Analysis on limitation of Using Solar Fraction Ratio as Solar Hot Water System Design and Evaluation Index

Solar fraction ratio is a key index and reference of solar hot water system design, andis also a key factor to evaluate solar hot water system according to Evaluation Standard for Application of Renewable Energy in Buildings in China. By analyzing relevant inspection data of actual projects, it was found that using solar fraction ratio to evaluate the actual running systems has certain limitation, which cannot reasonably reflect the actual supplementation of conventional energy, especially with the residential buildings applying central solar hot water system. Based on the total energy consumption control concept raised by government during the Twelfth Five-Year Plan period, the actual supplementation level of conventional energy should be used as a factor to evaluate solar hot water system. This study will analyze the limitation of solar fraction ratio in design and evaluation, and propose corresponding ideas of solution as references for relevant design and evaluation professionals.