Mars Rovers will work at noon on Mars time at around equator of mars. Temperature can be 20 degree C, while it will be -80 degree C.
At day time, when sunshine is strong on mars, the rover will use sun to generate electricity with its solar system. Parts for work, parts are stored in battery.
Normal Undecane is used in Mars Rovers as Energy storage material.
The material will absorb energy in daytime when temperature is high. it will become liquid. While at night, when temperature is low, the material will freeze and will release heat. Efficiency can be over 80%.