Geothermal Systems
Find Out How it Works
Geothermal systems take advantage of the constant temperature just a few metres below the surface. In Québec, it averages about 10°C, winter and summer alike.
Geothermal systems basically consist of a pump, a heat pump and a ground loop that warms or cools a circulating fluid, depending on the season.
COMPONENTS
Distribution system
The distribution system circulates heat or coolness throughout the house. It may be a central forced-air or hot water system, or a hybrid system involving hydronic floor heating, for instance. But only a system with air ducts can air-condition the whole house.
In the case of an existing house, it may be necessary to modify the distribution system to benefit fully from geothermal energy.
Heat pump
The heat pump is connected to the distribution system to transfer heat between the ground loop and the house. In winter, it concentrates heat from the ground loop and transfers it to the house. In summer, it transfers heat extracted from the house into the ground, thus cooling the house.
Underground loop
In geothermal systems, the ground loop serves as the heat source as well as the heat sink. The ground loop can be either open or closed.
In a closed-loop system, a mixture of antifreeze and water circulates through a ground loop and heat pump. There are four types of closed loops.
HORIZONTAL
VERTICAL
DIRECT EXPANSION
LAKE OR
POND
Vertical closed loops are the most common, because of their suitability for typical medium-sized lots.
Developed in Canada, direct expansion (DX) systems are especially suitable for existing houses. They are good in limited spaces, such as in urban areas, because drilling does not need to be as deep, and can be done by a very small drilling machine. In a DX system, a refrigerant fluid flows through copper piping buried about 30 m underground.
In open-loop systems, groundwater from a well is the heat source and heat sink. The pump draws water from the well, and the heat pump extracts heat from it or transfers heat to it (depending on the season) by means of a heat exchanger. The water is then discharged into the earth, usually through a return well.
