There are many options for the heating and cooling needs of buildings that developers and engineers can choose. These options are sometimes limited depending on the architecture of the building and the amount of available space for the necessary heating and cooling equipment. District energy offers not only a potential reduction in the physical footprint required for the generation equipment it also offers a potential reduction in the carbon footprint required by reducing the carbon dioxide emissions associated with the building’s heating and cooling energy use.
Within the TVA service area, electricity delivered to its customers is generated from coal, natural gas, nuclear energy or other renewable sources. The inclusion of nuclear energy and renewable sources aid in reducing the total level of CO2 emissions related to the production of electrical energy by TVA in the region. However, when compared to the delivery of heat energy to the customer from a natural gas-fired plant, district energy can deliver the same amount of energy while substantially reducing the amount of CO2 emissions from electric based heating.
The self-generation of cooling at an individual building can also be generated in a number of ways. Those methods of cooling, as well as, the water-cooled centrifugal chillers at the DES, primarily rely on electricity as the motive energy source. However, the DES is developing a cogeneration alternative that will reduce energy costs, improve plant efficiencies and reduce the annual CO2 emissions.
The attached graph shows the monthly CO2 emissions for the DES, including the production for both heating and cooling, and is based on actual electric and natural gas usage for the year. The graph also shows the anticipated CO2 emissions for the same heating and cooling loads if the buildings used 100% efficient electric heat and had cooling systems with an average 13 SEER. This analysis shows an estimated 26% annual reduction in CO2 emissions by using the DES over self-generating heating and cooling with electricity.