Geothermal resources of the Great Artesian Basin, Australia.

Objectives

There is a little resemblance between world geothermal hot spots and the Australian landscape pictured in Figure 1. However, vast parts of the Australian continent have considerable reserves of geothermal energy stored in deep artesian groundwater basins in the form of warm groundwater.

Artesian groundwater was discovered in central and eastern inland Australia around 1880. Further extensive geological investigations and water-well information helped to outline the shape and size of a large confined groundwater system, now known as the Great Artesian Basin (GAB). The
GAB extends across four Australian states underlying 22% of the Australian continent (Habermehl, 1980, 2001). Temperatures of the artesian groundwater (which is generally of a very good quality) range from 30o to 100o C at the well heads. As the groundwater is too hot for town water supply and for stock to drink, it needs to be cooled down before consumption. That is why cooling towers can be seen throughout the region.

Some cooling towers are equipped with electric fans, in which the case electric power is spent to remove the thermal energy of the groundwater (Figure 2). The efficiency of power generation from fluids of temperatures not exceeding 100o C is known to be low. However, there are some factors that may outweigh relatively low efficiency of electricity production from the GAB groundwater. One of such factors is a high cost of fossil-fuel electricity in remote locations of the GAB due to high transportation costs. Other factors, which one may need to consider, are the quality of the GAB groundwater and the flow rates of artesian wells.

In what follows we overview geothermal resources of the Great Artesian Basin and discuss prospective geothermal applications and their potential benefits for the region.

Outcomes

Geothermal energy of the artesian groundwater in the Great Artesian Basin is a valuable natural resource suitable for a variety of useful applications. Prospective applications include direct-use applications, such as space heating, bathing, aquaculture and air-conditioning, as well as electric power
generation. Bathing and aquaculture are most promising geothermal applications at the low temperature end of the GAB groundwater (30o - 40oC). Absorption refrigeration, which works at the high temperature end of 80oC and above, is another prospective geothermal application for the hot
climate of the region. Although the groundwater temperatures in the GAB do not exceed 100oC, the flow rates from the artesian wells are generally very good. Our calculations show that the flow rates from the GAB wells are capable of supporting heat inputs required for electric power production (see Table 1). With modern re-injection and numerical simulation technologies thermal energy of the artesian groundwater of the GAB aquifers can be utilized in a sustainable way to the benefits of remote communities. "Off-grid" communities will particularly benefit from a reliable electricity supply of small
easy-to-operate binary plants. The Kalina technology has a potential to improve efficiency of power production from the GAB groundwater.

The cost of electricity generated from local geothermal resources is not expected to be high compared to the costs of other types of electricity including fossil-fuel and power-grid electricity. Reduction of greenhouse gas emission will be an added benefit of geothermal developments in the
Great Artesian Basin.

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