Closed Loop Geothermal Systems
The well is classified as a coaxial design, closed loop downhole heat exchanger with an insulated inner tube for the hot ascending working fluid and a conductive outer casing to allow maximum heat transfer from the geothermal heat reservoir to the cooler descending working fluid.
All surface piping and equipment is not damaged by corrosive and potentially toxic water as the geothermal groundwater reservoir is kept isolated from the well, and only thermal energy (heat transfer) flows towards the well.
Using the single well system, no fluid is extracted from or injected into the geothermal reservoir and no fracking is required for communication between the two wells. Heat only transfers from the geothermal reservoir and is transferred to the surface by a controlled fluid that is isolated from the reservoir within corrosion resistant well casing. Pumping is from the surface and no surface plant equipment is exposed to corrosive saline groundwater. Organic Rankine Cycle fluid is heated by surface heat exchangers to drive turbines that in turn drive electricity generators.
Waste heat is taken from the turbine exhausts and used to boil seawater in Multi Effect Distillation (MED) desalination plants. Good Water Energy intends to establish salt management systems for the harvesting of high-quality sea salt to reduce or even totally eliminate salt brine return to the ocean. Where possible and approved, the company will install salt evaporation ponds to produce sea salt and other minerals such as lithium and other elements which may also be extracted during this process.
This methodology minimises the environmental impact and lengthens the lifetime of the well system.
This has historically been the main problem experienced with all conventional dual well geothermal projects in Australia to date. The single well system can therefore be implemented in any geothermal heat reservoir, irrespective of the presence of groundwater with a sufficient, inherent flow rate.
This means the project can be located at the marketplace where there is a demand for electricity and desalinated water, where there are existing distribution networks, and where there are other source materials such as seawater