The Viral ‘Sand Battery’ Is not What It Appears

The online is scorching for what’s being known as a “sand battery.” In our earlier put up about it, I was lukewarm. It appeared like a kind of seasonal thermal energy storage (STES), which has been completed for a few years, and that is nearly how the Finnish designers described it on their website. The time interval “sand battery” appeared to have come from BBC reporter Matt McGratha clever coinage that made it sound like one factor completely totally different and new. And it’s very totally different and new, merely not in the way in which wherein everybody appears to be talking about.

We despatched some inquiries to the designers, they often had not responded on the time of writing of the put up, nonetheless Polar Night time time Energy Chief Experience Officer Markku Ylönen apologized, noting that these are “crazy days” for them. He tells Treehugger:

“It is true that we have been making an attempt to steer clear of the phrase battery, since technically speaking it is not what we have. Anyhow, the phrase caught fireplace, and was an enormous part of the media success, and it almost definitely was McGrath’s invention. In spite of everything if we had been to generate electrical power from the heat, it won’t lower than act like a battery does: taking in electrical power and giving once more electrical power.”

Nonetheless strictly speaking, any machine that retailers energy produced at one time for use at one different time can be described as a battery. I often identify Passivhaus developing designs “thermal batteries” because of that’s what they’re going to do; as an alternative of wrapping sand in insulation as Polar Night time time Energy does, they wrap air. Now we have now moreover described how an energy-efficient dwelling can develop to be an enormous wind-powered battery, the place engineer Es Tressider proposed cranking up the heat when the wind blows. And really, even a lead-acid or lithium-ion battery wouldn’t retailer electrical power: It retailers chemical energy which may be remodeled into electrical energy. So it is not a important stretch to call it a kind of battery.

A very powerful distinction with Polar Night time time Energy’s system is the terribly extreme temperature at which it is storing thermal energy—as a lot as 1,000 ranges Celsius (1,832 ranges Fahrenheit), which is correctly over 10 situations as extreme as most STES applications run at. There are good the reason why this isn’t usually completed, the precept one being: The place do you get the heat?

Hydrosolara Quebec-based agency that has labored with STES. Ian Shulman, Hydrosolar’s technical product sales supervisor, tells Treehugger:

“The benefit of going with lower temperature applications permits the equivalent system (equal to hoover tube photograph voltaic panels) to be used for home heating, dwelling scorching water without having mixing valves, and so forth. Which does simplify the designs of the applications. The lower temperature design moreover lets you’ve got a lot much less insulation throughout the seasonal thermal storage (usually located beneath the house) which moreover drives the arrange costs down.”

That’s key. Cranking the heat as a lot as a thousand ranges should not be solely counterintuitive, but it surely absolutely moreover goes in opposition to the basic concepts of maximizing exergy—”the potential of energy to do useful work.” They’re cooking sand to extreme temperatures, which is ending up in a district heating system at one-tenth the temperature, using the highest-exergy sources for low exergy makes use of; it is what engineer Robert Bean known as “warming your palms with a blowtorch.” The one trigger that it makes any sense or anyone would actually do that’s that the high-quality power provide is definitely free—it is the additional electrical power from photograph voltaic energy collected in summer season season.

Ylönen clearly will get the exergy issue, and is hoping to utilize the system’s elevated top quality heat in numerous strategies: “With extreme temperature comes extreme versatility: we have to provide the heat to industries, producing for example steam at 200 ranges C, and even to produce course of heat at 400 ranges C or so. These processes are principally fueled by gasoline and coal.”

Resulting from that prime exergy, they actually may use it to generate electrical power making it an actual battery, although not very successfully. Ylönen says they’re looking at it.

“The extreme temperature of our storage would allow some low cost effectivity for {the electrical} power period, but it surely absolutely nonetheless is economically troublesome, as a result of the effectivity could be inside the order of 20%,” says Ylönen. “We’ve actually studied this pretty far, nonetheless there’s adequate to do on the heat facet of points for the second. Producing electrical power from heat could be simple, just by together with an ORC [Organic Rankine Cycle] or a steam turbine, or maybe a gasoline turbine (presumably Stirling moreover, nonetheless I do not see quite a lot of them commercially on the market however).”

As everyone knows from Aesop, it’s smart to take summer season season sunshine and retailer it away for winter. There are quite a lot of strategies to try this, nonetheless Ylönen, Tommi Eronen, and their group have found an fascinating twist.

Finally, it is actually type of a battery and far more than seasonal thermal energy storage as everyone knows them. And whereas I was blasé and lukewarm sooner than, I am positively getting further excited, as a result of it not solely retailers the facility nonetheless the exergy you get when you could possibly have quite a few free electrical power sitting spherical in summer season season. Aesop would approve.