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most of the losses experienced in the process have been relocated from upstream of the building meter to downstream of the building meter. Yet from a site measurement perspective, building energy efficiency appears to have fallen precipitously.
The on-site generator without heat recovery configuration admittedly is an unlikely configuration for year-round operation, but it represents the impact of on-site generation for peak shaving or load management. Such on-site generation systems will become more common as customers are exposed to real-time pricing of electricity due to energy industry restructuring. As the above example suggests, this shift to on-site generation would not decrease building energy efficiency, as a site measurement standard would indicate.
Mixed Fuel Building Configuration, Natural Gas Space Heating and Water Heating
When the building is reconfigured for mixed fuels, using pipeline natural gas, rather than grid electricity, for space heating and water heating, site-energy consumption increases by 14 percent, from 8.8 billion Btus per year to 10 billion Btus per year. This increase is the result of the energy losses in the natural gas equipment used to provide both space heating and water heating service to the building. However, the total energy consumption in this mixed fuel configuration decreases by 20 percent, from 32.6 billion Btus per year to 26.2 billion Btus per year. This reduction occurs, in spite of the relatively lower efficiency of the gas fueled equipment used in the building, because of the substantially higher efficiency of natural gas delivery from the well to meter than the generation and delivery of grid electricity. In this configuration, the building appears to be less energy efficient, when measured on a site-energy consumption basis, but is actually more efficient on a total energy consumption basis.
CHP Building Configuration-Recovered Thermal Energy for Space Heating, Space Cooling and Water Heating
When the building is reconfigured to receive energy service from an on-site CHP system, the site-energy consumption increases by 105 percent, from 8.8 billion BTUs per year to 18 billion Btus per year. In this configuration, thermal energy recovered from the electric generator at the site is used to provide the energy required for space heating, space cooling, and domestic water heating. While the site-energy consumption more than doubles-a highly undesirable result based on a site-energy consumption metric-the total energy consumption of the building declines by 39 percent, from 32.6 billion Btus per year to approximately 20 billion Btus per year. In this configuration, the building appears to be dramatically less efficient when measured on a site-energy consumption basis, but is actually dramatically more efficient when measured on a total energy efficiency basis. Efficiency increases because the CHP system captures and uses waste heat instead of rejecting it into the atmosphere.
District Energy System Building Configuration-Recovered Thermal Energy for Space Heating, Space Cooling and Water Heating
The final building configuration assumes energy service from a district energy system, which would provide both electricity and thermal energy to the building site. The recovered thermal energy would be used, as in the CHP case, for space heating, space cooling, and domestic water heating, while electricity