Geothermal Heat Pumps

Geothermal heat pump systems tap the constant temperature of the earth to provide efficient heating and cooling. The systems operate by using water-source heat pumps which can be distributed throughout the building. Heat energy can be extracted from the earth in the winter, and added to the building. In the summer the process can be reversed. Unwanted heat is extracted from the building and added to the earth.

A geothermal heat pump ground-loop header
as it enters the building.

A Geothermal Heat Pump System

• Geothermal pump systems couple the building's HVAC system to the earth.
• Geothermal heat pump systems eliminate the need for boilers, cooling towers etc.
• The ground provides a nearly constant temperature source of BTU's for efficient heating and serves as a sink for BTU's for efficient cooling.
• Geothermal pump systems are generally distributed systems rather than central systems.
• Energy can be efficiently recovered/ reused in buildings with simultaneous heating and cooling needs.

What are the Benefits of Geothermal Heat Pumps

Geothermal heat pump systems have several benefits, including:

• Low Operating Cost
• No Required Exposed Outdoor Equipment
• Level Seasonal Electric Demand
• No On-Site Combustion
• Long Life Expectancy
• Low Cost Integrated Water Heating
• Simplicity
• Low Maintenance
• No Supplemental Heat Required
• Low Environmental Impact

Vertical wells loop-field configuration.

Who Can Benefit

While not a fit for all situations, geothermal pump systems are applicable in both existing and new buildings. In general, their benefits are greatest in buildings with similarly sized annual heating and cooling loads, and those desiring independent climate control of many rooms. The systems can provide efficient heating and cooling of different zones simultaneously. In New York State, installations have ranged from single family homes to hotels and 500,000-square-foot office buildings.
Office buildings and schools are particularly good applications for geothermal heat pumps. These facilities have relatively high occupancy, fluctuating usage schedules, and widely varying heating and cooling requirements within individual zones (offices and classrooms) that are difficult to meet efficiently with conventional systems. Further, efforts to improve the efficiency of conventional systems employ control strategies that can add considerable cost and complexity to the systems, increase maintenance requirements, and often compromise occupant comfort.

How the system works

Geothermal heat pumps transfer heat between the constant temperature of the earth and the building to maintain the building's interior space conditions. Below the surface of the earth throughout New York the temperature remains in the low 50 °F range throughout the year. This stable temperature provides a source for heat in the winter and a means to reject excess heat in the summer. With geothermal heat pump systems, water is circulated between the building and the "ground-loop" piping buried in the ground. In the summer, the water picks up heat from the building and moves it to the ground. In the winter the fluid picks up heat from the ground and moves it to the building. Heat pumps make the collection and transfer of this heat to and from the building possible.

 

In the summer, the earth acts as a cooling tower.

Geothermal pump systems exchange thermal energy between a building and the ground. When the building needs heating, the system extracts heat energy from the ground, and pumps it into the building where it is boosted by the heat pump to a comfortably warm temperature. Conversely, when the building needs cooling, the heat from the building is collected by the heat pumps and sent into the ground, much as a refrigerator's compressor transfers heat from inside the refrigerator to the outside. This exchange of thermal energy makes the system efficient. Rather than creating heat by burning a fuel on site, or chilled water by rejecting heat to the hot summer air, the geothermal heat pump system moves thermal energy between the ground and the building using heat pump technology.

In the winter, the earth acts as the boiler.

The relatively constant temperature of the ground makes this energy transfer efficient through out the year - even during the coldest weather. When the building needs cooling the system takes advantage of the relatively constant ground temperature that is usually cooler than the outdoor air in the summer. Alternative systems must move energy from the building to the hotter outdoor air, while the geothermal heat pump system gains efficiency by transferring the energy to the cooler ground.

Geothermal Heat Pump System Manual

This document provides additional information about geothermal heat pump systems, [PDF] how they work, when they should be considered and describes the steps involved in evaluating the cost effectiveness of a geothermal heat pump system. It describes the system and options and attempts to anticipate questions that building owners and designers might have about the technology. This document is designed to assist the layman in understanding the main concepts in geothermal heat pump systems while providing initial sources of information for the designer to pursue a specific project evaluation.