A novel design for a solar powered multistage flash desalination

Abstract

Abstract This work presents a new design for a solar powered multistage flash (MSF) desalination plant, which reduces solar collector area compare to other designs and is capable of operating continuously. The proposed design uses an array of concentrating solar collectors and a pair of thermal storage tanks, each with enough capacity to supply the MSF with brine for one day. Unlike many other solar desalination approaches, the brine is directly circulated through the array, eliminating the need for a heat exchanger and medium fluid. Each day, one of the tanks receives pre-heated brine from the MSF, which is further heated to a top brine temperature (TBT) by circulation through the solar array (charging mode). At the end of each day, the fully charged tank switches to discharging mode, and feeds the MSF with brine while the other tank enters charging mode. The system is designed for the tanks to alternate roles at approximately sunset each day. Seasonal changes in available solar energy are handled by modifying the mass flows, such that the same TBT is always achieved. This novel dual-tank approach serves to isolate the MSF from daily variations in solar energy, and it allows the brine to gradually reach TBT each day, minimizing losses. A dynamic model of the heat and mass transfers is used to simulate this design, resulting in an average daily production of 53 kg of distillate per square meter of solar collector area. The resulting system uses a solar collection area of 42,552 square meters to provide the average daily production about 2230 cubic meters of fresh water with total water price $2.72 per cubic meters.