Good water energy - temperatures within the earths crust

By Prof. Hui Tong Chua,

FIEAust, FIChemE, Department of Chemical Engineering of UWA

Luck is smiling on geothermal energy. Last November, I was invited to the Australian Institute of Refrigeration, Air conditioning and Heating (AIRAH) Award Gala Dinner in Sydney. I was heartened to learn that geothermal energy was received favourably by the industry. For one, The Cool Earth project at The Vive, Craigie, which informed the public about the long term performance of a ground source heat pump over and above that of an air source heat pump, was declared a joint winner for the Award for Excellence in Heating, Ventilation, Air Conditioning & Refrigeration (HVAC&R) Research. Then, Alinta Energy Geothermal was handed the Award for Excellence in Innovation for its Fairwater geothermal installation, which as I learnt from AIRAH when completed, will be the largest geothermal community in the Southern Hemisphere, with ground source heat pumps being accessible by 800 homes onsite. During the dinner interaction, the Federal President of AIRAH told me that there was yet another Olympic sized swimming pool being heated by tepid geothermal energy!

Western Australia is the most active State in terms of the uptake of geothermal energy. Many Olympic sized swimming pools in the Perth Metropolitan Area are heated by tepid geothermal energy (at megawatt level) that goes to a depth of about 1km. Typically, ~46°C groundwater is pumped up from the production bore, and having heated up the pool water, is then summarily returned underground via the reinjection bore. Remarkably, the heating provision is baseload, and while the capex is fairly intensive (with a pair of boreholes and the drilling that goes with that), the infrastructure does not consume much real estate, which is ideally suited to built-up areas. Claremont Aquatic Centre, Beatty Park Leisure Centre and Scarborough Beach Pool are some of the names that readily leap to mind when it comes to geothermal energy uptake.

But we can certainly go further with geothermal energy. The prospect of geothermal power in Australia has been long and elusive. When I was the Aboveground Engineering Programme Leader of the Western Australian Geothermal Centre of Excellence from 2009 to 2011, I saw the boom and bust of the geothermal power industry. There are many challenges that confront the geothermal industry – some are technical and some market driven.

In terms of geothermal power, as opposed to heating provision as in swimming pool applications, one has to go a lot deeper – on the order of 6km instead of 1km. The standard notion is still to have at least a pair of production and reinjection boreholes, drawing out hot, corrosive brine instead of benign groundwater. Typically, at such great depths, the inherent lack of permeability often mandates for hydrofracking, which is known to be associated with seismic activities. The capex intensive drilling drives prospectors to known geothermal hotspots, which are often distant from demand centres thereby escalating the unit product costs.

Apart from the single successful Birdsville geothermal power station in Queensland, which benefitted from the artesian basin, geothermal power in Australia has been dormant over the ensuing years. I continue to work away on ground source heat pumps, geothermal swimming pools and low-grade waste heat driven desalination and evaporation until late last year Warren Strange and Susan Jardine of Good Water Energy came knocking at my door.

Warren has a long career in drilling, with a good number of drilling IPs under his belt and has helped shape some of the best drilling practices which have become the norm of Australian drilling. Warren recently sold out his European geothermal company where he etched the 6km Helsinki project into his CV. Warren’s company was contracted to drill Finland’s first production geothermal wells in hard granite for the purpose of replacing fossil fuel with geothermal heat to generate district heating.

We are on the same page when it comes to all the headaches that plague geothermal applications in Australia. I become intrigued when Warren assured me that he has mastered percussion drilling which can deliver unprecedented speed of penetration into granite – this is crucial for capex if we aim for 6km, and that he will instead use the single-well geothermal system where we will sink a pipe-in-pipe heat exchanger into each of the boreholes to simply extract geothermal heat with a closed-loop heat transfer fluid, rather than drawing corrosive brine from depth.

The single-well geothermal system requires no hydrofracking thereby removing the risk of induced seismic activities. The heat will then power a binary power cycle[1] with the reject heat from the power plant being used for the thermal desalination of seawater. Warren explained further that since he has a cost-effective drilling technology, he can locate the geothermal plant close to coastal demand centres. This immediately mirrors the successful business model of geothermal swimming pools, which is demand driven instead of supply driven.

Warren is a visionary and has certainly captured my attention and commitment. While power production is the name of the game, the co-production of water is crucial for the commercial viability in Australia, which is where my expertise lies. Most of the successful geothermal power plants worldwide are air cooled, which in the case of Australia erodes their production efficiency and profit margin. With water co-production, the power plant efficiency will be enhanced, and the water can be an additional revenue source. The latter is important for capex intensive projects.

Warren and Susan have since nimbly assembled a capable board of non-executive directors, comprising of a hydrologist, a desalination engineer, an aboveground process engineer and a financial and managerial expert for the effective running of the company.
We have been avidly knocking at doors, conducting market reconnaissance, and talking to potential suppliers. All in all, the horizon is looming very favourably.
I think the time for geothermal energy in Australia is now.
Resilience is paying off!