Multiple-effect diffusion solar still coupled with a vacuum-tube collector and heat pipe

•We design a multiple-effect diffusion solar still with a bended shape.•A vacuum-tube solar collector is used to produce high temperature for distillation.•A heat pipe is used to transfer solar heat for distillation.•A prototype MEDS-1L was built and tested outdoors.•MEDS-1L performs very well compared to other designs.

The present study develops a multiple-effect diffusion solar still (MEDS) with a bended-plate design in multiple-effect diffusion unit (MDU) to solve the peel-off problem of wick material. The MDU is coupled with a vacuum-tube solar collector to produce a high temperature gradient for high productivity. A heat pipe is used to transfer the solar heat to the MDU. A prototype MEDS-1L was built and tested outdoors. Four performance indexes are proposed for the performance evaluation of MEDS, including daily pure water production per unit area of glass cover, solar absorber, and evaporating surface (Mcov, Msol, Mevp, respectively), and solar distillation efficiency Rcov. The outdoor test results of MEDS-1L show that the solar collector supply temperature Th reaches 100 °C at solar radiation 800 W m− 2. The highest Mcov is 23.9 kg m− 2 d− 1 which is about 29% higher than the basin-type MEDS [11]. The highest value is 25.9 kg m− 2 d− 1 for Msol and 2.79 kg m− 2 d− 1 for Mevp. The measured Rcov is 1.5–2.44, higher than the basin-type MEDS (1.45–1.88). The Mcov, Msol, Mevp and Rcov of MEDS-1L are all higher than the theoretical calculation of a MEDS with a flat-plate solar collector coupled with a heat pipe (MEDS-FHP) [17].