Using Hot Sand To Store Energy
As communities, cities, and states develop ambitious energy efficiency and decarbonization goals, energy storage is an increasingly critical component of our energy economy. Renewable energy sources like solar and wind are changing how we power our buildings, industries, and grid; however, they are intermittent ― we need continuous power even after the sun sets or the wind dies down. As such, energy storage is critical to ensuring continuous power and allows energy producers to take full advantage during times of overgeneration on sunny (or windy) days.
When it comes to short-duration energy storage, lithium-ion batteries are considered the front-runner, but batteries are not the whole story. Our buildings, businesses, industries, and grid need more storage, at lower cost, for longer durations, and at larger capacities than batteries can provide to displace fossil fuels for a sustainable future.
To meet this energy storage challenge, researchers at the National Renewable Energy Laboratory (NREL) are in the late stages of prototype testing a game-changing new thermal energy storage technology that uses inexpensive silica sand as a storage medium. Economic Long-Duration Electricity Storage by Using Low-Cost Thermal Energy Storage and High-Efficiency Power Cycle (ENDURING) is a reliable, cost-effective, and scalable solution that can be sited anywhere.
The ENDURING Mechanism: Storable, Electrically Heated Sand Delivers On-Demand Electricity
ENDURING uses electricity from surplus solar or wind to heat a thermal storage material — silica sand. Particles are fed through an array of electric resistive heating elements to heat them to 1,200°C (imagine pouring sand through a giant toaster). The heated particles are then gravity-fed into insulated concrete silos for thermal energy storage. The baseline system is designed for economical storage of up to a staggering 26,000 MWh of thermal energy. With modular design, storage capacity can be scaled up or down with relative ease.
Particle thermal energy storage systems can be constructed with existing infrastructure from retired coal and gas power plants. Image by Al Hicks and Besiki Kazaishvili, NREL
When energy is needed, the hot particles are gravity-fed through a heat exchanger, heating and pressurizing a working gas inside to drive the turbomachinery and spin generators that create electricity for the grid. The system discharges during periods of high electricity demand and when limited solar photovoltaic or wind power are available, such as early in the morning and evening, during dinner preparation, and when TVs are on. Once discharged, the spent, cold particles are once again fed into insulated silos for storage until conditions (and economics) are appropriate again for charging.
How Hot Sand in a Silo Is Revolutionizing Energy Decarbonization
ENDURING offers several advantages relative to other electricity storage technologies.
As a storage medium, abundant silica sand is stable and inexpensive at $30‒$50/ton, and has a limited ecological impact both in extraction and end of life. For comparison, lithium-ion batteries have an exceptional energy storage density ― important for certain sectors such as transportation, where weight matters ― but it comes at a high cost. Particle thermal energy storage is a less energy dense form of storage, but is very inexpensive ($2‒$4 per kWh of thermal energy at a 900°C charge-to-discharge temperature difference). The energy storage system is safe because inert silica sand is used as storage media, making it an ideal candidate for massive, long-duration energy storage.
ENDURING systems have no particular siting constraints and can be located anywhere in the country. These systems may also be constructed using existing infrastructure from retired coal- and gas-fired power plants.
ENDURING technology can support the expansion of renewable energy generation across our country. Building these cost-effective particle thermal energy storage systems around the United States could help utilities to continue using solar and wind without running the risk of destabilizing the grid or needing to curtail renewable energy generation. Particle thermal energy storage will also provide energy reserves so our communities can better navigate through extended weather events, whether a week-long cold front or a summer heat wave.
Multiple Potential Economical Use Cases Support Decarbonization by 2050
The Biden Administration seeks to achieve a carbon-free power sector by 2035 and a net zero emissions economy by 2050. Zhiwen Ma, principal investigator of the ENDURING project, sees an important role for particle thermal energy storage in achieving these goals. “While decarbonization of electricity has a clear path, decarbonization of the whole economy ― which includes things like building heat and industrial processes ― is more challenging because natural gas is very cheap, making it hard to displace,” he said. “Decarbonizing industrial processes and building heat is very tough.”
Converting renewable electricity into heat is one way to decarbonize these sectors. Ma sees an opportunity for particle thermal energy storage to play a role in cost-effectively supplanting natural gas. By using a heat pump, one unit of electricity is transformed into two to three units of heat, which can be stored in the particle thermal energy storage system and then later delivered to the end user (depending on the coefficient of performance of the heat pump or the use of an emerging pumped thermal energy storage technology). These technologies can be used for building and industry process heating to replace coal or natural gas.
In addition to providing grid storage and building heat, ENDURING offers a steady source of heat for industrial and chemical processes that are otherwise incompatible with the intermittency associated with solar and wind power.
According to NREL researcher Patrick Davenport, the economic environment, decarbonization goals, and technology have aligned for particle thermal energy storage. “Sand and concrete silos with refractory insulation are very inexpensive materials that can lead to low-cost energy storage,” he said. “Traditional four-hour storage technologies don’t scale well to the grid or city scale. Now that we are in need of large-scale energy storage, this technology makes a lot of sense.”
Early Achievements and ENDURING Promise
The ENDURING project is seeing promising progress and early interest. The team recently won the American Society of Mechanical Engineers Advanced Energy Systems Division and Solar Energy Division 2021 First-Place Best Paper Award and several U.S. Department of Energy technology funding awards. Patents on concentrating solar power integration have been awarded, and several more are being filed.
The ENDURING prototype heaters and heat exchangers are currently undergoing testing in high-temperature conditions. If the prototype tasks are successful this fall, Ma is confident that ENDURING technology will offer great potential to support renewable integration for future carbon-free energy supply.
Ma is not the only one who sees promise: NREL and clean-energy technology firm Babcock & Wilcox have an exclusive intellectual property option agreement to license the ENDURING particle thermal energy storage technology. Babcock & Wilcox are among several industry and academic research partners that contributed to the ENDURING project, including General Electric, Allied Mineral Products, Worley, Purdue University, and Colorado School of Mines.
Learn more about NREL thermal systems and concentrating solar power research.
Article courtesy of NREL.
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On today’s exciting episode of Quick Charge, we don’t even mention “you know who,” focusing instead on EV news from Rivian, Lucid, Nissan, Ford, and what it takes to make a MAN in the heavy truck space. Check it out!
Sure, Nissan is pushing back production estimates on its yet-to-begin-production Nissan LEAF and Ford’s EV sales were down significantly in Q2, but there’s more to the story than the “Faux News” crowd would have you believe. Plus: some new electric success stories from Porsche and a disappointing (but still cool) dive into some new home backup battery tech.
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he 30% federal solar tax credit is ending this year. If you’ve ever considered going solar, now’s the time to act. To make sure you find a trusted, reliable solar installer near you that offers competitive pricing, check out EnergySage, a free service that makes it easy for you to go solar. It has hundreds of pre-vetted solar installers competing for your business, ensuring you get high-quality solutions and save 20-30% compared to going it alone. Plus, it’s free to use, and you won’t get sales calls until you select an installer and share your phone number with them.
Your personalized solar quotes are easy to compare online and you’ll get access to unbiased Energy Advisors to help you every step of the way. Get started here.
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Battery electric cars sold today in Europe produce 73% less life-cycle greenhouse gas emissions than gas cars, even when factoring in production, according to new research from the International Council on Clean Transportation (ICCT). That’s a big improvement from 2021, when the gap was 59%.
Meanwhile, hybrids and plug-in hybrids haven’t made much progress. The study confirms what clean transportation advocates have been saying for years: If Europe wants to seriously slash emissions from its dirtiest mode of transport – ICE passenger cars, which pump out nearly 75% of the sector’s pollution – it needs to go all-in on battery EVs.
“Battery electric cars in Europe are getting cleaner faster than we expected and outperform all other technologies, including hybrids and plug-in hybrids,” said ICCT researcher Dr. Marta Negri. Credit the continent’s rapid shift to renewables and the higher energy efficiency of EVs.
The makeup of the EU’s power grid is changing fast. By 2025, renewables are expected to generate 56% of Europe’s electricity, up from 38% in 2020. And that’s just the beginning: the share could hit 86% by 2045. Since cars bought today could still be on the road two decades from now, the growing use of clean electricity will only boost EVs’ climate benefits over time.
Gas-powered cars, on the other hand, will stay mostly tied to fossil fuels as the cost and availability of biofuels and e-fuels are still uncertain.
Hybrids and plug-in hybrids only cut lifetime emissions by 20% and 30%, respectively, compared to gas cars. That’s partly because plug-in hybrids tend to run on gas more than expected. So while hybrids aren’t useless, they’re just not good enough if we’re serious about climate goals.
Countering EV myths with hard data
There’s been a lot of noise lately about whether EVs are really that green. The ICCT study takes aim at the bad data and misleading claims floating around, like ignoring how the grid gets cleaner over time or using unrealistic gas mileage figures.
It’s true that manufacturing EVs creates more emissions upfront – about 40% more than making a gas car, mostly due to the battery. But EVs make up for it quickly: that extra emissions load is usually wiped out after about 17,000 km (10,563 miles) of driving, which most drivers hit in a year or two.
“We’ve recently seen auto industry leaders misrepresenting the emissions math on hybrids,” said Dr. Georg Bieker, senior researcher at the ICCT. “But life-cycle analysis is not a choose-your-own-adventure exercise.”
ICCT’s new analysis includes emissions from vehicle and battery production and recycling, fuel and electricity production, and fuel consumption and maintenance. It even adjusts for how the electricity mix will change in the coming years – a key detail when measuring plug-in hybrid performance.
Read more: Volkswagen’s 47% BEV sales jump includes a 24% boost in the US
The 30% federal solar tax credit is ending this year. If you’ve ever considered going solar, now’s the time to act. To make sure you find a trusted, reliable solar installer near you that offers competitive pricing, check out EnergySage, a free service that makes it easy for you to go solar. It has hundreds of pre-vetted solar installers competing for your business, ensuring you get high-quality solutions and save 20-30% compared to going it alone. Plus, it’s free to use, and you won’t get sales calls until you select an installer and share your phone number with them.
Your personalized solar quotes are easy to compare online and you’ll get access to unbiased Energy Advisors to help you every step of the way. Get started here.
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![Here's our closest look at the Kia EV2 caught testing in the Alps [Video]](https://i0.wp.com/electrek.co/wp-content/uploads/sites/3/2025/07/Kia-EV2-closest-look.jpeg?resize=1200,628&quality=82&strip=all&ssl=1)
The EV2 may be Kia’s smallest electric vehicle, but it has a big presence on the road. Kia promises it won’t feel so small when you’re inside, thanks to clever storage and flexible seating. After a prototype was spotted testing in the Alps, we are getting our closest look at the Kia EV2 so far.
Kia EV2 spotted in the Alps offers our closest look yet
Kia first unveiled the Concept EV2 during its 2025 EV Day event (see our recap of the event) in April, a preview of its upcoming entry-level electric SUV.
Despite its small size, Kia claims it will “redefine urban electric mobility” with new innovative features and more. Kia has yet to say exactly how big it will be, but given it will sit below the EV3, it’s expected to be around 4,000 mm (157″) in length. The EV3 is 4,300 mm (169.3″) in length.
Looking at it from the side, it sits much higher than you’d expect, similar to Kia’s larger EV9. During an exclusive event at Milan Design Week in April, Kia gave a sneak peek of the interior.
Kia said the interior is inspired by a “picnic in the city,” or in other words, a retreat from the busy city life. With a flat-floor design and flexible seating, you can quite literally have a picnic in the city.
Although we’ve seen the EV2 out in public testing a few times, a new video provides the closest look at Kia’s upcoming electric SUV.
The video, courtesy of CarSpyMedia, shows an EV2 prototype testing in the Alps with European license plates. There’s also a “Testfahrt” sticker on the back, which translates to “Test Car” in German.
As the prototype drives by, you can get a good look at it from all angles. Like in past sightings, the front features stacked vertical headlights with Kia’s signature Star Map lighting. Even the rear lights appear to be identical to those of the concept.
The interior will feature Kia’s next-gen ccNC (connected car Navigation Cockpit) infotainment system. The setup includes dual 12.3″ instrument clusters and infotainment screens in a curved panoramic display. Depending on the model, it could also include an added 5.3″ climate control screen.
Last month, a crossover coupe-like model was spotted on a car carrier in Korea, hinting at a new variant. The new model featured a design similar to that of the Genesis GV60.
Kia’s CEO, Ho Sung Song, also recently told Autocar that a smaller, more affordable EV was in the works to sit below the EV2. Song said the new EV, priced under €25,000 ($30,000), was “one area we are studying and developing.”
With the EV4 and EV5 launching this year, followed by the EV2 in 2026, it could be closer toward the end of the decade before we see it hit the market. Next-gen EV6 and EV9 models are also due out around then.
The Kia EV2 is set to launch in Europe and other global regions in 2026. Unfortunately, it’s not expected to make the trip to the US.
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