Solar industrial air and water systems
There are two types of applications employing solar air collectors the open circuit, and the recirculating applications. In open circuit, heated ambient air is used in industrial applications where because of contaminants recirculation of air is not possible. Examples are drying, paint spraying, and supplying fresh air to hospitals. It should be noted that heating of outside air is an ideal operation for the collector, as it operates very close to ambient temperature, thus more efficiently.
In recirculating air systems a mixture of recycled air from the dryer and ambient air is supplied to the solar collectors. Solar-heated air supplied to a drying chamber, can be applied to a variety of materials, including food crops, and lumber. In these applications, adequate control of the rate of drying, which can be obtained by controlling the temperature and humidity of the supply air, can lead to improved product quality.
Similarly, there are also two types of applications employing solar water collectors the once-through systems and the recirculating water heating applications. The latter are exactly similar to domestic water heating systems presented in Section 5.1. Once-through systems are employed in cases where large quantities of water are used for cleaning in food industries, and recycling of used water is not practical because of the contaminants picked up by the water in the cleaning process.