Solar Thermal Technology

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Solar thermal technology converts radiant solar energy (sunlight) to heat. This heat can then be used to cook in a solar oven, produce power, heat water for domestic or industrial uses, passively or actively heat space, or cool space with an absorptive cooling system.

• Solar ovens come in many shapes and sizes. The basic design is a well-insulated box with a transparent cover that allows light to enter. The inside of the box is generally black for maximum absorption of the incoming solar energy. Basic solar ovens of this design can achieve temperatures above 300°F, depending on available sunlight and ambient air temperatures. Some commercially available models can achieve higher temperatures.

• Power production through solar thermal technology involves concentration of sunlight with mirrors and/or lenses onto a receiver located at the mirror or lens focal point. At the focal point, energy from the sun is converted to heat, which is transferred to the working fluid (water, molten salt, other). The working fluid is then piped to a steam generator or engine that produces electricity.

• Flat plate collectors are a common way to harness solar energy. Flat plate collectors consist of a shallow, well-insulated enclosure with a transparent cover. Inside the enclosure is an absorber plate (usually made of copper or another metal) that converts radiant solar energy into heat. A series of parallel flow tubes is mounted on the absorber plate. Water or another working fluid passes through the flow tubes and absorbs heat generated in the absorber plate. The heated fluid is then used directly (e.g. to heat homes or for domestic hot water) or in parallel with a heat exchanger. 

• Passive solar building design is another very effective solar thermal technology.  With proper site assessment, structure orientation, insulation, and window type and placement, homes can absorb much of the sun’s radiant energy.  Direct solar gain systems use thermal mass such as water or concrete to store much of the thermal energy that falls onto the structure. A simple direct gain system works as follows. A large south-facing (in the northern hemisphere) window exposes a concrete slab floor to the sun.  The slab is strategically placed to maximize exposure to the sun in winter months and minimize exposure in the summer months. Throughout the winter day, the slab absorbs sunlight and stores the energy as heat. After the sun goes down, the floor radiates the heat it has stored into the building.  Conversely in summer months, the slab absorbs only heat from the warm air in the structure because it is not directly exposed to the sun, lowering the ambient air temperature. Therefore, these systems can effectively heat in winter and cool in summer.