EARTH ENERGY SOCIETY OF CANADA
Société canadienne de l'énergie du sol

 

OPTIONS

There are four basic loop designs available to earth energy systems or ground-source heat pump (GSHP) customers:

1) OPEN-WATER OR OPEN-WELL...

These systems take water from a well or a drilled well, direct the flow through the GSHP unit where the heat is extracted, and then return the cooled water to the lake or well, in accordance with environmental regulations. 

If the source of water is a lake, the body of water must be large enough to provide a sufficient 'heat sink' capacity. Rivers can be used as a source of water, but sources with high levels of salt, chlorides or other minerals are not recommended for most units. Each province has regulations concerning the use of water from Crown lands, and there are federal laws concerning the position of GSHP loops in navigable waterways. 

If the source of water is a well, most provinces have regulations concerning the extraction and re-injection of water to protect natural aquifers. In some jurisdictions, a licensed well driller must be used. Although a GSHP system only extracts heat from the water in winter, there is a difference of opinion over whether this change in temperature then classifies the discharge water as sewage. 

open

Advantages of open-loop systems:
  higher efficiency of heat transfer
  lower installed cost
  no need to use a chemical fluid for the heat transfer medium

Disadvantages:
  environmental concerns with disruption of water tables and aquifers
  fluctuations in water temperature can affect system performance

 

2) LAKE LOOPS OR POND LOOPS...

A closed loop system is positioned on the floor of a body of water, instead of buried in the ground. The pipe must be weighted properly to remain on the bottom of the lake and to avoid shifting caused by spring ice movement. 

Advantages of lake loops:
  usually less expensive to install than trenching into the ground
  relatively easy to diagnose leaks in the loop

Disadvantages:
  potential environmental damage to aquaculture
  water temperature fluctuation (especially in spring runoff) can affect system performance 

 

3) HORIZONTAL CLOSED LOOPS...

These are a common configuration in Canada. A trench is dug on the property, and pipe is buried in a continuous or parallel loop (depending on size of unit). The national installation standard (CSA C445) states that the loop must be located at least 600 mm (2 feet) below ground, but industry guidelines are at least twice that depth. It is possible to lay more than two pipes in each trench, thereby reducing the cost of digging. It is important to backfill the trench properly, to avoid air pockets that can reduce the transfer of heat, and to ensure that the pipe is not damaged by large rocks.
closed

Advantages of horizontal closed loops:
  relatively easy to install
  high flexibility of design
  greater control over entering fluid temperature 

Disadvantages:
  cost of trenching can be high
  it is more difficult to find a leak in the loop
  landscaping may be required on retrofit installations

 

4) VERTICAL CLOSED LOOPS...

These are the most expensive but the most efficient configuration, due to the fact that the under-earth level of heat increases and stabilizes with depth. This option is viable when surface property is limited or difficult terrain, but care must be taken to ensure that the vertical borehole is drilled according to provincial regulations. 

Advantages of vertical closed loops:
  highest efficiency
  less property space is required
  most secure from accidental post-installation damage

Disadvantages:
  usually the highest-cost option
  potential environmental damage to aquifers if not installed properly
 




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(613) 371-3372 (371-EESC)          (fax) 822-4987
 (e-mail)  Eggertson@EarthEnergy.ca
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