What is Geothermal Heating?

 A geothermal system, apart from solar, is the most economical heating and cooling system available today. Because it uses free energy from the earth, its efficiency ratings are from 300% to 400% it is endorsed as having the least environmental impact and the lowest energy consumption.

 

Geothermal energy systems result in a 40% to 80% operating cost reduction when compared to alternate heating and cooling systems.

 

How it works?

 Geothermal heat pump share a technology that may look like black magic to a non-engineer. How is it possible, one might reasonably ask, to heat a house to a comfortable 20 degrees Celsius with water that is only 4 degrees Celsius or maybe less?

A geothermal heat pump works on a principle of vapour compression; it is simply a refrigerator running in reverse.

At the start of the heating cycle, water warms up a liquid medium in a heat exchanger, turning liquid into a gas. Next, gas is compressed by an electrically driven pump, which boosts its temperature. When gas passes through a condenser and then an expansion valve, it gives off heat and eventually returns to a liquid state to start the process again. The captured heat can be used to warm air or water.

Geothermal heat pumps, as well as all other types of heat pumps, have efficiencies rated according to their coefficient of performance, or COP. It’s a scientific way of determining how much energy the system moves versus how much it uses. Most geothermal heat pump systems have COPs of 3.0 to 5.0. This means for every unit of energy used to power the system, three to five units are supplied as heat.

 

Who invented geothermal heating and cooling?

Lord Kelvin had already invented the heat pump in 1852, and Heinrich Zoelly had patented the idea of using it to draw heat from the ground in 1912. But it was not until the late 1940s that the geothermal heat pump was successfully implemented.

 

Types of Geothermal Systems

Horizontal Loop Installation

If a horizontal loop system were installed, it would involve the excavation of parallel trenches, each 5 feet deep and 3 feet wide and about 130 to 150 feet long. The minimum distance between each channel is about 15 feet. All parallel trenches are connected to a supply and return header that enters the house through the basement to the geothermal flow centre.

 

Vertical Loop Installation

The vertical loop would involve vertical boreholes 4 inches in diameter drilled about 150 feet each. Each borehole would be separated from the next by about 10 feet. Two ¾ inch polyethylene pipes are inserted into the 150-foot borehole. The tubes are connected at the bottom using a U-bend.

 

Pond Loop Installation

A pond loop system consists of 300-foot coils of polyethylene pipe circuited in parallel via 1¼-inch polyethylene header pipes. The header and coil assembly is mounted on a PVC frame that holds the coils at the proper spacing and depth allowing water to flow underneath and through the center of each coil.

 

Open Loop Well Water Installation

Where ground water is abundant, water well can also be used as the energy source/sink, reducing the installed cost by eliminating the closed loop. However, a return well or acceptable surface discharge is required. Also, an open loop system will require periodic cleaning of the heat exchanger to remove mineral deposits. This is regularly done once a year.

Benefits and Drawbacks

 

Benefits:

  • Comfortable – Provides precise distribution of warmer air in winter. Gone are the uneven temperatures experienced with conventional furnaces. In the summer, you get central air conditioning with better dehumidification.
  • Quiet operation – A super efficient compressor and soft-start, variable-speed fan make the Premier line so quiet that many people find themselves checking to make sure the system is actually on.
  • Flexible – Heating, central air conditioning and domestic hot water — three systems: all from the same compact unit.
  • Lower operating costs – Operates more efficiently than ordinary heating and air conditioning systems, saving up to 80% in most cases.
  • Safe and clean – No flame, no flue, no odours, and no danger of fire or carbon monoxide. High-efficiency filters remove dust and pollen to improve indoor air quality
  • Environmentally Friendly – The system emits no carbon dioxide, carbon monoxide, or other greenhouse gasses that are considered to be major contributors to environmental air pollution.
  • Attractive – The completely self-contained unit is maintained indoors. There is no need for noisy, unsightly, outdoor condensing equipment.
  • Reliable – Microprocessor controls and state-of-the-art components allow smooth operation and years of maintenance-free service.

 

Drawbacks:

  • High Installation Costs
  • Pipe installation is disruptive
  • Pipe repairs can be costly

 

Cost

Standard air-source HVAC systems cost around $3,000 per ton of heating or cooling capacity, during new construction (homes usually use between one and five tons). Geothermal HVAC systems start at about $5,000 per ton, and can go as high as $8,000 or $9,000 per ton. However, new installation practices are reducing costs, to the point where the price is getting closer to conventional systems under the right conditions.

Factors that help reduce cost include economies of scale for community, commercial, or even large residential applications and increasing competition for geothermal equipment (especially from major brands like Bosch, Carrier, and Trane). Open loops, using a pump and reinjection well, are cheaper to install than closed loops.

 

Use of Geothermal Heating in Ontario 

Wind and solar technologies may hog the spotlight (and subsidies) in Ontario, but behind the scene geo-exchange heating and cooling systems are being quietly deployed by the thousands across the province every year.

In fact, Ontario dominates when it comes to deploying these systems, according to a just released national report from the Canadian GeoExchange Coalition, a non-profit organization representing the industry.

The province saw more than 7,000 geothermal heat pump units installed in 2010. This is down from more than 9,000 in each of 2009 and 2008, but far higher than next-best ranking Quebec and British Columbia, which have only installed between 1,000 and 2,000 units annually between 2008 and 2010.

“The residential market has definitely shrunk,” says Stanley Reitsma, president of Caledonia, Ont.-based Geosource Energy Inc. “But the commercial market in Ontario is a different story. It’s still strong.”

Geosource has been busy installing systems in midrise and high-rise buildings. It’s not fuelled by incentives. Instead developers are increasingly seeing the long-term financial and environmental benefits of moving in this direction.

Changes to the province’s building code in 2011 that require buildings to be 25 per cent more efficient has further boosted interest in the technology.

It’s the savings that come from cooling, not heating, that are proving most attractive to large building owners, says Reitsma. “Heating costs (from natural gas) are small compared to cooling costs (from electricity).”

Meanwhile, more building developers are choosing to play the role of energy supplier. They install the geo-exchange systems and sell the resulting heat or cool air to the building owner or tenant under fixed-priced, long-term contracts.

“It’s competitive and eliminates price volatility,” Reitsma says. “It’s also part of their green marketing.”

 

 Additional Resources

Publications

The Ontario Ministry of Energy and Infrastructure offer a good overview of geothermal systems. For more detailed information, check Natural Resources Canada’s Residential Earth Energy Systems: A Buyer’s Guide and Heating and Cooling with a Heat Pump.

Associations

 

 

 

RESOURCES

  1. Geothermal heating – Wikipedia, the free encyclopedia  en.wikipedia.org/wiki/Geothermal_heating
  2. http://energyblog.nationalgeographic.com/2013/09/17/10-myths-about-geothermal-heating-and-cooling/
  3. https://www.thestar.com/business/2012/02/17/geothermal_heatingcooling_canadians_are_hot_and_cold_about_it.html
  4. http://www.omafra.gov.on.ca/english/engineer/ge_bib/geotherm.htm#7
  5. http://buildersontario.com/geothermal-heating-costs
  6. Toward a Zero Energy Home: A Complete Guide to Energy Self-Sufficiency at Home, by David Johnston, Scott Gibson.
  7. http://www.achrnews.com/articles/120191-maryland-legislature-passes-geothermal-heat-pump-bill