Geothermal energy can be utilized in three different forms. First, by using geothermal heat pumps for heating and cooling purposes of buildings, second by utilizing geothermal reservoirs for the commercial production of electricity and third by the use of Enhance Geothermal Systems for the commercial production of electricity.
Below we analyze the pros and cons of each of the above types.
Geothermal Heat Pumps Pros and Cons
Geothermal heat pumps (GHP) are used in buildings for heating and cooling purposes. The main advantage of a geothermal heat pump system is that it can significantly reduce the heating costs of a building. Studies have shown that heating cost savings can be up to 80% when compared with fossil fuels. Moreover, GHP are up to 50% more efficient than a heating system based on gas and up to 75% more efficient than a heating system based on oil.
Another advantage is that the same system used for heating of a building can be used for cooling purposes as well. A GHP system will operate quietly throughout the year maintaining a uniform and constant temperature and improved humidity control all over the building with no cold or hot spots.
A GHP system also has low maintenance costs. Compared to other systems, all is needed is changing the heat pumps air filters. The lifetime of a GHP system is more than 25 years and the lifetime of the underground pipes more than 50 years.
A GHP system also provides better aesthetics than other heating and cooling systems as it has no large visible components (like roof top equipment and chimneys). All components are under the ground or inside the building, providing better safety, as the system is not exposed to whether conditions or to vandalism.
Finally, a building with a GHP system installed has better resale value, as it adds value to the property.
On the other hand the major disadvantage of a GHP system is the very high initial installation cost. It is estimated that a GHP installation has a payback period 15 – 20 years.
Even though GHP systems have as an advantage the fact that they can be used anywhere in the world, there are some shortcomings associated with installation locations. A GHP system can be difficult to install in cities because of small plots and because the system may not be compatible with the existing system (in the case of existing installations). In the case of the horizontal installation of a GHP system, a large area of yard is required (which may not be available), and in the case of a vertical installation the installation may be not possible due to a rocky ground.
To sum up, using a geothermal heat pump system provides a lot of advantages, particularly in the long term, even when you take into consideration the long payback period and the high initial installation cost. So if the initial cost is not an issue, you should definitely consider installing a GHP system in your house.
Geothermal Reservoir System Pros and Cons
This type of geothermal energy is used for the commercial production of electricity and requires a natural geothermal reservoir. Its main advantage is that we can generate electricity from a practically unlimited source of energy with no fuel and almost zero emissions. Moreover, it is relatively simple and reliable and can generate electricity quite competitively compared to other sources of energy. Another major advantage, is that it is a non-intermittent source of energy i.e. it is not subject to fluctuations throughout the day as solar energy and wind energy systems.
On the other hand, its main disadvantage is that the prime locations, that can be utilized for commercial purposes, are very limited throughout the world and often relatively far from large urban areas causing many losses in the transmission system. Another disadvantage is the high initial installation cost and large amounts of water that it requires to operate.
To sum up, even though there are significant advantages in the use of geothermal energy its use is quite limited due to the limited prime locations that can be used. Though, there is a lot of potential for the future as we will be able to use geothermal energy by utilizing lower temperatures. This will allow us to utilize geothermal energy in more locations throughout the world and closer to large urban areas.
Enhanced Geothermal System (EGS) Pros and Cons
The biggest advantage of an Enhanced Geothermal System is that it doesn’t require a natural geothermal reservoir to produce electricity. Instead it requires deep solid, hot and dry rocks (like granite) insulated by a thick layer of sediment (in order to prevent heat loss). Even though, it is more widely available good locations must still be selected carefully.
Its major disadvantage is that it is not completely renewable form of energy in the sense that an EGS system has a useful life of 20 – 30 years before the temperature of the rock drops to a point where it will no longer be viable to support.