and alloy steels, chemicals, and refractory products. Using material flow analysis, all major anthropogenic chromium flows are characterized for the year 2000, from mining through discard, on three spatial levels: fifty-four countries, nine world regions, and the planet. Included is the first detailed quantification of chromium in internationally traded finished products and diverse waste streams. Findings include (1) 78% of chromium flow entering final use is added as a net addition to stock on the global level; most countries are close to this figure; (2) the majority of mining occurs in Africa (2400 Gg Cr/yr) and the Commonwealth of Independent States (1090 Gg Cr/yr), while the major end-users are Asia, Europe, and North America at 1150, 1140, and 751 Gg Cr/yr, respectively; (3) waste flows of chromium are the greatest in Europe (420 Gg Cr/yr), Asia (370 Gg Cr/yr), and North America (290 Gg Cr/yr), but the composition of these waste flows varies greatly among the world regions; (4) releases of chromium by the global system, which total 2630 Gg Cr/yr, are nearly evenly divided among tailings, ferrochromium slag, downgraded scrap, and post-consumer losses; (5) many countries have a heavy foreign dependence on chromium in the all forms, as is demonstrated for the United States. The findings relating to in-use stock changes and finished product trade are relevant to industry, allowing for more accurate planning for future scrap availability. The quantification of releases due to discards and dissipation hold environmental and human health relevance, while the full life cycle international trade assessment addresses local scarcity.}, number={22}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Johnson, Jeremiah and Schewel, Laura and Graedel, T. E.}, year={2006}, month={Nov}, pages={7060–7069} }
 @article{johnson_jirikowic_bertram_van beers_gordon_henderson_klee_lanzano_lifset_oetjen_et al._2005, title={Contemporary Anthropogenic Silver Cycle:  A Multilevel Analysis}, volume={39}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es048319x}, DOI={10.1021/es048319x}, abstractNote={Anthropogenic cycling of silver in 1997 is presented using three discrete governmental units: 64 countries encompassing what we believe to be over 90% of global silver flows, 9 world regions, and the entire planet. Using material flow analysis (MFA) techniques, the country level cycles are aggregated to produce the regional cycles, which are used to form a "best estimate" global cycle. Interesting findings include the following: (1) several silver-mining countries export ore and concentrate but also import silver-containing semiproducts and products; (2) the level of development for a country, as indicated by the gross domestic product, is a fair indicator of silver use, but several significant outliers exist; (3) the countries with the greatest mine production include Mexico, the United States, Peru, and China, whereas the United States, Japan, India, Germany, and Italy lead in the fabrication and manufacture of products; (4) North America and Europe's use of silver products exceed that of other regions on a per capita basis; (5) global silver discards, including tailings and separation waste, totaled approximately 57% of the silver mined; (6) approximately 57% of the silver entering waste management globally is recycled; and (7) the amount of silver entering landfills globally is comparable to the amount found in tailings. The results of this MFA lay the basis for further analysis, which in turn can offer insight into natural resource policy, the characterization of environmental impact, and better resource management.}, number={12}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Johnson, Jeremiah and Jirikowic, Julie and Bertram, Marlen and van Beers, D. and Gordon, R. B. and Henderson, Kathryn and Klee, R. J. and Lanzano, Ted and Lifset, R. and Oetjen, Lucia and et al.}, year={2005}, month={Jun}, pages={4655–4665} }
 @article{johnson_bertram_henderson_jirikowic_graedel_2005, title={The contemporary Asian silver cycle: 1-year stocks and flows}, volume={7}, ISSN={1438-4957 1611-8227}, url={http://dx.doi.org/10.1007/s10163-005-0132-7}, DOI={10.1007/s10163-005-0132-7}, number={2}, journal={Journal of Material Cycles and Waste Management}, publisher={Springer Science and Business Media LLC}, author={Johnson, Jeremiah and Bertram, Marlen and Henderson, Kathryn and Jirikowic, Julie and Graedel, T. E.}, year={2005}, month={Aug}, pages={93–103} }