Geothermal Heating & Cooling Requirements

In any geothermal project, the first step of designing a system is to determine the amount of heat required for the building.  This is done by utilizing a traditional heat load analysis software program such as the CSA F280 program for Canada, or an implementation of the ASHRAE Manual J Residential Building Load Standard commonly used in the United States.  Such a program will determine the amount of heating and cooling needed for the structure at the design temperature for your location. 

Once the building load information is obtained you can choose the heat pump model required to supply the energy needs of the home.  The homeowner then needs to decide whether heating or cooling is the priority requirement of the home. 

Heating and cooling loads are only equal if the area of the country in question falls within a specific lattitude.  Lattitudes in the Northern hemisphere will have a predominantly heating load, while southern lattitudes are predominantly cooling as one moves towards the equator. For example, if a home required 50,000 BTUs/hr. in New York to satisfy the heating load it may only require 25,000 BTUs/hr. in the cooling mode.     

Since most people select a geothermal heatpump to save energy and reduce their heating costs, it makes sense to select a heat pump which will meet the entire heating load of the home.  In this way a home owner can maximize energy savings. With the advent of 2-stage heat pumps it is no longer such a concern in regard to oversizing a system for the cooling mode, since the unit can adapt to the lesser cooling requirement by operating in low speed. 

Once the load of the building is known and the heat pump capacity is selected, the type of earth connection to be used must be determined.  If the home is located in a rural area and a well is already needed to supply water to the home the least expensive technique for supplying energy to the heat pump is to use a common water well.

 

• A return well is usually the best technique for returning the water back to the earth.  In this manner no water is wasted, and the system is ecologically sound.  In areas where sufficient water cannot be obtained, then the next best option is a horizontal ground loop. One quarter to 1/2 an acre of land space is required for this implementation.

• The ground heat collector plastic piping system is buried 6 feet under ground and thus the land can still be used for other purposes once the collector is in place.  If the land space is not available, then the final option (although most costly) is to install a vertical borehole system where the ground heat collector piping system is placed in vertically drilled boreholes.

 

• A vertical borehole system can be used on any lot since the space in between the boreholes is only 15 or 20 feet.  In very tight locatons angle drilling is possible requiring only approximately a 10 foot diameter area free of obstruction at the surface.

Heating & Cooling Distribution   

The final area of concern would be how the heat/cooling is to be distributed throughout the home.  A forced air duct system or infloor heating with fan coils are the 2 common types of heat distribution.  A forced air system provides heating and cooling through the same distribution duct network, thus minimizing capital costs, while an in-floor heating system generally provides greater comfort but requires a duct system and fan coils for cooling.  Capital cost for the combination distribution system are, of course, higher.