Engineers have built a new solar powered desalination system that doesn’t require batteries because it operates in sync with the rhythms of the sun.
As the team from the Massachusetts Institute of Technology (MIT) in the United States explain it, the system removes salt from water at a pace that closely follows changes in solar energy.
As sunlight increases through the day, the system ramps up its desalting process and automatically adjusts to any sudden variation in sunlight, for example by dialling down in response to a passing cloud or revving up as the skies clear.
Because the system can quickly react to subtle changes in sunlight, it maximises the use of solar energy, producing large quantities of clean water despite variations in sunlight throughout the day.
In contrast to other solar-driven desalination designs, MIT says its system requires no extra batteries for energy storage, nor a supplemental power supply, such as from the grid.
The engineers tested a community-scale prototype on groundwater wells in Alamogordo, New Mexico over six months, working in variable weather conditions and water types.
The system harnessed on average over 94% of the electrical energy generated from the system’s solar panels to produce up to 5,000 litres of water per day despite large swings in weather and available sunlight.
Amos Winter, the university’s Germeshausen professor of mechanical engineering, and director of the K Lisa Yang Global Engineering & Research (GEAR) Centre at MIT, said: “Conventional desalination technologies require steady power and need battery storage to smooth out a variable power source like solar.
“By continually varying power consumption in sync with the sun, our technology directly and efficiently uses solar power to make water. Being able to make drinking water with renewables, without requiring battery storage, is a massive grand challenge. And we’ve done it.”
Untapped resource
The system is geared toward desalinating brackish groundwater – a salty source of water that is found in underground reservoirs, and is more prevalent than fresh groundwater resources. The researchers see brackish groundwater as a huge untapped source of potential drinking water, particularly as reserves of fresh water are stressed in parts of the world.
They envision that the new renewable, battery-free system could provide much-needed drinking water at low costs, especially for inland communities where access to seawater and grid power are limited.
Jonathan Bessette, MIT PhD student in mechanical engineering, said: “The majority of the population actually lives far enough from the coast, that seawater desalination could never reach them.
“They consequently rely heavily on groundwater, especially in remote, low-income regions. And unfortunately, this groundwater is becoming more and more saline due to climate change. This technology could bring sustainable, affordable clean water to under-reached places around the world.”
The researchers report details the new system in a paper published in the journal, Nature Water. The study’s co-authors are Bessette, Winter, and staff engineer, Shane Pratt.
Pratt said: “Our focus now is on testing, maximising reliability, and building out a product line that can provide desalinated water using renewables to multiple markets around the world.”
Main image: Jon Bessette sits atop a trailer housing the desalination system at the research facility in Alamogordo, New Mexico. Credit: Shane Pratt
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