Optimization and design of a novel small-scale integrated vacuum membrane distillation - solar flat-plate collector module with heat recovery strategy through heat pumps

摘要

This work aims to design a small-scale desalination unit for producing drinking water in remote places (similar to 2 L/ person). It considers an equipment where vacuum membrane distillation (VMD) and direct solar heating through solar flat-plate collector (FPC) are coupled within the same intensified module, with photovoltaic (PV) panels providing electricity. An adapted heat pumping strategy is conceived to bridge between the heat-demanding feed recirculation and the heat-releasing vapor condensation, aiming both to recover latent heat of evaporation and to condense vapor without using an additional intensive cooling system. Sensitivity analyses and multi-objective optimizations are provided, based on water production and electric consumption of both pumping and cooling, to orientate the design and to discuss the key issues for an optimal operation. Results reveal that for a tiny module (0.18 m(2)), a daily freshwater production of 3.7 L can be obtained with an average electric consumption of 17 W (similar to 0.13 m(2) PV). At a relatively bigger scale (3 m(2)), 96 L of freshwater is attained at a consumption of 449 W (similar to 3.26 m(2) PV). The need for PV power capacity per unit water production is almost constant, ranging in 4.2-5 W L-1.