Storing wind energy 1

[SomptingGuy]

http://www.globalnewenergynetwork.org/news.php?news_id=2190696

Can anyone shine more light on this?

It looks quite simple the way it's described: excess power created by the turbine is used to pump out the vessel against (big) hydrostatic pressure. Power is returned by reversing the process.

But what's left in the vessel as it's pumped out? A vacuum (which would boil off the remaining sea water), air from some breather pipe? Other?

- Steve

 

[cranky108]

Sounds great, until you point out the losses involved in storing energy (typically 50% for several different storage methods).

If you really want to store energy, try consumer site ice storage.

 

[stevenal]

I would guess a breather hose to allow atmospheric pressure air into the chamber. Basically you have pumped storage, pumping seawater from the bottom to the surface. Boiling and re-condensing seawater seems like it would be extremely inefficient.

 

[BigInch]

There are vacuum breaker valves for vessels that are supposed to remain closed when in service, however for water you'd just need any ole vent somewhere at the top.

Why store anything. Make ice and sell it. Well ... if you're not at the North Pole.

Independent events are seldomly independent.

 

[BigInch]

If I was at the N.P. I'd probably make hot water.

Independent events are seldomly independent.

 

[msquared48]

Seems like this would work well in Washington DC.

Mike McCann
MMC Engineering

 

[Timelord]

I would be willing to bet that the vessel is vented to the surface atmosphere. Then as you pump it out the interior will always be at surface pressure as opposed to depth pressure and the pumping head almost constant (ignoring the height of the vessel). As you let the water back in, it is the same as releasing water held at a height equivalent to the vessel depth. Pumping water uphill for energy storage is a very common method to store energy, i.e. a dam and reservoir. Plus, the vessel will always be loaded with external pressure, placing it in compression, ideal for a low cost concrete vessel. Neat idea!

Timelord

 

[BigInch]

The tank will be in tension as soon as it gets some water. Inside pressure is the same as atmospheric, but you've got water inside too.

Independent events are seldomly independent.

 

[IRstuff]

The MIT article claims 70% roundtrip efficiency is achievable:

http://dspace.mit.edu/handle/1721.1/78934

TTFN
faq731-376

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[ornerynorsk]

One such 25-meter sphere in 400-meter-deep water could store up to 6 megawatt-hours of power, the MIT researchers have calculated

Does this seem just a tad optimistic? I think we've got some wandering decimal points in the equations.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[77JQX]

I get about 8.9 MWh at 100% efficiency.

 

[BigInch]

They themselves admit it's going to be probably more like 60-65% and I expect the scaled up system will probably come in at 55-60% tops, if that, but it's a nice idea.

Independent events are seldomly independent.

 

[SomptingGuy]

So the potential energy of the water is 4/3*pi*12.5^3 * 1000 * 9.81 * 400 = 32e9 (Joules) = 8.9MWh

Using the quoted 70% round-trip conversion efficiency, gives 6.2MWh.

Maybe I've done something wrong, but I get the same kind of answer they quote.


- Steve

 

[GregLocock]

The Dinorwig pumped water storage facility in the UK has a claimed round trip efficiency of 74%, not bad for 40 year old technology. That means the turbines themselves must be up around 90%, which is news to me.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[BigInch]

Or...?

Independent events are seldomly independent.

 

[ccfowler]

Unfortunately, there is a strong tendency for the underlying idealizations and assumptions behind the wonderful claimed performance capabilities of any system to not be very clearly stated along with the advertising or marketing literature. These idealizations and assumptions are seldom well matched to the realistic operating duty of the system. As a result, the actual performance rarely matches the lofty expectations for the system, but the system may be able to perform near its expected characteristics under testing set to fairly well match the ideal circumstances.

I'm sure that I am not alone in observing this well established tradition.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[SomptingGuy]

Negative, ccfowler. Greg has a good point. That energy storage thing in Wales is the dog's danglies.

- Steve

 

[ccfowler]

At first glance all seems so nice--then one needs to contemplate some significant considerations.

Economies and efficiencies influenced by scale: hundreds of MW vs. single digit MW

Access for maintenance and repair at atmospheric conditions vs. hundreds of feet below the sea surface (the pump/turbine must be below the bottom of the reservoir)

Relative burden of resources required vs. the magnitude of energy storage and recovery available (staggering amounts of concrete, steel, ...) for proportionately minuscule amounts of energy. Cost vs. resources required vs. benefits are unlikely to get into a "happy" range.

The amount of wind energy that can actually be recovered from the wind vs. the nameplate rating. Most wind turbines recover somewhere around 15%. "Traditional" pumped storage works with adequate power available to operate the pump(s) at near BEP conditions. Given the variability of winds, the proportion if time when the pump can get near BEP conditions will usually be a very small percentage.

As wind turbines become more and more plentiful, a time will probably come when serious attention will be turned to the number of birds killed per MWHr, per year, ....

I've spent very much time and effort with "alternative energy" concepts that have looked so very promising until their troublesome little quirks get in the way. The phrase "reality is" has much value. I confess to being a hopeful but many-times-disappointed fan of alternative energy.


Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[SomptingGuy]

... a uni study. Some say they are a waste. Some don't. I veer towards the don't team.

- Steve

 

[cranky108]

Can I ask my usual question: After 30+ years, and the thing is worn out, how do you decomission it? Or do we just leave them there to become an eyesore.

I.m tot trying to be a pessimest with this question, but a realist, from the experence of the concrete structures from oil production. Or is the answer, someone will figgure it out at the time (It's not my problem).

Most nucular plants are required to have a decomissioning fund, so why shoulden't alternitive energy.