Geothermal technology relies on the fact that the Earth remains at a relatively constant temperature throughout the year, warmer than the air above it during the winter and cooler in the summer, similar at a cave. The geothermal heat pump takes advantage of this by transferring heat stored in the Earth or in ground water into a building during the winter, and transferring it out of the building and back into the ground during the summer. The ground acts as a heat source in winter and a heat sink in summer.

Its great advantage is that it works by concentrating naturally existing heat, rather than by producing heat through combustion of fossil fuels. A geothermal heat pump does not create heat by burning fuel. In winter it collects heat stored in the ground. In summer it remove heat from the space being serviced and transfers it to the ground.

There are two types of geothermal appellations: Geothermal and Geo-exchange.

Old Faithful at Yellowstone National Park (USA).

Geothermal, also referred as high-grade geothermal energy is the heat of the earth’s pressure that turns water into stream. Old Faithful at Yellowstone National Park (USA) is an excellent example ¹⁾.

Geo-Exchange system that can transfer heat from or to ground.

Geo-exchange systems refer to heat pump systems connected to the earth to provide a source for energy. This heat is actually stored solar energy. The heat can also be taken from a stream of water as a well, a lake or a river. It is also called low grade geothermal. The heating system that collect heat this way have different names as Geothermal Heat Pumps, Earth-coupled Water Source Heat Pumps, Earth Exchange Systems, Geo-exchange Systems and Underground Thermal Energy Storage Systems.

• Date as far back as 1912.
• Gained significant market acceptance in the 1970’s.
• The 1980’s saw large uptake in installations and presently the new grants available have seen a resurrection in popularity.
• The technology transfers heat from or to the earth/water to provide space conditioning at greater efficiencies than a conventional system.
• Maybe renewable maybe not. The fact that electricity is required to run the system (compressor, circulating pump, etc.) raise the question: is it or is it not a renewable energy system. The efficiency of energy transferred in comparison of the energy required to transfer it (1:4) may bring someone to classify it as a renewable resource, but maybe not everyone.

• Low Life Cycle Cost
• Lower operating and maintenance costs
• Improved comfort
• Small equipment size (physical)
• Improved aesthetic design (no visible outdoor equipment or visible wall penetrations)
• No noisy outdoor fan, more peaceful backyard
• Protected from vandalism
• Increased equipment life span
• Heating can be up to 400% efficient
• Cooling can be up to 300% efficient

• Higher initial installation cost
• Lower supply air temperatures
• Increased airflow requirements
• Landscaping costs
• Possible backup system needed
• Circulating anti-freeze solution

• GCHP – Ground coupled Heat Pump: Is where the heat pump cycle is direct linked to a closed ground heat exchanger buried in the soil.
• GWHP- Ground Water Heat Pump: Where one of the heat exchangers is water cooled and the water is pumped from/to wells within the earth via open or closed pumping.
• SWHP – Surface Water Heat Pump: Is where one of the heat exchangers is water cooled and the water is either closed loop or open loop pumped to/from a surface water body.
• GHP- Geothermal Heat Pump: Is a widely used term which could reference any of the above or the water flow through buried loops.

• Usually utilize surface water bodies or well water fields
• More dependent on climate as water temperatures fluctuate to a higher degree
• Potential for contamination

• Greater flexibility in usage
• Usually have higher pumps requirements
• Anti-freeze is usually required
• More stable loop temperature with some designs

• Installation costs are less than closed loop
• Pumping costs are typically less

• Typically limited to smaller systems
• Climate conditions can limit usage
• Environmental issues
• Fouling is a large maintenance issue

closed loop - vertical

A vertical loop uses drilling to install the loop in a 100 to 200 foot bore hole.

• Requires the least amount of land
• Least amount of total piping
• Can require the least amount of pumping energy
• The loop can often be filled with water rather than antifreeze since the great depth eliminates chances of freezing²⁾.

• Drilling costs are high
• Back filling requires special material & skill
• Potential for heat build-up

closed loop horizontal

A horizontal loop uses a trencher or backhoe to install the coil below the frost line in a six to eight-foot deep trench.

• Trenching costs are less than drilling costs
• Heat build up is not as sensitive as vertical loop

• Requires more land
• Greater ground temperature variance
• Typically more piping is required
• Greater risk of piping damage during backfilling

closed loop - slinky / spiral

A slinky loop is a spiral of pipe laid about six feet below the surface.

• Requires less land & trenching than horizontal
• Less installed cost than horizontal

• Still requires more land than vertical loops
• Requires more piping than horizontal & vertical loops
• Typically higher pumping requirements

Earth's temperature changes in response to weather changes, but there is less change at greater depths. Less obvious, but important to earth coil performance, is the time lag. The earth temperature several feet deep reaches its coldest or warmest temperature several weeks after building loads peak, with an annual swing ranging from 18 to 26°F for most sodded surfaces.

At depths of twenty feet or more, there is no significant change from summer to winter, and the mean ground temperature approaches the annual average air temperature plus 2°F. down to about 200 feet. Thus, vertical loops generally require much less pipe than horizontal loops closer to the surface ³⁾.

• How much space is required?

• Soil/rock type
• Ground water

• Piping/borehole layout
• Heat transfer fluid?

• Noise
• Cleanup
• Access

• Foundation drilling
• Trenching
• Backfill
• Grouting
• Landscaping
• Equipment commissioning

• Permit?
• Local Bylaws?
• Drawings?

• Certificate of Installation
• CSA C448 Standard

Compared to the same output gas fired heating system, the cost of operation might be reduced by 66%

• EcoEnergy Retrofit
• Up to $4375.00 for Earth energy systems (CSA-C448 compliant)
• Must have EcoEnergy audit performed
• ecoENERGY

• Ontario Home Energy Retrofit program
• Matches EcoEnergy grants
• Ontario Home Energy Savings

• $15-$20 per foot
• Depth 200 to 300 feet
• 5 or 6 holes required

• 1200-1600 feet of piping
• 5-6 feet deep
• 2 foot wide
• 600 - 800 foot trench
• $2-$3 per foot

• $20K to $30K for a 3-4 ton system
• Viewed as the primary barrier
• Much higher than the new generation of high efficiency air source heat pumps and gas furnaces

• Most significant when replacing electric resistance or heating oil
• Marginal to no savings when compared high efficiency air source heat pumps and gas furnaces/AC systems
• Highly dependant on the price of electricity vs natural gas/heating oil

• Assessing Needs
  • Land area? Water Source? Heat Loss/Heat Gain
• Specification of Equipment
• Acquiring Approvals
  • Municipal
• Project Planning
• Engaging Contractors
  • Multiple bids
  • References
  • Accreditation
• Follow-ups & Maintenance
  • Service contract

• Canadian Geothermal Energy Association