Even with the many recent advances in battery technologies, the limited un-recharged range of electric vehicles in comparison to their gasoline counterparts is a “deal breaker” for many potential purchasers. In extreme climates (hot or cold), the need to power either resistance heating or air conditioning units to maintain a comfortable environment within the vehicle significantly drains power from the batteries, adversely impacting the range of the vehicle.
The proposed solution is to design a compact and lightweight thermal heat storage unit that wraps around the electric motor. This unit would consist of phase change material that would be “charged” with heat using a traditional electrical resistance heater while the vehicle is plugged in for recharging. Since the thermal energy would be stored in the phase change of the material, a significant amount of heat can be stored in a relatively small volume. A liquid heat transfer system can carry the heat from the unit to a liquid to air heat exchanger in the car cabin, where a small electric blower can direct the warm air into the cabin. This unit can also capture the waste heat generated by the electric motor while it was operating and make it available to the cabin heating system.
The most suitable phase change materials are paraffins or salt hydrates with melting points ranging from 30 to 65 oC and with latent heats of fusion as high as 295 KJ/Kg. This means that a system using as little as 11 Kg of phase change material could store as much as 3 x 106 J of thermal energy, significantly reducing the load placed on the batteries for cabin heating during periods of cold weather.