Electricity and water can be a good combination
Saudi researchers hope they can bring them together in one system. Natalie Parletta reports.
Researchers in Saudi Arabia have created a single device they say improves on previous attempts to combine energy and water production using solar power.
This has been an important goal in recent years, with the World Bank warning back in 2014 that these two vital commodities are on an unsustainable “collision course”.
Globally, 10% of water is used to produce energy from nuclear or fossil fuels, and this increases to between 50% and 90% in the US, Western Europe and China.
In turn, a significant amount of energy – and costly infrastructure – is needed to produce clean drinking water via desalination.
The impacts of this water-energy nexus are especially severe in arid and semi-arid regions, driving scientists to explore how to produce clean water from solar power.
Previous methods – which use, for example, salinity gradient and thermoelectrical conversions – reduced the efficiency of producing electricity, says Peng Wang from the King Abdullah University of Science and Technology.
To address this, he and colleagues developed a three-stage device that captures and recycles the heat generated by photovoltaic (PV) solar panels to produce clean water using multi-stage membrane distillation.
The PV panel generates a lot of heat, and the heat is considered a headache in PV,” Wang explains.
Recycling this heat several times within the membrane distillation system leads to a high water conversion rate while not compromising electricity generation, the researchers say in a paper published in the journal Nature Communications.
"The uniqueness of the device lies in its smart and effective use of the waste heat of the PV as a resource, which leads to its high efficiency in both electricity and fresh water production,” Wang says.
“In a sense, it utilises solar energy to a much fuller capacity.”
Tests show one square metre of solar panels can produce more than 1.64 kilograms of fresh water per hour from seawater, contaminated groundwater or industrial waste.
The researchers calculate that if the device were installed on the four billion square metres of land needed to generate global solar power capacity, expected to increase to 969 gigawatts by 2025, about four billion cubic metres of fresh water could be produced each year – equivalent to 10% of the total global drinking water consumption in 2017.
This could help make clean water more affordable and accessible for more than two billion people worldwide who struggle to access safe water.
The researchers are now working on a second-generation device with a much higher water production rate, Wang says.
To scale it up and make it affordable, they will need to overcome engineering and technological barriers.