In Canada, much of our ecological impact comes from heating and cooling our houses. In winter, the outdoor air temperature can be 40 Celsius degrees cooler than indoors; in summer, it can be 15 degrees warmer outside. Meanwhile, several meters underground, the temperature is a constant 10 C.
Conventional heating and cooling systems need to raise or lower the air temperature significantly to change the outdoor temperature to a comfortable room temperature. There is an efficient technology that makes use of the steady underground temperature: a geothermal or ground source heat pump.
During the heating season, a geothermal system works like a refrigerator in reverse. The system has a circuit of pipes buried in the ground. A refrigerant solution circulates through the pipes, extracting the heat from underground and bringing it into the home. About 70-90% of the energy needed to heat the home is transferred from the ground.
A properly designed geothermal system is able to provide enough heat for average winter temperatures. During extremely cold weather or when rapid heating is required, a back-up electric heater incorporated into the geothermal system is used as well. An existing furnace could also act as a more efficient backup. Geothermal heat is best for holding steady temperatures. If you set your thermostat back, the heat pump can still be set to raise the temperature slowly and efficiently without invoking the electrical backup.
A geothermal system can also use the same steady underground temperature to cool the house in summer. A geothermal system is more efficient than a traditional air conditioning system, which is particularly important at a time of year when electricity production and smog are at their peak.
A geothermal system can even pre-heat your domestic hot water. In summer the waste heat removed from the house helps to heat the water, with an energy saving of over 50%.
Geothermal is one of most efficient heating and cooling technologies available today. Since the heat pump simply transfers energy instead of producing heat itself, it is 300 to 500% more efficient than traditional heating systems. Compared to a conventional electric heating and cooling system, a heat pump can cut energy costs by 40% to 70%.
Efficiency is important but the overall emissions from the system must also be considered. Many houses are heated with a relatively clean fuel like propane or natural gas, while in Ontario the electricity to run a heat pump comes partly from burning coal. Even so, on average, geothermal systems still result in decreased emissions of 3 to 7 tonnes of CO2 (carbon dioxide) per year.
The Cost: Geothermal systems would add about $8,000 to the cost of a new home. The payback on this should be quick, a matter of 4-10 years. As Ron Denbo, the well known financial engineer and environmentalist states, “It’s a no brainer; it should be incorporated into the building code.” Installing a geothermal system in an existing average house would cost about $20,000. Subsidies of up to $4,375 are available from the provincial government.
The Payback: With the subsidy, a heat pump system would pay for itself in 11 years for a house heated by electricity, 17 years for natural gas, 7 years for oil and 8 years for propane.
The Environmental Bonus: If you currently heat and cool an average house with electricity, moving to geothermal heating and cooling will save 4 tonnes of CO2 emissions per year and 1 tonne of CO2 for water heating – about the same as taking a car off the road.
If you currently heat with propane, gas or oil and have central air conditioning, you will save 3 to 6 tonnes of CO2 per year for heating, 1 to 2 tonnes of CO2 on the water heating and another 0.5 to 1 tonne of CO2 on the air conditioning.
The ideal solution would be to run a geothermal system on 100% clean energy from Bullfrog Power, saving an additional 2 to 3 tonnes of CO2 and making your heating and cooling system almost emission free!
Dr. Richard Ehrlich