The device combines a traditional photovoltaic solar panel and a distillation unit composed of three membranes. The excess heat produced by the photovoltaic module is recovered to produce steam and purify polluted or salt water.

Electricity production and access to drinking water are two of the biggest problems in developing countries: if, on the one hand, electricity production is linked to water (in Europe, 50% of water consumption is attributable to power plants), on the other hand, the production of drinking water resources in particularly arid contexts requires large amounts of energy (such as desalination plants).

To solve these two problems with a single solution, a team of researchers from the King Abdullah University of Science and Technology of Saudi Arabia developed a photovoltaic module capable of producing electricity and, at the same time, purifying the polluted or salt water.

The device consists of a traditional photovoltaic module with silicon cells, below which has been installed a distillation unit made up of 3 layers of membranes in which salt, brackish or polluted water can circulate.

Part of the heat produced by the photovoltaic cells is recovered by the distillation unit: the system allows the water to be heated to relatively low temperatures which, when it passes through the first membrane, gives off salts and pollutants . Hot water also initiates the same process in the lower layer of the membrane, in a cascade process that optimizes the heat produced by the photovoltaic module.

The procedure is also useful for purify water heavily contaminated with heavy metals: in the samples analyzed, the levels of lead, copper, sodium, calcium and magnesium present in the treated water were always well below the limits recommended by the World Health Organization.

The innovation was presented in a publication in the scientific journal Nature Communications. According to the researchers, the performance of the photovoltaic module should be greater than 11% and would not be limited by the incorporation of the purification unit.

Residual heat from photovoltaic panels has always been ignored and so far no one has tried to regard it as a resource.

Peng Wang, senior author of the King Abdullah University study.

The device would also solve logistical problems, since desalination plants and industrial photovoltaic installations require large spaces. Saudi researchers have envisioned that large-scale use of the device could produce 10% of the drinking water consumed in 2017.

This method could be used in coastal areas as long as it is not a question of supplying drinking water to cities of more than one million inhabitants, because it is a suitable technology for supplying water on a small and medium scale.

Peng Wang.

Via: wdrc.kaust.edu.sa

More information: www.nature.com