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Geothermal 101


The warm earth and ground water below the surface provide a free, renewable source of energy that can generate savings in heating, cooling and hot water up to 70%.

What is Earth Energy?

The sun has always provided heat for the earth. Its energy warms the earth directly, but also indirectly. Its heat evaporates water from the lakes and streams, which eventually falls back to earth and filters into the ground. A few metres of surface soil insulate the earth and ground water below. The warm earth and ground water below the surface provide a free, renewable source of energy for as long as the sun continues to shine. The earth under an average suburban residential lot can easily provide enough free energy to heat and cool the home built on it.

The free energy has only to be moved from the ground into your home. This is done by drawing ground water directly from a well and using a heat pump to extract heat from it. As well, a circuit of underground piping called a loop can be buried in the soil outside the home through which fluid – water or antifreeze – is pumped. The fluid, called the heat transfer fluid, absorbs the heat in the ground water or soil and transfers it to the heat pump.

The heat absorbed by the fluid from the solar-heated ground is extracted from it by the heat pump, and the now-chilled fluid is circulated through a heat exchanger over and over again to extract more heat from the earth. If your home is located near a suitable pond or lake, you can use an Earth Energy System (EES) to draw on this excellent source of free energy.

Burying a loop in the ground around your home is like owning your own oil well, but instead of pumping oil from an underground pool and burning it to create heat (and greenhouse gases), you tap into clean energy that will be there for as long as there is a sun. A well-designed ground loop will not hurt the earth or plants growing above it. There is no visible part to show that it is buried in your yard. If your system uses ground water, it has no effect on the water other than changing its temperature by a few degrees. Finally, a well-designed ground water system will not waste the water, but put it back into the ground.

(Source : Natural Resources Canada)

How Earth Energy Systems Work?

The heat energy taken from the ground by your EES is considered low-grade heat. In other words, it is not warm enough to heat your home without being concentrated or upgraded somehow. However, there is plenty of it – the average temperature of the ground just a few metres below the surface is similar to (or even higher than) the average annual outdoor air temperature. For example, in Toronto, the average annual air temperature is about 8.9°C, but the average ground temperature is 10.1°C. It is important to note that this ground temperature is 10.1°C on the hottest day of summer as well as on the coldest day of winter. That is why some of the first humans lived in caves – the caves would protect them from the temperature extremes of winter and summer. That is also why an EES works so efficiently – it uses a constant, relatively warm source (ground or water) from which to draw energy.

(Source: Natural Resources Canada)

Geothermal Loop Types

The ground loop, which can be opened or closed, is the source of your geothermal system. Geothermal dealers are trained to determine the best type of earth loop to use in any situation. The type of loop used is based on available land space and installation costs for specific areas.

Vertical loops are used when space is limited. Holes are bored using a drilling rig, and a pair of pipes with special u-bend fittings is inserted into the holes.


Used where adequate land is available, horizontal loops involve one or more trenches that are dug using a backhoe or chain trencher. Polyethylene pipes are inserted, and the trenches are backfilled.
If an adequately sized body of water is close to your home, a pond loop can be installed. A series of closed loops can be coiled and sunk to the bottom. A 1/2 acre, 8-foot-deep pond is usually sufficient for the average home.
An open loop is used where there is an abundant supply of quality well water. The well must have enough capacity to provide adequate flow for both domestic use and the unit.


Basic Components of an EES

A typical EES is made up of three main parts: a loop, the heat pump and the distribution system. The following section describes some of the various loop designs, heat pumps and distribution systems commonly used in a Canadian EES.

The loop is built from plastic pipe which is buried in the ground outside your home either in a horizontal trench (horizontal loop) or through holes drilled in the earth (vertical loop). The loop may also be laid on the bottom of a nearby lake or pond (lake loop or pond loop).Your EES circulates liquid (the heat transfer fluid) through the loop and to the heat pump located inside the home. The heat pump chills the liquid and distributes the heat collected from it throughout the home. The chilled liquid is pumped back into the loop and, because it is colder than the ground, is able to draw more heat from the surrounding soil. These loops are often referred to collectively as a closed loop, as the same liquid circulates through the closed system over and over again.

Another way is to pump ground water or well water directly through the heat pump. An EES that uses ground water is often referred to as an open-loop system. The heat pump cools the well water, which is usually returned to the ground in a return well. To run an open-loop EES, you need two reliable wells with water that contains few dissolved minerals that can cause scale build-up or rust over the long term, as it is pumped through the heat pump’s heat exchanger.

In both cases, a pump circulates liquid through the loop and the heat pump. The heat pump chills (or collects the heat stored in) the liquid when it is being used as a source of heat, and circulates it back through the loop to pick up more heat. A system for a large home will require a larger heat pump and ground loop, with a circulation pump to match. After the EES has taken the heat energy from the ground loop and upgraded it to a temperature usable in your home, it delivers the heat evenly to all parts of the building through a distribution system. It can use either air or water to move the heat from the heat pump into the home. Forced air is the most common distribution system in most parts of Canada, although a hot-water or hydronic system can also be used.

(Source: Natural Resources Canada)

Forced-Air Systems

A heat pump in a forced-air EES uses a heat exchanger to take the heat energy from the refrigerant to heat the air that is blown over it. The air is directed through ducts to the different rooms in the home, as with any forced-air fossil fuel or electric furnace. The advantages of a forced-air EES are as follows:

  • it can distribute fresh, outside air throughout the home;
  • it can air-condition the home (by taking the heat from the air in your home and transferring it to the ground loop) as well as heat it; and
  • it can filter the air in your home as it circulates through the system.

An EES is designed to raise the heat of the air flowing through the heat pump by between 10 and 15°C; fossil fuel or electric furnaces are designed to raise it by 20 to 30°C. That difference means an EES must move more air through the home to distribute the same amount of heat as a conventional furnace. So to design an efficient, quiet forced-air EES, the contractor designing the ductwork must take into account the larger amount of air to be moved. The ductwork should also have acoustic insulation installed inside the plenum and the first few metres of duct, as well as a flexible connection between the heat pump and the main duct to ensure quiet operation.


(Source : Natural Resources Canada)

Hydronic (Hot-Water) Heating Systems

As we said earlier, a heat pump can heat either air or water. The latter type distributes the heat by means of a hydronic (or hot-water) heating system. If you choose it for your home, keep in mind that currently available heat pumps can heat water to no more than about 50°C.

This limits your choices for equipment to distribute the heat to your home. Hot-water baseboard radiators are designed to operate with water heated to at least 65 to 70°C; they are less effective when the water is not as warm. As a result, you will need larger radiators – or more of them – to distribute the same amount of heat. Or you can reduce the heat loss from your home by installing more insulation, so you need less heat.

You can also install radiant floor, or in-floor, heating systems.

These are becoming more common because they can increase comfort and improve system efficiency. Again, you must make sure that your radiant floor heating system is designed to operate within the temperature capabilities of your EES.

The temperature difference between the ground loop and the hot water distribution system depends on the efficiency of the EES; the greater the difference, the less efficient the system. Typically, an EES will extract heat from the earth at about 0°C. If a radiant floor heating system requires a temperature of 50°C to heat your home, the heat pump will produce about 2.5 units of heat for every unit of electricity used to operate the system. If the system can be designed to operate with water at 40°C, it will produce 3.1 units of heat for every unit of electricity used to operate it. In other words, it will be about 25 percent more efficient.

Think about it this way – if you have hot spring water to heat your home, you do not need a heat pump. The hot spring is a totally free, 100 percent efficient source of energy. But if the temperature of the water from the well needs to be raised 5°C to be high enough to heat your home, you need some additional energy. If it has to be raised 20°C, you need even more energy. The greater the temperature difference, the greater the additional energy need.

(Source: Natural Resources Canada)

Installing a radiant floor heating system

If you are thinking of installing a radiant floor heating system in your home, you should tell the person designing it that you are planning to use an EES. Make sure you take the following factors into account:

  • placing your floor pipe 20 cm (rather than 30 cm) apart reduces the water temperature required to heat your home by 4 to 5°C and increases the efficiency of your EES by about 10 percent;
  • laying your floor heating pipe in concrete or Gypcrete rather than using aluminum reflective plates with the pipe reduces the required temperature by 12 to 15°C, increasing the efficiency of your EES by 25 to 30 percent;
  • suspending pipe in the joist space under a floor means that you will need temperatures higher than what your EES can produce, unless the heat loss in the space is very low;
  • placing insulation under a slab-on-grade floor or under a basement floor reduces heat loss to the ground below; and
  • installing a control system that lowers the water temperature pumped through the floor as the outdoor temperature rises increases the efficiency of the EES. This type of control is commonly called an outdoor reset control.

(Source : Natural Resources Canada)

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