interesting variant for pumped hydro storage

[kristopher]

Gravity Power’s New Take on Pumped-Hydro Energy Storage

Gravity Power's entire system is underground and doesn't require lots of land. A seven-acre site can easily accommodate more than two gigawatts, according to Fiske. When asked about seismic issues, Fiske said that the only time seismic is going to be critical is during construction. The finished system is a deep shaft lined with heavy reinforced concrete and then filled with water. He assured me that "It's going to be quite sturdy."

The Gravity Power Module (GPM) is a vertical column excavated hundreds of feet into the earth. An immense weight rests on a column of water which is raised, like a piston, to store energy and lowered to discharge energy using an additional return pipe. Here's a link to the patent application.

The pressure depends on the vertical dimension of the "heavy-concrete" weight moved up and down, while the distance traveled dictates the storage time available. When energy is cheap or available from variable sources, you pump, and then move the weight and water column upwards. Releasing the weight drives water through a turbine and produces power when needed or when costly. The energy coming in from the grid could be a wind farm or solar farm or nuclear power plant.

Round trip efficiency is about the same as conventional pumped hydro energy storage according to Grieco -- in the range of 75 percent to 80 percent. The cost of these machines is difficult to determine. "Cost is very dependent on where we put these things" and "local labor," according to the CEO. He envisions building them in clusters.

"If you look a...

http://www.greentechmedia.com/articles/read/Gravity-Power/



I personally think this is already outmoded, but it is an interesting approach.

[lumberjack_jeff]

1. What's the benefit of this relative to the air bladder tank on my well?

I suppose making bladder tanks big is a challenge, but making the seal in the above diagram will be challenging too.

[Tesha]

3. One benefit is that if the force really is coming from the weight of the concrete, ...

...then the force remains constant throughout the entire stroke,
whereas the force from your well tank's air bladder decreases
as the bladder expands.

Still, people are experimenting with utility-scale compressed
air storage; see:

http://www.generalcompression.com/

Tesha

[Tesha]

2. Why do you think it's outmoded? (NT)

[kristopher]

4. Thermal storage

Here is a sample of one company that uses "rock batteries", and you could google "ice energy storage" for another slant.
http://www.isentropic.co.uk/


There is also vast potential in electric vehicles and redesigned home heating/cooling systems that will phase in over the next 40 years.

The system in the OP offers another possibility though, and I don't doubt it will find some applications where it is seen as the best answer.

[Nihil]

5. Slightly OT ...

Have you heard any more about Isentropic's work recently?

Their site doesn't seem to have any real news other than "we're going to
another conference" and there doesn't seem to be a follow-up to their
second prototype (unless I missed it of course).

I share your doubts w.r.t. the effectiveness of the OP system - although
it would "fit" in more places than the alternative hydro systems, it doesn't
seem to show any advantage over the hot-rock option.

(That said, I've still recommended this as we need to be watching what is
actually happening with storage systems.)

Another OT comment: I was somewhat disappointed to see that bit about
a conventional pumped hydro scheme ...
> He cited the Lake Elsinore Advanced Pumped Storage, a project
> started in 1987 on which construction has not yet begun.
:-(

[txlibdem]

6. Isentropic's tech sounds promising

Here's an excerpt from their site:

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."

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

The key to their success (or failure) as compared to the other energy storage efforts is going to lie with their efficiency. It sounds promising but I'll reserve judgment till we get more info and some pilot plants up and running.

That being said, I don't think there will be a single "winner" in the storage game. There is going to be a huge market for storage for renewable energy (or at least there had better be) and perhaps one technique will be cheapest in one locale but a different method would best suit a different location. There need be no winners and losers. If it expands our renewable energy usage... we all win.

[kristopher]

7. That depends on what you mean when refer to success and efficiency

The standard for a heat pump/heat engine is around 92% efficiency. Isentropic is claiming 99%.

However, the overall system efficiency is between 70-80%, probably due temperature bleeding incurred during the storage phase.

It is likely that other innovators will be able to tweak the concept into a range that is competitive with Isentropic.

So the company itself has an advantage in the market, but the advantage isn't a fundamental breakthrough that will ensure them success.

The generic technology however, is a new entry into large scale energy storage. Because of its compact size ability to be placed almost anywhere, even at multiples of the large scale projected capital costs of $10/kwh the overall concept itself is certain to be a winner.

[kristopher]

8. Just for comparison

Although the flow battery for home use is noteworthy in and of itself, it is also an interesting read in light of the other technologies discussed in this thread.

Flow Batteries Coming Into Homes?

For approximately $7,500, you might soon be able to get a 30-kilowatt-hour flow battery to match your solar panels.
Flow Batteries Coming Into Homes?

Sacramento--Flow batteries soon won't be just for utilities and cell phone carriers anymore if Premium Power is right.

The North Reading, Mass.-based company is currently working on a device called the HomeFlow, a scaled-down version of the zinc bromide flow batteries it currently sells to industrial customers. The HomeFlow will store approximately 30 kilowatt-hours of energy, have a 10-kilowatt rating, and cost around $7,500, said Doug Alderton, director of government sales at the company during a session at the Emerging Technologies Summit earlier this week in Sacramento.

The price includes an inverter, so if you are linking it up to a solar system, your costs will be lower.

The ambitious company seems to want to become the Dell Computers of flow batteries. It plans on bringing out a variety of flow batteries -- ranging from the HomeFlow to a 6 megawatt-hour/2-megawatt behemoth that would function like a power plant -- based around a basic building block made from 54 cells. (Dell, in its heyday, mastered the art of designing a few basic SKUs and tweaking them to produce a complete product line.)

Just above the HomeFlow in the product line is...

http://www.greentechmedia.com/articles/read/flow-batteries-coming-into-homes/