Contents

1. Energy storage technologies for intermittent renewable energy systemsS R Awasthi Dr. PragyaNemaConsultant, CECL, Bhopal Professor, Electrical Engineering DepartmentEx. General Manager, BHEL NetajiSubhash Engineering College, Kolkata (W.B.)

2. Contents • Introduction • Background of storage system • Different energy storage technology • Comparison of different storage technology • Conclusion

3. Introduction • What is energy storage system for renewable energy ? • Why is it required ? • Function of energy storage system

4. Background of storage system Storage is an essential unit that stores unstable electric energy during wind and photovoltaic power generation, which is sharply growing new renewable energy, and supplies the unstable energy to electric power system again in necessary moment. If there is no such energy storage unit, any kinds of serious problems like sudden blackout occurs because of unstable sunlight-dependent electricity supply. This Storage takes an important part in the electricity storage systems for households, the medium-size system for industrial/commercial use, and the extra-large system for power plants and substations like Frequency Regulations

5. different Energy storage technologies • Pumped storage • Batteries • Superconducting magnet energy storage • Flywheel energy storage • Regenerative fuel cell storage • Compressed air energy storage

6. Pumped storage • A pumped storage hydro power plant may store huge energy by pumping water from a lower reservoir to a higher pond. In a pumped storage hydro plant, we usually make the height of the reservoir equal to a small hill and at bottom a cavity is made so that water may not run away downward. • Water is pumped during off-peak times and may be utilized to generate electricity. Other innovations may store electricity in small quantity but pumped storage hydro power plant may store electricity in Megawatts (MW) or even Gigawatts(GW).

7. Batteries Battery Battery working Battery Bank

8. Flywheel energy storage • Flywheel energy storage systems are one of energy storage devices. They store energy mechanically in the flywheel rotor by rotating the rotor while as chemical batteries stores energy electrically. When we want to use the stored energy in the rotor, a generator is used to convert mechanical energy to electrical energy. • Flywheel systems are not sensitive to temperature since they are operating in a vacuum containment. Therefore, the hybrid vehicle with flywheel systems can run without any problem at very cold or hot areas. And, flywheel systems can store more energy per system weight compared to chemical batteries, • The flywheel system is a very efficient energy storage device, it can be used for various applications.

9. Superconducting magnet energy storage Superconducting magnetic energy storage systems store energy in the magnetic field created by the flow of direct current in a superconducting coil. This advanced systems store energy within a magnet and release it within a fraction of a cycle.

10. Regenerative fuel cell storage • A fuel cell is an electrochemical cell that converts a source fuel (from combustible substances such as hydrogen, methane, propane, and methanol) into an electric current. • A fuel cell is a device that generates electricity by a chemical reaction. Every fuel cell has two electrodes, one positive and one negative, called, respectively, the anode and cathode. The reactions that produce electricity take place at the electrodes. • Hydrogen is the basic fuel, but fuel cells also require oxygen. One great appeal of fuel cells is that they generate electricity with very little pollution—much of the hydrogen and oxygen used in generating electricity ultimately combine to form a harmless byproduct, namely water.

11. continue… Compressed air energy storage • Energy from solar or wind and even electricity from thermal power plant during off-peak period may be utilized to compress air by compressor and same air may be utilized to produce electricity during peak-hour. • Compressed air energy storage is done in underground caverns and abandoned mines.

12. References • Milborrow, D., 2000, “Trading Rules Trap Wind in the Balance,” Windpower Monthly, Vol. 16, pp 40-43. • Cavallo, A. 1995, “High Capacity Factor Wind Energy Systems,” J. Solar Energy Eng., Vol. 117, pp 137-143. • Schainker, R., 1996, private communication, Electric Power Research Institute, Palo Alto, CA, presented at the PowerGen Conference, Orlando, FL USA. • Innogy PLC, 2001, Innogy Technology Ventures Ltd., Harwell International Business Center, Harwell,Didcot OX11 0QA (www.innogy.com). • Cavallo, A., 1996, Storage System Size as a Function of Wind Speed Autocorrelation time for a Wind Energy Baseload System, Proceedings of the European Wind Conference, Goeteborg, Sweden, pp 476-479. • Schainker, R.B., Mehta, B. and Pollak, R., 1993, Overview of CAES Technology, Proceedings of the American Power Conference, Chicago, IL, Illinois Institute of Technology, pp 992-997. • Ter-Garzarin, A, Energy Storage for Power Systems, Chapter 7, IEEE, London, UK, Peter PergrinusLtd.Redwood Books, Trowbridge, Wiltshire, UK. • Obert, E.F., “Thermodynamics,” McGraw-Hill, New York, London, Toronto, pp 478-490. • Nakhamkin, M., Swensen, E., Abitante, P, Schainker, R and Pollak, R., 1993, Technical and Economic Characteristics of Compressed Air Energy Storage Concepts with Air Humidification, Proceedings of the American Power Conference Chicago, IL, Illinois Institute of Technology, pp 1004-1009. • Cavallo, A., and Keck, M., 1995, Cost Effictive Seasonal Storage of Wind Energy, SED-Vol 16, Wind Energy, Editors, W.D. Musial, S.M. Hock, E. Berg, Book No. H00926-1995, pp 119-125. • De Laquill III, P., Kearney, D., Geyer, M., and Diver, R. Solar Thermal Electric Technology,” 1993, • Renewable Energy: Sources for Fuels and Electricity, T.B. Johannson, H. Kelly, A.K. Reddy and R.H.Williams, eds., Island Press, Washington, DC.