Energy
Geothermal plants could have a seismic impact on energy demand-literally.
As the gradual shift from fossil fuels to renewables gets further under way, a number of researchers are beginning to look more closely at the promise of geothermal energy. While the geothermal process is not completely emission-free, the amount of greenhouse gases released is far less than that from conventional fossil fuels. Like wind and solar, heat from the earth is safer and cleaner than fossil fuels and provides an inexhaustible source of energy.
Currently, most geothermal energy comes from around 200 meters deep, at temperatures of less than 10�C-which is actually not very hot when compared with the temperatures just a little further down.
It is estimated that 99% of the earth has a temperature of more than 1,000�C. According to researchers at the Norwegian-based organization SINTEF, harnessing just a tiny fraction of this heat could theoretically provide enough energy for the entire world population.
Several Norwegian companies and organizations- including SINTEF, which has experience with petroleum exploration- are planning an ambitious pilot project that would harness the geothermal energy from 5,500 meters deep in the earth-about the same depth as some of the more recent onshore oil wells. According to researchers, the energy is there-all that is needed is a truly safe, effective means to tap into it.
Current wisdom favors binary cycle geothermal power plants. This type of plant features two deep, interconnected wells that operate in a cyclical fashion. Cold water is pumped down an injection well and heated by the underground rock (to around 95�C at that depth), then pumped back up via a production well, giving off steam, driving turbines, and generating electricity.
After around three decades, this process will have cooled the bedrock to the point where it is no longer hot enough to be productive, not unlike a tapped oil field run dry. The wells would be sealed off and the power plant shut down.
Then, three decades later, the temperature will have risen again, and it will be time to unseal the wells and begin the process anew, after upgrading the plant. This "ace in the hole" helps make geothermal power plants more cost-effective than oil rigs, researchers argue.
The Norwegian coalition is planning to go two or even three times deeper if the pilot plant is successful. That would require new technologies, however, and greatly increases the likelihood of incurring very serious risks. Most severely, fracturing or eroding the crust's bedrock in order to recover its heat could trigger earthquakes in the region. This notably occurred in Basel, Switzerland, in 2006, when Geothermal Explorers Limited's field operations set off a series of quakes.
At such high temperatures in the earth's crust, the rock is liquefied, so anything else there runs the risk of being liquefied or broken. Electronic equipment shorts out very quickly at temperatures over 200�C. New technologies are needed in order to meet those challenges.
ExxonMobil and other oil companies are beginning to drill exploration wells at 10,000 meters, depths once believed to be too risky. Geothermal researchers now hope to adapt these oil drilling technologies, perhaps working in tandem with oil companies, and make them safer and more affordable for clean, renewable energy.
"Geothermal energy is a unique opportunity for the oil industry to develop in a new way," says Are Lund, senior researcher at SINTEF Materials and Chemistry. "They will come to realize this, it's just a matter of time." -Aaron M. Cohen
Source: SINTEF, www.sintef.no.
Author: Cohen, Aaron M
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