One of the most significant stories in years...

[kristopher]

At least, in terms of creating an inexpensive renewable electric infrastructure.

Is a Heat Pump and Gravel the Answer to Energy Storage for the Grid?
Thu May 14, 2009 1:29pm EDT
By Katie Fehrenbacher - Earth2Tech

Some 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 hydro"). 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 ...
http://www.reuters.com/article/earthToTech/idUS183390834520090514

[NJCher]

1. I have an idea using this technology

A lot of people in the U.S. have swimming pools they no longer want. They could fill them with gravel in place of the above-ground silos as designated in this article.

I wish this technology were further along. I would be picking up the phone right now!


Cher

[pscot]

2. But, but, this is so "common"

Anyone could do it. People will start filling pits in their back yards with gravel. Where's the expensive engineering, the billion dollar cost+ contracts for Bechtel or GE? We want pipes that circulate water to the Earth's molten core; vast mirror arrays in space concentrating the Suns rays. Gravel is no fun.

[Nihil]

3. Will be interesting to see how this works out. (n/t)

:shrug:

[NNadir]

4. Well so much for the laws of thermodynamics.

:eyes:

No one should ever be troubled by scientific laws when magical thinking can replace it.

[kristopher]

5. We should have more information soon

They presented the technology at the energy storage conference that concluded today in DC. You better hold on to all the magical thinking you can get your hands on, because that is all that nuclear has going for it.

[Dead_Parrot]

6. Interestingly, Isentropic only claim 70% on their website

Fact checking? wossat then?

:shrug:

[kristopher]

7. Do you have a link for the website?

I couldn't find it when I googled.

[Dead_Parrot]

8. I won't ask what you put into google...

I used "isentropic", and lo!

http://isentropic.co.uk/

[kristopher]

10. The same thing - see post 9. nt

[kristopher]

9. Never mind, here it is.

http://isentropic.co.uk/index.php?page=storage

Thanks for the find. Either I missed it earlier or it wasn't there and they just got it up as a part of their conference presentation.

It is still sounds like an extremely effective and affordable storage option that can be widely deployed. Because of its price, scalability and near-universal geographic adaptability it is exactly what the renewable system needs to move forward rapidly even at a 70% round trip efficiency.

[Greyskye]

11. The 99% number comes from their 'Technology' page

http://isentropic.co.uk/index.php?page=technology
The Isentropic Energy Converter (IEC) is a completely new kind of energy conversion device - a fundamental advance in energy processing machines. The IEC has three critical features:

* Exceptional efficiency - 99% isentropic efficiency is, we believe, a record. Turbines have an isentropic efficiency of ~90%
* High reversibility - the machine works both as an engine and a heat pump (an engine turns a temperature difference into work, a heat pump turns work into a temperature difference - every fridge has one). High reversibility means that if it first turns electricity into a temperature difference, it can then regenerate most of the electricity from the temperature difference it has created. No other machine to date can do this efficiently.
* Gas cycle machine - no use of damaging refrigerants, chemicals or water

The 70% figure was round trip efficiency for the entire process.

[Dead_Parrot]

15. Ahh, got it.

Comprehension: fail. ;)
Still somewhat skeptical, but we'll see what happens.

[madokie]

12. sounds like something that could be used in the home too

I've read about systems where they stored heat in rocks using hot air, then when you passed air back through the rocks they would give up the heat to help in heating ones adobe but this adds a twist to it that would make it work in a much more efficient way. We have many days where it warms up pretty good during the day and then drop at night so something like this could be used, looks to me like.

[AZCat]

16. You can also do the reverse.

During the hot season you can blow outside air through the rock bed at night and then during the day use the same bed to cool the recirculated air from inside the building. This isn't as common as ice storage (only used when you have a chilled water system), but it's simpler.

[TheWraith]

13. I don't believe this for one split second.

Conversion to heat and back is incredibly inefficient, no matter what tweaks you've done to it.

[Tommy_J]

14. 99% isentropic efficiency is clearly BS -

- and the 70% figure cited in the website is highly suspect. Having said that, the idea might still have merits worthy of commercialization.