Our research group seeks to offer new understanding into the environmental impacts of emerging technologies and operational strategies, with a particular focus on the electric power and transportation systems. Our work relies on life cycle assessment and energy system optimization modeling, at times combined with experiments and surveys, and is often interdisciplinary, engaging with collaborators from economics, public policy, sciences, and other engineering disciplines.

Example of ongoing and recent projects include:

Environmental life cycle assessment of emerging technologies

Life cycle assessment (LCA) is a method to quantify the environmental impacts of a product or process. Our research group conducts LCAs on emerging technologies with the overarching goal of identifying the most effective points of intervention to achieve favorable environmental outcomes. Our research group is leading efforts to conduct an LCA on sedimentary basin CO2-enabled geothermal power (also called concentrating plume geothermal or CPG). Many climate change mitigation pathways require significant increases in dispatchable renewable energy generation and the geologic storage of CO2. Utilizing CO2 as a working fluid for geothermal energy production 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 siting near CO2 sources or where power system flexibility is needed. With collaborators at the University of Michigan and Ohio State University, and with funding from the Sloan Foundation, we are advancing the state of knowledge of this technology, investigating the parameters that most influence the climate change mitigation impacts of this technology, including the impacts of the CO2 source, the sedimentary basin characteristics, and the power system into which the geothermal plant is interconnected.

Other projects using LCA to assess emerging technologies include novel techniques for plastic waste management, the first comprehensive study on the environmental impacts of shared dockless e-scooters, an evaluation of solar-integrated greenhouses, and assessment of key parameters influencing the impacts of reverse electrodialysis for power production.

Using buildings as (efficient) batteries

Power systems require balancing of supply and demand, which is increasingly challenging with higher penetrations of solar and wind power. Altering real-time electricity consumption in buildings can help these balancing efforts, but little is known about the implications for long-term and short-term building efficiency. In collaboration with researchers at Michigan and Stanford, we are conducting thousands of experiments on university buildings to better understand the impacts of using HVAC loads to provide power system services. This work is funded by the Department of Energy’s Building Technology Office. Published work on grid-interactive buildings includes an extensive dataset, a perspective piece on the role of building experimentation, and severalresearch papers.

Open Energy Outlook: transparent energy system optimization

The Open Energy Outlook (OEO) is a collaboration with researchers at Carnegie Mellon University, with a far reaching advisory board, to examine U.S. energy futures using fully open-sourced data and models. This work is supported by the Sloan Foundation. The first OEO report showed the range of technology choices under deep decarbonization. Ongoing work seeks to advance methods to characterize uncertainty using modeling to generate alternatives.

Reducing human health impacts from power system emissions

In an ongoing NSF-funded study, we are exploring the potential to reduce adverse human health outcomes by altering power system operations while relying on the existing generation infrastructure. Specifically, we explore how to cost-effectively reduce health impacts due to fine particulate matter (PM2.5) attributable to power plant emissions by internalizing real-time health costs in plant dispatch decisions. By re-formulating a unit commitment and economic dispatch model, the optimal operations of the grid shift generation away from those units that cause the greatest adverse human health impacts. Our work has demonstrated that power system operational changes can reduce the majority of adverse health impacts through decreases in coal generation and strategic shifts in the location and timing of pollutant releases. Further study showed that power system decarbonization would yield broad health benefits, but fail to alleviate racial and socioeconomic air pollution exposure inequities. We have expanded this work to China, demonstrating the health and climate benefits of economic dispatch and decarbonization of the power sector.

Improving power system operations, planning, and environmental outcomes under high penetrations of renewables and storage

The integration of variable renewables such as solar and wind, as well as the expanding adoption of grid-connected batteries, requires new methods to evaluate operations and planning on the grid. Our research group has offered early and clear insights into the key drivers for emissions impacts from grid-connected energy storage. We assessed the role that grid-scale energy storage can play in achieving deep decarbonization of the power sector, quantified the life cycle environmental impacts of using distributed energy storage for power system ancillary services, and identified the 12 Principles of Green Energy Storage in Grid Applications. Recently, with a multi-university team, we characterized the current state of energy storage modeling, earning the 2023 IEEE Power and Energy Society Prize Paper Award.

With funding from the State of North Carolina and with collaborators across NC State, we completed a comprehensive evaluation of the potential benefits and costs of energy storage for the state. We have examined the capacity benefits of solar and energy storage, including symbiotic effects of technologies. We also have explored the policy implications of potential shifts from  summer peaking to winter peaking systems.

This collection of projects has deepened our understanding of the relationship between grid-connected energy storage, renewable deployment, and environmental outcomes, showing that emissions reductions are possible, but not certain, and operational strategies are needed to enable emissions reductions from energy storage.

Food-energy-water nexus: optimizing the use of solar water pumps in India

Solar water pumps can facilitate the irrigation of remote areas, improving the productivity of farms and the economic potential of rural areas. The Indian Government has set ambitious targets for distributed energy resources and solar water pumps will play an essential role.  To better understand the benefits and the optimal use of solar pumps, we conducted a field study in Chhattisgarh, a state located in central India, coupling farmer surveys with extensive water pump operational data. This study is an inter-institutional collaboration with the National Institute of Technology-Raipur, under U.S.-India State and Urban Initiative spearheaded by the Centre for Strategic and International Studies, with funding under the Partnership2020 program. The results of our work have been published in a special issue of Environmental Science & Technology.