Senator Annette Hurley has an interesting speech on geothermal energy [pdf] in South Australia. She argues that a responsible greenhouse gas policy will lead to new industries and jobs, an opinion which has been discussed on this site in the past, and that South Australian leadership in geothermal energy investment is one such example.

From the speech;

I would like to explain a little bit about what geothermal energy is, because often people bandy around these terms, and I do not necessarily think it is well understood. Geothermal energy is not new. It has been known about since the early 1900s. It is currently used in over 20 countries, where it is mostly based on heat sources that use water reservoirs--for example, in New Zealand and in Queensland, where there is currently an energy source that uses water reservoirs. But the area that is opening up in Australia and the area I want to talk about is the use of hot fractured rocks. These are rocks deep in the earth that maintain a high level of heat but that are overlain with insulating rocks which trap the heat.

The process that can be used relies on very well-known processes in the mining industry to produce energy from that heat. The process is that water is circulated through the hot rocks up to the surface and that the heat is captured by a heat exchanger using groundwater cooling. Once the heat passes through the heat exchanger, it is transferred into another closed cycle system that has an ammonia-water working fluid which has a lower boiling point than water. It is this system that generates the vapour to spin turbines to create power generation. The beauty of it--especially in South Australia, which has few water resources--is that the water used in the process is continually under pressure and never turns to steam. This means that the water in the system is continually recycled.

Interesting technology to harness the natural rhythms of the earth but as Hurley notes it is currently not economically competitive with coal as it costs about $50 AUD per megawatt hour. Another issue is the costs of transmission are high as many of the geothermal locations are far from the high density population centres.

This is the same issue that water faces, many of our largest cities are not in water rich areas. There was a time when cities were founded on rich arable land when agriculture was the dominant economic form. Australia as a post industrial country, sort of skipped those steps, since it used industrial technology to bring water and energy to where people were, not the other other way round. Consequently our cities are reliant upon the fossil fuel era of heavily centralised infrastructure to bring water and energy to us.

This is not unique to Australia; Phoenix, Arizona would not exist without such a system of support, just as the resort at the Uluru is not viable without industrial era technologies and cheap energy.

There would have to be great energy pressures to have populations move in this day and age to where the energy and water is; pressure such as complete collapse. Which I doubt will happen. Then again some smart companies got me to pay $4 USD for a CLF light bulb when a normal one is under a dollar. And last night we lined up a landscape designer friend of ours to buy rain barrels for us - when our spouts and town tap water work perfectly well. It is question of maximising efficiency and resources within economic bounds.

It may be that geothermal energy producers will get the cost down enough to be able to market it to me that I will pay more for it as an energy supplier - in part or as a full energy solution.

Hurley finishes the speech with:

Recently the 2006 annual report of the Australian Geothermal Implementing Agreement was released. That is a group consisting of most of the companies involved in this process looking at how they go forward. I am certainly hopeful that they get strong support from the government and that next time around we have a Labor government in place that is willing to look seriously at a carbon pricing regime and how companies in this form of energy, where carbon emissions are very low, will be properly supported and encouraged by the federal government.

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