Water Source/Ground Source Heat Pump Heating and Cooling System
Heat Pump System: Water Source/Ground Source Heating and Cooling System vs. Air Source Heat Pump
Heat pumps that extract heat from a water source (well, river, pond) and distribute it to residential and commercial spaces, such as assisted living units, hotels, dorms, schools, jails or district heating systems.
Item ID: 29
Technical Advisory Group: 2009 HVAC TAG (#2)
Water source district heating and cooling projects consist of heat pumps connected to a source of nearly constant-temperature water, such as groundwater or a well, river, pond or municipal water supply. A district heating system distributes the heat generated in a centralized location to meet residential and commercial space and water heating needs.
Use of water source heat pumps (WSHPs) for district heating applications is not a new concept but is underutilized. In 1984, a project was commissioned at the Point Defiance Zoo and Aquarium in Tacoma that involves pumping 50ºF groundwater from a well into an equalization tank. The water then circulates to three buildings where water-to-air heat pumps extract heat from the groundwater. Rejected water is used for watering lawns and recirculation needs at the zoo and aquarium. A second heat pump project, installed in 1994, uses large chillers to provide cooling at the Boeing Longacres Industrial Park and extracts heat from the Renton Wastewater Treatment Facility (WWTF) effluent pipeline.
Other project concepts include geothermal hot water and ground-source variable refrigerant flow (VRF) heat pumps. The refrigerant exchanges heat with groundwater through a network of pipes buried in trenches. Use of VRF heat pump technology is much more efficient, especially in cold climates, and enables the recovery of heat or cooling from the water source for use in district heating systems or buildings such as assisted living units, hotels, dorms, schools and jails. WSHP projects can reduce energy consumption for heating and cooling by as much as one-third relative to current energy code efficiency requirements. Another development, the hybrid geothermal heat pump, lowers the installed costs by decreasing the size of the ground-coupled heat exchanger through using auxiliary, above ground equipment for meeting peak loads (Navigant Consulting, 2012).
Baseline Description: HVAC with Electric Heating
Baseline Energy Use: 10.5 kWh per year per square foot
The 2009 Commercial Building Stock Assessment gives the actual electrical building Energy Use Index (EUI) for various types of heating and cooling systems (Table D-EA5). Office buildings with electric heating and cooling have an EUI of 20.1 kWh/sf-year. Office buildings with no electric heating or cooling use only 8.2 kWh/sf-year, indicating that the combined HVAC heating and cooling energy use is 11.9 kWh/sf-year. For all commercial buildings, the corresponding numbers are 19.9 and 9.4 kWh/sf-year, respectively. Since this technology can be applied to many types of non-office buildings, a baseline energy use of 10.5 kWh/sf-year is assumed (NEEA, 12/21/2009).
Manufacturer's Energy Savings Claims:
Currently no data available.
Best Estimate of Energy Savings:
"Typical" Savings: 25%
Low and High Energy Savings: 10% to 51%
Energy Savings Reliability: 6 - Approved Measure
Actual savings will vary depending on the climate and the performance of existing or baseline heating and cooling equipment. Many energy modeling cases show that geothermal or ground source heat pumps will save, on average about 25% when compared with conventional air source heat pumps. Note: the FEMP Promising Technologies List indicates that HVAC savings can be as much as 51%.
Note: the AHRI ratings of ground source heat pumps do not include auxiliary pumping energy for ground loop water distribution. A 2.5 ton ground source heat pump would typically require a 1/3 hp circulating water pump. This pump would consume approximately 0.23 kW when providing 7.5 gpm at 30 feet of head. This is an adder of about 11.5% to the energy consumed by the heat pump itself (Pennsylvania Public Utilities Commission, "Technical Reference Manual", to support Energy Efficiency and Conservation Programs, June 2014) (Pennsylvania Public Utility Commission, 2014).
This is also a deemed measure under the October 1, 2014 BPA "Energy Efficiency Implementation Manual". The deemed amount is $3,000 for single-family homes.
Energy Use of Emerging Technology:
7.9 kWh per square foot per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
The numbers are taken from preliminary updated numbers from the 2013 update to the Commercial Building Stock Assessment (CBSA) using the estimates for 2014 (before the update was completed -- from early January,2014 ( NEEA, 01/1/2014)) subtracting out warehouse space multiplied times the percentage of commercial space that is conditioned (85%) and heated electrically (27%) based on the 2009 CBSA (NEEA, 2009): (3,118,000,000 - 382,000,000) * 0.85 * 0.27 = 627,872,900 sf.
As a retrofit, this technology is best suited to commercial buildings that have water-source HVAC systems rather than more typical air-source packaged type systems. According to the 2009 CBSA, these systems represent approximately 30% of the systems. There is also a need to have access to a water source. There are no estimates for this, but many commercial buildings are not likely to have access to a water source. For the purposes of this analysis, assume 10%: 627,872,900 *0.30 * 0.10 = 18,836,190 sf.
This measure could be applied to new construction and major renovation. The potential will be small and is not included in the potential estimates.
Regional Technical Potential:
0.05 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Installed first cost per: square foot
Emerging Technology Unit Cost (Equipment Only): $30.00
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.00
Baseline Technology Unit Cost (Equipment Only): $16.00
Little data is available. The cost for accessing a water source and linking this to the HVAC system will be very site specific. There may not be any incremental cost for the HVAC system itself for new construction assuming the building application already has a water source HVAC system or is a good application for such a system. The water source can also produce cost saving by eliminating or reducing the need for a cooling tower and a supplemental heating source.
The ground source heat exchanger must be sized to meet peak heating and cooling loads. It makes little sense to design a system to meet loads that may occur for only a few hours per year. A hybrid system utilizes a less-expensive surface mounted supplementary system to meet peak loads. System and installation costs significantly are reduced while energy savings are little changed. Cost effectiveness will be based upon an assumed cost for ground source systems of $30 per square foot versus $14 to $18 per square foot for variable flow air-source heat pump projects.
Simple payback, new construction (years): 59.3
Simple payback, retrofit (years): 127.0
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.