Project: Ground Source Heat Pump
Completed: Spring of 2010
Reducing the use of fossil fuels is a key directive for the Army National Guard. Moving toward a renewable energy future not only creates a healthier, cleaner environment, but also reduces dependence on foreign oil, increasing energy security. Also, there is a requirement that any major renovation must attempt to reduce the use of all energy sources by 30% greater than ASHRAE 90.1, 2007 standards (the energy standard for buildings except low-rise residential buildings).
Loans and investments into green energy technology are a significant part of the American Recovery and Reinvestment Act of 2009.
An office/warehouse building was audited by TCorp and identified as a candidate for a major energy conservation retrofit using American Recovery and Reinvestment Act (ARRA) monies. Building improvements would include improved ventilation, re-zoning of the heat distribution system, replacement of the old building time-clock controls with a modern building automation system, and the installation of air conditioning throughout the office area.
As the contracted Energy Management Services Company for the Vermont Military Department, TCorp initiated a design and development project to install a hybrid heat pump system. A local engineering company was consulted and hired to develop the concept into reality.
The 8,500 square foot building is approximately 45 years old, with insulated walls and roof and thermal windows. A combination of baseboard hot water serves the rooms adjacent to the exterior walls. Air is mixed with outside air and passed through a hot water coil to provide heat to the interior rooms and fresh air ventilation throughout. Hot water for heat was provided by a 350 kBtu natural gas fired boiler. Air conditioning was limited to only one office space and one conference room. An old time-clock style energy management system was present but not operational and parts were not available. Several rooms had been renovated and interior partition walls had been constructed that separated baseboard heat from the thermostats that controlled them. In some cases, return air diffusers were located in different rooms from the supply air. Therefore, the building was out of balance, zoning for heat was dysfunctional and the working conditions of occupants was less than optimal.
The Intent of the Project:
• Exceed ASHRAE 90.1 2007 efficiency recommendations by 30%
• Provide fresh air to all rooms in building
• Provide ventilation to all areas to meet current ASHRAE Standard 62.1
• Integrate temperature and ventilation control with a modern building automation system
• Update heating controls and re-define zones
• Provide air-conditioning to everyone
Ground Source Heat Pump Option:
A ground source heat pump is an electrically powered system that taps the stored energy of the earth. These systems use the earth’s relatively constant temperature to provide heating, cooling, and hot water for homes and commercial buildings. Ground source heat pumps are a cost effective, energy efficient, and environmentally friendly way of heating and cooling buildings. They are appropriate for both new construction as well as retrofits of older buildings. The flexible design requirements make them the smart choice for almost all commercial applications.
In the winter, the earth acts as the boiler.
In the summer, the earth acts as a cooling tower.
A geothermal ground source heat pump system supported by a single standing column well was installed. The standing column well is sized to accommodate the cooling load and accommodated the heating needs in spring and fall. The existing boiler provides additional heat to the building when necessary to maintain temperature. Ventilation air is provided via an energy wheel type energy recovery unit utilizing the existing supply air ductwork. Ventilation is controlled by carbon dioxide sensors. The supply air from the energy recovery unit is conditioned via the cooling and heating coils.
Note: Because, for all intents, there was no air conditioning in the building, potential energy savings for air conditioning were calculated as the difference between the base model DX air conditioning expected energy use and that expected if the high efficiency heat pumps and standing column well were used - ClimateMaster heat pumps with ground source water yields 22 kilowatt hours of effective work for every 1 kilowatt hour spent.