Allied Consulting Engineering Services, Inc.

New technology in earth coupled heating and cooling systems are helping companies save money

Design innovations in HVAC equipment are breathing new life into a technology that has been around for decades. Earth coupled systems are revolutionizing the way both commercial and residential properties are heated and cooled. Generally, heat rejection equipment, such as cooling towers and chillers, are installed on rooftops or on the ground. Drawbacks to this equipment include size, heat generation, vibration, and most of all, noise. If the equipment is placed on the roof, safe access for maintenance is required and structural reinforcement is often necessary. Placing equipment on the ground can also be problematic, because in some areas, there may not be enough property to place the equipment far enough from the building and the neighbors, so that noise will not be an issue. Additionally, the costs associated with the heating of buildings are escalating. Due to rising oil and gas prices, traditional fuel fired equipment is becoming more costly to operate. Maintenance and the venting of gaseous emissions, such as carbon monoxide, are also concerns with fuel burning equipment.

The solution lies with “Earth Coupled” heating and cooling systems, which utilize the earth’s natural resources to reject and store heat. There are different installations for this type of system; however the geology of the New England area lends itself to the “standing column well” installation. The well is six inches in diameter and approximately 1,500 feet deep. The pump is installed inside a four-inch diameter induction tube that extends down to the bottom of the well. PVC or HDPE piping connects the earth coupled system to the building’s heating and cooling system. Well water circulates from the well to a plate and frame heat exchanger, located in the building’s mechanical room, and then back into the well. A heat exchanger is used to keep the well water and the building water loop separate, so if the quality of the well water is questionable, the heating and cooling equipment in the building is not susceptible to any detrimental effects. In the cooling season, the building system rejects heat to the well water as it passes through heat exchanger. The well water returns to the well, and as it travels down the depth of the well, rejects heat to the bedrock. By the time the water reaches the bottom, it has been sufficiently cooled. In the heating season, the building water loop extracts heat from the warmer well water, in just the opposite process, to heat the building. In an earth coupled system, the heat is simply being moved- from the earth to the interior space.

To measure the benefits of an earth coupled system, we can assess comparatives with industry standards. The Energy Efficiency Ratio (EER), as defined by the Federal Energy Management Program is, “the measure of the instantaneous energy efficiency of room air conditioners; the cooling capacity in Btu/hr divided by the watts of power consumed…”. Traditional air conditioning units have an EER of 10, air-to-air heat pumps can achieve an EER of 12, but an earth coupled system will consistently achieve EERs of 16 or higher. Unlike air-to-air heat pumps, where the efficiency of the unit in the heating mode depends on the fluctuating outdoor air temperature, the efficiency of an earth coupled system is much more consistent, since the well water stays between 50 and 60 degrees year round, and no supplemental electric heat is required. In addition, earth coupling reduces the emissions of carbon monoxide and other greenhouse gases by 30%, because no fossil fuel is being burned to create heat. Replacing bulky, noisy HVAC equipment with an earth coupled design is easy on the eyes and ears - it not only eliminates large equipment eyesores, but it also eradicates the fan noise associated with heat rejection equipment.

Earth coupled systems have been successfully implemented in Europe and the United States. While the energy efficiency of earth coupled systems can result in paybacks of 5-10 years for residential and commercial projects, for some projects an earth coupled system is the system of choice because it requires no outdoor equipment, is virtually invisible and makes absolutely no noise outside. We have designed many earth coupled heating and cooling systems including a mixed use building that houses a professional performing arts theatre and multi-tenant office space in Harvard Sq., 70,000 s/f of converted mill buildings on Harrison Ave. in Boston and several high-end residences in urban and suburban locations in Mass., Conn. and Vermont. We have helped a number of forward looking owners and developers discover the environmental and economic benefits of earth coupled systems.

In addition to significant savings in fuel cost, maintenance costs can be lowered by as much as 30% over “conventional” systems. An earth coupled heat pump system is an environmentally friendly, low profile, low maintenance, energy efficient, cost effective alternative to fossil fuel burning systems with a positive cash flow.

While there are no utility company “rebates” or cost deferring grants available for earth coupled heat pumps, the State of Mass. has declared an earth coupled heat pump system to be exempt from sales tax. Not only that, but the State Energy Code declares that energy derived from the earth does not have to be included in the energy budget of a project when determining the compliance of the project with the State Energy Code.

There are lots of good reasons to consider earth coupled heat pumps. You don’t have to be a tofu chewing, sandal wearing tree hugger to like them, you only have to be an intelligent, informed individual with a strong desire to save money, energy and the environment.

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