Geothermal, off the Greek "geographia" and "therm" ("heat"), taps earth's energy in order to produce heat. Contrary to air temperature, which fluctuates with the seasons and climates, that of the earth's crust is relatively stable and not influenced by variations of ambient temperature from 15 metres deep. At depths below these 15 metres, ground temperature rises approximately 1°C to 3°C per 100 metres.
- It all depends on your land availability
Geothermal systems are divided in three categories: open loop exchangers, closed loop exchangers and standing column wells.
- Not all the same...
Geothermal grouts secure the transfer of heat between the geothermal loop and the exchange environment (soil, rock). They are normally composed of bentonite, a thermal booster (sand) and water. Besides assuring the heat transfer between the geothermal loop and the exchange environment, grouts protect the environment due to their very low hydraulic conductivity. By completely filling the annular space found between the ground geothermal exchanger and the walls of the borehole, the grout ensures the isolation of the various aquifers and keeps contamination from subsoil waters.
- Far from sight perhaps, but they must be cared for
The piping used for the construction of the geothermal exchangers is mostly composed of high density polyethylene (HDPE). This type of plastic allows the joining of different sections or accessories by thermo-fusion, which permits an underground network without screwed or glued joints. The CSA C448 standard requires that the subterranean or submerged piping respects the CSA B137.1 standard as to its identification and raw materials used.
- Glycol or alcohol?
The heat transfer fluid is a fluid, usually liquid which is circulated to transport, extract and dissipate energy in the form of heat, from an energy source to a thermal load. Each heat transfer fluid is chosen according to its physicochemical properties, such as viscosity, volumetric thermal capacity, potential heat of evaporation or liquefaction in case of a change in phase, and thermal conductivity.
- Enough or not enough flow
To be effective, flushing must maintain a minimum velocity flow rate of 0,61m/sec. in all points of the piping network, until the complete elimination of all air and debris inside the piping network.
- A step best not rushed
The commissioning of a geothermal system, as for all HVAC systems, is a crucial stage to its performance. The commissioning of a geothermal system must be done by qualified professionals and coordinated with all the stakeholders, including the designers, pipe fitters, automation professionals, general contractors and owners.
- La Coalition canadienne de l'énergie géothermique (CCÉG)
The Canadian GeoExchange Coalition (CGC) was created to promote and encourage growth of the geothermal industry. One of the CGC's objectives is to promote standards by developing a professional database and granting certifications. In a geothermal project, this certification applies mainly to the designer, the system installer as well as the ground energy exchanger installer.
Link to their website: CCEG
History and Principles
Heat Transfer Fluids
Flushing and Filling
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