close up of an EV being charged

Ask a Scientist: In Search of a ‘Green’ Electric Car Battery

Lithium-ion batteries are the most popular battery in use today. First commercialized in 1991, their cost has declined by a remarkable 97 percent over the last three decades, enabling the rapid growth of mobile phones, laptops and more recently, electric cars. Global demand for the batteries is projected to increase dramatically by the end of this decade, largely due to the growing adoption of electric vehicles (EVs) around the world.

More EVs is good news for the climate. After all, as a 2020 Union of Concerned Scientists (UCS) analysis shows—and an updated, soon-to-be-released analysis will confirm—EVs’ lifecycle global warming emissions are dramatically lower than that of gas- and diesel-powered vehicles. But mining the materials used in EV batteries, including cobalt, lithium and nickel, comes with its own set of public-health, environmental and human-rights challenges. Despite EVs’ considerable environmental benefits, it will be imperative to “green” the material sourcing process to ensure a more sustainable and ethical supply chain as the world transitions to an electrified transportation system.

Fortunately, scientists are on the case. They are altering battery chemistries to reduce reliance on certain metals, such as cobalt, for example, and coming up with ways to recycle and repurpose batteries to minimize the need for new raw materials altogether.

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Research Team Selected for $4.6 M Department of Energy Award to Advance Concentrating Solar-Thermal Power

Concentrating solar-thermal power technologies can help eliminate carbon dioxide emissions from the energy sector. UC Davis and eight partnering institutions were selected to receive $4.6 M from the Department of Energy to advance high temperature receiver development for industrial process heat and solar thermal power generation. The team, led by Vinod Narayanan and Erfan Rasouli at UC Davis, will design, develop, and de-risk a 150-kilowatt solar-thermal receiver able to heat supercritcal carbon dioxide or air to temperatures from 600-900°C.

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Market Transformation Research Group Publishes Study on Human Factors and Indoor Air Quality in Schools

Classrooms are often under-ventilated, posing risks for airborne disease transmission as schools have reopened amidst the COVID-19 pandemic. While technical solutions to ensure adequate air exchange are crucial, this research focuses on teachers’ perceptions and practices that may also have important implications for achieving a safe classroom environment. We report on a (pre- pandemic) survey of 84 teachers across 11 California schools, exploring their perceptions of environmental quality in relation to monitored indoor environmental quality (IEQ) data from their classrooms. Teachers were not educated regarding mechanical ventilation. Errors in HVAC system installation and programming contributed to misunderstandings (because mechanical ventilation was often not performing as it should) and even occasionally made it possible for teachers to turn off the HVAC fan (to reduce noise). Teachers did not accurately perceive (in)sufficient ventilation; in fact, those in classrooms with poorer ventilation were more satisfied with IEQ, likely due to more temperature fluctuations when ventilation rates were higher combined with occupants’ tendency to conflate perceptions of air quality and temperature. We conclude that classroom CO2 monitoring and teacher education are vital to ensure that teachers feel safe in the classroom and empowered to protect the health of themselves and their students.

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WCEC Newly Published Journal Article on Greenhouse Gas Emission Forecasts for Residential Heat Pumps

This study aims to inform policymakers about the greenhouse gas emission impacts of heat pump deployment in residential homes. Electric heat pumps eliminate direct burning of fossil fuels in homes but result in indirect emissions due to fossil fuels burned for electricity production. This paper presents the first detailed emission forecasts for operating either a heat pump or gas furnace for residential heating over a 15-year period, starting in year 2022 through 2036, in six regions across the US. The study accounted for long-run marginal emissions from electricity generation, emissions from natural gas combustion in homes, and fugitive methane and refrigerant emissions from leaks. The population weighted US average results show emission reductions for a heat pump over furnace to be 38–53% for carbon dioxide, 53–67% for 20-Year global warming potential (GWP), and 44–60% for 100-Year GWP, with reductions increasing over time. The impact of fugitive emissions from the furnace is significantly higher than that of the heat pump. While more energy efficient construction reduces overall emissions for both heating types, the forecasted percent emission reduction for replacement of a gas furnace with heat pump was not impacted by changes in home construction parameters.

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Institute Executive Director Benjamin Finkelor to Serve “On Loan” as Special Advisor at the California Energy Commission

Benjamin Finkelor, Executive Director for UC Davis’ Energy and Efficiency Institute (EEI), will serve “on loan” to the California Energy Commission as a Special Advisor to Vice Chair Siva Gunda. The appointment starts February 1st and will extend for 14 months. Ben has been Executive Director of the EEI since its inception in 2016 (then the Energy and Efficiency Center). His leadership has helped the campus’ energy programs grow and advance over the past 15 years.

“Ben has played a tremendous role in developing and strengthening UC Davis’ energy research, education and engagement,” said Kelly Kissock, Faculty Director of the Energy and Efficiency Institute. “We have been fortunate to have him on our team and will miss him during his assignment. At the same time, we know that his work at the Commission will help us all further achieve our common goal of building a more sustainable, accessible, and resilient energy system and we are excited for him.”

While on loan to the Commission, Finkelor will continue to teach the Sustainable Energy Industry Immersion Course at the UC Davis Graduate School of Management in Winter quarters 2022 and 2023.

“I am honored to have this opportunity to support the California Energy Commission and  Vice Chair Gunda and his team, especially as the State takes on the challenge of decarbonizing our energy in an equitable way, while maintaining safety and reliability,” Finkelor said. “It is a privilege to be able to contribute at such a critical time, and I’ll be delighted to bring my experiences back to UC Davis when I return.”

During Ben’s absence, Alan Meier will serve as Acting Executive Director. Alan is a Research Scientist at EEI, an Adjunct Faculty member in the Department of Environmental Science & Policy, and a Senior Scientist at Lawrence Berkeley National Laboratory. “I am pleased to take on this role for the Institute and look forward to continuing to engage with students, faculty, and partners to advance our work,” said Meier. When on campus, he will occupy Ben’s former office at 1605 Tilia Street.

R-466A Refrigerant Demonstration and Performance

Refrigerants used in vapor-compression air conditioners and heat pumps have been the subject of environmental regulations requiring the need to develop alternative solutions with lower global warming potential (GWP). In general, there is a trade-off when choosing alternative refrigerants between safety, performance, and GWP.

The California Air Resources Board (CARB) has approved a new regulation requiring refrigerants used in all new stationary residential air conditioning systems to have a 100-year GWP value of 750 or less. For reference, the most common refrigerant currently used in unitary air conditioning equipment is R-410A, which has a 100-year GWP of 2,088.

A number of refrigerant solutions have been developed to meet the CARB GWP requirement, but the majority of these refrigerants have a low level of flammability (A2L). While there are strategies for mitigating the risk of using flammable refrigerants, finding a non-flammable solution presents the easiest path to market and would not require additional safety controls and updates to codes and standards.

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Student-Built Air Purifiers Tackle Wildfire Smoke and Covid-19: UC Davis Engages Students with Hands-On Citizen Science

Students at Rio Tierra Junior High School in Sacramento build a portable air cleaner using a box fan and high efficiency air filters.

Schools are facing many challenges this fall, including minimizing risks to students and staff from Covid-19 and wildfire smoke exposure. Air purifiers are one tool that can help.

Researchers from the UC Davis Energy and Efficiency Institute (EEI) partnered with science teachers at Rio Tierra Junior High School in Sacramento to teach a two-day lesson on air quality and build 30 portable air cleaners with approximately 150 8th grade students. The portable air cleaners will be distributed to every classroom on campus.

Knowledge to action

“It is really important to empower students and help them understand indoor and outdoor pollution sources, and how to measure and improve indoor air quality,” explained UC Davis researcher and project lead Theresa Pistochini. The lesson culminated with groups of 4-5 students constructing do-it-yourself (DIY) portable air cleaners using a Corsi-Rosenthal cube design, which uses a box fan and four filters with a MERV 13 rating. The materials for each air cleaner cost $75. Each air cleaner is expected to provide about the same amount of air cleaning effectiveness as small commercially available portable air cleaners that cost about $200.

Science teachers Amber Mitchell and Kathryn Graf planned the visit with UC Davis researchers Theresa Pistochini and Robert McMurry. “I love having outside speakers come in. Air quality is such a relevant topic that we are able to teach the kids about,” Mitchell said. “We are always trying to relate science to current events and student’s lives. There’s not much more relatable right now than making air purifiers to help our school.”

Students at Rio Tierra Junior High School in Sacramento investigate filter samples of various filtration efficiencies and discuss their observations with science teacher Amber Mitchell.

Importance of air quality

“Air quality is such an important topic that historically has not received much attention. I hope that our outreach to students will encourage them to think about the air they breathe, and consider engineering and environmental science as a career path,” Pistochini said. “While investments in permanent ventilation and filtration systems are the best way to improve indoor air quality long-term, portable air cleaners are a quick way to achieve some immediate benefits.”

Principal Adam Sinor supported the project and visited the classrooms to see the air cleaner construction in action. “With the wildfires and Covid, and the way Covid is spread through aerosols, it’s a way kids can take action to make their internal environment better and learn science and engineering at the same time,” Sinor said.

UC Davis researcher Theresa Pistochini working with students to build a portable air cleaner.

Project support

This project was funded by the UC Davis Sustainable Campus, Sustainable Cities initiative, which received funding from the Sacramento Municipal Utility District Sustainable Community Program. The initiative aims to engage K-12 students in energy-oriented STEM education, using experiential learning as well as citizen and community science to empower students to measure, analyze, understand, and manage their environment.

Media contacts

Theresa Pistochini, UC Davis Western Cooling Efficiency Center, 916-612-6418,
Kat Kerlin, UC Davis News and Media Relations, 530-752-7704,

Media sources

DIY Portable Air Cleaner Testing –
Photos –

Testing Different Configurations of Do-It-Yourself Portable Air Cleaners

A recent case study by the Western Cooling Efficiency Center (WCEC) seeks to answer: does making your own portable air cleaner match the cleaning performance of off-the shelf products and do so in a cost effective way?

Portable air cleaners are increasingly in demand to reduce concentrations of particulates and respiratory aerosols indoors. Researchers at the UC Davis Western Cooling Efficiency Center (WCEC) tested two types of Do-It-Yourself (DIY) portable air cleaners (standard box fans modified with added filtration on the suction side of the box fan) and documented the power draw, airflow, and noise for each configuration. Researchers calculated the clean air delivery rate based on filter test reports and reported energy efficiency and cost metrics for each configuration.

Note that while DIY portable air cleaners are a useful and easily accessible tool to reduce particulates in buildings, they should not be considered a substitute for ensuring adequate ventilation and filtration is provided by central building heating, ventilation, and air conditioning (HVAC) systems.

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Report – Residential Electrification in Sacramento and Its Impact on Residential Appliance Sales

In this report, researchers investigate and quantify the market for appliances related to residential electrification and decarbonization, using the Sacramento Municipal Utility District (SMUD) as a case study.

This report addresses three questions:
1. What is the status of residential electrification plans in Sacramento?
2. What are the estimated equipment sales expected to result from residential electrification plans in Sacramento?
3. What are the key barriers to residential electrification in Sacramento?

This report focuses on Sacramento but puts its activities in the context of statewide activities.

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graphic for the importance of filtration at schools. cartoon illustration of an HVAC tech testing airflows on a classroom BARD system.

Video on the Importance of Filtration in Schools

Filtration works together with ventilation to improve indoor air quality.

Filtration can capture and reduce exposure to some indoor and outdoor pollutants. In this video, we cover the basics of mechanical filtration and make simple recommendations to improve indoor air quality.

Watch the video