Exercises and Sample solutions
Exercises and Sample solutions
Pumped Hydro
Energy storage is a key enabler for a carbon free future, especially to tackle the intermittency of renewables. There are several types of primary energy storage ranging from thermal to electromechanical. Write an article, no more than 3 sides of A4 pages in total, briefly explaining the method of pumped hydro as a mechanical storage system. In the same article, then write about recovering the stored energy using hydro power. Discuss the various technologies and their principles of operation, and environmental impact.
Main points to be expected in the essay:
In everything there is a need to balance supply and demand Ø We store food, clothes, vehicles and nearly everything Ø Why? Matching of supply and demand Ø Can be a matter of necessity or just to satisfy convenience Ø Need and ability to store affects timing, transformations, efficiency and, of course, finance Ø It is the same with energy and the form of energy is just as important Ø Electrical energy is the most valuable and flexible form of energy but directly storing electricity is very difficult and expensive
Pumped hydro: Electricity generated in a turbine generator Ø Energy stored by pumping water back by reversing the turbine to act as a pump and used when needed. A mechanical type of energy storage
§ Measured in terms of annual energy generated e.g. Terawatts hours/year § Either stored behind dams (potential energy) or run of the river (kinetic energy) § A well established technology accounting for 20% of global electricity production § 1.2% of UK electricity. Weird are used. Different turbine types, depending on flow and head.
Rapid response to changing demand (can be used for base load and peak load) § Reserve energy store- buffers variation in input. § Constant availability (exception, run of the river) § Power generation efficiency can reach 90%. § Depending on location, can be used for large scale energy storage
Displacement of population and wild life § High cost of the infrastructure – very long payback periods. § Danger of dam failures and flooding § Silt, useful for downstream agriculture stopped by the dam. Downstream soil erosion § Water pollution and deforestation § Problems for fish migration upstream of the river. § Could produce methane due to decaying organic matter under the lake – 30 times more potent than carbon dioxide for greenhouse effect.
Fish ladders