How geothermal electricity works
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How Geothermal Electricity Works
Introduction to Geothermal Energy
Geothermal energy is derived from the heat stored beneath the Earth's surface. This heat can be harnessed to generate electricity, making it a renewable and sustainable energy source. The process involves tapping into geothermal reservoirs of steam or hot water, which are then used to drive turbines connected to electricity generators 45.
Types of Geothermal Power Plants
Dry Steam Plants
Dry steam plants are the simplest and oldest type of geothermal power plants. They directly use geothermal steam to turn turbines. The steam is piped from underground wells to the power plant, where it drives the turbine connected to a generator, producing electricity 45.
Flash Steam Plants
Flash steam plants are the most common type of geothermal power plants. They operate by pumping high-pressure hot water from underground reservoirs into lower-pressure tanks. The sudden drop in pressure causes the water to "flash" into steam, which is then used to drive a turbine and generate electricity. The remaining water and condensed steam are reinjected back into the reservoir 45.
Binary Cycle Plants
Binary cycle plants are used for lower-temperature geothermal resources. In these plants, geothermal water is passed through a heat exchanger, where it heats a secondary fluid with a lower boiling point than water. This secondary fluid vaporizes and drives the turbine. The geothermal water is then reinjected into the ground, making the process highly efficient and environmentally friendly 457.
Advanced Geothermal Systems
Double Flash Steam Cycle and Organic Rankine Cycle
Advanced geothermal systems, such as those utilizing a double flash steam cycle and an organic Rankine cycle, can significantly enhance the efficiency of electricity generation. These systems can produce multiple outputs, including electric power, freshwater, and hydrogen, by utilizing excess energy from geothermal wells. For instance, a high-temperature geothermal well can produce up to 22.1 MW of net electricity output with an energy efficiency of 49.1% and an exergy efficiency of 67.9% .
Hybrid Geothermal-Solar Power Plants
Hybrid geothermal-solar power plants combine geothermal energy with solar power to increase electricity generation, especially during peak demand periods. These plants can switch between a binary geothermal power plant mode and a hybrid mode that incorporates solar energy, significantly boosting power output and efficiency. Thermal energy storage allows for continuous power generation, even during non-sunny periods, achieving an exergetic efficiency higher than 30% .
CO2-Based Geothermal Systems
Innovative approaches, such as using CO2 as the working fluid in geothermal systems, can enhance heat extraction rates. CO2 has higher mobility compared to water, making it an attractive option for heat exchange. This method not only increases the efficiency of geothermal energy extraction but also allows for the geological sequestration of CO2, resulting in a negative carbon footprint .
Conclusion
Geothermal electricity generation is a versatile and sustainable energy solution. By utilizing various types of power plants—dry steam, flash steam, and binary cycle—geothermal energy can be harnessed efficiently. Advanced systems and hybrid configurations further enhance the potential of geothermal energy, making it a viable option for meeting future energy demands while minimizing environmental impact.
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