“The most compact, modular and scalable solar-powered membrane desalinization system that can effectively desalinate seawater and waste brine to WHO accepted salinity levels”
Current state of the art membrane desalination systems utilizes reverse osmosis (RO), where brine is forced through a semipermeable membrane to produce fresh water, using high pressures to overcome osmotic pressures. For seawater desalination the required pressures can be greater than 350 psi. To achieve these pressures, large, heavy and bulky pumps are required, which require high levels of continuous electric power and maintenance.
Vacuum distillation (VD) of seawater is an alternative to RO. VD involves evaporating water from a briny liquid to vapor, and then condensing the water vapor back to a now pure liquid. This system can be scaled down for small throughput systems much easier than RO system. However, one major disadvantage of a vacuum distillation system is that since the water must now undergo a phase change from liquid to vapor in the distillation process, the high latent heat of vaporization of water must be provided to the system.
In a Polymer Electrolyte Membrane Vacuum Distillation (PEMVD) system, Xergy overcomes this energy-intensive limitation of conventional vacuum distillation systems by capturing the latent heat of condensation released when water vapor is condensed to liquid water, and cycling it back to the evaporator stage where it is utilized along with solar thermal energy to heat the brine, enhancing the water production rate.
Xergy’s is developing this system to provide the U.S. Department of Energy / U.S. Navy with a 100 gallon per day Solar Vacuum Desalination System based on its Advanced Composite Polymer Electrolyte membranes for installation at San Clemente Island (California).