Yesterday I talked about some background and the basics of geothermal energy. Today, it’s time to talk about the pros and cons.
Geothermal power plants do not burn fuel to generate electricity, so their emission levels are very low. They release less than 1% of the carbon dioxide emissions of a fossil fuel plant. They don’t have radioactive or ash wastes, particulates or other combustion byproduct, so there is no waste management involved or needed. Geothermal plants use scrubber systems to clean the air of hydrogen sulfide that is naturally found in the steam and hot water.
A few sites do produce some silica and sulfur dioxide, both of which are largely removed from the vapors and either returned to the hydrothermal well or processed and sold for industrial uses.
Almost 100% of the visible, airborne effluent seen rising from geothermal plants is water vapor.
Geothermal plants don’t have to transport fuel, like most power plants. Geothermal plants sit on top of their fuel source. Geothermal power plants have been built in deserts, in the middle of crops, and in mountain forests.
Geothermal plants emit 97% less acid rain-causing sulfur compounds than are emitted by fossil fuel plants. After the steam and water from a geothermal reservoir have been used, they are injected back into the Earth.
Geothermal reservoirs come from natural resources that are naturally replenished. Geothermal energy is therefore a renewable and reliable energy source. There are little to no fluctuations in the flow of energy. Geothermal power plants have a high capacity factor, so geothermal is an excellent candidate for supplying the base load energy.
Beneath our feet we have more usable geothermal energy resources than oil, coal, gas, and mineable nuclear fuels combined.
Geothermal Resource Council Data shown below compares global continental (not including deep ocean resources) geothermal energy resources to global oil reserves.
Units: Billions of barrels of oil equivalent
*Annual Global Energy Consumption—-70
*A Stanford University Wind Power Studyshows total annual global Btu consumption from all sources of about 50 to 70 billion barrels of oil equivalent.
Thermal aquifers are the primary source of geothermal electrical power using current technology. Those 130 billion barrels of oil equivalent masks the fact that geothermal resources are a form of nuclear power and can continue to provide those energy supplies year after year, decade after decade, century after century.
Once in operation, geothermal plants may be the most reliable of all energy production methods. Every plant that was built in the last 100 years ago is still running. Since they are fundamentally simpler than most other power systems, there is less to go wrong.
This article also says that scientists believe our geothermal resources will outlast the Sun. How they decided that and why it matters, I don’t know. Everything living depends on the sun, so geothermal energy will not help us on that point.
Geothermal energy has the smallest land use of any major power generation technology. A typical geothermal facility occupies about the same space as a gas fired plant of the same capacity. But the geothermal facility does not require miles of buried pipeline to carry fuel to keep it running.
The burning of this electricity doesn’t create pollution, but the collection part of it seems to create some problems. There is an abundance of greenhouse gases below the surface of the Earth, which may mitigate towards the surface and be released into the atmosphere. There can also be traces of heavy metals such as mercury, arsenic and boron. If waste is released into rivers or lakes instead of being injected into the geothermal field, these pollutants can damage aquatic life and make the water unsafe for drinking or irrigation. http://www.teara.govt.nz/en/geothermal-energy/5
Construction of geothermal power plants can affect the stability of the land. In fact, both in Germany and New Zealand, geothermal power plants have led to earthquakes. In January 1997, the construction of a geothermal power plant in Switzerland triggered an earthquake with a magnitude of 3.4 on the Richter scale. I read a comment on an article about this that said the reason that these plants are causing earthquakes is because the supply of energy isn’t replenished as quickly as it’s being collected. To back that up I found Earthquakes typically occur around unstable areas such as volcanoes, fault lines and geothermal regions. So, any area ripe for enhanced geothermal tinkering is already prone to get the shakes. On top of that, pumping water down to subteranian regions of heated bedrock causes the rock to expand and contract, fracturing the rock. As such, seismic activity isn’t just a side effect of the process, it’s a part of the process. The deeper the shaft, the greater the chance that increased levels of seismic activity could reach nearby fault lines, generating an even more powerful earthquake. http://science.howstuffworks.com/environmental/earth/geophysics/geothermal-energy-cause-earthquakes1.htm I also found that at the rate of current removal of power for production, they typically remove heat from natural reservoirs at over 10 times their rate of replenishment. This imbalance may be partially improved by injecting waste fluids back into the geothermal system, but they never say that this causes earthquakes.
Earthquakes can be triggered due to hydraulic fracturing, which is an important aspect of constructing enhanced geothermal system (EGS) power plants.
Also, I think places like Yellowstone with geothermal type features would be destroyed by the drilling. When the Wairākei geothermal field was tapped for power generation in 1958, the withdrawal of hot fluids from the underground reservoir began to cause long-term changes to the famous Geyser Valley, the nearby Waiora Valley, and the mighty Karapiti blowhole. The ground sagged 3 meters in some places, and hot springs and geysers began to decline and die as the supply of steaming water from below was depleted.
A commercial geothermal power project is expensive. Exploration and drilling for new resources carries a steep price tag. The costs usually end up somewhere around $2-7 million for a capacity of 1 MW. This is included drilling, which is accountable for over half of the expenses. The big key to universal use of geothermal resources is the development of deep, hot dry rock resources. The key to that is drilling technology. Due to the hot, often corrosive, environment of geothermal resource areas, drilling for geothermal resources is far more expensive than any other kind of drilling. Drilling technology is improving. Drilling costs, on average, have dropped by a fourth in the last two decades. As drilling technology improves, geothermal power plants could become universally available.
According to some sites, geothermal power costs are currently competitive with coal power plants, making them among the cheapest power providers around and getting cheaper with every project, but current cost figures are based on projects that are located at the best geothermal sites. The key to economically exploiting geothermal resources using current technologies is finding the best producing hydrothermal wells.
Initial cost of residential geothermal heating and cooling systems are also expensive and for individual homes it often more expensive than solar power. To be both usable and economical a site must have an adequate volume of hot water or steam that is not too impure to use, a surface water source to cool generating equipment, and close proximity to power transmission lines. So, even in promising areas, economically usable sites are few and they are difficult to locate. The U.S. Geological Survey Circular 790 estimates a hydrothermal resource base in the U.S. of between 95,000 and 150,000 MW (Megawatts), of which 25,000 MW are known resources.
While that is a significant amount, it’s roughly one fourth of our current electrical need, less if we start plugging our cars into the electric grid. And most of that geothermal resource is way out west. That’s good for the West Coast, Hawaii, and the few people who live in Alaska, but it falls far short of being able to serve our Nation or the world.
For those it’s available to, it can save them money years down the line, and should be looked upon as long-term investments.
Geothermal power plants have less aesthetics problems than other power plants.
Since they occupy the smallest space per kilowatt generated, it follows that they have the least visual impact of any power generation technology available.
If river water is used as a cooling medium, the entire power plant could be built underground or within structures already built for other uses.