Integration of Ground Source Heat Pump Systems Using Existing Wells
Owners of facilities with non-potable water wells may have the opportunity to reduce their costs for heating and cooling as well as reducing their carbon footprint by installing a ground source heat pump (GSHP) system to meet their heating and cooling needs. Advancing energy efficiency and conservation are priorities for the Commonwealth and MassDEP is helping our regulated community better understand how our energy use has critical environmental consequences. Facilities with non-potable wells should consider whether adding a GSHP to existing water withdrawal schemes can save heating and cooling costs, while also reducing fossil fuel use and associated green house gas emissions.
What is a GSHP?
Ground source heat pump systems are a relatively new technology that uses the ambient temperature of the earth to heat and cool a structure. The advantages of ground source heat pump systems are that they are one of the most efficient heating and cooling systems available today, with EPA estimated cost saving of 30 to 70% on heating and 20 to 50% on cooling costs over conventional systems; they reduce the amount of CO2 emissions; they are highly reliable (they have few moving parts); have a long life expectancy; low maintenance costs and require no combustion or explosive gases. Operating costs are limited to the electrical costs to run the heat exchange pump and depending on the type of system, a well pump.
Types of GSHPs
There are basically three types of ground source heat pump systems; open loop, closed loop and direct exchange. Open loop systems are the oldest and most well established of the ground source heat pump systems. These systems take advantage of large local sources of water. By pumping water from existing non-potable wells to the heat pump, heat is extracted or expelled into the water as it passes through the heat pump. The water is then returned to its source either via the same well (standing column well) or via another well (doublet system). Standing column well systems share the same advantages, in terms of energy efficiency, environmental benefits, low maintenance, etc, as other forms of geothermal heat pump systems, but have a higher heat exchange rate enhanced by the pumping action, which promotes movement of groundwater to and from the well requiring less depth to meet the system demand than other types of ground heat exchange systems. Since the installation of the well(s) usually represents the greatest percentage of the cost of installing these systems, considerable cost savings can be realized if an existing well can be utilized. Closed loop systems vary in design from open loop systems in that the ground heat exchanger consists of a sealed loop of pipe buried either horizontally or vertically in the ground. A variation of the closed loop system is to have the sealed loop of pipe circulate refrigerant directly through the ground heat exchanger. These systems are called direct exchange (DX) systems.
Is a GSHP for You?
Some of the factors that should be considered and discussed with a GSHP designer when deciding whether a ground source heat pump system retrofit is feasible using your existing non-potable well are:
- the type of heating and cooling systems currently installed, and fuels used;
- the carbon consequences of the fuels currently being used;
- the heating and cooling demands of the facility and the annual operational schedule (year round or seasonal?)
- whether the existing non-potable well(s) can meet the needs of the facility:
- is there enough well depth to meet heating and cooling needs?
- will the well(s) be operational to meet other demands (irrigation, etc.) when they are required to meet cooling needs?
- what effect will this have on the well hydraulics?
- where is the well(s) in relation to the space to be conditioned?
- is the investment worthwhile?
- what is the projected pay back period and the return on investment?
Additional information about installing a GSHP can be obtained by contacting an International Ground Source Heat Pump Association (IGSHPA) certified designer.
Will my Water Management Act permit/registration change?
Depending on the type of system selected, adding a GSHP that uses an existing non-potable well may not require any modifications to your Water Management Act registration or permit because no additional consumptive volume will be withdrawn and all the water that flows through the heat pump will be returned to its withdrawal point.
Examples of GSHP systems
Numerous GSHP systems are currently in operation in Massachusetts. Some of the larger systems include:
- the Hastings School in Westborough where six standing column wells meet the 200 ton design load of the facility. Installed in 1995, the system saves the school approximately $65,000 annually in energy costs while reducing CO2 emissions by 577 tons annually.
- the Trinity Church in Boston's Copley Square has its 130 ton design load met by four standing column wells that were installed in 2005. Estimated savings for this facility is $67,000 annually with an annual reduction in CO2 emissions of 375 tons.
- Harvard University's QRAC Studio and Byerly Hall systems were installed in 2006/2007 with design loads of 40 and 150 tons respectively. Estimated cost savings for QRAC Studio is $21,000 annually with a reduction of 115 tons of CO2 emissions while Byerly Hall has estimated annual cost savings of $77,000 and a reduction of 432 tons of CO2 emissions.
Resources and Additional Information:
- National Renewable Energy Laboratory
- U.S. Department of Energy - Geothermal Technologies Program
- The Canadian Geo-exchange Coalition
- International Ground Source Heat Pump Association
MassDEP Contacts and Resources:
For additional information about whether your facility is a candidate for retrofitting with a ground source heat pump system, please call 617- 292-5770 at the Massachusetts Department of Environmental Protection or email us at Program.Director-DWP@state.ma.us. Please also consult the MassDEP Guidelines for GSHP Wells on our website: Underground Injection Control