Techno-Economic Analysis of Packed Bed Type Thermal Batteries for Surplus Renewable Energy Storage

Abstract

Low carbon electricity from renewables will form the bed rock of the energy transition necessary for climate change mitigation. However, variable renewable generators suffer from intermittency and variability – there can be large surplus power available at times which cannot be dispatched to the grid. At many times, the practice is to curtail surplus renewable output, which is wasteful and not economic. There are also phases when generation is not adequate to meet the demand. Energy storage options are therefore crucial for enabling steady operation of a grid connected to large shares of renewables, to ensure balance between power supply and demand at all times. A potential option for renewable generators is to convert surplus electricity to heat and store it in a variety of inexpensive solid state thermal energy storage media. The stored heat may then be reconverted to electricity through the usual turbine generator cycle using water or organic fluids or it can be used directly via integration with thermal networks. This storage arrangement is generically called a thermal battery. Different thermal energy storage media in the form of packed beds may be coupled to the generators to take up surplus power in the form of heat. Thus, these systems can provide operational flexibility to renewables without power curtailment and can become cost effective and sustainable alternatives to battery-based electricity storage systems. This study examines the techno-economics of the heat storage hardware to better understand their role in the future energy systems and power markets.