I wonder if this could be implemented on a home scale, for storage of co-generated power/heat/cooling or photovoltaic.
Is a Heat Pump and Gravel the Answer to Energy Storage for the Grid?
View ImageSome energy storage technologies for the power grid are expensive but can be deployed anywhere, like advanced batteries, while others are cheap but can only be built in certain locations, like pumping water up and down hilly terrain (known as “pumped hydroâ€). But a group of English engineers have built an advanced heat pump and connected it to an energy storage system using two silos full of plain old gravel that they say is as cheap as pumped hydro, as location-agnostic as a battery — and is super efficient. The startup they founded two years ago called Isentropic, named after a reversible process in thermodynamics, is now looking for a Series B round of $5 million and will be showing off its technology at the Energy Storage Association conference next week in Washington, D.C.
Founders and engineers Jon Howes and James Macnaghten developed the design of the heat pump a decade ago, and a couple years ago brought on Mark Wagner as chairman to help with business direction. Heat pumps are basically engines that can work in reverse; Isentropic’s device is indeed reversible, both storing and releasing energy when needed. Wagner told us in a phone interview that the key to the company’s heat pump is that it can be reversed extremely efficiently, and has an isentropic efficiency (reversible efficiency) of 99 percent.
Using the heat pump as the key, the team built an energy storage system that compresses argon gas to produce a temperature differential and deposits heat and cold into two separate large silos of gravel. Wagner says any inert substance with particles around the same size as gravel can also be used — the filling just needs to hold the heat and cold well. Energy is stored in the gravel and when the process is reversed, it can be released.
Wagner says the low cost of all the basic ingredients — the heat pump, gravel and gas — make the system among the cheapest energy storage options out there, undercutting options like batteries, which often require costly materials. Wagner says the system costs between a half and a third of that of implementing flow batteries on the grid. The system is relatively quick to set up, too, says Wagner, compared to a technology like compressed air, which has a years-long regulatory process to approve the underground caverns where compressed air needs to be stored. It’s almost plug-and-play, says Wagner — as a result he says that wind turbine companies have approached the team to see if their storage device could be installed for each wind farm, enabling wind developers to help combat the variability of wind (the wind doesn’t always blow when energy is needed).
Another benefit, says Wagner, is that the system could be used underground and underwater, which could be useful when it comes to providing storage for offshore wind deployments. Danish utility DONG Energy, German energy company E.ON and Abu Dhabi’s clean energy initiative MasdarWagner are building the world’s largest offshore wind project called the London Array. Wagner says the company will soon be starting a study using its technology for the offshore wind plants that are being developed in the UK.
For now, Isentropic’s energy storage benefits are still just company intentions. It’s been building out two demonstrations of its technology and is looking for $5 million to help construct a larger, commercial-scale demo project. Last year Isentropic raised a Series A round from Credit Suisse Securities Europe and won a £250,000 ($380,112) research grant from The Carbon Trust; Wagner says so far the company has raised about $1 million. Next week at the Energy Storage Association conference in Washington, D.C. Isentropic will be discussing its technology and showing off its designs. It’s a good time to jump into the U.S. energy storage market, which, as we pointed out this week, is just starting to get attention from Congress, investors and entrepreneurs.
Tu stultus es
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
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Looks interesting.
I suspect that the capital cost will be to high for most residential applications.
But sounds like it might be easy to scale down to smaller applications such as schools and similar size buildings.
William the Geezer, the sequel to Billy the Kid - Shoe
Ther'e something called the Peltier (sp?) Effect too, and it is reversible; heat one side of a circuit and cool the other, and current flows. Seems like you could use geo for the coolness (or the heat, I guess) and solar for the heat, and generate electricity. Or, if you had an excess of electricity from another generating method, you could store it as heat and cold and even turn it back to electricity later.
Yes.And it used for small coolers and warns for food that goes into cars.And they are used with a nuclear source for the heat for some satellite applications.I don't have any idea is you they would have enough temperature difference to be effective as a energy storage device..
William the Geezer, the sequel to Billy the Kid - Shoe
When I built my house 1997, I was planning to put a insulated rock heat silo and pull my incoming air for the air to air heat exchanger, through it.
I thought that the heat would slowly gather in the summer and then preheat the air coming in the winter. then pre-cool the air for summer. but never got around to it. but still able to do.
Any thoughts on how much rock would be needed to make any differance. rock around here is plentiful.Have any of you folks ever think about making a solar air preheater for air to air heat exchanger. I have a Venmar HEX. and this last long COLD winter cost us big bucks for NG, in a well insulated and sealed house.
You need LOTS of thermal mass to store enough energy to last a month, much less all winter.Use the advanced search for PAHS, passive annual heat storage. I think that is the right term.And post by VATom on his house.But it is not a system that can be used as an add on..
William the Geezer, the sequel to Billy the Kid - Shoe
Did not see this thread before.
Like Bill says, LOTS of rock.
Say typical house takes 30E6 BTU for a season.
Say you heat or cool the rocks to a 20F differential
Rock has a specific heat of about 0.2, so running the numbers gives
3750 TONS of rock for a single house.
About 1.6 tons per cu yard, size = 2300+ cu yards or a 40 ft on a side cube = another house.
Does not seem too cost effective, probably more cost effective to have one house in Tuscon and another in Calgary. Wait, there are lots of folks do that, eh?
I don't see any advantage over a regular ground source (aka geothermal) heat pump, perhaps other than not having to dig. Building the silos and making all that gravel must be a huge cost.
I suppose in areas with an extremely high water table, where it's difficult to dig, it might be a viable option.
Scott.
I think they use silos so they can be super insulated - rocks stay hot or cold for extended periods, instead of trying to return to 55 degrees earth temp.
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.