Dry steam cycle. Figure 4. Flash steam cycle. Figure 5. Binary cycle. The lighter brown is vaporized butane, while darker brown is liquid butane. Fossil Fuels. Nuclear Fuels. Acid Rain. Climate Change. There are three main types of geothermal energy plants that generate power in slightly different ways.
Dry steam plants are the most common types of geothermal power plants, accounting for about half of the installed geothermal plants. They work by piping hot steam from underground reservoirs directly into turbines from geothermal reservoirs, which power the generators to provide electricity.
After powering the turbines, the steam condenses into water and is piped back into the earth via the injection well. Flash steam plants differ from dry steam because they pump hot water, rather than steam, directly to the surface.
The steam produced powers the turbines. The steam is cooled and condenses into water, where it is pumped back into the ground through the injection well. In these binary cycle plants, the main difference is that the water or steam from below the earth never comes in direct contact with the turbines.
Instead, water from geothermal reservoirs is pumped through a heat exchanger where it heats a second liquid—like isobutene which boils at a lower temperature than water. This second liquid is heated into steam, which powers the turbines that drives a generator. The U. Geological Survey estimates that potentially , megawatts of EGS resource is available in the western U.
Low-temperature and co-produced geothermal resources are typically found at temperatures of F C or less. Some low-temperature resources can be harnessed to generate electricity using binary cycle technology. Co-produced hot water is a byproduct of oil and gas wells in the United States. This hot water is being examined for its potential to produce electricity, helping to lower greenhouse gas emissions and extend the life of oil and gas fields. Low Temperature and Coproduced Resources U.
Built in , the first flash steam plant was in New Zealand, and is the most common type of geothermal plant today. The fluids never mix. Instead, a heat exchanger allows the thermal energy to be exchanged. Ground water is then injected back into the ground to regain the thermal energy lost.
This variant is gaining popularity because geothermal resources with moderate water temperatures are more common. The efficiency rates of geothermal power plants are generally low. They are never more than 23 percent, and sometimes as low as 10 percent. However, the operational costs of a facility are not affected because it does not depend on fuel. Plus, byproducts such as exhaust heat, warm water, and others contain thermal energy can be used helps to increase actual efficiency.
Another means to tap this energy is to use ground-source heat pumps. Air or antifreeze can be pumped through pipes that go where these temperatures are found and return to buildings where it can be re-circulated.
Heat can be removed from buildings in the summer, and drawn in during the winter. There are three main processes to cool water after it is used. Water cooling is the most efficient way to manage super-heated steam.
There may be minerals and other solids in the fluid that need to be filtered out; otherwise, the strain on the heat exchanger will lead to more maintenance. A condensing system consists of a hot well, tube sheets, flanges, and a water inlet and outlet.
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