Efficiency and Economics of Passive Solar Heating
Technically, PSH is highly efficient. Direct-gain systems can utilize (i.e. convert into "useful" heat) 65-70% of the energy of solar radiation that strikes the aperture or collector. To put this in perspective relative to another energy conversion process, the photosynthetic efficiency theoretical limit is around 11%.
Passive solar fraction (PSF) is the percentage of the required heat load met by PSH and hence represents potential reduction in heating costs. RETScreen International has reported a PSF of 20-50%. Within the field of sustainability, energy conservation even of the order of 15% is considered substantial.
Other sources report the following PSFs:
- 5-25% for modest systems
- 40% for "highly optimized" systems
- Up to 75% for "very intense" systems
In favorable climates such as the southwest United States, highly optimized systems can exceed 75% PSF.
Read more about this topic: Passive Solar Building Design
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