A gravity driven Thermosiphon solar water heating system to harness solar insolation in low sunshine regions. This innovatory system uses CO.sub.2 as the working fluid to collect even mild sunlight to heat the water in sub-zero temperature areas. This solar water heater harnesses solar energy by fitting U-shaped copper heat removal pipes in evacuated glass tubes. This system works automatically by natural thermosiphon circulation force caused by density difference of supercritical CO.sub.2 at different temperatures. This innovatory solar water heater can perform in ice cold temperature areas where water based systems cease to function after freezing.

A solar liquid-heating-and-cooling system (20) includes: 1. a hot-liquid storage-tank (22); 2. a hot-liquid manifold-tank (26); 3. a coaxial heating-and-cooling-tube (24) that connects downward from the hot-liquid storage-tank (22) to the hot-liquid manifold-tank (26); 4. a double layer heating-and-cooling collector-array-panel (32) located beneath the hot-liquid manifold-tank (26), the panel (32) including, connected to the hot-liquid manifold-tank (26): a. an upper layer of glazed heating-tubes (36); and b. a lower layer of unglazed cooling-tubes (56); 5. parabolic-trough mirror reflectors (64) that are located between the upper and lower layers of tubes (36, 56); 6. cold-liquid manifold-tank (92) located below the panel (32) connected to lower ends both of the glazed heating-tubes (36) and of the unglazed cooling-tubes (56); 7. a cold liquid storage tank (98); and 8. a coaxial heating-and-cooling-tube (96) that connects downward from the cold-liquid manifold-tank (92) to the cold liquid storage tank (98).

The present invention limits fluid temperature at a point in a fluidic system to below a predetermined temperature by cooling the fluid when needed and without requiring a separate cold fluid source. The present invention “clips” the temperature of the fluid at a point in the system to within a temperature range and prevents overcooling the fluid. When the fluid temperature is below the temperature range, the temperature of the fluid is unchanged as it passes through the apparatus of the present invention. The present invention may operate without external power, can function in any orientation, and works for unpressurized and pressurized systems. The present invention has application in the areas of solar thermal energy systems, fluid tanks, engine oil and coolant systems, transmission fluid systems, hydraulic systems, machining fluid systems, cutting fluid systems, nuclear reactors and chemical reactors, among others.

An automatic over-temperature control system for a solar collection is provided in which a light sensor in combination with an electronic solenoid valve is used to prevent entry of cold water into a thermosiphon solar collector during daylight intervals. By delaying entry of water until dusk (low light), the solar tubes have cooled sufficiently so water can be safely introduced into an empty or depleted solar collector without damaging the collector tubes.

A solar concentrator assembly includes a tripod, a base, a reflective dish, a receptacle, and a thermoelectric module or a heat transfer module. The tripod includes legs and a top tripod connector coupled to top portions thereof. The base includes a rod coupled to the tripod; a bottom support structure coupled to the rod; a top support structure coupled to the bottom support structure; an extension coupled to the bottom support structure and the top support structure; and a cap with recesses mounted to the top support structure. The reflective dish includes support rods received within the recesses; a pliable material forms panels, wherein the support rods are inserted into seams between the panels; and a reflective material disposed on the pliable material. The receptacle is connected to the base and disposed within the reflective dish. The thermoelectric module or the heat transfer module is partially disposed within the receptacle.

In one aspect, the present disclosure includes a solar fluid preheating system having a storage heater tank configured to store fluid which is in the process of being heated. The storage heater tank is encased by a cover, thereby creating an aperture extending therebetween. In another aspect, the solar fluid preheating system includes a nanoimprint lithographic layer having a plurality of nanolenses configured to concentrate and accelerate solar radiation rays. In a further aspect, the solar fluid preheating system includes a fluid vacuum system in fluidic commutation with the storage heater tank.