The following points highlight the four main types of geothermal power plants.
The types are:
1. Flash steam plants
2. Dry Steam Plants
3. Binary Power Plants
4. Hybrid Plants.
To convert geothermal energy into electrical energy, heat must first be extracted to convert it into a usable form. Deeper or deeper wells can be drilled into underground reservoirs to extract steam and very hot water that drives turbines coupled to electrical generators.
types of geothermal plantsRead more: Energy Basics Various Forms of Energy Energy Conservation
There are basically four types of geothermal plants in operation today:
Type 1. Flash steam plants:
Extremely hot borehole water, when released from deep reservoirs, releases high-pressure steam (known as flash steam). The power of the steam is used to turn turbines. The steam condenses and turns back into water, which returns to the reservoir. Discharge steam plants are widely distributed throughout the world.
Type 2. Dry Steam Plants:
Typically geysers are the main source of dry steam. Geothermal reservoirs that produce mainly steam and little water are used in electricity generation schemes. As steam is expelled from the reservoir, it is used to drive a turbine, after sending the steam through a stone trap. The rock collector protects the turbine from rocks that come with the steam.
Type 3. Binary Power Plants:
In this type of power plant, geothermal water passes through a heat exchanger where its heat is transferred to a secondary liquid, i.e. isobutene, isopentane or ammonia-water mixture present in a separate adjacent pipe. Because of this dual liquid heat exchanger system, it is called a binary power plant. The secondary liquid, also known as working fluid, must have a lower boiling point than water. It turns into steam upon obtaining the required heat from hot water.
The steam from the working fluid is used to rotate the turbines. The binary system is therefore useful in geothermal reservoirs with a relatively low temperature gradient. As the system is completely closed, there is a minimal chance of heat loss. The hot water is immediately recycled back to the reservoir. The working fluid is also condensed back to liquid and used repeatedly.
Type 4. Hybrid Plants:
Some geothermal fields produce boiling water and steam, which are also used to generate energy. In this power generation system, flash and binary systems are combined to utilize steam and hot water. The efficiency of hybrid plants is, however, lower than that of dry steam plants.
