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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Tesla (TSLA) is no longer confidently stating growth in its automotive business for 2025, and it has delayed updating its guidance until the next quarter after a disappointing performance in the first three months of the year.
2024 was Tesla’s first year in a decade where its vehicle deliveries went down year-over-year.
Just a few months ago, in January, Tesla was confident in predicting that it would return to growth in 2025:
“With the advancements in vehicle autonomy and the introduction of new products, we expect the vehicle business to return to growth in 2025.”
Today, Tesla released its Q1 2025 financial results, confirming that it had its worst quarter in years to start 2025.
The automaker is now clearly not as confident about returning to growth in its automotive business this year.
Tesla updated its “outlook” section this quarter to highlight the potential impact of trade policies and now no longer discusses automotive growth in isolation. Instead, it bundled automotive and energy businesses together and said that it will “revisit its 2025 guidance” next quarter:
It is difficult to measure the impacts of shifting global trade policy on the automotive and energy supply chains, our cost structure and demand for durable goods and related services. While we are making prudent investments that will set up both our vehicle and energy businesses for growth, the rate of growth this year will depend on a variety of factors, including the rate of acceleration of our autonomy efforts, production ramp at our factories and the broader macroeconomic environment. We will revisit our 2025 guidance in our Q2 update.
Tesla’s vehicle deliveries are already down about 50,000 units so far this year compared to last year.
It will be challenging to catch up in the current macroeconomic situation.
Tesla again guided the start of production of “new affordable models” in the first half of 2025, which could help the automaker to deliver more cars.
However, as we have previously reported, these new vehicles are expected to be stripped-down Model Y and Model 3, which will cannibalize Tesla’s current sales and limit its growth to those products.
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US DC fast charging is becoming more reliable, and charging stations are getting bigger and busier, according to a new Q1 2025 report from the EV data analysts at Paren.
DC fast charging station reliability is on the rise
Paren’s latest US Reliability Index – “Can I successfully charge at this charger?” – increased from 81.2 points in Q4 2024 to 82.6 points in Q1 2025, a notable jump of 1.7%. According to Bill Ferro, CTO at Paren, “This continues a quarterly trend across the US non-Tesla fast charging infrastructure, which suggests that the ongoing efforts to replace or sunset older hardware are having a positive impact on station uptime. In addition, newer entrants into the field are bringing time-tested hardware along with enhanced driver experiences.”
Utah, Alaska, Tennessee, North Carolina, and Nevada were the top-ranked states for DC fast charging reliability in Q1 2025.
Growth slows, but charging stations are getting larger
New DC fast charging ports grew to 55,580 at the end of Q1 2025, up 3,667 from last quarter, with total stations reaching 10,839, an increase of 794. This is fewer new additions compared to the surge seen at the end of 2024, reflecting typical seasonal slowdowns due to winter weather. However, there’s a bright spot: the average number of ports per station among non-Tesla networks rose to 3.9, compared to 2.7 year-over-year. The Tesla Supercharger network now averages 13 ports per station.
Utilization rates reflect the urban-rural divide
Average utilization – that’s the minutes of a charging session as a percentage of time a station is open each day – dropped slightly from 16.6% in Q4 2024 to 16.2% in Q1 2025, following typical holiday travel patterns. But overall, charging use is climbing, especially in dense urban areas with significant rideshare and apartment communities that rely heavily on public chargers.
Early days for NACS transition
The Combined Charging System (CCS) remains dominant, with 59% of new ports, and the shift toward Tesla’s NACS (J3400) standard is still in its very early stages. Only 104 non-Tesla NACS ports were added this quarter at non-Tesla networks, so drivers of new non-Tesla vehicles need to use their adapters if they want to use Superchargers.
Fixed pricing prevails
Charging operators primarily use fixed pricing (80%), with Time of Use (TOU) pricing making up 16%. Pay-by-time options are rare, used only 4.2% of the time.
California is the only major state where TOU pricing surpasses fixed pricing, while many states, such as Oklahoma, Vermont, and Arkansas, almost exclusively utilize fixed pricing models.
As for the most expensive places to fast charge your EV? The top four metropolitan statistical areas are all in California, with average rates at $0.60 or $0.61 per kWh.
Rural and low-income areas at risk
The Trump administration’s cancellation of the National Electric Vehicle Infrastructure (NEVI) program poses a significant threat to rural and low-income communities. Loren McDonald, chief analyst at Paren, cautioned, “Our data is a harbinger of less expansion in rural and lower-income markets as CPOs will increasingly focus on urban markets, seeing high utilization, often north of 30%, versus markets with less than 5% utilization.”
‘Charging 2.0’ – a new industry phase
McDonald summed up the report by marking 2024 as a pivotal year, stating, “2024 was a year of mixed news in the US DC fast charging industry, but it will be remembered as a pivotal turn to a new era we are calling ‘Charging 2.0’. Charge-point operators and new players in the industry are increasingly focused on creating a great customer experience, improving reliability of chargers, and reaching profitability – a shift from chasing the availability of incentives, racing to get chargers in the ground, and then crossing your fingers that utilization will grow over time.”
Read more: Trump just canceled the federal NEVI EV charger program
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Tesla (TSLA) released its financial results and shareholders’ letter for the first quarter (Q1) and full-year 2025 after market close today.
We are updating this post with all the details from the financial results, shareholders’ letter, and the conference call later tonight. Refresh for the latest information.
Tesla Q1 2025 earnings expectations
As we reported in our Tesla Q1 2025 earnings preview yesterday, the Wall Street consensus for this quarter was $21.345 billion in revenue and earnings of $0.41 per share.
The expectations had been significantly downgraded over the last month, as analysts were surprised by Tesla’s announcement of much lower deliveries than expected in the first quarter.
Did Tesla meet them?`
Tesla Q1 2025 financial results
After the market closed today, Tesla released its financial results for the first quarter and confirmed that it missed expectations with earnings of $0.27 per share (non-GAAP), and it also missed revenue expectations with $19.335 billion during the last quarter.
This is a big miss for Tesla despite the company admitting to selling a lot more regulatory credits this quarter.
At $595 million in credit sales, Tesla would have lost money without it in Q1 2025:
In short, Tesla is on the verge of being a money-losing company.
We will be posting our follow-up posts here about the earnings and conference call to expand on the most important points (refresh the page to see the most recent posts):
Here’s Tesla’s Q1 2025 shareholder presentation in full:
Here’s Tesla’s conference call for the Q1 2025 results:
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