3.  Survey of Geothermal Heat Pump Shipments
Introduction

This chapter provides information on geothermal heat pump shipments, based on the Energy Information Administration's (EIA) Form EIA-902, "Annual Geothermal Heat Pump Manufacturers Survey." It begins with a general discussion of heat pumps, followed by a discussion of the survey results and some salient characteristics of the data, and ends with a technical discussion of heat pump operation.
Overview
"Heat pump" is a term applied to a machine that can transfer heat both to and from a source. Therefore, a heat pump can be used both for space heating in the winter and for cooling (air conditioning) in the summer. The most common type of heat pump for domestic use is the air-to-air (air source) system in which heat is taken from air (heat source) at one location and transferred to air (heat sink) at another location.
Another type of heat pump transfers heat from air to water and has been designed for domestic hot-water heating. Geothermal heat pumps are a special type of air-to-water heat pump that use the earth as a heat source or sink, depending on the season. Since the earth's temperature a few feet below the surface stays relatively constant (about 55 degrees Fahrenheit) year round, one can extract heat from the earth when the air temperature is below the earth's temperature (winter), and transfer heat to the earth when the air temperature is above the in-ground temperature (summer). Geothermal heat pumps are generally more expensive to install but more efficient (costing less to operate and maintain) than an air-to-air heat pump. The technical section at the end of this chapter further explains the operation and rating of heat pumps.
EIA Survey of Geothermal Heat Pumps
The Energy Information Administration's (EIA) new survey, Form EIA-902, "Annual Geothermal Heat Pump Manufacturers Survey," shows that manufacturers shipped almost 58,000 geothermal heat pumps in 1997 and over 213,000 during the period 1994 through 1997. The survey was completed by approximately 18 known domestic manufacturers of geothermal heat pumps. Data from the survey are collected under a confidentiality provision. As a result, only aggregated statistics are released. The Form EIA-902 tracks shipments of the three main types of geothermal heat pumps, as certified by the Air Conditioning and Refrigeration Institute (ARI), and a small volume of non-ARI rated heat pumps (Tables 37-40). The three ARI-rated classifications for geothermal heat pumps are as follows:- ARI-320, Water-Source Heat Pumps (WSHP). These systems are installed in commercial buildings, where a central chiller or boiler supplies chilled or heated water, respectively, to heat pumps installed in series. The heat pumps reject building heat to chilled water during the cooling season and, during the heating season, take heat from boiler water; ARI-325, Ground Water-Source Heat Pumps (GWHP). The GWHP is an open-loop system in which ground water is drawn from an aquifer or other natural body of water into piping. At the heat pump, heat is drawn from or dumped into the water through a heat exchanger to the refrigerant in the heat pump. The heated or cooled water returns to its source; andARI-330, Ground-Source Closed-Loop Heat Pumps (GSHP). A water or water/glycol (antifreeze) solution flows continuously through a closed loop of pipe buried underground. Ground heat is absorbed into or rejected from the solution flowing in the closed loop. At the heat pump, heat is drawn from or dumped to the closed loop solution via heat transfer through a heat exchanger, which passes heat to, or removes heat from, the refrigerant in the heat pump.
Manufacturers shipped nearly 58,000 heat pumps of all types in 1997 (Table 37) compared with about 52,000 in 1996--an increase of almost 13 percent. Of those shipped in 1997, over 28,000 were ARI-320 rated, 9,700 were ARI-325 rated, 18,600 were ARI-330 rated, and approximately 1,300 were non-ARI-rated units.
**Table 37.****Geothermal Heat Pump Shipments by Model Type 1994�1997** (Number of Units)Model Type1994199519961997ARI-32026,75726,78724,83228,260ARI-3255,9248,6157,6039,724ARI-33016,02318,18518,09418,611Non-ARI Rated7578389911,327**Totals****49,461****54,425****51,520****57,922**Note: Data for ARI-320 units are subject to substantial revision.  See Appendix B.