Geothermal energy produces base-load power. That is, it is not intermittent like wind and solar, but instead can produce electricity 24 hours per day, seven days per week with little downtime. It provides a consistent, reliable and predictable source of power. There are three power plant technologies being used to convert geothermal fluids to electricity. The conversion technologies are dry steam, flash, and binary cycle. The type of conversion used depends on the state of the fluid (whether steam or water) and its temperature.
Dry steam power plants use the steam directly from the geothermal reservoir to drive turbines that produce electricity. Because they require steam temperatures > 250ºC they will not be suitable for most Australian applications.
Flash steam plants are the most common type of geothermal power plants in operation today. They use water at temperatures greater than 180°C that is pumped under high pressure to the generation equipment at the surface. The water is seperated from the steam, and the steam used to drive turbines for electricity production. These are ideally suited to Hot Rock resources.
Binary cycle geothermal power generation plants (Figure 3) differ from Dry Steam and Flash Steam systems in that the hot water from the geothermal reservoir never comes in contact with the turbine/generator units. Instead the geothermal fluid is used to heat and vaporise another fluid that boils at a lower temperature than water. They can generate electricity from temperatures as low as 90ºC, but operate with better efficiency at higher temperature. This style of power station is likely to become the dominant type used in Australia.