Geothermal power plant operates under various cycles: single flash steam cycle; double flash steam cycle; triple flash steam cycle; kalina cycle; and pure cycle power plant. These cycles are discussed below.
Single Flash Steam Cycle
Single flash steam cycle is as illustrated in figure 1.
Figure 1: Single flash steam cycle (source (Chegg))
The liquid is tapped from the production well. It is then flashed to a required pressure. The vapour separated from the liquid in the separation chamber is then passed to the turbine. The liquid from the condenser and separator is reinjected back to the well.
Double Flash Steam Cycle
This cycle has two flash chambers as illustrated in figure 2.
Figure 2: Double flash steam power plant (source (Mines Paristech))
In this cycle, the liquid is extracted from the production well. It is then flashed to a required pressure in the flash chamber 1. It is then passed through a separator, where the vapour is separated from the liquid. The liquid from separator 1 is still flashed to extract further energy remaining. The vapour from separator 1 is passed to the first turbine, and the vapour from separator 2 is passed to the second turbine. The liquid from the condenser and both separators are reinjected into the ground. This cycle has high efficiency as compared to a single flash steam cycle.
Triple Flash Steam Cycle
A typical flash chamber is illustrated in figure 3. The steam is flashed in three stages; high pressure chamber, intermediate pressure chamber, and low pressure chamber. Vapour separated from high-pressure separator is taken to the first and the second turbine. Vapour from the intermediate pressure separator is taken to a second turbine. Vapour from the low pressure separator is taken to the low pressure turbine.
Figure 3: Triple flash steam cycle (source (Yoshihiro, Yoshiki and Hideo))
Kalina Cycle
Kalina cycle is as illustrated in figure 4. It is a type of binary cycle, which uses ammonia – water as the working fluids. The power plant is operated by ammonia. The liquid from the well is used to heat ammonia in the steam generator. Ammonia vapour then runs the turbine. After it passed through recuperator and separator, ammonia is passed to the condenser then back to the steam generator.
Figure 4: Kalina cycle (source (Mines Paristech))
Pure Cycle Power Plant
The heated water from the well is passed to the dryer, where the vapour is separated from the liquid (as shown in figure 5). The vapour is then expanded in the turbine. The liquid from the dryer and condenser is reinjected into the ground. This cycle is not as efficient as the others discussed earlier.
Figure 5: Direct steam plant (source (Mines Paristech))
Works Cited
Chegg. "Thermodynamics: Geothermal Power Plant." 2013. www.chegg.com. 26 05 2013.
Mines Paristech. "Geothermal Energy." 2013. http://direns.mines-paristech.fr.com. 26 05 2013.
Yoshihiro, Sakai, Oka Yoshiki and Kato Hideo. "The Latest Geothermal Steam Turbines." 2013. https://www.fujielectric.com/company/tech/. 26 05 2013.
