...Is this the future of energy?
The world is constantly under pressure to find and implement a reliable, sustainable and cheap way of generating electrical power. While there are many viable options, most people on the street would not be able to tell you what geothermal energy is in a broad sense, much less go into a discussion about geothermal power advantages and disadvantages. It's a shame really, because we all should be aware and able to contribute to the important discussions going on around sustainable and responsible power generation.
What is geothermal power?
Geothermal power is basically a way of generating electrical energy using the heat of the planet. To do so it is necessary to build a geothermal energy plant in an area with volcanic activity, and there are plants in countries such as New Zealand and Iceland for that reason. A discussion of geothermal energy advantages and disadvatages must necessarily begin with the contruction and method of operation of these power plants though - as they have a palpable impact in the earth. The financial ost must also be considered as we are asked more and more- "is geothermal energy expensive?"
In a geothermal plant electrical power is generated by using purified steam to turn turbines, using the same concept as wind turbines to generate electrical energy. To turn the turbines there must be a regular and predictable method of harnessing steam. Geothermal enegy plants drill into the surface of the earth to a depth where the rock is super heated. Once drilled, those wells become injection points where cold water is pumped down to meet with the hot rock which results in the generation of steam. In some areas there is sufficient groundwater to avoid the need for cold water injection - relying instead on existing resources in the earth.
This steam rises to the geothermal energy plant and goes through a process of purification before being vented to one of a number of turbines. As these turbines turn, electrical power begins to be generated. The steam must be purified in order to be used without damaging the plant - it's just part of the process.
See below a CalTech video on how geothermal energy is transformed to electrical energy. The technical aspects of the example shown in the video are not applicable in all geothermal plants though - some use the groundwater found under the surface and above the magma, and others do not. The video is however a good indication of how geothermal energy works in a practical sense.
Note the representation of the geothermal power plant sitting at a location where a vent is able to be drilled down to the groundwater level. The necessity of locating the plant in an area where the required hot layer of rock is reasonably close to the surface is not discussed in the video either - nor are general points about geothermal energy advantages and disadvantages, but we'll get to that after the video describing the process of harnessing geothermal energy and turning it into electrical energy.
Advatages of geothermal energy
One of the main advantages of geothermal energy has to be that it is a sustainable and non polluting way of generating electrical power. Unlike your more traditional methods of generating electrical energy, geothermal technology does not involve the burning off of fossil fuels, which results in polluton. The small size of the geothermal plant makes the placement and design of the plant quite simple also.
Due to its small size and the fact that there is zero pollution emitted from the plant, there is no need to isolate the geothermal plant from neighboring communities or population centres. In regards to safety, geothermal power plants have been in constant use for a good while now, in various countries around the world and there have been no major accidents or incidents. This is in stark contrast to another method of generating electrical power - nuclear power plants - which are also often claimed to be non polluting and safe (Fukushima, Three Mile Island, Chernobyl anyone?).
Disadvantages of geothermal energy
One of the major disadvantages of geothermal energy as a method of generating electrical power is the real limitation in terms of plant placement. The plant must be built in an area which has reasonably significant volvanic activity resulting in magma being located reasonably close to the earth's surface. This does not occur all around the world, so geothermal energy cannot be seen as a one size fits all solution to the world's energy problems.
The permanent impact on the earth in terms of drilling holes down to very deep levels within the earth's crust does not really smack of pure sustainability to me. Really, the practice leaves open wounds on the earth and detractors of the use of the technology liken it to parasitic behaviour.
Any implementation of geothermal energy should only be conducted with a careful and considered review of the geothermal energy advantages and disadvantages. These may not all be the same in different areas of the world, and it should be up to locals to solve their local energy usage needs and fill the requirements in the way that is best for their local area and for their local community. While geothermal energy is a good option to be considered, it will not always be the best.