Simulation of fresh water production using a humidification–dehumidification seawater greenhouse

A thermodynamic simulation study was performed on the influence of greenhouse-related parameters on a desalination process that combines fresh water production using humidification–dehumidification with the growth of crops in a greenhouse. With the system under study, surface seawater trickles down a porous front wall evaporator through which air is drawn into the greenhouse. The saturated air passes through a condenser, which is cooled using cold deep seawater or cool seawater coming out of the evaporators. Thermodynamic modeling of the seawater greenhouse system in our laboratory has shown that the dimension of the greenhouse had the greatest overall effect on water production and energy consumption. A wide shallow greenhouse, 200 m wide by 50 m deep gave 125 m3.d!1 of fresh water. This was greater than a factor of two compared to the worst-case scenario with the same area (50 m wide by 200 m deep), which gave 58 m3.d!1. Low power consumption went hand-in-hand with high efficiency. The wide shallow greenhouse consumed 1.16 kWh.m!3, while the narrow deep structure consumed 5.02 kWh.m!3. The benefits of the development of the seawater greenhouse for arid regions are discussed.

We are currently building a commercial size seawater greenhouse at our SQU Desalination Research Laboratory site by the sea. The aim is to demonstrate the technology to local farmers and companies in the Arabian Gulf. However, there are still numerous questions that need to be answered. Are we trying to minimize the cost of the structure or do we want to maximize the water production rate? Will the experimental results confirm the model predictions? Should we aim the technology at the small-scale farm, the large commercial farm, or both? There are several benefits for the development of the humidification–dehumidification seawater greenhouse system in arid regions. It provides for additional water supplies for other purposes such as the development of environmental projects. It also allows the reclamation of salt-infected land by not relying, at all, on groundwater resources. In addition, it gives the opportunity to develop a high value agricultural sector that is sustainable in the long term and immune to climatic varia-tions. In closing, we believe that this technology will be of real benefit to coastal farmers, worldwide, who are struggling with the problems of salt infected soil and increasing shortages of groundwater.