Join day by day information updates from CleanTechnica on e-mail. Or observe us on Google Information!
Anybody who has ever hot-footed it barefoot throughout the seashore on a sunny day walks away with a better understanding of simply how a lot warmth sand can retain. That skill is anticipated to play a significant position sooner or later, as expertise involving heated sand turns into a part of the reply to vitality storage wants.
Batteries are seemingly what most individuals take into consideration when it comes to storing vitality for later use, however different applied sciences exist. Pumped storage hydropower is one widespread technique, albeit one which requires reservoirs at completely different elevations and is proscribed by geography. One other strategy depends on what is named thermal vitality storage, or TES, which makes use of molten salt and even superheated rocks.
TES reveals promise as a low-cost different to current storage applied sciences, and storing vitality in strong particles akin to sand supplies a prepared reply, with out geological restrictions.
In any case, sand, like air and water, is all over the place.
“Sand is straightforward to entry. It’s environmentally pleasant. It’s steady, fairly steady, in a large temperature vary. It is usually low price,” mentioned Zhiwen Ma, a mechanical engineer within the laboratory’s Thermal Power Methods Group.
The Want for Lengthy-Time period Storage
Patented expertise developed and prototyped at NREL reveals how heaters powered by renewable vitality sources like wind and photo voltaic can increase the temperature of sand particles to the specified temperature. The sand is then deposited right into a silo for storage and use later, both to generate electrical energy or for course of warmth in industrial functions. A laboratory-scale prototype validated the expertise and allowed researchers to create a pc mannequin that reveals a commercial-scale gadget would retain greater than 95% of its warmth for a minimum of 5 days.
“Lithium-ion batteries have actually cornered the market at two to 4 hours of storage, but when we need to obtain our carbon discount objectives, we’ll want long-duration vitality storage units—issues that may retailer vitality for days,” mentioned Jeffrey Gifford, a postdoctoral researcher at NREL.
Gifford, who already shares two patents with Ma on warmth exchangers that convert saved thermal vitality to electrical energy, mentioned using sand or different particles to retailer thermal vitality has one other benefit over batteries. “Particle thermal vitality storage doesn’t depend on rare-earth supplies or supplies which have complicated and unsustainable provide chains. For instance, in lithium-ion batteries, there are loads of tales concerning the problem of mining cobalt extra ethically.”
Along with TES, Gifford’s experience is in computational fluid dynamics. That information is vital as a result of the sand must circulation via the storage gadget. Different TES media contains concrete and rocks, which might simply retain warmth however stay solidly in place. “Your warmth switch is far increased and far faster and way more efficient should you’re transferring your media,” Gifford mentioned.
TES additionally has one other key benefit: the associated fee. Ma has calculated sand is the most cost effective choice for vitality storage when in comparison with 4 rival applied sciences, together with compressed air vitality storage (CAES), pumped hydropower, and two forms of batteries. CAES and pumped hydropower can solely retailer vitality for tens of hours. The associated fee per kilowatt-hour for CAES ranges from $150 to $300, whereas for pumped hydropower it’s about $60. A lithium-ion battery would price $300 a kilowatt-hour and solely have a capability to retailer vitality from one to 4 hours. With a period lasting a whole bunch of hours, sand as a storage medium would price from $4 to $10 a kilowatt-hour. To make sure low price, the warmth can be generated utilizing off-peak, low-price electrical energy.
Ma, who holds a handful of patents on the expertise, beforehand served because the principal investigator on an ARPA-E funded challenge referred to as ENDURING, for Financial Lengthy-Length Electrical energy Storage by Utilizing Low-Price Thermal Power Storage and Excessive-Effectivity Energy Cycle. The prototype got here from this challenge. Subsequent up is the groundbreaking in 2025 on an electrical thermal vitality storage (ETES) system at NREL’s Flatirons Campus outdoors Boulder, Colorado, that will likely be designed to retailer vitality for between 10 and 100 hours. The stand-alone system is free from any siting restrictions that restrict the place CAES or pumped storage hydropower will be established.
The DOE-funded demonstration challenge, Ma mentioned, is meant to indicate the business potential of sand for TES.
Molten salts are already in use to briefly retailer vitality, however they freeze at about 220 levels Celsius (428 levels Fahrenheit) and begin to decompose at 600 C. The sand Ma intends to make use of comes out of the bottom within the Midwest of the US, doesn’t have to be saved from “freezing,” and might retain significantly extra warmth, within the vary of 1,100 C (2,012 F) that may retailer warmth for energy technology or to exchange burning fossil fuels for industrial warmth.
“This represents a brand new technology of storage past molten salt,” Ma mentioned.
Deciding What Will Retailer the Warmth
However will simply any previous sand do? Not in accordance with NREL researchers, who examined varied strong particles for his or her skill to circulation and to retain warmth. In a paper revealed final fall, Ma and others experimented on eight strong particle candidates. Among the many particles thought-about had been man-made ceramic supplies utilized in fracking, calcined flint clay, brown fused alumina, and silica sand. The clay and fused alumina had been rejected due to thermal instability on the goal temperature of 1,200 levels Celsius (2,192 levels Fahrenheit).
The ceramic supplies outperformed the sand in all classes, however the marginal efficiency positive aspects had been thought-about inadequate to justify the upper price. Whereas the sand prices from $30 to $80 a ton, the costs of the ceramic supplies had been about two magnitudes increased. The sand is within the ultra-pure type of alpha quartz and available within the Midwest.
Increasing the quantity of vitality that may be saved in sand is so simple as including extra sand, mentioned Craig Turchi, supervisor of the Thermal Power Science and Applied sciences Analysis Group at NREL.
“That’s a marginal price so as to add extra storage capability,” he mentioned. “We want storage starting from minutes to months. Batteries labored very well within the minutes to hours area when it comes to how they scale. And while you get into months of storage, you’re often taking a look at making a gasoline like hydrogen to offer that long-term storage. However within the interval between a number of hours and two weeks, there’s not a very good match proper now. Hydrogen is just too costly for that. Batteries are too costly for that.”
The parts wanted to transform the superheated sand again to electrical energy does require an upfront price. “However when you’ve paid for that,” Turchi mentioned, “should you simply need to have extra period to your energy it’s a lot, less expensive so as to add extra sand than the choice, which is to maintain including batteries.”
By Wayne Hicks. Courtesy of Division of Power, NREL.
Have a tip for CleanTechnica? Wish to promote? Wish to counsel a visitor for our CleanTech Speak podcast? Contact us right here.
Newest CleanTechnica TV Video
CleanTechnica makes use of affiliate hyperlinks. See our coverage right here.
