Generating energy using natural sources such as the sun and wind does promise a future where electricity can be provided to the masses without adding any CO2 to the atmosphere. However, systems that are used to store all that energy for times when the climate isn’t favorable for energy generation add to the already high cost of renewable energy. As a solution, UK-based startup Isentropic Energy has proposed a unique Pumped Heat Electricity Storage System (PHES), which can affordably store electricity in the form of pumped heat.
The system is based on the use of a highly reversible heat engine, which is based on two insulated storage vessels containing gravel. The first stage of the process begins with the use of compressed gas, which is passed through one of the vessels, heating up the gravel to a temperature of about 500 degrees Celsius. The gas is then made to expand to its original pressure causing the temperature to drop to -160 degrees Celsius. This cool gas is then passed through the other vessel. On coming in contact with gravel, heat is again exchanged, reducing the temperature of gravel and increasing the temperature of gas.
The energy supply is provided by a motor, which doubles as an energy storage element. When energy is used, the entire cycle is reversed. The passage of heat from the hot vessel to the cold vessel powers up a generator which produces electricity. The company claims that the system can be used to store excess electricity in a cost effective way, which can then be released when energy demand is high. The first PHES system is being targeted at 16MWh and can be scaled as required. Utility scale energy storage prototype based on the above system will require about two years at a cost of about $16 million.
Via: Dr. Robert Peltier, PE @PowerMag
