Hydro & Geothermal Energy - People, Development and Environment Notes

Hydro & Geothermal Energy

There are three types of hydropower stations facility which are as follows:

1. Impoundments: In such type of facility, dams are constructed to store river water in the reservoir. Water released from these reservoir flows through turbines, spinning it, which in turn activates the generator to produce electricity.
2. Pumped storage: When the demand for electricity is low, the stored electricity generated by other sources like solar, wind and nuclear is used for pumping water from low reservoir to high reservoir. During the periods of high electrical demand, the water released back to the lower reservoir, which turns the turbines to produce electricity.
3. Diversion: It is sometimes called a run-of-river facility, channels a portion of a river through a canal or penstock and then to flow through a turbine, spinning it, which later converts into electricity. It may not require the use of a dam.

2. Small Hydro Power (SHP): is defined as any hydropower project which has an installed capacity of less than 25 MW.

• It is in most cases a run-of-river, where a dam or barrage is quite small, usually, just a weir with little or no water is stored. Therefore run-of-river installation does not have the same kind of adverse effect on the local environment as large scale hydro projects.
• Small hydro plants can serve the needs of remote rural areas independently. Indian and China are the major players of the SHP sector, holding the highest number of installed plants.
• An estimated 5415 sites of small hydropower have been identified with the potential of around 19,750 MW. River-based projects in the Himalayan region and irrigation canals in other states have massive potential for such small hydropower projects. MNRE (Ministry of New and Renewable Energy) is encouraging the development of Small Hydro Projects in both public and private sectors and aims to exploit at least 50% of the current potential in the next 10 years.

3. Geothermal Energy
Geothermal generation refers to harnessing of the geothermal energy or the vast reservoir of heat stored in the earth’s inner core. Below the earth’s crust, there is a layer of hot & molten rock also known as magma. Heat is continually produced in earth's crust, mostly from the decay of the naturally radioactive materials such as uranium and potassium.

• Geothermal can be found in regions with normal or slightly above the geothermal gradient (thermal change in temperature is known as geothermal gradient, which expresses the increase in temperature with the depth in the earth’s crust. 
• The average geothermal gradient is about 2.5 - 3 degree per 100 meters and especially in the region around the plate margins where the geothermal gradient many be significantly higher than average value.
• The most common current way to capture the energy from geothermal sources is to tap into the naturally occurring “hydrothermal convection” system where cooler water seeps into the earth’s crust. When heated water is forced to the surface, it is relatively easy to capture that steam and use to drive an electric generator.
• India has the potential for producing around 10600 MW of power from geothermal resources. Although India was among the earliest countries to begin geothermal projects since the 1970s, but very few working geothermal plants are working presently. So, MNRE (Ministry of New and Renewable Energy) is now promoting geothermal energy.