NOVELTY - The solar collector for transmitting heat energy by heat conducting fluid (3) such as heat boron, which forms a substance, comprises a double-walled collector pipe, which is built into a metal or plastic housing (7) consisting of radiation-permeable glass. Water (4) to be heated flows through the inner pipe. The inner chamber of the outer pipe is provided with a pressure-proof feed valve (5) via which the heat boron is introduced. The inner pipe and the outer pipe consist of metal, plastic or glass. In systems comprising pipes, the water to be heated is supplied to the collector pipes.    USE - Solar collector useful for transmitting heat energy by heatconducting fluid such as heat boron.    ADVANTAGE - The solar collector ensures simple and efficient transmitting of heat energy without heat loss.    DETAILED DESCRIPTION - The solar collector for transmitting heat energy by heatconducting fluid (3) such as heat boron, which forms a substance, comprises a double-walled collector pipe, which is built into a metal or plastic housing (7) consisting of radiation-permeable glass. Water (4) to be heated flows through the inner pipe. The inner chamber of the outer pipe is provided with a pressure-proof feed valve (5) via which the heat boron is introduced. The inner pipe and the outer pipe consist of metal, plastic or glass. In systems comprising collector pipes, the water to be heated is supplied to the collector pipes by a distributor (8). The heated water is collected in a collector and transported to the consumer. Distributors and collectors are arranged in the collector housing. The double-walled collector pipes are mounted between the distributor and the collector. A parabolic-shaped reflector is arranged behind the collector tube in order to bundle the sunbeams to produce the steam. The heat boron substances comprise 1-20% of dicalcium pentahydrate, borax, datolite, colemanite, priceite, ulexite, boracite, hydroboracite, MgBO3(OH) or zeolite Mx/n((AlO2)x(SiO2)y)zH2O (M, x, y, z are undefined); and 80-99 % of carbon dioxide, or difluorochloromethane, or trifluoromethane, or difluoromethane, or hexafluoroethane, or tetrahydrofluoroethane, or difluorochloroethane, or trifluoroethane, pentane, or ethylene, or propylene, or ethane, or octafluoropropane, hepatafluoropropane, or hexafluoropropane, or pentafluoropropane, or butane, or pentafluoroethane, or propane, or difluoromethane.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic representation of a solar collector.    Heatconducting fluid (3)    Water (4)    Feed valve (5)    Housing (7)    Distributor. (8)