Report analyzes greenhouse gas emissions of two heating and cooling systems

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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