Unlike the other sources of green energy which needs to be harnessed, geothermal energy is naturally occuring in the earth. Its history started in the Palaeolithic times with hot springs which were used for bathing. The heat from these springs were used as public baths which also serve as space heaters in the first century AD. The dues required by the Romans for the baths were the first commercial use for the geothermal energy. This is just a glimpse of the past related to it. There are other interesting facts about it, including an in depth look into the geothermal source as well as the pros and cons of this green energy.
Geothermal energy is naturally found stored in the earth and its primary source is the molten rock or magma which is located under the earth’s crust. The heat is produced from the radioactive decay of minerals such as uranium and potassium. Since the heat is coming from earth itself, the amount of it within a ten thousand meter-range of the earth’s surface have 50,000 times more energy compared to all the available fossil fuel and natural gas put together. And when it comes to the part of the earth’s surface which has the highest temperatures underground, these are in areas where there are active volcanoes.
The areas where the active volcanoes are found are called “hot spots”. Such hot spots are normally found in areas where the crust of the earth is very thin that it allows the heat to pass through. They are also found in tectonic plate boundaries. An example of an area on the earth where hot spots are abundant is in the Pacific Rim. Because many volcanoes are found here, it was given the title of The Ring of Fire. There are also hot spots located on tectonic plate boundaries which are seismically active. When earthquakes happen, the thin rock crust covering is broken and allows the water to mix. Hot springs and geysers occur when the water which is circulated reaches the earth’s surface.
Since geothermal power is naturally occurring it is found to be environment friendly and sustainable. These factors make it a good source of green energy. With the help of Enhanced Geothermal Systems, the energy present in the earth is converted into electricity that will be utilized by households and businesses. In transforming geothermal energy to electricity, there is a need for a well-built facility which is governed by technological advances. There are three types of power station plants for geothermal energy.
- Dry Steam Power Plant- the oldest and has the most simple of all the designs. It uses more than 150 degrees Celsius of geothermal steam that turns turbines. It uses direct steam that comes from the earth’s grounds.
- Flash Steam Power Plant- It is the most common type of geothermal power plant we have today. It uses a blast of steam to turn turbines. In order to get the flash of steam needed, high pressured hot water is pumped to the surface. The fluid temperature starts from 180 degrees Celsius.
- Binary Cycle Power Plant- It is a geothermal power plant which is the most recent development in terms of taking advantage the energy to be converted to geothermal electricity. It uses fluid temperatures which is as low as 57 degrees Celsius. Instead of using the water to turn turbines, it uses vapor from a secondary fluid which has a lower boiling point than that of water. The water pumped from the geothermal well is passed through the secondary fluid which produces vapor.
Although there are three types of geothermal power plants, it goes through the same steps of getting water and steam from the ground source, use it to turn turbines and put it back warmed. The warm water is returned to the geothermal well in order to extend the life of the spring. Geothermal sources are limited which is why it is used with care. The same reason of scarcity of geothermal areas is considered in choosing the right design of power plant to be used.
Aside from electricity, geothermal energy has other direct uses. Geothermal resources differ in temperatures for it is located in different areas. Low temperature resources can be used for district heating, a system that promotes heat generation in a centralized facility to be used for residential and commercial purposes. It can also be used for greenhouses to regulate the temperature inside in order to protect the plants. Geothermal energy is also used to heat fisheries and even remove ice on roads.
The geothermal energy itself does not require fuel, except for the pumps that get water for steam. In relation to this, it is not directly affected by the unstable oil prices and costs. However, it is not immune to high costs during the start of the power plant building. It includes drilling and exploration that may be costly. On the other hand, direct applications do not need so much money for it can use the available geothermal energy without spending too much.
It has also been said that the whole process of plant construction have an opposing impact. It can lead to earthquakes because of hydraulic fracturing. Hydraulic fracturing is the procedure where there is proliferation of a crack in the rock layer of the earth with the use of fluid pressure. In fact, many geothermal power plant projects have been shut down because there had been many seismic events as a result of the building.
And although geothermal energy is sustainable, many question the emissions it produces. Since the heat is caused by the radioactive decay happening beneath the crust of the earth, the water that is being pumped out carry little amounts of ammonia, carbon dioxide, methane and hydrogen sulphide. It is a very small amount of greenhouse gases released compared to power plants using fossil fuel. While this is true, geothermal power plants have emission control systems in order to reduce the environmental impact.
Another concern that is being raised is the presence of toxic substances that precipitate during the cooling of the water. Some of these chemicals are antimony, arsenic, mercury and boron. These chemicals are known to cause harm to the environment when released. This is why the injecting back of the used geothermal water offers an advantage not only to the environment but also to the main source of the energy. This step prevents the leaking of the toxic chemicals into the surroundings.
The amount of heat which is extracted by plants and people who use it directly is just a small amount compared to the available geothermal energy present in the earth. This is why geothermal energy is considered to be sustainable. The internal heat content alone of the earth is measured to be 10 to the 31st power joules. However, the availability of heat does not mean that people can go on extraction whenever they want to. Just like the other sources of green energy, it is important to regulate such extractions to prevent exhaustion of the available natural resource.
The pros and cons are always present in the duration of the whole geothermal energy harnessing process. Most of the drawbacks were compensated by the benefits and the convenience of reversing such disadvantages. Mother Nature is truly generous for giving us what we need and in this case the heat that can be transformed into electricity, comes from the earth itself. Geothermal power is a different source of green energy but it is just like the other sources which make lives better.