A heating system comprising a non-flat transparent housing comprising walls made of heat isolating material; a tank within the housing for receiving liquid; a platform laid on the ground; legs holding the tank on the platform; light-absorbent and heat conductive fins coupled to the tank, and a cold fluid inlet with a non-return valve therein, and a hot water fluid, the inlet and outlet extending from the tank to outside the housing; means to transfer heated air from inside the housing to outside the housing.