Geothermal power’s potential as an alternative energy source is becoming ever clearer. Global geothermal investment last year rose 83%, to 1.7 billion dollars, and some 80% of high-grade geothermal resources are believed to remain undiscovered. The technology received plenty of news coverage in the summer with the announcement that Google’s charitable arm was planning 11 billion dollars of investment into so-called enhanced geothermal systems (EGS).
Traditional geothermal energy requires engineers to drill near a hot spring, volcano or geyser, and inserting a valve and turbine on top of the hot water. This requires the power station to be sited in an area where the earth’s heat comes close to the surface.
EGS, on the other hand, involves drilling deep into hot rock, with cold water being injected into the cracks created. The water heats up and rises under its own pressure, running turbines and generating electricity. This allows engineers to produce geothermal power across a much wider area of the globe, taking advantage of geothermal power’s other advantages:
- It is an extremely clean way of generating electricity, and does not need the ‘dirty’ gas turbine back-up or large storage systems that other alternative energy sources, such as wind and solar, require.
- Unlike all other renewable sources, but like fossil fuels and nuclear power, it would be able -- over time -- to deliver close to installed capacity, which would reduce costs.
In spite of its enormous potential, obstacles remain to the exploitation of EGS:
- Costs of the technology are currently high per unit generated. While the cost per kilowatt hour could eventually fall to 0.04 dollars, which would compare favourably with solar at 0.31 dollars and gas at 0.08 dollars, costs at the start are estimated at 0.09 dollars. Indeed, Australian company Geodynamics, carrying out the first major commercial test of EGS, estimates that its first 50-megawatt (MW) power station will cost a substantial 250 million dollars.
- Meanwhile, EGS companies would have to compete with their much wealthier oil and gas counterparts for drilling rigs, in short supply in the current energy environment.
- Maps of geothermal potential have not been updated since the 1970s, even though the discovery of over 1 million new oil and gas wells means that a wealth of more recent data is available.
A boom in geothermal -- and particularly EGS -- research is likely in the coming years. In addition to Geodynamics’ work in Australia, there is another major test in France, and a first US test is to take place in Nevada this year. A recent Massachusetts Institute of Technology study showed that EGS could provide a further 100,000 MW of generating capacity in the United States by 2050. Nonetheless, as none of its tests have so far been completed, and since much of the technology it requires is at an early stage of development, EGS risks being oversold as a “magic bullet” of alternative energy.