Low pressure solar thermal converter

The current development of solar power converters with air as working fluid focuses mostly on concentrating collectors combined with hot-air engines, and on very low temperature solar tower concepts. Whilst concentrating collectors and Stirling engines need complex technology, solar tower converters have very low efficiencies and require large installations. Pressurized containers as energy converters offer the advantage of simplicity, but appear not to have been investigated in detail. In order to assess their performance potential, an idealised thermal pressure converter was analysed theoretically. Two improvements to increase the initially low efficiency derived from theory were found. Neglecting losses, maximum theoretical efficiencies ranged from 6.7% for a temperature difference of 60 K to 17.7% for a difference of 195 K. The low pressure solar thermal converter appears to offer development potential for low-tech solar energy conversion.