Thermal energy storage for electric vehicles at low temperatures: Concepts, systems, devices and materials

In cold climates, heating the cabin of an electric vehicle (EV) consumes a large portion of battery stored energy. The use of battery as an energy source for heating significantly reduces driving range and battery life. Thermal energy storage (TES) provides a potential solution to the problem. Such a technology is also known as thermal batteries or heat batteries, which can store heat at a high energy density. Thermal energy storage is generally much cheaper with a longer cycle life than electrochemical batteries. Therefore, using thermal batteries with high energy storage density to provide heat for EVs in cold environments can reduce vehicle costs, increase driving range, and prolong battery life. This is especially so for large EVs with a high heat demand such as electric buses. This article examines the influence of temperature on EVs and heat demands of different EVs in low temperature environments. The heat storage concepts, devices and systems proposed and developed for EVs are then reviewed, and potential TES materials for different types of TES devices are discussed. Different TES technologies for EVs are compared and analysed. Finally, the advantages and disadvantages and applicable scenarios of different thermal batteries are discussed, and research gaps are identified for further research and development.