Dual Source Heat Pumps
Source: UFTO
Date: 2/20/97    Record No.: 10434
Contact: Eugene L. Cornett, Energy Technologies, Inc., Odessa FL
813-376-9000, or fax, 813-376-5211

Mike Housh, Geothermal Technologies, Inc. , Middletown OH

Dual Source Heat Pumps
New types of heat pumps are coming on the market. Dual Source heat pumps combine both ground-source (geothermal) and air-source, and promise significant cost and performance improvements over existing systems. (E-Source will issue a major report in the very near future entitled "Dual Source Heat Pumps, The Sleeping Giant".) Note that is not the same thing as "dual-fuel", which usually refers to gas/electric systems.

Compared with ground source, the dual source uses a smaller ground loop, which is easier and cheaper to install, especially in retrofit situations. It's cold weather performance and overall efficiency is better than air source systems.

There are two basic types. One is "direct expansion", where the refrigerant itself is circulated in the ground loop. The other uses a glycol solution in the ground loop.

Energy Technologies, Inc. (OTC Bulletin Board: ETCH), has an advanced and proprietary geothermal heat transfer technology which is now being marketed under the trademarked name ENVIRONS Dual Source System(TM). This patented technology will reduce energy consumption by forty to sixty percent, and has successfully completed its commercial testing process, with a recommendation from the National Institute of Standards and Technology (NIST).

In the cooling mode, hot gases from the compressor are pre-cooled by the ground-loop via the desuperheating heat exchanger before reaching the air coil. After air cooling, refrigerant is cooled further by the ground loop solution at a subcooler heat exchanger. A greater drop in refrigerant temperature than with a conventional air-source system is the basis for its superior performance. Additional power savings over geothermal heat pumps is achieved by using a 35 watt pump for ground-loop circulation for the 3 ton model, compared with a 650 watt pump typically used in geothermal systems.

In cooling mode, the EER can range from 16 to over 18, depending on air and ground loop temperatures. In heating mode, the COP ranges from 3 to 4. Installed costs are comparable to a high end air source split system, including the ground loop, which uses 240 feet of 5/8" pipe (the 6 twenty foot vertical loops can be installed for $6-800). A heat recovery unit can also supply free hot water.

Contact: Eugene L. Cornett, 813-376-9000, or fax, 813-376-5211
Energy Technologies, Inc., Odessa FL 33556

Geothermal Technologies, Inc. (GeoTech) offers the direct expansion type of system that circulates refrigerant through both ground loop and air coil. In the milder portion of the heating and cooling seasons when conventional heat pumps are still very efficient, the heat pump provides heating or cooling via the air coil. During extreme temperatures, the system relies entirely on the ground coil for heat exchange. According to the manufacturer, this configuration allows their dual-source system to operate most efficiently in middle latitude states.

Currently, GeoTech dual-source heat pumps operate in 12 test homes. According to preliminary findings, GeoTech expects its energy-efficiency to be within 5% of geothermal heat pumps but with a total installed cost of $1,000 to $2,500 less. Although payback periods for most geothermal systems are said to range from 3 to 7 years depending on climate, GeoTech expects its system to have a payback of 1-1/2 to 4 years.

GeoTech also offers an improved lower cost ground source heat pump system, based on design inprovements over poorly performing units sold by U.S. Power which went out of business.

Contact: Mike Housh, (513)423-1923.
Geothermal Technologies, Inc. , Middletown OH 45042