GHPs Provide Efficiency and Low Costs

November 9, 2009
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In cooling mode, geothermal heat pumps (GHPs) are used to move heat from the conditioned space and dispose of the excess heat in the cooler ground. In heating mode, the GHP will move heat from the relatively warm ground and put it into the conditioned space. This, combined with the heat recovery capability, is exampled by moving excess heat from a cooling-dominated building core area and placing it in a heating-dominated perimeter zone. (Feature photos courtesy of waterfurnace.com.)


In regard to conventional HVACR systems using either energy from fossil fuels, such as natural gas, or utilizing the energy from the ambient air surrounding a building, geothermal technology uses energy from the ground to ultimately condition the space.

As defined by Robert Brown, vice president of engineering, WaterFurnace International, in the cooling mode, geothermal heat pumps (GHPs) are used to move heat from the conditioned space and dispose of the excess heat in the cooler ground. In the heating mode, the GHP will move heat from the relatively warm ground and put it into the conditioned space. Brown’s engineering responsibilities include product research, design, and development as well as applications engineering of the earth loop technology, including application software used in designing earth loops.

“This basic operation, combined with the heat recovery capability, is exampled by moving excess heat from a cooling-dominated building core area and placing it in a heating-dominated perimeter zone,” Brown said. “These two concepts allow GHPs to provide the lowest operating costs of any commercial system.”

A READILY AVAILABLE TECHNOLOGY

According to Brown, applications are varied and widespread.

“Commercial geothermal is thriving today in ‘owner-driven’ markets, such as new school construction, due to its industry low operating costs,” Brown said. “Other commercial sectors are slowly gaining ground against traditional technologies.”

The gains are slow mainly due to the perceived increase in first costs associated with geothermal, although compared to four pipe systems it is actually much less.

Engineers are also on a learning curve with the technology, Brown said, and with every year passing, are becoming more comfortable designing and specifying the technology.

There are many issues currently affecting the HVAC industry and causing concern. This presents a need for change, according to Brown, who said that first, the overall efficiency of GHPs are the highest available.

Secondly, since residential GHPs tend to be package systems without long line sets, and therefore smaller refrigerant charges, the potential amount of refrigerant that can leak into the environment is reduced when compared to air source heat pumps.

Third, Brown said, being an electric-based technology, we are assured that the most advantageous fuel can be used to generate that electricity whether it is nuclear, gas turbine, hydroelectric, or even wind and solar.

“This allows us to greatly reduce our greenhouse gas emissions,” Brown said. “It truly is a perfect technology to exploit, and the best part is we don’t have to wait to develop it. It is here now and ready - more than 500,000 GHPs have been installed since 1980.”

Typically, GHPs encompass a very small mechanical footprint.

SIMPLE BY DESIGN

Certainly the earth loop installation can experience much reduced costs in large-scale systems, Brown said, noting that practically every application is possible with GHPs.

“Their flexibility in configurations with water-to-air versions of console, vertical stack, horizontal, vertical, downflow, split, and rooftop units provide a great selection for the designing engineer. Water-to-water configurations allow flexibility in providing hot or chilled water, as well as replacements to traditional chiller systems.”

One application, which is more expensive to design, is for continuous refrigeration loads to be rejected to the ground. According to Brown, these are the least cost-effective to design due to the large geothermal loop required to dissipate the continual rejection of heat, year ’round.

Typically, GHPs are simple systems to design, with a very small mechanical footprint in the building, Brown said. Novice engineers have at times designed large system pumps into the system to overcome a poorly designed piping system.

“These pumps can consume a very large amount of energy if improperly sized,” Brown said. “Secondly, some have also not trusted in the GHP concept totally, and installed unnecessary backup boilers etc., overcomplicating the system design. However, overall most owners are well pleased with both the operating and maintenance costs of GHPs. ASHRAE has done several studies on the maintenance costs of GHPs.”

In terms of challenges regarding implementing geothermal technology into HVAC systems, Brown said that coordinating the system/loop design with an engineer who is unfamiliar with the technology, and, overcoming the first cost objections, are perhaps the two most prevalent obstacles.

Residential GHPs have been primarily applied to new construction, but the development of horizontal boring (shown) has allowed geothermal loops to be installed with little disturbance of landscaping in existing homes.

GEOTHERMAL GROWTH

There has been much advancement for geothermal. The most notable recently, according to Brown, has been the 50 percent growth in the last three years. Per Brown, 2008 was the first year that more GHPs had been sold than oil furnaces.

“From a technology standpoint, residential GHPs have been primarily applied to new construction. However, the development of horizontal boring has allowed geothermal loops to be installed with little disturbance of landscaping in existing homes,” Brown said.

“We are now installing a much higher percentage of retrofit systems than in the past,” Brown said. Also, residential GHPs tend to be dual-capacity systems, utilizing ECM fan motors, and can provide very high EERs, now for the first time topping 30.”

“I think we have seen a shift in source energy from fossil fuels to electric-based systems. This change is related to higher natural gas costs and the energy efficiency trends we see flowing from the global warming response.”

With this shift, Brown said that GHPs have a distinct advantage in efficiency and environmental friendliness, and will ultimately benefit the HVAC industry. “GHPs currently enjoy a market share of less than 1 percent,” Brown said. “Predictions are that the market will grow to a 3 percent market share within the next five years.”

In terms of advice for HVAC contractors looking to add geothermal technology/capabilities to their outfit’s services, Brown said this: “Find a reputable manufacturer with a complete product, good training, and support. The transition can be painless.”

Publication date: 11/09/2009

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