Is there a liquid or compounds that can change from gas then to liquid and back in a vacuum or with air?
In the picture below the hour glass looking devise liquid comes in contact with light or heat it vaporizes passes the neck turning a electric turbine. At the absence of heat or light it would drain back into the lower half. Water is not the only liquid that could be used. Can this work?
In a vacuum water cannot be a liquid but under enough pressure like on the lowest picture, the weight would be measured allow enough pressure for water to be in a liquid state when it is out of the sun. A balance between a super cooled liquid, gas state and heat/or light. Black dye could be added to increase performance.