Optical Analysis of a New Solar Distiller with Cylindrical Surface Concentrator and Vertical Gap Evaporator

Abstract

In this paper, a new solar distiller floating on ocean with cylindrical surface concentrator and vertical gap evaporator is proposed for solving the problem of freshwater shortage in islands. When the distiller is floating on ocean, the vertical gap will fill with seawater automatically due to the siphon effect of hydrophilic material. Then the seawater is heated to generate vapor when the incidence sunlight is concentrated to the gap by the cylindrical concentrator. Finally, the vapor reaches the arched transparent glass at the top of the device and condenses to produce fresh water. Optical simulation for the solar distiller is carried out to find the optimal radius of the cylindrical concentrator and the height of the vertical gap. The results indicate that when the radius and height is 6 cm and 5 cm respectively, 80% of the sunlight number within the incidence angle of 45° can be captured by the seawater in the vertical gap. The annual optical performance of the distiller is analyzed for the region within 17° north latitude. As the result, the device placed in east-west direction possesses superior performance. There are more than 10 working hours and 5 working hours in which the reception rate is more than 80% in summer solstice and winter solstice respectively. In autumnal equinox, there are more than 11 working hours with the reception rate exceeding 90%. Energy balance analysis for the whole system is carried out and the stable evaporation rate per unit solar collector area increases gently from 0.12 g/ (m2‧s) to 0.65 g/(m2‧s) when the solar irradiance increases from 500 W/m2 to 1000 W/m2.