MIT scientists used solar power to make drinking water cheaper than tap water
MIT scientists have designed a solar-powered desalination system that turns saltwater into drinkable water at a higher volume – and lower cost.
Researchers from MIT and Shanghai Jiao Tong University have published a paper, “Extreme salt-resisting multistage solar distillation with thermohaline convection,” in the journal Joule about a study that has the potential to make a big leap forward in reducing the cost of water production because it doesn’t require electricity to run.
The device they built creates circular currents of water known as eddies that look like small whirlpools that function similarly to the ocean’s much larger thermohaline circulation. This circulation, combined with the sun’s heat, drives water to evaporate, leaving salt behind.
Lenan Zhang, a research scientist in MIT’s Device Research Laboratory, explains:
When seawater is exposed to air, sunlight drives water to evaporate. Once water leaves the surface, salt remains. And the higher the salt concentration, the denser the liquid, and this heavier water wants to flow downward.
By mimicking this kilometer-wide phenomena in a small box, we can take advantage of this feature to reject salt.
How it works
Scientists used a small, thin box topped with a dark material that efficiently absorbs the sun’s heat. Inside, the box is separated into a top and bottom section. Water can flow through the top half, where the ceiling is lined with an evaporator layer that uses the sun’s heat to warm up and evaporate any water in direct contact. The water vapor is then funneled to the bottom half of the box, where a condensing layer air-cools the vapor into pure drinkable water.
The researchers set the entire box at a tilt within a larger empty vessel, then attached a tube from the top half of the box down through the bottom of the vessel, and floated the vessel in salt water. The water naturally pushes up through the tube and into the box, where the tilt of the box, combined with thermal energy from the sun, induces the water to swirl as it flows through. The small eddies help to bring water in contact with the upper evaporating layer while keeping salt circulating rather than settling and clogging.
Other passive solar desalination concepts are currently being tested by other teams, but the MIT researchers say their new system has higher water-production and salt-rejection rates.
They assert that if the system is scaled up to the size of a small suitcase, it could produce about 4 to 6 liters (1 to 1.5 gallons) of drinking water per hour and last several years before requiring replacement parts. At that scale and performance, the system could produce drinking water at a rate and price that’s cheaper than tap water.
A scaled-up device could passively produce enough drinking water to meet the daily requirements of a small family. It could also supply off-grid coastal communities near seawater.
What do you think of this solar-powered desalination system? Do you think this would, in theory, provide relief for folks in Louisiana whose drinking water is threatened by saltwater from the Gulf of Mexico that’s infiltrating the Mississippi River due to drought? Let us know in the comments below.
Read more: US solar is booming – here’s the newly released data
Photo: MIT
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Solar panel giant Qcells announced today that it’s temporarily furloughing 1,000 US workers – 25% of its workforce – and reducing pay and shifts at its factories in northeast Georgia due to supply chain delays caused by US Customs.
Qcells furloughs 1,000 workers
The supply chain delays are hindering the company’s ability to import components to build its solar panels. This has resulted in Qcells’ two factories in Cartersville and Dalton being unable to operate at full capacity for several months.
Qcells spokeswoman Marta Stoepker shared the following statement in an exclusive with Channel 2 Action News in Atlanta:
The company says the furloughed workers, who were notified this afternoon, will retain full benefits and won’t be laid off. However, Qcells will no longer be using staffing agency employees in Georgia “at this time.”
As Qcells introduced new supply chains to support its growing solar panel manufacturing facilities in Georgia, the company was recently forced to scale back production while our shipments into the US were delayed in the customs clearance process.
Although our supply chain operations are beginning to normalize, today we shared with our employees that HR actions must be taken to improve operational efficiency until production capacity returns to normal levels.
Stoepker said it expects to bring the furloughed workers back “in the coming weeks and months.” She continued:
Our commitment to building the entire solar supply chain in the United States remains. We will soon be back on track with the full force of our Georgia team delivering American-made energy to communities around the country.
Electrek’s Take
In January 2023, the Seoul-headquartered Qcells announced it would invest more than $2.5 billion to build a solar supply chain in Georgia – the largest-ever investment in clean energy manufacturing in the US to date. That included expanding the Dalton solar factory and building a fully integrated solar supply chain factory in Cartersville, Georgia, that will manufacture solar ingots, wafers, cells, and finished panels.
It’s not quite there yet, because that takes time. In the meantime, it’s being penalized by Customs. The US government under Trump says it’s keen on boosting domestic manufacturing. Why would it work against a company that’s onshoring an entire solar supply chain, including recycling?
Dalton and Cartersville employ nearly 4,000 people. Its total output will reach 8.4 GW of solar production capacity per year, which is equivalent to nearly 46,000 panels per day – enough to power approximately 1.3 million homes annually.
It’s ludicrous that it has been forced to furlough a quarter of its workforce due to the ineptness of the Trump administration’s US Customs policies. This is right up there with the ICE arrests at Hyundai’s plant in Georgia. Bravo.
Read more: Georgia gives US solar panel manufacturing a big boost with a new factory
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The breakthrough EV batteries Toyota says will double driving range and cut charging times are facing another setback. The company is once again delaying plans for a new battery plant in Japan.
Why is Toyota delaying its EV battery plant this time?
Earlier this year, Toyota bought a 280,000-square-meter plot of land in Fukuoka, Japan, where it planned to build a plant to produce the more advanced EV batteries.
A location agreement was expected to be signed by April, but Toyota pushed back construction by several months, blaming slower-than-expected demand for electric vehicles.
The agreement was expected to be finalized this Fall, but that will no longer be the case. According to Nikkei, Toyota is delaying the EV battery plant for the second time. Toyota will review and adjust plans over the next year.
Fukuoka governor, Seitaro Hattori, confirmed the news with reporters on Friday following a meeting with Toyota’s president, Koji Sato. Hattori also shut down claims that Toyota was planning to scrap the battery plant altogether.
Toyota again blamed slowing EV demand for the delay. The decision comes despite Keiji Kaita, president of Toyota’s Carbon Neutral Advanced Engineering Development Center, confirming at the Japan Mobility Show just last week that it’s “sticking on the schedule” to introduce its first solid-state battery-powered EV by 2028.
Last month, Toyota said it aimed to “achieve the world’s first practical use of all-solid-state batteries in BEVs” after securing a partnership with Sumitomo Metal Mining Co. to mass-produce them. It’s also working with Japanese oil giant Idemitsu.
The company recently revealed a solid-state battery pack prototype that it claims can deliver 747 miles (1,200 km) range and 10-minute fast charging, but will we ever see it actually in production?
Electrek’s Take
Toyota has been making empty promises about EV batteries for almost a decade now. It initially planned to introduce solid-state EV batteries in 2020, then pushed it to 2023, then 2026, and now it’s saying it will be around 2028.
Mass production is likely closer to the end of the decade, if Toyota doesn’t delay it again. While it’s blaming the slowing demand, global EV sales are still on the rise. According to Rho Motion, global EV sales topped 2 million for the first time in a single month in September 2025. Through the first nine months of the year, EV sales are up 26% compared to the same period in 2024.
Even with the US ending the $7,500 federal tax credit and other policies designed to promote electric vehicles, global adoption will continue building momentum over the next few years.
Is it a demand issue, or is Toyota just looking for another excuse? With rivals like Volkswagen, Mercedes-Benz, Hyundai, BMW, and Honda advancing next-gen EV batteries, Toyota will only fall further behind if it continues delaying key projects.
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