The Old Faithful, a hot water geyser, while visiting the Yellow Stone National Park, with its timely bursts may have surprised you. Among other countries which boasts of hot water springs and geyser is New Zealand. It's hot springs of Waiwera are famous and the water, here, is so hot that you can cook your food in it. Where does this ground water draws heat from and can the source be put to use in our homes? The water in these springs and geysers is heated by the geothermal energy. Yes, it can be used in homes, however, obtaining this energy, also means dealing, first, with its disadvantages.
There are many critics who point out that the limitations of geothermal energy outweigh its advantages. The geothermal energy which is entrapped in the Earth's crust, is a free source of renewable energy. At the core of the Earth, the superheated fluids exist under tremendous pressure. In certain parts of the world, especially, in areas where volcanoes are present and the fault areas, where continents rub shoulders with each other, we can gain access to this energy. We can do this, by boring a well into the earth, and by pumping water in it. The heat present at this level is absorbed by the water which rises back to the surface. The temperature of this water can go as high as hundreds of degrees Celsius and on reaching Earth's surface it may take the form of steam. This steam is used to drive turbines in a power plant to produce electricity for us to use.
Cons of Geothermal Energy
If geothermal energy is free, you may think, why there is so much of arguing about its disadvantages. Why everyone is not hurrying to grab the land, bore a well and start producing and selling electricity. Or, is there some truth in the arguments?
Location
First of all, drilling a deep hole into the earth, is a hard task. To make this project economically viable, an ideal site must provide sufficiently hot rocks at the reachable levels in the Earth's crust. Next, it must be easy enough to bore the well to the hot rocks. This can be achieved, only if the layers of rocks sitting above the hot rocks are soft enough to drill through. The use of geothermal energy is hampered because of the low number of suitable sites to drill a well. Critics say that such a project, if it is realized, can only be useful to provide heat and electricity to the local area only. In this case, remoteness of the site negates its usefulness as the loss of energy during transportation will be high.
Lifespan of the Project
As the sites, where you can obtain easy access to the hot rocks, are located in areas of volcanoes, investors are not willing to invest. The sites in the fault areas where an earthquake can happen any time, are also not attracting investment. Even after building a power station to use this type of energy, there is no guarantee of steam production coming up to the required mark, which can make the project economically difficult to sustain. The movements of the layers of rocks or the Earth crust can easily damage the well, disturb the production of steam and result in the closure of the electricity plant and financial losses. Uncertainty over the lifespan of the project is big enough an issue for the investors to count it as the biggest disadvantage.
Hazardous Gases
Geothermal energy cannot be put to use without first dealing with hazards associated with it. Important among the disadvantages is the issue of hazardous gases, like hydrogen sulfide coming up with the hot water to the surface of the Earth. Materials like arsenic, boron, antimony, mercury, ammonia, which are known health hazards can also come up to the surface with the hot water. These materials, which are known to cause environmental pollution as the water cools, are not easy to get rid of.
Geological Changes
Earthquake
To prolong the life of the heat source the practice of injecting the hot water, after it has been used, back into the earth is followed. This also take care of the harmful elements. However, the process uses pressurized water which can lead to hydraulic fracturing which can trigger earthquakes. Basel in Switzerland, experienced upward of 10,000 sesmic incidences measuring up to 3.4 on the Richter Scale within 6 days after a plant located nearby, started water injection program.
Land Subsidence
If the plant uses wet steam from the field, as is the case with Wairakei Power Station from Taupo volcanic zone, New Zealand, it has more chances of affecting the local environment. The retrieval of steam affects the water table/water pressure within the ground, leading to changes in the volume of the steam created, its flow and distribution. This can cause creation of new steam vents that are constantly shifting, collapsing and reforming as can be observed in Craters of the Moon thermal area. It may also cause land subsidence, a process in which retrieval of material from the underground leaves a hallow behind, causing the land to shift downward to fill it.
Lifting up of Land
An attempt to use this form of energy to heat the city hall in Staufen im Breisgau, in Germany lead to a bizzarre situation. The drilling operation conducted in 2007, penetrated an anhydrite layer containing anhydrous calcium sulfate. When pressurized hot water mixed with the layer it caused anhydrite swelling, a process which converted anhydrous calcium sulfate into gypsum (hydrous calcium sulfate). The gypsum stores water in its crystalline structure which lead to expansion of the layer and lifting up of the land. Now some of the sections of city had risen by 30 centimeter and the city hall along with the other structures in the vicinity, has cracks in its structure.
I have not covered the advantages in this article, but as you can see, the disadvantages look intimidating enough. It is granted that using this form of energy for producing electricity is cleaner than using fossil fuels which contribute to global warming by producing greenhouse gases. Until and unless, we can come up with a new technology that can negate the disadvantages discussed above, use of geothermal energy as a dependable source is going to be sporadic.
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