A device for collecting solar energy and conveying it to a zone to be heated. It comprises a tube in two parts, the first part (evaporator) being surrounded by a vacuum and being covered with a heat absorbing material and exposed to the solar radiation. The tube contains a fluid which vaporized in the first part and absorbs heat and condenses in the second part and gives up the previously-stored heat. The fluid in the liquid phase is returned to the first part by a capillary system.