Worldwide, hydropower plants produce about 24 percent of the world’s electricity and supply more than 1 billion people with power. The world’s hydropower plants output a combined total of 675,000 megawatts, the energy equivalent of 3.6 billion barrels of oil, according to the National Renewable Energy Laboratory. There are more than 2,000 hydropower plants operating in the United States, making hydropower the country’s largest renewable energy source.
A few of many advantages of hydropower are fuel is not burned so there is minimal pollution; water to run the power plant is provided free by nature; relatively low operations and maintenance costs; and technology is reliable and proven over time.
Typical hydroelectric power plant
Hydroelectric energy is produced by the force of falling water. The capacity to produce this energy is dependent on both the available flow and the height from which it falls. Building up behind a high dam, water accumulates potential energy. This is transformed into mechanical energy when the water rushes down the sluice and strikes the rotary blades of turbine. The turbine’s rotation spins electromagnets which generate current in stationary coils of wire. Finally, the current is put through a transformer where the voltage is increased for long distance transmission over power lines.
Pumped storage: Reusing water for peak electricity demand
Demand for electricity is not “flat” and constant. Demand goes up and down during the day, and overnight there is less need for electricity in homes, businesses, and other facilities. Hydroelectric plants are more efficient at providing for peak power demands during short periods than are fossil-fuel and nuclear power plants, and one way of doing that is by using “pumped storage”, which reuses the same water more than once.
Pumped storage is a method of keeping water in reserve for peak period power demands by pumping water that has already flowed through the turbines back up a storage pool above the power plant at a time when customer demand for energy is low, such as during the middle of the night. The water is then allowed to flow back through the turbine-generators at times when demand is high and a heavy load is placed on the system.
The reservoir acts much like a battery, storing power in the form of water when demands are low and producing maximum power during daily and seasonal peak periods. An advantage of pumped storage is that hydroelectric generating units are able to start up quickly and make rapid adjustments in output. They operate efficiently when used for one hour or several hours. Because pumped storage reservoirs are relatively small, construction costs are generally low compared with conventional hydropower facilities.
Hydroelectric Power Plant Compressed Air Applications:
In hydroelectric power plants, the mechanical energy of the water is converted into electrical current using turbines and generators connected to them. Given that the effective head varies; a distinction is made between low, medium and high-pressure power plants. Similarly, there are run-of-river plants as well as storage plants (including pumped-storage plants) depending on the way in which the available water is used.
What high pressure air compressors used for in hydroelectric power plants:
· Braking air for pneumatic brakes
· Adjusting turbine blades and large valves (e. g. governor)
· Blowing air (blowing out the water to eliminate the load during starting)
· Preventing pulsation and cavitation