How do Geothermal Power Stations generate electricity?
The first geothermal power stations were operated by hot steam and hot water which came from underground sources, such as geysers. Geyser(s) coming from the Icelandic word geysa (meaning to gush) are natural springs located on the Earth’s surface, where the (boiling) water and steam ‘gush’ high into the air. This is the called the 'hydrothermal geothermal system'. Wells are drilled down to reservoirs containing hot water and steam, which rises to the surface.
In natural underground reservoirs called 'aquifers', which are formed by porous sedimentary rocks sealed by other rocks on top (cap rocks), the trapped water in the sedimentary rocks is heated by the surrounding hot rocks. Aquifers such as these are called hot sedimentary aquifers, or HSA. The steam, which is under a lot of pressure, then pushes and rises up to the surface via the 'escape routes' of the wells.
Geothermal power stations also operate on the 'hot rock/enhanced geothermal system', where cold water is carried underground to hot rocks close to active volcanoes and magma chambers, via wells. The heat from the hot rocks heat up the water and the hot water is then carried back to the surface via other wells.
Once the hot/heated water is cooled, it is carried back to the reservoirs or hot rocks via separate wells, which re-heat the water up again. When the steam rises to the surface, it is used in one the following two ways:
The process of recycling the water by piping it back to re-heat it forms a 'closed loop' (only applies to Binary Cycle Power Plant). This allows a continuous supply of hot water to exist for years.
Hot rocks, also known as 'hot fractured rocks' are granite rocks (4 or 5 kilometres underground - around 200 degrees Celsius) that are drilled to allow cold water to be pumped into the rocks under very high pressure, in which the water is heated. Granite contains amounts of naturally radioactive elements uranium (U), thorium (Th) and potassium (K), in which have generated heat over the millions of years of radioactive decay. This is basically a human-made version of a reservoir, as no natural reservoir can be created with the granite rocks. This is because water takes an extraordinary long time to seep into granite rocks.
The pumping of cold water under high pressure into the hot rock forces the rock itself to fracture, therefore making the rock a 'hot fractured rock (HFR)'. When cold water is pumped through the rock through an injection well, it is heated while seeping though the drilled cracks of the hot rock. The hot water then travels up the productions wells to the surface under high pressure.
In natural underground reservoirs called 'aquifers', which are formed by porous sedimentary rocks sealed by other rocks on top (cap rocks), the trapped water in the sedimentary rocks is heated by the surrounding hot rocks. Aquifers such as these are called hot sedimentary aquifers, or HSA. The steam, which is under a lot of pressure, then pushes and rises up to the surface via the 'escape routes' of the wells.
Geothermal power stations also operate on the 'hot rock/enhanced geothermal system', where cold water is carried underground to hot rocks close to active volcanoes and magma chambers, via wells. The heat from the hot rocks heat up the water and the hot water is then carried back to the surface via other wells.
Once the hot/heated water is cooled, it is carried back to the reservoirs or hot rocks via separate wells, which re-heat the water up again. When the steam rises to the surface, it is used in one the following two ways:
- The hot water rises up due to high pressure and is collected into a flash tank, in which the sudden drop in temperature and pressure boils the water into steam. The steam is separated from the water and then turns turbines to generate electricity. (Flash Steam Power Plant)
- When the steam reaches the surface, it is directly used to generate electricity by turning turbines. Afterwards, the steam condenses back into its original state; liquid water. (Dry Steam Power Plant
- Using the hot water, an oily fluid with a low boiling point is boiled, which in return, produces gas. The high pressure of the gas drives turbines and electricity is generated from the generator connected to the turbines . The hot gas is then recycled after turning back into water. (Binary Cycle Power Plant)
The process of recycling the water by piping it back to re-heat it forms a 'closed loop' (only applies to Binary Cycle Power Plant). This allows a continuous supply of hot water to exist for years.
Hot rocks, also known as 'hot fractured rocks' are granite rocks (4 or 5 kilometres underground - around 200 degrees Celsius) that are drilled to allow cold water to be pumped into the rocks under very high pressure, in which the water is heated. Granite contains amounts of naturally radioactive elements uranium (U), thorium (Th) and potassium (K), in which have generated heat over the millions of years of radioactive decay. This is basically a human-made version of a reservoir, as no natural reservoir can be created with the granite rocks. This is because water takes an extraordinary long time to seep into granite rocks.
The pumping of cold water under high pressure into the hot rock forces the rock itself to fracture, therefore making the rock a 'hot fractured rock (HFR)'. When cold water is pumped through the rock through an injection well, it is heated while seeping though the drilled cracks of the hot rock. The hot water then travels up the productions wells to the surface under high pressure.