Researchers in Saudi Arabia have fabricated an integrated system powered entirely by PV to extract fresh water from the atmosphere. The system uses excess heat from the solar modules to evaporate and condense water which can then be used to grow crops. Part of the water is also used to cool the solar modules using an active cooling technique.
Researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia have developed an integrated solar-powered water, electricity and crop production system capable of producing water from atmospheric water vapour.
“Our system is particularly suitable for off-grid communities, wherever they are, as it provides an easy way to obtain electricity, water and agricultural products for consumption points,” said the corresponding author of the research, Peng Wang. photo magazine.
Called WEC2P, the system relies on a PV system to generate power and an atmospheric water harvesting (AWH) material to produce water vapor from the air. The fresh water produced by the AWH device is used either to grow crops or to reduce the operating temperature of the solar modules. The system operates in two modes of operation, which the scientists called the AWH-PV cooling mode and the AWH crop and water production mode.
The cooling device is made of a polyethylene (PE) anti-corrosion film with a thickness of about 0.04 mm, polymer-based atmospheric water vapor absorbers and a polyacrylamide-calcium chloride (PAM-CaCl2) hydrogel. “PAM-CaCl as obtained2 the hydrogel was directly attached to the back of each individual photovoltaic cell in the photovoltaic panels via its self-adhesive properties,” the Saudi group explained. “A poly (methyl methacrylate) (PMMA) plate-like frame was installed by spring bolts to reinforce the adhesion of the PAM-CaCl2 hydrogel with PV panel and secure their close contact.
Excess heat extracted during cooling operations is used to cause water to evaporate from polymer-based absorbers during the day. This evaporated water vapor is then collected during the day in a condensation chamber which is used as a passive condenser.
The area of the condensing chamber, which is made of an aluminum alloy with a copper nozzle on the lower side wall, is 1.6 times larger than that of the four south-facing photovoltaic panels, which were deployed at an angle of inclination of 22 degrees. A cotton wick passing through the nozzle was used to aid in the extraction of condensed water into a water collection bottle. “Each PV panel was considered an independent module and was connected to an MPPT system and a 12V lead-acid battery,” the scientists pointed out. “In addition, each module was connected to a total of 20W light-emitting diode (LED) light strips as a load to discharge the battery at night when the PV panel was not in operation.”
The performance of this system design, with and without the cooling system, was analyzed in an outdoor test facility for growing spinach located in Thuwal, Saudi Arabia over a period of 3 months during the last summer.
The proposed system configuration was found to achieve a 9.9% increase in electricity production due to a reduction in the solar module operating temperature down to 17 degrees Celsius. The small spinach growing unit recorded a crop survival rate of 95%.
The costs of the systems have not yet been estimated by the researchers. “Performance is far from optimized and therefore it would not be possible to reasonably estimate the overall cost of the system once scaled up,” Wang said.
The system was introduced in the newspaper An integrated solar system generates electricity with fresh water and crops in arid regionsPosted in Physical Sciences Cell Reports.
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