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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Newly published data from the Federal Energy Regulatory Commission (FERC), reviewed by the SUN DAY Campaign, reveal that solar accounted for over 75% of US electrical generating capacity added in the first nine months of 2025. In September alone, solar provided 98% of new capacity, marking 25 consecutive months in which solar has led among all energy sources.
Year-to-date (YTD), solar and wind have each added more new capacity than natural gas has. The mix of all renewables remains on track to exceed 40% of installed capacity within three years; solar alone may be 20%.
Solar was 75% of new generating capacity YTD
In its latest monthly “Energy Infrastructure Update” report (with data through September 30, 2025), FERC says 48 “units” of solar totaling 2,014 megawatts (MW) were placed into service in September, accounting for 98% of all new generating capacity added during the month. Oil provided the balance (40 MW).
The 567 units of utility-scale (>1 MW) solar added during the first nine months of 2025 total 21,257 MW and were 75.3% of the total new capacity placed into service by all sources. Solar capacity added YTD is 6.5% more than that added during the same period a year earlier.
Solar has now been the largest source of new generating capacity added each month for 25 consecutive months, from September 2023 to September 2025. During that period, total utility-scale solar capacity grew from 91.82 gigawatts (GW) to 158.43 GW. No other energy source added anything close to that amount of new capacity. Wind, for example, expanded by 11.07 GW while natural gas’s net increase was just 4.60 GW.
Between January and September, new wind energy has provided 3,724 MW of capacity additions – an increase of 28.6% compared to the same period last year and more than the new capacity provided by natural gas (3,161 MW). Wind accounted for 13.2% of all new capacity added during the first nine months of 2025.
Renewables were 88% of new capacity added YTD
Wind and solar (plus 4 MW of hydropower and 6 MW of biomass) accounted for 88.5% of all new generating capacity while natural gas added just 11.2% YTD. The balance of net capacity additions came from oil (63 MW) and waste heat (17 MW).
Utility-scale solar’s share of total installed capacity (11.78%) is now virtually tied with that of wind (11.80%). If recent growth rates continue, utility-scale solar capacity should surpass that of wind in FERC’s next “Energy Infrastructure Update” report.
Taken together, wind and solar make up 23.58% of the US’s total available installed utility-scale generating capacity.
Moreover, more than 25% of US solar capacity is in the form of small-scale (e.g., rooftop) systems that are not reflected in FERC’s data. Including that additional solar capacity would bring the share provided by solar and wind to more than a quarter of the US total.
With the inclusion of hydropower (7.59%), biomass (1.05%) and geothermal (0.31%), renewables currently claim a 32.53% share of total US utility-scale generating capacity. If small-scale solar capacity is included, renewables now account for more than one-third of the total US generating capacity.
Solar soon to be No. 2 source of US generating capacity
FERC reports that net “high probability” net additions of solar between October 2025 and September 2028 total 90,614 MW – an amount almost four times the forecast net “high probability” additions for wind (23,093 MW), the second fastest growing resource.
FERC also foresees net growth for hydropower (566 MW) and geothermal (92 MW) but a decrease of 126 MW in biomass capacity.
Meanwhile, natural gas capacity is projected to expand by 6,667 MW, while nuclear power is expected to add just 335 MW. In contrast, coal and oil are projected to contract by 24,011 MW and 1,587 MW, respectively.
Taken together, the net new “high probability” net utility-scale capacity additions by all renewable energy sources over the next three years – the Trump administration’s remaining time in office – would total 114,239 MW. On the other hand, the installed capacity of fossil fuels and nuclear power combined would shrink by 18,596 MW.
Should FERC’s three-year forecast materialize, by mid-fall 2028, utility-scale solar would account for 17.3% of installed U.S. generating capacity, more than any other source besides natural gas (39.9%). Further, the capacity of the mix of all utility-scale renewable energy sources would exceed 38%. The inclusion of small-scale solar, assuming it retains its 25% share of all solar energy, could push solar’s share to over 20% and that of all renewables to over 41%, while the share of natural gas would drop to less than 38%.
In fact, the numbers for renewables could be significantly higher.
FERC notes that “all additions” (net) for utility-scale solar over the next three years could be as high as 232,487 MW, while those for wind could total 65,658 MW. Hydro’s net additions could reach 9,927 MW while geothermal and biomass could increase by 202 MW and 32 MW, respectively. Such growth by renewable sources would swamp that of natural gas (29,859 MW).
“In an effort to deny reality, the Trump Administration has just announced a renaming of the National Renewable Energy Laboratory (NREL) in which it has removed the word ‘renewable’,” noted the SUN DAY Campaign’s executive director Ken Bossong. “However, FERC’s latest data show that no amount of rhetorical manipulation can change the fact that solar, wind, and other renewables continue on the path to eventual domination of the energy market.”
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The Century is considered the most luxurious Toyota, and now it’s being spun off into its own high-end brand. Despite the rumors, the ultra-luxury brand won’t be as electric as expected.
Toyota sets new luxury brand up to fail with ICE plans
First introduced in 1967, the Century was launched in celebration of Toyota’s founder, Sakichi Toyoda’s 100th birthday.
The Century has since become a symbol of status and wealth in Japan, often used as a chauffeur car by high-profile company officials.
Toyota previewed the future of the ultra-luxury marquee at the 2025 Japan Mobility Show in October, launching it as a new standalone brand positioned above Lexus.
The new Century brand is set to rival higher-end automakers like Rolls-Royce and Bentley, but it won’t be as electric as initially expected. Toyota’s powertrain boss, Takashi Uehara, told CarExpert that the luxury brand’s first vehicle will, in fact, have an internal combustion engine.
Although no other details were offered, Uehara confirmed, “Yes, it will have an engine.” As to what kind, that has yet to be decided, Toyota’s powertrain president explained.
Like the next-gen Lexus supercar and upcoming Toyota GR GT, Uehara said the Century model could include a V8 engine.
The Century has been Toyota’s only vehicle with a V12 engine. In 2018, Toyota dropped the V12 in favor of a V8 hybrid powertrain for its third-generation.
Toyota’s Century launched its first SUV in 2023, currently on sale in Japan with a V6 plug-in hybrid system alongside the sedan.
Already widely considered the biggest laggard in the shift to fully electric vehicles, Toyota doubled down, developing a series of new internal combustion engines for upcoming models.
Century is one of the five global brands the Japanese auto giant introduced in October, along with Daihatsu, GR Sport, Lexus, and Toyota.
Electrek’s Take
It’s not surprising to see Toyota sticking with ICE for its ultra-luxury Century brand, but it will likely be a costly move.
Chinese auto giants, such as BYD and FAW Group, are quickly expanding into new segments, including high-end models under luxury brands such as Yangwang and Hongqi.
These companies are now expanding into new overseas markets, like Europe and Southeast Asia, where Japanese brands like Toyota have traditionally dominated, to drive growth.
Top luxury brands, including Porsche, BMW, and Mercedes-Benz, are already struggling to keep pace with Chinese EV brands. How does Toyota plan to compete with an “ultra-luxury” brand that still sells outdated ICE vehicles? We will find out more over the coming months and years as new sales data is released.
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SparkCharge has partnered with the Massachusetts Clean Energy Center (MassCEC) and Zipcar to launch the Northeast’s first off‑grid, mobile DC fast‑charging hub for shared EVs. The goal is to bring fast, reliable EV charging infrastructure into communities without having to wait for costly or slow grid upgrades.
The hub sits at Zipcar’s maintenance facility in East Boston, an Environmental Justice community. It’s funded through MassCEC’s InnovateMass program and gives onsite mechanics the ability to quickly recharge a rotating fleet of Zipcar EVs before they’re dispatched across Greater Boston. Members and rideshare drivers who rent Zipcars will get steadier access to charged EVs.
“Electrification should never be limited by where the grid is or how long it takes,” SparkCharge founder and CEO Joshua Aviv said. “With this program in East Boston, we’re showing how fleets can deploy at scale, in any community, and deliver clean mobility today.”
At the center of the setup is SparkCharge’s Mobile Battery‑Powered Trailer, which delivers 320 kW of DC fast charging without the delays and big price tags that usually come with fixed infrastructure. The trailer can recharge from Zipcar’s existing onsite power between sessions, topping up its high‑capacity batteries without stressing the local grid. Since it avoids major grid upgrades entirely, the model is designed to deploy quickly and at zero upfront cost for fleets.
MassCEC says the project shows what community‑first fast charging can look like. “Every resident deserves access to clean, reliable transportation,” said Leslie Nash, MassCEC’s senior director of Technology‑to‑Market. “By partnering with SparkCharge and Zipcar in East Boston, we’re showing how Massachusetts is leading the way in clean transportation innovation.”
The hub also plays into Massachusetts’ push to hit its net‑zero 2050 targets. As shared mobility grows, electrifying fleets will be key to cutting emissions in dense urban corridors. This project introduces a scalable charging option to a part of Boston that is underserved by public charging, helping to keep Zipcar’s EVs reliably on the road.
“For twenty‑five years, Zipcar has been a leader in shared mobility, and we’re proud to take another step toward a more sustainable future,” said Angelo Adams, Zipcar’s president. “Working with SparkCharge and MassCEC allows us to bring fast, reliable EV charging directly to our members and rideshare drivers.”
Zipcar, which is owned by car rental company Avis Budget, announced on December 1 that it was shutting down its UK operations by December 31, 2025. An Avis Budget spokesperson stated that the reason was “to streamline operations, improve returns, and position the company for long-term sustainability and growth,” adding that “all other markets remain unaffected.”
Read more: With a $30M raise, SparkCharge takes EV fleet charging off-grid
If you’re looking to replace your old HVAC equipment, it’s always a good idea to get quotes from a few installers. To make sure you’re finding a trusted, reliable HVAC installer near you that offers competitive pricing on heat pumps, check out EnergySage. EnergySage is a free service that makes it easy for you to get a heat pump. They have pre-vetted heat pump installers competing for your business, ensuring you get high quality solutions. Plus, it’s free to use!
Your personalized heat pump 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. – *ad
FTC: We use income earning auto affiliate links. More.
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