Wanna forget your underground heat exchanger??
An Important “Proof-of-Concept” Project in Valley Stream NY taps flow from a water main for thermal exchange
[This important HVAC retrofit at the William L. Buck Elementary School in Nassau County took on the first-cost issue of needing a ground heat exchanger for geo heat pumps head-on. Bosch Thermotechnology Corp.’s Business Development Manager Heather Anderson led a team of collaborators proving that the thermal fluid connection serving geo heat pumps does not have to be a closed loop, pumped to-and-from underground strata. This project was featured in the International Ground Source Heat Pump Association’s, Geo Outlook, Volume 14, number one in February 2017.]
Dressing up an older building-
Thermal energy exchange with the municipal water supply were the key to reducing first costs of installation when a 1950s-era elementary school found itself with first time ever cooling, a 56% reduction in energy consumption per square foot, and a 6% annual reduction in energy costs ($40,000). In short, this yielded a school with four-season comfort with less expense and no more carbon. Tapping the flow from a water main substituted for a geothermal heat exchanger bored or trenched underground.
This was possible because of the collaboration of school district officials, consulting engineer Don Penn, Jack DiEnna of Geo NII, American Water Company, the NY Public Utility Commission, Bosch Thermotechnology, and mechanical contractor Bancker Construction. This geothermal heat pump retrofit saved $600,000 by not drilling standard, closed loop grouted bore holes in a loop field. Instead, it tapped the flow of the water utility’s main line for its thermal exchange.
Don’t drill downward, tap the water line-
A pumped, bypass loop from and to the water main at 200 gallons per minute serves the school. Pumped community water enters one side of a food-grade heat exchanger with a glycol-added loop feeding multiple heat pumps serving 40,000 square feet of conditioned space on the other side of this double-walled exchanger.
American Water Company monitors the quality of post-heat exchanger water on its way to a diffusion well for return to the aquifer, but on the strength of those tests, a return path connection back to the water main awaits approval from the health department and regulators. In heating or cooling, there has been a maximum of only 2°F change in the loop’s water temperature. All other performance monitoring of the school’s energy consumption is being verified by Oak Ridge National Laboratory.
Knocking down the first cost of geo-
The project has proven the feasibility of this 63-year old school’s retrofit to geo, and the substitution of a water main connection as the system’s heat exchanger. New buildings will be able to utilize less heat pump capacity and a corresponding reduction in water bypass volume due to greater building efficiency. But the important fact is that in areas serving large buildings in tight spaces, a water utility’s main connection could substitute for the traditional underground geo heat exchanger.