Energy efficiency for sunk Chinese solar greenhouses.

Solar energy gain from and heat loss to the outside were varied with the floor sunk depths for Chinese solar greenhouses,hence a reasonable method should be built to evaluate the property of the sunk greenhouses.A calculation model was built for predicting solar energy gain,heat loss and solar energy heating guarantee for Chinese solar greenhouses.Then the solar energy efficiencies were evaluated by the model for 10m,12 m and 14 m span greenhouses with 0.3m,0.6 m and 1.0m floor sunk depths on Dec.22,Jan.20 and Feb.20,respectively,in Shenyang region.Calculation results showed that solar energy heating guarantee decreased with the increase of the sunk depth and the span length.The average solar energy heating guarantee reached by 20% in Jan.20 with the average value of 67.5% in Feb.20.The calculation model could be generalized to other regions for evaluating solar energy efficiencies in sunk Chinese solar greenhouses.