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XemaSab Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 06:28 PM
Original message
Possibly silly question about storing energy
One of the big impediments to solar and wind power seems to be storage of the energy for later. Also, coupled with this is the problem of irregularity.

Why is mechanical storage not a solution?

Like, either pulling a heavy weight up and later releasing it, or off-channel water storage and release.

I'm assuming these have been thought of, but what's the problem with using these as interim methods until decent batteries can be devised?

(PS I am not a fan of wind, and I think PV is a silly toy for the rich, so it's not about arguing the merits of these methods of electrical generation.)
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Schema Thing Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 06:30 PM
Response to Original message
1. flywheels are a pretty cool way of storing energy
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phantom power Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 06:33 PM
Response to Original message
2. There is some pumped-water and compressed-air storage in operation.
The main issue with either of those is, there are a limited number of sites that support it. If you start talking about manufacturing big reservoirs, or big air tanks, the problem becomes one of scale. They have to be really really big. And/or really really numerous. and, they require resources, and land footprint, to build, etc.
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jimlup Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 06:33 PM
Response to Original message
3. Water storage is already used
Most of the major power companies do this. They pump it up hill during the night and then run it down during the high demand period of the day is standard policy in Michigan were we have lots of water ...
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ayeshahaqqiqa Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 06:35 PM
Response to Original message
4. You can store the energy in different ways
we are getting ready to put up our wind generator and solar panels, and hubby has decided to store the extra energy as compressed air. The idea is that an engine running on this air can power a generator when we need more power, and also be used in cooling our house. One could also use it to create hydrogen via electrolysis.
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nichomachus Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 06:38 PM
Response to Original message
5. I guess I need to ask why
you don't like wind and you think PV is a "silly toy" for the rich.
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madokie Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 06:41 PM
Response to Original message
6. We have a pumped back lake that is used as a hugh battery
during the night and early morning hours when the demand is low they pump water up then release it during the peak use times. It saves GRDA much money in not having to buy peak electric all they have to do is open the valves up.
Many years ago I used to fish that lake almost every day, some nice largemouth to be caught there. 750 or so acres surface area and 185 ft deep, I would say the average depth is somewhere more that 50 or 60 ft at least.

you're willing to shut off all discussion on wind or solar, how nice
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XemaSab Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 06:55 PM
Response to Reply #6
7. Thanks for your response
Here's the deal: it's not that I'm not interested in discussing the merits or faults of these forms of energy, but it's that I'm not interested in doing it TODAY. :hi:
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kristopher Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 07:04 PM
Response to Original message
8. Pumped water, Compressed air, and V2G
Here is some information I out together on another DU thread. I'm responding to a question about how we transition from fossil fuels. I would add to it the tread I just started on EE titled MIT Technology Review... for more specific information about the state of battery technology.
An important point to remember is that our personal transportation vehicle fleet sits idle over 90% of the time, and miles driven are less than 40 each day. See the UDEL website for more information on this crucial plan that makes a transition to renewables, with their increased intermittency, a viable economic possibility.

both V2G and CAES are part of the strategy to minimize the costs of integrating higher levels of intermittent energy into the grid. It already has a great deal of flexibility, but it needs strengthening in many regions and some major investment in upgraded control technology, particularly a mechanism that allows instant pricing of electricity to be available to the consumer. That would be a part of the infrastructure installed in the garage along with the interface for recharging automobiles. This allows people to realize when they are overloading the system on a hot summer day, for example. When the price of the electricity spikes in the afternoon, people will defer purchasing power until a time of less demand.

"...Another good point about both V2G and CAES is that the costs of developing the infrastructure is much lower than had previously thought would be possible for storage on such a spectacular scale. That is most true for V2G where the consumer's transportation purchase will actually pay the largest part of the cost of the system. The price of the rest of the infrastructure in minor compared to the avoided corporate capital outlay.

So what you have that your worries do not incorporate is a technologically and economically viable alternative to a fossil fuel world. When you factor that in along with high reserve to production ratios, increasingly high costs for all carbon fuels, and a coming change in political recognition of the climate change issue - remember Obama has said he will bring Gore on board to manage the response to CC - do you still think we are preparing to drop off a cliff?


I've provided some background below.


The economics of large-scale wind power in a carbon constrained world
Joseph F. DeCarolis, and David W. Keith

Department of Engineering and Public Policy, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA


Abstract

The environmental impacts of fossil-fueled electricity drive interest in a cleaner electricity supply. Electricity from wind provides an alternative to conventional generation that could, in principle, be used to achieve deep reductions (>50%) in carbon dioxide emissions and fossil fuel use. Estimates of the average cost of generationnow roughly do not address costs arising from the spatial distribution and intermittency of wind. The greenfield analysis presented in this paper provides an economic characterization of a wind system in which long-distance electricity transmission, storage, and gas turbines are used to supplement variable wind power output to meet a time-varying load. We find that, with somewhat optimistic assumptions about the cost of wind turbines, the use of wind to serve 50% of demand adds 1 to the cost of electricity, a cost comparable to that of other large-scale low carbon technologies. Even when wind serves an infinitesimal fraction of demand, its intermittency imposes costs beyond the average cost of delivered wind power. Due to residual CO2 emissions, compressed air storage is surprisingly uncompetitive, and there is a tradeoff between the use of wind site diversity and storage as means of managing intermittency.

Keywords: Wind; Optimization; Carbon
****************************************************
You can find links to the papers below at http://www.stanford.edu/~lozej/publications.html

Archer, C. L. and M. Z. Jacobson, 2007: Supplying baseload power and reducing transmissions requirements by interconnecting wind farms. Journal of Applied Meteorology and Climatology, 46, 1701-1717.

W. Kempton, C. L. Archer, A. Dhanju, R. W. Garvine, and M. Z. Jacobson, 2007: Large CO2 reductions via offshore wind power matched to inherent storage in energy end-uses.Geophysical Research Letters, 34, L02817, doi:10.1029/2006GL028016.


Archer, C. L. and M. Z. Jacobson, 2005: Evaluation of global windpower. J. Geophys. Res.-Atm., 110, D12110, doi:10.1029/2004JD005462.

V2G:
http://www.udel.edu/V2G /

Good summary of battery technology:
"In search of the perfect battery"
Mar 6th 2008
From The Economist print edition

For CAES look for the project at Iowa Association of Municipal Utilities, and the existing plants in Alabama and Germany; plus read:
Energy Policy 35 (2007) 14741492

"Baseload wind energy: modeling the competition between gas turbines
and compressed air energy storage for supplemental generation"

Jeffery B. Greenblatt et al
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Dogmudgeon Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 07:37 PM
Response to Original message
9. The problem is poor efficiency
Energy can be stored in many ways, and some of the posts here have given illustrations. But the overall problem is that there is always a loss of energy when you store it, and currently, those losses are huge. If and when wind/solar begin to contribute more than a few percent of our energy needs, we will have to have some kind of storage available, and if it's not cheap and efficient, it's going to kill the favorable economics these methods now enjoy.

That's why non-intermittent energy is so desirable. It doesn't have to be stored; it's always "on". But aside from organic fuel (i.e., fossil, "bio", and some synthetics), the only two reliable forms of large-scale non-intermittent energy we have are nuclear and deep geothermal. Deep geothermal is still an "immature" technology, and you've seen what happens when anyone proposes nuclear energy in these parts. (Hydro is a marginal case, and it's causing severe watershed-management problems in lots of areas.)

A lot of people are hoping for a magic gadget the size of a TV set that you can put in the basement or backyard that will produce 100 kWH forever without heat, chemical emissions, ionizing radiation, and at a cost of a buck a day -- and it's never going to happen. (But there are a dozen or more entrepreneurs who could make it work if only you would invest $9,999.95 -- or whatever you can spare.)

Okay, in theory, a large enough pendulum should be able to generate energy converting its responses to the Earth's movements into some kind of electromagnetic flux, and it should do it forever. I would guess that with a 5-mile-high tower hanging a 30-ton magnetic weight moving across a couple hundred miles of wire wound into coils, you could juice up your laptop until the Omega Point resurrects Nikola Tesla. But what do we do once we reach Peak Angular Momentum?

Yeah, if you're a science geek, feel free to correct the physics and math of my wild-assed scheme. Not that it will work anyway. I'll still advocating thorium and/or digging real deep. Other half-solutions will also need to be pursued. But there will be no magic any time soon. The physical universe sucks like that.

--p!
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jpak Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 07:48 PM
Response to Reply #9
10. Flywheel storage is 80% efficient - similar to pumped hydro - and they already exist
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kristopher Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 08:05 PM
Response to Reply #10
12. Flywheels don't have the capacity due to material limitations.
To store large amounts of energy they require such tremendous speeds that the materials available are inclined to disintegrate. There are other better existing methods for renewable backup.

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jpak Donating Member (1000+ posts) Send PM | Profile | Ignore Thu May-01-08 10:44 AM
Response to Reply #12
16. Beacon Power has a 20 MW flywheel package that can buffer output from a mid-sized wind/solar farm
NaS batteries and hydrogen fuel cells can do the rest...

:hi:
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Dead_Parrot Donating Member (1000+ posts) Send PM | Profile | Ignore Thu May-01-08 11:00 AM
Response to Reply #16
18. For 5 minutes, or a week?
Edited on Thu May-01-08 11:11 AM by Dead_Parrot
Just curious.

Possibly worth reading the thread title, which concerns energy, not power. Although since the difference has been pointed out to you dozens of times, without effect, we don't really expect you to get it now. :hi: :dunce:
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jpak Donating Member (1000+ posts) Send PM | Profile | Ignore Thu May-01-08 01:29 PM
Response to Reply #18
20. milliseconds to weeks depending on requirement
clue: I "got it" from Day One - a nuclear hobbyist made up that canard and people still fall for it....

:hi:

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Dead_Parrot Donating Member (1000+ posts) Send PM | Profile | Ignore Thu May-01-08 04:16 PM
Response to Reply #20
22. Beacon Power have a flywheel that can supply 20MW for weeks?
link?
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phantom power Donating Member (1000+ posts) Send PM | Profile | Ignore Thu May-01-08 04:22 PM
Response to Reply #22
23. You just have to build a bank of them...
And if anybody wants to, I won't stand in their way. I'm a stockholder.
:evilgrin:
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jpak Donating Member (1000+ posts) Send PM | Profile | Ignore Thu May-01-08 07:08 PM
Response to Reply #22
25. Ugh - it's a modular system two hundred 100 kW flywheels each storing 25 kWh
They can regenerate power over a few hours or weeks (depending on grid requirements) with a very rapid response to up or down fluctuations in output from a wind farm...

which is exactly what they will be used for at the Tehachapi, California wind farm complex...

http://phx.corporate-ir.net/phoenix.zhtml?c=123367&p=ir...

Ok???
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Dead_Parrot Donating Member (1000+ posts) Send PM | Profile | Ignore Fri May-02-08 04:14 AM
Response to Reply #25
26. Exactly
Is not "a 20 MW flywheel package", it's 200 100kW flywheel packages joined together.

Slight difference. Especially when you add up all the flywheels you'd need to maintain 1 GW through a windless night: according to these costs, $27.3 billion (life-cycle costs, internal).

Want to run it for a windless week? It appears to cost just under half a trillion dollars per GW.

Now, feel free to check my math, because there must be something wrong there. But I hope (probably in vain) that you'll twig the difference between load balancing a fluctuating energy source, and actually storing baseload energy.

Unless you're going to claim baseload is a figment of the imagination again, in which case I give up.





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jpak Donating Member (1000+ posts) Send PM | Profile | Ignore Fri May-02-08 06:19 AM
Response to Reply #26
27. Ummm...wind farms produce power 60-90% of the time - windless weeks are rare at these sites
and when backed up by solar and biomass, the need and costs of storage is minimized (as is demand on "windless nights")

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Dead_Parrot Donating Member (1000+ posts) Send PM | Profile | Ignore Fri May-02-08 06:55 AM
Response to Reply #27
28. Slightly OT...
...but have you seen a production curve for a typical turbine? It strikes me that if the are doing 'something' 90% of the time, but only average 35-odd percent, they can't spend a lot at time generating at their rated capacity...

But I digress. The weekly backup was an (obviously failed) attempt to point out how expensive large-scale fly wheel storage is. And yes, it I'm sure it will come down, but at roughly 5 cents per Joule it's a very long way from replacing fossil fuels (like CAES).

The only question is, then, just how much baseload can you shovel onto hydro and biomass? (Actually, that always was the question, and my own answer suggests nuclear is needed to fill the gap - but I'd be interested to see your sums).

:)

(Oh, BTW - I disagree with your efficiency figure in post #10. I think it's more like 90-95% for modern mag-bearing wheels, but I'd have to google it up). :D
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One_Life_To_Give Donating Member (1000+ posts) Send PM | Profile | Ignore Fri May-02-08 10:45 AM
Response to Reply #28
29. Any idea what current / Joule for Pumped Storage?
Curious if these things can compete with large scale pumped storage systems. Or are they just a small backup system to replace say the diesel generator used to backup corporate servers, etc.
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Dead_Parrot Donating Member (1000+ posts) Send PM | Profile | Ignore Fri May-02-08 08:57 PM
Response to Reply #29
32. Well, Dinorwig (Wales) holds 9.1GWh, at ~2.5billion in today's money...
...or 32TJ for $5B: 0.015c/J, if I've hit the right buttons. With the caveat I've had to stick to capital costs - I don't have the running costs handy, so you might want to double it (and check my math!).

Flywheels are great at smoothing production (taking the gusts out of wind, for instance) or as a large UPSs: Personally, I don't see them as a realistic TJ/GWh-scale storage technology anytime soon.
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kristopher Donating Member (1000+ posts) Send PM | Profile | Ignore Fri May-02-08 02:18 PM
Response to Reply #27
30. Where did you get that statistic?
I think it isn't being applied properly.
Flywheel storage isn't practical as a backup for wind. The most cost effective BU right now is just the rest of the grid. Nothing special is really required except scheduling standby, something that is routinely factored into the costs of developing a wind farm.
At higher levels of penetration, converting natgas generators to CAES is the most cost effective technology out there right now, by a wide margin. That will change if/when plug in battery electric (V2G ready) achieves about 3% penetration in the auto market.
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One_Life_To_Give Donating Member (1000+ posts) Send PM | Profile | Ignore Thu May-01-08 03:12 PM
Response to Reply #16
21. After the first 15 minutes people will get pissed
200 25kWhr will only supply a 20MW load for 15 minutes. After that Grandma's O2 concentrator is going to stop working.
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kristopher Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 08:00 PM
Response to Reply #9
11. You are probably correct on people's expectations, but
You are probably correct on people's expectations, but you are off target about the consequences of storage.

First, it is important to recognize the large degree of variability that currently exists in the present grid and the way that this variability in load and generation are managed. It is a fairly short step from that to calculating the costs of various storage technologies.

AS far as your claim regarding energy losses incurred by storage being expensive and inefficient, you are pretty far out of date. I gave references in my post above that directly address these cost issues as they work with renewables.

Finally you've totally ignored the high costs and inefficiencies in the current system that is dominated by thermal generation. The maximum efficiency of a coal plant is just north of 40% and if you can find a use for the exhaust heat you might get it to 60% but don't hold your breath. And don't get me started about the 12% efficiency of the internal combustion engine in automobiles. 88% of every dollar you pump into the tank is lost. So even though a system built around renewables does incur losses in storage and transmission, there are offsetting gains that have to be taken into account.

We need people to stop believing that a transition to renewables is something that can't get done or that it is going to be an inferior system to what we have now. It can be done and the system can provide the basis for a technologically advanced society. We don't need magic, the solutions available aren't "half-solutions" and it can be done as soon as we set our minds to doing it.
And the only thing that sucks is that people are so damned beaten down that they have lost the ability to have a vision.
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hunter Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 09:08 PM
Response to Original message
13. The water system in California does a lot of load balancing.
For example they run the water up the grapevine mostly at night when electric demand is low, and they let it back down the other side generating electricity when electric demand is high.

Ultimately someplace like the Salton Sea could probably do load leveling for the entire Southwest no matter what form of electricity generation we use, and in the process we could stabilize the shorelines and clean up the mess, hopefully optimizing the environment for wildlife and not expensive waterfront condos.
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NNadir Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 09:52 PM
Response to Original message
14. I covered this some time ago, but in fact, mechanical storage is the world's largest means of...
renewable energy storage.

It's called pumped storage, and it involves pumping water (using excess power) behind dams.

It is currently an industrial method, although it is, considering the scale of energy use, trivial, even more trivial than the rest of the renewable industry.

I had an elaborate proposal for wind, solar, geothermal and nuclear energy that I threw out for discussion one day when I was bored, involving the Salton Sea basin.

It's here: http://www.democraticunderground.com/discuss/duboard.ph...

As part of the discussion, it turns out that the Irealis have been contemplating a similar idea involving the Dead Sea, according to one correspondent.
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losthills Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Apr-30-08 10:05 PM
Response to Original message
15. PV is a silly toy for the rich?
That's a pretty ridiculous statement.
In rural california pv is used extensively by ordinary middle class homeowners. Their method of storage is a bank of batteries and an inverter. It's affordable and it works fine.
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GliderGuider Donating Member (1000+ posts) Send PM | Profile | Ignore Thu May-01-08 10:49 AM
Response to Reply #15
17. Ordinary middle class California homeowners
ARE rich, compared to any global measure you care to use.
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losthills Donating Member (1000+ posts) Send PM | Profile | Ignore Thu May-01-08 11:17 AM
Response to Reply #17
19. I'm gonna run out and tell all my neighbors!
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JohnWxy Donating Member (1000+ posts) Send PM | Profile | Ignore Thu May-01-08 04:30 PM
Response to Original message
24. VRB Power Systems - vanadium-based redox regenerative fuel cell
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TheWraith Donating Member (1000+ posts) Send PM | Profile | Ignore Fri May-02-08 04:42 PM
Response to Original message
31. There are a bunch of ways to do this, but unfortunately they're all fairly lossy.
You lose a large amount of the energy you put into spinning up a flywheel, or pumping water uphill, etcetera. That means you need even more generating capacity to account for the energy you're losing.
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