Abstracts

Solar powered multi-stage natural vacuum low temperature desalination process

Author(s): Steinwinder, J.; Martinez-Guerra, E.; Guerra, H.; Spiller, B.; Byrd, C.; Solis, M.; Gude, V.

Desalination has emerged as a viable alternative for water supply in many water-stressed regions of the world. In US, some of the states such as California, Texas and Florida are faced with major challenges of ensuring adequate water supplies to meet the demands as a result of population growth, severe drought, decreasing aquifer levels and increasing industrialization. Desalination can be performed through membrane and thermal processes. These processes are energy-intensive. Powering the desalination processes through conventional energy sources is not a sustainable approach as these sources are not renewable. Utilization of renewable energy such as solar energy for water desalination is an ideal approach for thermal desalination processes. In this research, a low temperature desalination process operating at near-vacuum pressures was studied. Near vacuum pressures are created by exploiting the barometric head and gravitational force. As a result, this process reduces the specific energy consumption for freshwater production due to reduced heat losses to the ambient. This allows for efficient utilization of solar energy. Preliminary data of a multi-stage (3 stages) solar powered low temperature desalination process will be presented. Working principles of the novel desalination process as well as energy and mass balances, heat and mass transfer analysis will be presented. Solar collectors will be used to provide the thermal energy required for the desalination process. Our preliminary economic analysis shows that when this desalination system is powered by a low grade flat plate solar collector heat source, the desalination costs are less than $7/m3 which falls in acceptable range for small scale desalination systems of similar capacity. When using a cheap waste heat source purchased at $0.5/GJ, the desalination costs can be reduced to $3/m3. Most small scale domestic desalination systems are designed in combination with a renewable energy source.

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