Closed-Loop System - Description

The closed-loop ground-coupled system uses a buried or submerged geothermal heat exchanger. This heat exchanger can reject or draw heat from a source such as the earth, a lake, or a pond, by circulating water through a loop.

These closed-loop systems can further be divided by design and application in the following ways:

A central system has all heat pumps in a central room and air or water is ducted or circulated to conditioned spaces. Applications include chiller retrofits such as in the Louisiana Association Building in Baton Rouge, Louisiana, the new Daily YMCA building in Bixby, Oklahoma and the rooftop unit retrofits at Stockton State College.

Distributed systems use a central water pump and heat pumps serving individual rooms and areas. Types of buildings served include offices, schools, new construction, and retrofits. The Oklahoma State Capitol building uses more than 400 heat pumps. Since multiple units are heating and cooling simultaneously, the distributed system can provide heat recovery from core zones to heat perimeter zones.

A distribution system permits location of relatively small individual units in restricted areas, such as historic buildings like Shields Tavern in Colonial Williamsburg.

Modular systems have dedicated heat pumps, water pumps, and loops. This type of system allows for independent individual control, operation, and maintenance. Types of buildings served include schools, with modules serving individual classrooms, and other buildings where usage and environment are clearly separated. An example of this type of building is the Bailey Middle School in Austin, Texas, where console units serve individual classrooms.

A hybrid system uses a cooling tower or other means to reject excess heat in the summer. The cooling tower reduces the size of the ground heat exchanger and installed cost. Examples of these systems include the Oklahoma State Capitol building which uses a very compact ground heat exchanger and a cooling tower located away from the capitol building. A federal government building in Louisiana reduced the cost of the ground heat exchanger by $30,000 by using a cooling tower. Shields Tavern in Colonial Williamsburg uses a plate and frame heat exchanger cooled with well water to reject additional heat during periods of high cooling demand.