Modeling Impacts of Ventilation and Filtration Methods on Energy Use and Airborne Disease Transmission in Classrooms

Lowering the potential of airborne disease transmission in school buildings is especially important in the wake of the COVID-19 pandemic. The benefits of increased ventilation and filtration for reducing disease transmission compared to drawbacks of reduced thermal comfort and increased energy consumption and electricity demand are not well described. A comprehensive simulation of outdoor air ventilation rates and filtration methods was performed with a modified Wells-Riley equation and EnergyPlus building simulation to understand the trade-offs between infection probability and energy consumption for a simulated classroom in 13 cities across the US. A packaged heating, ventilation, and air conditioning unit was configured, sized, and simulated for each city to understand the impact of five ventilation flow rates and three filtration systems. Higher ventilation rates increased energy consumption and resulted in a high number of unmet heating and cooling hours in most cities (excluding Los Angeles and San Francisco). On average, across the 13 cities simulated, annual energy consumed by an improved filtration system was 31% lower than the energy consumed by 100% outdoor air ventilation. In addition, the infection probability was 29% lower with improved filtration.

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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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Activists fear a new threat to biodiversity—renewable energy

A small Nevada wildflower named Tiehm’s buckwheat might still be living in obscurity if it had not happened to grow in soil full of lithium. As it is, that could prove its downfall.

Lithium is needed to make the high-powered batteries that are helping the world transition to electric vehicles. Demand is soaring, and mining companies are eager to take it out of the ground at several new sites in Nevada, already home to the only existing lithium mine in the U.S.

But Tiehm’s buckwheat is rarer than lithium. It grows only on approximately 10 acres of land at Rhyolite Ridge in southwestern Nevada—right where one of the new lithium mines is planned.

“One guy on a bulldozer could drive it extinct in one afternoon,” says Patrick Donnelly, the Great Basin Director for the Center for Biological Diversity and one of the flower’s biggest advocates. 

He and some other conservationists see the flower and the mine as emblematic of a broad and disturbing trend: There is a growing conflict, they say, between efforts to address two environmental crises—a rapidly warming climate on the one hand, and a staggering rise in extinction on the other. 

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A District Energy System Design Could Cut More Emissions for Proposed Davis Innovation Sustainability Campus

Homes and businesses use over 25 percent of California’s energy. With a number of different space heating and cooling technologies available to developers, it is important to understand and quantify potential greenhouse gas (GHG) impacts.

A study, completed by the UC Davis Western Cooling Efficiency Center (WCEC), analyzed the GHG emissions for two different heating and cooling options for a proposed development in Davis – the Davis Innovation Sustainability Campus (DiSC). Researchers analyzed GHG emissions for: 1) the proposed all-electric, high-efficiency design, which would use packaged heat pump equipment for heating and cooling the buildings and 2) a potential upgrade to an all-electric, very high efficiency design, which would use a district energy system. A district energy system uses a central plant heat pump and chiller to heat and cool water that is piped to buildings for heating and cooling. 

“Based on predicted energy consumption data provided by Trane, we found that a district energy system could further improve energy efficiency by 26%, reduce total energy consumption by 14%, and reduce GHG emissions by 16% over the already highly efficient proposed design,” said lead researcher David Vernon, Co-Director of Engineering for the UC Davis Western Cooling Efficiency Center.

DiSC energy system options

DiSC is a proposed development that would build new residential, office, laboratory, and manufacturing buildings on the eastern edge of Davis. The developer team is required by the Davis City Council to build an all-electric design with an energy efficiency level 30% more efficient than required by Title 24 building codes.

“The developer funded us to look at a district energy system design with large thermal energy storage because it has the potential to greatly reduce GHG emissions,” Vernon said. “It can help stabilize the grid by using energy when renewable generation is high and reducing energy consumption when renewable generation is low.”

To meet California’s climate goals requires large increases in renewable energy generation, energy storage, and load shifting technologies. District energy systems with large thermal energy storage have the potential to be an effective energy storage and load shifting strategy. The WCEC mission is to advance design, monitoring, and objective reporting of the performance of these types of technologies to inform policy and economic decisionmakers.

Energy modeling and analysis

The heating, ventilation, and air conditioning (HVAC) manufacturer Trane completed energy models of the proposed baseline and district energy system designs and provided the hourly energy consumption results. The WCEC researchers then used these hourly energy consumption results to calculate Time Dependent Valuation—a metric that incorporates the social and environmental impacts of energy used to evaluate energy efficiency, total energy consumption, and GHG emissions of the designs.   

“Our analysis shows that district energy systems offer significant opportunities to reduce energy consumption and GHG emissions compared to more common HVAC designs,” said Vernon. “It is important to note that our results are on the conservative side, and implementation of this design could result in even larger GHG savings.”

This study was funded by Ramco Enterprises, Inc. and the Buzz Oates Group of Companies.

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Energy Bites Seminar May 19, 2022

Thursday, May 19, 2022  |  12pm – 1:00pm PST

Bite 1: “So What Happens to the Batteries?” Electric Vehicle Battery End-of-Life Management and Policy Recommendations for California
Meg Slattery, Energy Graduate Group

Bite 2: UC System Central Plants and the Transition to Carbon Neutral Operation
Leslie Nelson, UCOP Carbon Neutrality Fellowship

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Energy Bites Seminar May 12, 2022

Thursday, May 12, 2022  |  12pm – 1:00pm PST

Bite 1: High-Temperature High-Pressure Heat Transfer – STEEL Lab Research Update
Erfan Rasouli, Western Cooling Efficiency Center

Bite 2: District Energy Update & Electrification Strategies
Josh Morejohn, Facilities Energy & Engineering

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How Eco-Friendly are Electric Vehicles? It All Depends on the Battery

OAKLAND, Calif. (KGO) — By 2035, every passenger vehicle sold in California must be a zero-emission vehicle.

That means it must run on electricity, hydrogen or another alternative fuel that does not generate air pollution to operate.

The mandate is expected to reduce greenhouse gases in the state by about 35%.

But, while zero-emission vehicles are being touted as one solution to our climate crisis, their batteries could also represent an environmental hazard.

Currently, batteries from first-generation hybrid vehicles are starting to make their way to junkyards.

We visited several auto recyclers in the San Francisco area and found hybrid batteries tossed among other car parts or piled up in a corner. One was dangling from the engine compartment of an old Prius that no longer had a hood and had many parts already pulled out.

Operators did not know what to do with them.

“There are risks associated with these aged batteries or damaged batteries. Lithium-ion batteries that we use in electric vehicles are a fire hazard. It’s important to make sure that these batteries are managed correctly at the end of life,” said Alissa Kendal, a professor of Civil and Environmental Engineering at UC Davis.

Kendall said the metals in the batteries are hazardous and could leach into the environment if they are not properly handled.

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Energy Bites Seminar May 5, 2022

Thursday, May 5, 2022  |  12pm – 1:00pm PST

Bite 1: UC Davis Fossil Fuel Free Pathway Plan and UC Davis Greenhouse Gas Emissions
Camille Kirk, Office of Sustainability

Bite 2: Hourly Accounting of Carbon Emissions from Electricity Consumption
Greg Miller, Energy Graduate Group

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Energy Bites Seminar April 28, 2022

Thursday, April 28, 2022  |  12pm – 1:00pm PST

Bite 1: Substituting Internal Combustion Engine Vehicles with Plug-In Electric Vehicles: How Does Household’s Vehicle Portfolio Affect Choice of Vehicle Class?
Jean Ji, Energy Graduate Group / Plug-In Hybrid & Electric Vehicle Research Center

Bite 2: How do Cities Approach Sustainability? A Survey on the Importance of Lifecycle Assessment, Equity, and Funding in Local Climate Action
Mark Lozano, Energy Graduate Group

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Energy Bites Seminar April 21, 2022

Thursday, April 21, 2022  |  12pm – 1:00pm PST

Bite 1: Aerosol Sealing of Occupied Homes Through the Attic
Fred Meyers, Western Cooling Efficiency Center

Bite 2: Energy Savings Potential of a Combined Heat Recovery Ventilator in Winter and Indirect Evaporative Cooler in Summer
Subhrajit Chakraborty, Energy Graduate Group & Western Cooling Efficiency Center

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