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Geoexchange in New York City

2013-11-26

N.Y. is a city that stands out for its architecture and building density. However, with 40% of the total U.S. energy consumption in 2012 attributed to residential and commercial buildings, a densely developed city has an impact upon the environment. N.Y.C. has recognized this and is committed to making its buildings greener and more sustainable as part of the PlaNYC effort. To achieve this goal, it is imperative that renewable and sustainable technologies are incorporated in both new and existing buildings. Geoexchange is one of the technologies emerging from this initiative.

Geoexchange, often referred to as geothermal heating and cooling, is the process of harnessing the ground temperature to heat and cool a building. Below the earth's surface the temperature is a consistent 50-60oF, and this stable temperature allows the earth to be used as a heat source during the winter and a heat sink during the summer.

There are two distinct types of geoexchange systems, closed loop and open loop. A closed loop system is comprised of a series of high density polyethylene pipes buried below the frost line. A water and environmentally friendly anti-freeze solution runs through the pipes and serves as the heat transfer medium. The water and anti-freeze solution never comes in contact with the earth, thus maintaining the closed loop. An open loop system uses deep wells to reach an underground water source. One of the most common systems in N.Y.C. is the Standing Column Well (SCW). A SCW pumps the water from the bottom of the well into the building where it passes through a heat exchanger and heat pump, and then is returned, unaltered, back into the top of the same well.

When a geoexchange system works to its full potential, the energy efficiency ratio (EER) is between 15 to 20, while a traditional system typically has an EER range of 11 to 12. The higher EER translates directly to cost savings and is important to consider when reviewing the initial installation costs. Payback on a geoexchange system tends to fall between two and eight years. The EPA advises a geoexchange system can reduce energy consumption, and corresponding emissions, up to 44% compared to air-source heat pumps and up to 72% compared to electric resistance heating with standard air-conditioning equipment

Although geoexchange is not a new technology, its implementation in N.Y.C. is still gaining traction. In April of this year, mayor Bloomberg signed a bill which tasks the N.Y.C. Office of Long-Term Planning & Sustainability to study geothermal energy resources and the feasibility of city-wide adoption of geothermal heating and cooling. Bloomberg is even installing a geoexchange system in his new home. Geoexchange systems are a technology to keep an eye on, and it's only a matter of time before its implementation is widespread in N.Y.C.

Zoe Reich is an environmental specialist at Edwards & Zuck, P.C., New York, N.Y.



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Zoe Reich, Edwards & Zuck



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