4. Solar Ventilation Air Preheating Available to Purchase

Solar ventilation air preheating has the lowest cost and highest efficiency compared to other solar technologies such as photovoltaics or solar water heating, but it is only used for one thing, which is preheating ventilation air. It is also used for crop-drying in California and Latin America. It can be used to preheat air for conventional boilers in thermal and power plants, but not for gas-turbines since to do so would increase compressor work.