Geothermal Heat Pumps for Hotwater and Space Heating and Cooling

Drilling for geothermal energy in Hobart (left) and in Adelaide, South Australia (right)

Above photo left: The Tasmanian Integrated Energy Management Centre (IEMC) went 36 metres underground, in the search for greater energy efficiency, because the ground is warmer than the air most nights, and on cold wintery days.  In fact the ground temperature doesn’t change much all year round.  In Hobart it was measured at 15 deg C at a depth of 50 metres.

How Geothermal Works   Ground loops can be installed vertically (above left) or horizontally (above right).

A geothermal heat pump was installed at the IEMC’s Moonah showroom, to demonstrate the capacity of the ground to supply or absorb heat and how this can be harnessed for domestic and commercial hot water and space heating and space cooling.  The IEMC Manager said the installation of the geothermal heat pump was an exciting addition to the Centre’s range of energy efficient options for homes and businesses.  The heat pump was removed when the IEMC showroom was closed.

Air-source heat pumps are already widely recognised for their high energy efficiency, but the additional efficiency and benefits of geothermal heat pumps are relatively unknown among the general public.  Geothermal heat pumps have a higher seasonal efficiency than their air-source counterparts and are several times more efficient than electric radiators.  They also have a longer life expectancy - of more than 28 years - and the polyethylene pipes buried in the ground are guaranteed for 55 years.

And the benefits don’t stop there.  Because the outdoor heat exchanger is located underground, there is reduced maintenance, no external noise or equipment to mar the environment, no vandalism and no de-frost cycles or iced-up coils when you need the heat most.  They are also much quieter inside, due to the variable speed fans and lightly loaded 2-speed compressors. The compressors don't have to work as hard as air-source heat pumps because the ground heat source is 15 degrees warmer when the outside air temperature is freezing. Similarly if the air temperature is 30 degrees outside, then the ground heat source is 15 degrees cooler. Hence the compressors last much longer and are much quieter in operation.  

An added advantage of the geothermal system is the optional hot water produced, which can be used for a swimming pool as in the Hobart Aquatic Centre, heating a concrete slab for space heating and to supplement the normal hot water supply.

Above: A domestic swimming pool and a nursing home serviced by geothermal heat pump systems

While geothermal heat pumps involve a higher investment cost, the energy cost savings are much greater, giving reduced life-cycle costs compared to other heating systems.  The set up costs may exceed the budget of many domestic customers, but there are definite financial gains to be made over the long term, particularly with the construction of new homes, when energy cost savings can match or exceed monthly loan repayment increases.

The system is particularly well-suited to commercial uses such as supermarkets, shops, offices, restaurants and motels, as well as public facilities such as schools.  The IEMC recommended geothermal technology as the best energy option for the Rosary Gardens Nursing Home at New Town and the Hobart Aquatic Centre, both of which are now operating successfully. This was the first modern geothermal heat pump technology installed in Tasmania.

The Hobart Aquatic Centre actually draws heat from warm treated sewage effluent that flows through a nearby pipeline, which was another IEMC recommendation - and a first in Australia.  Geothermal technology heat pumps produce warm water for the pool at night, which is stored in an insulated underground tank and pumped to the pool next morning, and space heating for the Centre during the day, thus maximising the use of the capital investment.     

Geothermal heat pump technology has since been installed in Tasmania at a private residence in Hobart, Antarctic Centre (Salamanca Place, Hobart), Ansett Call Centre (Launceston), Vodafone Call Centre (Kingston), Aurora Energy Offices (Launceston) and Southern Cross Homes' Sandown Village in Hobart, where heat is drawn from sewage effluent removed from the Residential Care Complex - another first in Australia.

Some 40,000 geothermal units are sold annually in the USA, mostly for residential use.  Over 200 schools in three USA states use these units, the largest being a 5.63 megawatt system for a New Jersey college.

Above: An apartment building serviced by geothermal heat pump system - showing underground pipes in basement

For some tips on saving energy at home please visit Dallas's page on Energy Efficiency

For more info on energy efficiency and energy management in Tasmania visit ...

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Centre for the Analysis and Dissemination of Demonstrated Energy Technologies (CADDET)

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