Researchers from UWA and the WA Geothermal Centre of Excellence have studied the use of geothermal energy to provide base load cooling for UWA’s Crawley campus.
The case study explored its economic viability in relation to electricity power savings, water pumping costs, capital costs for drilling and cooling tower water consumption.
The proposed geothermal cooling system could be integrated with existing air-conditioning units and infrastructure.
In the system, hot water (≈95°C) would be pumped up from the Yarragadee aquifer to power cascaded absorption chillers—which work directly on heat rather than electricity.
Having passed through the chillers the water, now at a cooler temperature (≈70°) would be returned to the aquifer at a shallower depth.
Co-author of the study, Peter Whittaker, says that while the results were positive and the technology is sound, the project is unlikely to go ahead.
The high initial cost of drilling and the relatively low base load demand, leads to too long a payback period for investors —in this case 11–13 years.
“As energy costs, particularly electricity costs, start to rise this becomes a more attractive option,” Mr Whittaker says.
“If you were building a new community or new construction project this would be a way of future proofing that against rising electricity costs and you could do a district cooling system or combined district cooling and heating system to increase the base load.”
Two different heat rejection methods were also analysed by the team.
The currently used cooling tower method which uses large amounts of water, was compared with extracting cooling water from the superficial aquifer as a cooling source, and then reinjecting it to the same aquifer at some distance.
Between 2008–10 the campuses cooling load peaked at 15MW in summer, however the base load—the average cooling required year round, was only 1MW to 3MW, which lead to a proposed 2MW cooling capacity project.
This proposed system has an estimated annual electricity saving of 2,165 MWh for cooling tower heat rejection or 1,568 MWh for the shallow aquifer method but with greater savings coming from decreased water use.
Researchers say the savings in electricity, and therefore carbon emissions, has direct benefits through the Australian Government’s carbon credits scheme and carbon tax savings.
The projects viability was found to be heavily reliant on drilling costs, geothermal resource quality and effects of various proposed emissions trading schemes.
