Why Geothermal, Why Now?
Humans have been using geothermal energy since Paleolithic times, and harnessing this energy for electricity has existed since the 1900s. Still, even though the technology is old, it is only recently that we are turning again to geothermal. Currently, geothermal energy supplies 0.3% of global electricity demand with output growing 3% annually. An extra 28 GW of geothermal heating is used for space heating, spa heating, desalination and more. [Source: Wikipedia].
One of the major benefits of geothermal is its reliability. Unlike solar and wind, geothermal energy does not rely on variable sources of energy as the energy comes from the formation of the earth, radioactive decay of minerals and solar energy absorbed from the surface. Geothermal has an average capacity factor (how often the power plant runs) of about 73% [Source: IEA Geothermal Energy] though some have been recorded as high as 98%. Compare that to 20-40% for wind farms, around 19% for solar [Source: Treehugger] and coal running at 65-75% [Source: REPP], and it becomes clear to see why more countries are investing in geothermal.
It’s not just the capacity factor that makes geothermal very attractive, but the fact that this energy source alone could potentially power the entire world. The heat from the core to surface flows via conduction at a rate of 44.2 terrawatts (TW) [Source: AGU], though not all of the energy is recoverable. Technological advances have allowed countries to utilize areas that might not have been possible. Generally, geothermal plants require sites to have a reservoir of water/steam and porous rocks. With the creation of the enhanced geothermal system (EGS), however, many of these issues have been resolved. The EGS pumps high pressure cold water through fissures in non-porous bedrock (generally granite). The injection increases the fluid pressure in these fractures which then creates a shearing event to increase fractures in the rocks. The cold water travels through the fissures and absorbs the heat from the rocks. Eventually they exit as hot water and produces electricity [Source: US Department of Energy]. An MIT report stated that with the EGS, currently 200 zettajoules (ZJ) were extractable, though with technological advances 2,000 ZJ could be possible, enough to power the world for several millenia. Unfortunately, the EGS has been reported in 2008 as causing earthquakes. Markus Haring was injecting high pressure water into rock fissures and caused some 30 earthquakes in Basel, Switzerland. While the EGS is bound to cause some seismic activity, the key is to find the proper balance between the amount and speed at which the fluid is pumped [Source: Popular Science].
Many countries have begun to recognize the power of geothermal and are incorporating it into their power grid. Iceland is the most famous example, but Indonesia has recently hosted the largest geothermal forum in the world (Australia will host the next one in 2015) and also set some ambitious plans on harnessing the power of volcanoes in the pacific “Ring of Fire”. Unfortunately, startup costs for these power plants are very expensive and can take much longer to build than coal plants. Luckily, countries like Iceland and Japan are investing heavily in overseas building. Japan has invested $100 million USD in Indonesia [Source: Think Geo Energy] and $320 million USD to Kenya [Source: Venture Beats]. Corporations like Mitsubishi and Reykjavik Energy are packaging geothermal products to underdeveloped countries. The package includes: “funding, digging, construction and provision of operational know-how” [Source: Google AFP].
Other countries are implementing geothermal powers locally. The US has seen a growth of 26% new geothermal projects around the country thanks to the $787 billion federal stimulus. California and Nevada make up for 2,927 megawatts online of geothermal [Source: New York Times]. No surpise since the largest factory is located in California. Japan is also investing locally and has built their first geothermal plant in nearly twenty years though it won’t be in operation until 2016. The new project will aim to generate up to 60,000 kW of power [Source: Telegraph]. While many countries are taking strides in incorporating geothermal, there are only five countries that generate more than 15% of their electricity from geothermal sources: Iceland, Kenya, Costa Rica, El Salvador and the Philippines [Source: IEA Geothermal Energy]. Many countries, even Japan, are hesistant to incorporate geothermal for fear of depleting the resource. While geothermal is practically inexhaustible there have been reports of local depletion, though it will recover after a century. The modern practice of reinjecting spent geothermal fluids back into the earth and monitoring extraction, can be sustainably long-term as evidenced at Lardello fields in Italy and Wairaiki Fields in New Zealand [Source: Wikipedia].
As technology advances, the process of creating geothermal energy will become safer and more efficient. While the initial cost may be higher, the rate for electricity itself will decrease as will the environmental damage. Geothermal energy has been in practice for over a century and while we have yet to reach its full potential, we’ve finally begun to see the pressing issue of obtaining renewable and reliable sources of energy.