How geothermal energy works
Posted on November 10th 2009
Geothermal energy is the process of utilizing the Earth’s own natural heat in order to create electricity. Geothermal itself is made up of two key root words to describe the energy source — “geo-” for “Earth” and “thermal” for “heat”. In order to fully understand how geothermal energy works, is important to consider two primary aspects:
1. The primary natural heat production source, and
2. How to harness the energy produced by the geothermal source into useful electricity.
Understanding the heat resource used to generate geothermal power is the basic foundation of geothermal energy. Geothermal energy by the very nature of the term utilizes the very earth’s heat in order to create a power source to draw upon for power production needs. To do this an adequate spot on the Earth needs to be located in order to generate enough heat to produce a stable strong output for application of various power production methods. These spots are typically located near fault lines or young volcanoes were the Earth’s crust is thin enough to allow internal heat to escape and be accessed by as little drilling is possible.
The effects of geothermal energy can be found throughout the world naturally in the form of geysers, such as Old Faithful in Yellowstone Park in the United States. By the Earth’s crust shifting and allowing water to mix into natural hot-spots water is superheated and then vented through holes in the Earth’s surface with tremendous power. The superheated water generated at these locations can naturally reach temperatures of up to 200°C (430°F).
Applying the already natural occurrence of superheated steam production in a controlled industrial sense allows geothermal power production facilities to generate massive amounts of electricity by using the superheated steam created by the Earth to power turbines that generate electricity for general public use. Geothermal power plants in the most basic sense apply a process of drilling into these geographic hot-spots in order to allow direct access to the natural heat source and establishing a water circulation system and in which cold water is pumped into the drilled hole and the superheated steam is allowed to escape through a secondary vent, being channeled into power generating turbines upon its exit.
There are three common designs for geothermal power plants — two of which rely entirely upon the power generated by steam alone while a third utilizes an additional agent to generate increased steam power. The two primary production facilities that rely entirely on water for their power production are simpler to design and implement, however they require a massive amount of geothermal power to be available in order to create a constant amount of heat that is usable for power production, therefore they can not be established in as many locations. The most basic and common form of geothermal power is where water is pumped into a drilled hole in the steam that is produced from this go directly through a turbine for power production and then into a condenser were the steam is converted back into water for the process to repeat once again.
An alternative approach to the first basic geothermal plant production system is to first pump the water into the Earth and then collect the steam into a pressurized system and that can be depressurized over time directly into a turbine to create the driving force that generates electricity. This can allow moderate geothermal spots with slightly less heat production capability than his optimal to still generate enough pressure to turn turbines at regular rates and generate considerable amounts of power and has allowed additional geothermal spots to be utilized for power production throughout the world that may have been previously unfeasible due to their lack of enough geothermal energy.
The third approach involves both the hot water used in the first two with a second liquid with a lower boiling point than water (such as isobutane). As isobutane has a significantly lower boiling temperature than water the this has allowed geothermal plants in locations where thermal energy may not be enough to create adequate amounts of steam to drive a power plant normally to still generate enough heat in the water to vaporize the secondary liquid which can then generate enough steam necessary to power electrical turbines.
There are also ways that geothermal heat is used throughout the world without the industrial application of a power plant to it. Geothermal springs (commonly referred to as “hot springs”) can be found throughout the world and are a direct source of naturally water, allowing for people across the globe to use these to heat greenhouses, improve some resource recovery (such as oil), assist with various food production (such as fish farms and other agricultural products) and provide a relaxing environment for spas. They can also be an excellent source of heat for homes and other buildings in an area as is commonly seen in countries such as Iceland were geothermal heat is readily available and much more economically feasible as a heat source than alternative means.
Geothermal heat can also be used as heat transfer systems that directly transfers thermal energy between the ground and any buildings that utilize the system. As the average year-round temperature of the Earth is approximately 50°F at five to ten feet below the surface these heat transfer pumps are connected to buildings and placed directly into the earth and are then filled with either air or some sort of anti-freeze liquid that can circulate through the pipes into the building in order to regulate temperatures and transfer heat throughout the structure. This can help provide pre-heated or pre-cooled air and structural material in the winter and summer, respectively, and are extremely effective in saving on heating costs and energy consumption, especially in areas where extreme climate changes exist (such as harsh winters or extremely hot summers).
Ongoing research is still being conducted now to develop more feasible and efficient methods to utilize geothermal resources to both produce power and cut power consumption around the world. These include new forms of geothermal power plants and alternative methods of generating electricity, such as one method currently being explored of pumping water directly into the Earth’s crust and utilizing the heated water that is produced from this that may be too cool to produce steam however hot enough to generate electricity through some other means. As we continue to see developments in geothermal power we should be able to see increased growth in power production by geothermal means in coming years. Unfortunately there is no accurate appraisal available at this time as to when sufficient means to efficiently tap geothermal energy at many currently unsuitable locations across the globe will be available, however it is estimated that increased geothermal plant developments can be seen across the western United States in the near future.
