Going geothermal for green energy

Geothermal heat pumps/air-conditioners are one such option. So, what’s the USP of these devices?

 Extremely cold Western winters render heating devices mandatory there. So, the conventional solution consists of separate heating and cooling devices, the latter being air-conditioners (ACs). Geothermal heat pumps (GHPs) are today generating interest as they can combine the two systems into one. They provide heat for warming up the house and water during winter. In summer, they offer solace from heat! All this with minimum electricity-consumption and space-usage!

The basic principle here is the exploitation of the near-constant temperature of the earth instead of above-the-surface air temperature.

Depending on location variation, ground temperature varies from 7°C-21°C. This temperature is higher than above-ground temperature during winter and lower during summer. GHPs harness this advantage to offer warmth in winter and coolness in summer sans any heating devices/furnaces or ACs/cooling towers.

Also known as geo-exchange, earth energy, earth-coupled, water-source or ground-source heat pumps, GHPs extract ground heat in winter usable for heating and channelise the building-interiors’ heat towards the earth in summer, cooling the premises. This is achieved by circulation of water/refrigerant naturally cooled/heated by the earth. There are also systems designed to operate in solely the heating or only cooling mode. 

Goethermal heat pumps are most easily installed during fresh construction of new buildings– both commercial and residential - running loops in the basement or around basement walls either vertically or horizontally to enable water/refrigerant circulation. Nevertheless, they can be retro-fitted too, i.e., they can be implemented in existing buildings too. 

Goethermal heat pumps can incorporate horizontal, vertical and pond/lake closed-loop, ground-loop systems or the open loop-system.

Horizontal systems require two ft wide trenches at least four ft deep to place the pipes, while vertical ones have loops inserted into holes 100-400ft. deep.

Vertical systems are suitable where there’s insufficient space around the building, where the existing landscaping shouldn’t be disturbed or for larger buildings (like schools or commercial establishments).

Pond or lake ground-loop is feasible only if the site has a water-body to harbour the pipes running out of the building. Open-loop systems need a well, recharge well or surface body water and are thus of limited practicability.

What determines GHP type and location? The soil-type (ex: exceedingly rocky soil prefers vertical looping), ground/surface water availability (closed/open looping) and land-availability (vertical loops are space-economising). 

 Benefits include slashed electricity bills (owing to reduced running/maintenance costs) translating too into smaller back-up power-generation systems and carbon footprint reduction, space saving (since separate external installations for cooling/heating are dispensed with) and consequent opportunity to use space on terrace, etc. for display of architectural aesthetics or other purposes besides lesser incidence of allergies contributed by greater humidity control and absence of on-site emissions or inflammable materials’ use and underground location preventing wilful damage of systems. 

 So, where’s the catch? The high initial investment demanded. Still, remember, it can be retrieved within a few years owing to low operational costs and complementary benefits.