Geothermal energy facts

You’ve probably heard a mention of the term geothermal energy in recent times with all the talk of renewable energy sources and alternative ways of generating power due to dwindling fossil fuel reserves, but most people still lack the knowledge about this often overlooked source of power. Can it be a replacement for fossil fuels like coal, or is it simply wishful thinking? Let’s first take a basic look at how geothermal energy works, as well as its advantages and disadvantages.

Geothermal energy is a renewable energy source, the basis of which lies in using the heat being produced under the Earth’s surface, as well as hot water reserves. This allows for a two-fold use: the heat/hot water can be used to turn water to steam, which in turn spins turbines and produces electricity, or it can be used to heat/cool buildings. The creation of electricity is achieved through 3 different methods, the use of each depending on the particular nature of underground heat sources in a given area.

Large Scale (Electricity)

The first method (Dry Steam Power) makes use of a “dry steam” reservoir, an underground collection of water vapor which holds a lot of steam but not much water. This steam is piped up into the power plant and spins turbines which produce electricity. The largest example of such use is “The Geysers”, a large complex of geothermal power plants located close to San Francisco. Together, these plants produce enough power to supply a large metropolitan city, such as San Francisco itself.

The second method (Flash Steam Power)makes use of an underground hot water reservoir, which is mostly hot water rather than steam. This water, usually ranging from 150 °C to 370 °C, is pumped up to the surface through a production well, where it turns into steam due to being released from its deep pressure reservoir (as the boiling point of water is greatly increased due to the pressure underground) and powers turbines, much like the first method.

The third and method of producing electricity with geothermal energy (Binary-Cycle Power) is the use of a much cooler water reservoir (120 °C to 180 °C). Since this water temperature is not enough to produce steam the water is pumped and transferred to a “heat exchanger”, where it is used to heat up a secondary liquid (therefore the term “binary”), such as isopentane, which boils at a lower temperature than water (in the example of isopentane, the boiling point is 28°C). The steam produced from this liquid then turns turbines much like the previous methods, except for the fact that the vapor of the liquid is later recondensed to be reused, and therefore produces no emissions into the atmosphere.

Small Scale (heating/cooling)

In terms of cooling and heating, geothermal energy can also be used on a small scale with homes and small buildings. Much like the large scale collection of geothermal energy, pipes are sent down into the ground, but not to a very deep level as in the case of geothermic power plants. However, instead of pumping water or stream, these pipes send down their own liquid (usually anti-freeze) which is heated and then sent back up into the foundation of the building. This is only possible in the winter, as the ground holds heat much better than air or water, and as such is able to heat the house rather than cool it. In the summer, respectively, the air is hotter than the ground, and therefore the liquid that is sent underground is cooled rather than heated and cools the building.

Geothermal energy seems like a simple enough transfer of heat from the body of the Earth up to the surface, but can it be used on a global scale as a major power source? We can now take a look at some advantages and disadvantages of using geothermal energy, in order to figure out whether it has the potential to help solve the looming energy crisis.

Geothermal energy has a lot of substantial advantages. Most importantly, from an environmental point of view geothermal energy is one of the safest and cleanest ways to produce energy. Unlike other sources of energy, such as coal and natural gas, it does not, for example, generate any noteworthy greenhouse gases or pollution smokes which have a variety of negative impacts on the environment. While there is a possibility of releasing some harmful gases from underground, the amount of these gases is a minuscule fraction of the amount released by burning fossil fuels. Even a hydroelectric (the use of water movement to produce electricity) power plant, which produces seemingly clean energy, has a huge impact on the river which it dams. Furthermore, geothermal power plants take up very little space in comparison to other types of power plants, simply because they do not require things such as dams, mine shafts, tunnels or open pits.

Another advantage is the fact that geothermal power plants run 24/7 without any stops, because the fuel source is unaffected by outside factors such as weather, and is both renewable and sustainable. This also goes along with the fact that the energy is practically free, and perhaps the only budget spent on the plant is required to keep the pumps working and for maintenance. Furthermore, geothermal energy presents a source of fuel which does not experience any price fluctuations, and does not need to be imported, as for example oil or natural gas, which grow more expensive every day. Lastly, geothermal power cost is comparable to that of fossil fuels, with an average $0.03 to $0.035 per kWh (kilowatt hour), compared to natural gas going at an average of $0.03. While from this standpoint geothermal energy seems like the best choice in today’s world, it is unfortunately hindered by a number of major disadvantages.

By far the biggest disadvantage of geothermal energy is the inability to build a plant in most places around the world. A geothermal plant requires a type of rock underneath which not only can be easily drilled through, but is also standing on a stable foundation, and has vast enough steam/hot water reserves, as well as the availability of said water and steam at a small enough depth (usually about a kilometer). Due to this restriction the majority of the geothermal power plants currently operating around the world are located around areas of tectonic activity, (areas where plates of the Earth’s crust collide). Smaller disadvantages include the possibility of running out of steam or water and the risk of hazardous gases and minerals coming up from underground. Furthermore, geothermal power plants are very cost-heavy during construction and take some time to recover the costs of the original drilling and pipeline construction, while fossil fuel power pants recover costs quite fast.

Conclusion

In sum, we can conclude with these facts that geothermal energy provides tremendous advantages over other fossil fuels, but is too restricted by its locational disadvantage. In fact, much due to these restrictions, geothermal energy accounts for only about 0.3% of total power production in the world today.

It is nonetheless important to note its importance in the future as fossil fuels increase in price and come close to being exhausted and a new major power source will have to take their place, in order to fill the gap of the 85% of worldwide energy consumption being produced by fossil fuel combustion. While geothermal power is still largely restricted by location, advances are being made that are slowly but surely making it possible to build geothermal power plants in more places. The potential is definitely there, we just need to take the time and money to use geothermal power most efficiently and on a much bigger scale to help solve the impending energy crisis.