Research Project Summary Information
Dehumidification & Cooling with ERV/HRV(ST11047-1)
Michael McDonough Architect PC
Under a previous Next generation/Emerging Technologies PON 1062, the project Geothermal Dehumidification and Radiant Hydronic Cooling Systems in Balanced Ventilation Homes was funded to examine the feasibility of this concept. It included the installation of a prototype system at a site known as e-House. Work from that project demonstrated that a compressor-less dehumidification and cooling system, combined with whole-house balanced ventilation and a geothermal open loop ground well system, could satisfy the criteria of ASHRAE Standard 55-2004, Thermal Environmental Conditions for Human Occupancy 100% of the time. This dehumidification system was fully instrumented and run through an entire cooling season, collecting data, and compared with a conventional air conditioning system that meets ASHRAE standards.
The project focused on demonstrating the operation of an installed dehumidification system through a complete cooling season, collecting pertinent data from the operation and providing an analysis of the system’s overall performance. This lead to an expanded and more focused series of testing protocols, monitoring, inputs, and evaluations. The data produced from the prototype system was evaluated to determine if results of such operations are favorable for further demonstrations and wider adoption. Data collection included the use of a BTU meter that recorded input and output energy information, and was used to make a direct correlation to system performance, and measurement of totalized flow rates.
Typical air conditioning systems use hermetic or scroll type compressors that consume relatively large amounts of electrical power. Temperature set point determines the duty cycle in which the compressor drives temperatures low to achieve cooling and a form of dehumidification. The geothermal dehumidification system analyzed in this project uses the flow of groundwater, already cooler than the desired set point temperature of a home, passed through a coil in line with a low air flow stream that is ducted to rooms within a residential building. This low flow of dehumidified air is circulated via a small electrically commutated motor (ECM) within a whole house ventilation unit, in contrast to a single phase induction motor requiring relatively large amperage levels to start and then operate. The ventilation unit can provide the desired set point comfort level for very low energy, while also providing filtered fresh air, balanced ventilation and energy recovery. If a residence already has a drilled well for potable water or irrigation, the initial costs of drilling the supply well can be avoided. Due to the low power draw of this dehumidification system, it also lends itself to coupling with a small photovoltaic solar array, which could supply the power required to drive the water pump extraction and air circulation devices, making it truly grid neutral.
Using the industry standard for rating air conditioning systems, Seasonal Energy Efficiency Ratio (SEER), the geothermal dehumidification system performs at a SEER of 28.3, when compared and modeled against a baseline conventional air conditioning system that meets ASHRAE 90.2-2007 standards, which performs at a SEER 13.0. This represents a significant improvement in energy efficiency, above the conventional system. This system configuration performs optimally when installed in a well insulated, low air leakage, and properly balanced and ventilated site. The annual operating costs of the dehumidification system are significantly less than the costs to operate a conventional cooling system, applying NY State average residential electrical rates. Accounting for the installation costs of a supply and return well, and the reduced annual operating costs, the geothermal dehumidification system total costs can be recovered within 20 years. If a drilled well exists for irrigation or potable water, this total cost recovery can be sooner, depending on ground water temperature, flow rates and return well costs. The greenhouse gas emissions for the dehumidification system are 55% less in terms of pounds of CO2 over a 30 year period. The control of relative humidity (RH) provided by the geothermal dehumidification system was slightly better than the conventional systems RH control, measured over the three month cooling test period.
Michael McDonough Architect PC
131 Spring St
New York, NY 10012
Heating, Ventilation, & Air Conditioning
Cooling & Ventilation
NYSERDA Contact Information
R&D - Buildings Research