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Underwater Pumped-Storage Hydroelectric Project Completes Its First Practical Test (forschung-energiespeicher.info)
What if you built massive concrete spheres -- 98 feet in diameter, with 10-foot walls -- under the ocean to help generate electricity during peak periods? Slashdot reader nachtkap reports that German researchers just finished testing their 1:10-scale prototype StEnSEA:
It was retrieved from Lake Constance, where it was submerged at a depth of 100 meters [328-feet] since November. The system was developed by the Fraunhofer-Institut IWES in Kassel, Germany in collaboration with its inventors... The German Trade Department and Department of Education and Research as well as the German construction company Hochtief are also involved with the project.
The system's hollow concrete spheres are intended to be used in conjunction with off-shore wind-farms to serve as energy storage for peak hours. The spheres are ultimately supposed to be submerged near off-shore wind-farms and pumped free of water with excess energy. When additional energy is needed during peak hours the system goes into reverse and water rushes in, driving a turbine... At 700 meters the system has a capacity of 20MWh, with a linear capacity increase as depth increases.
The system's hollow concrete spheres are intended to be used in conjunction with off-shore wind-farms to serve as energy storage for peak hours. The spheres are ultimately supposed to be submerged near off-shore wind-farms and pumped free of water with excess energy. When additional energy is needed during peak hours the system goes into reverse and water rushes in, driving a turbine... At 700 meters the system has a capacity of 20MWh, with a linear capacity increase as depth increases.
When it implodes it goes MOOB!
In what ways is this better than simply pumping water uphill
It's better if you don't have hills.
Pumps are very inefficient. I wonder why they wouldn't just use the excess energy to drive a motor/generator to pull an empty sphere towards the bottom with a cable and then generate energy in reverse as it rises up?
Sounds like that would create more moving parts in an environment that's not kind to them.
I have a cottage outside of Marmora, who has a lovely pumped-storage kit in the form of a large mine (see the picture at
http://www.marmoraandlake.ca/w...) that's well above the Crow river. A good modern pump/turbine could do a sparkling job of storing wind-/solar-power until night.
davecb@spamcop.net
Advantages that I can see;
More places they can go, and the places they go (off the coast) are usually closer to places that want the electricity.
If it works, you can scale it by building more spheres.
A change in height of 700m is easy to obtain in the ocean. On land, not so much.
Out of sight, out of mind - Since fewer people will see it, fewer will complain about it.
If a sphere fails, it's far less catastrophic than a dam failing.
Sure, but not everybody lives around Lake Constance. They have tested the system there, but the may want to use it near the coast, or at the bottom of the sea where the offshore wind farms are.
This. Offshore wind farms have lots of water, but no hills and no place to pump water.
Pumped hydro is great, if you have the water and the geography to impound the water.
I thought now the EPA and other government agencies were banned from reporting on climate change and NASA has been essentially told it isn't getting any money to research it that the problem has magically gone away?! It seems odd that Trumps alternative truth wouldn't actually be the truth...
This was research funded by the German Federal Government, not the US Federal Government. We have not, so far, elected Trump or anyone of a similar disposition to a major government position.
Stephan
First, that pressure is extremely important. As per Mythbusters episode, it can take a human and crush it inside an underwater pressurized suit when the suit breaks.
More important, water pumped up hill has multiple issues you are not considering. Evaporation, rain, land use areas, pollution, danger of dams breaking, are all major issues.
But the most important issue is simple power transmission is expensive. We lose more power moving it around than you would believe.
If you are inland, with natural hills, then pumping water up hill makes sense.
But if you are near a shore line, where beach front property is prime real estate, then finding a way to store energy OFFSHORE makes a lot more sense, as all the land near the ocean is to valuable.
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Pumps are very inefficient. I wonder why they wouldn't just use the excess energy to drive a motor/generator to pull an empty sphere towards the bottom with a cable and then generate energy in reverse as it rises up?
Conventional pumped storage systems have about 75-80% round trip efficiency, which is not that bad. One reason for the loss is evaporation from the upper reservoir, which would not be a problem for this system, so round trip efficiency in the 80+% range is realistic. That is not to bad if you have free electricity to begin with.
Stephan
The advantage of the pump system becomes even greater when you scale up the storage capacity, as that only requires adding more empty storage spheres, and not more pumps.
The ultimate end of this thought-experiment is just to use water.
What if - and stay with me here for a second, but what if we pumped the water into the clouds? It works for data, surely it would work with water.
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When I want to get numbers that are too optimistic, I use values above 100%.
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No bullshit grab-for-the-stars (and never get them) waste of money and time, but practical, pragmatic and addressed at real problems. Of course, this will take another 10 years or so to practical deployment, but it is highly likely to work and be both reliable and cost-effective. Things like these drive progress.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
I think you should learn some German history.
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You're going to get all kinds of sea life growing on all those moving parts, turbine blades and such. Be nasty, expensive work trying to clean it all off. Maybe they can engineer around that??
Have these people ever lived by the sea? There is no way a pump is going to sit at depth without needing to be taken out and cleaned every few weeks. There is no way the generator turbine is going to sit at depth without getting furred up. There is no way the influx and drain pipes will remain clear. Even the sphere itself will slowly fill.
The sea is not just salty water. It's a soup of animals, plants and minerals in suspension. The test might work in a fresh water lake for a few months but the sea is far more active at destroying machinery. Otherwise we'd just build big turbines and let the tides generate all of our electricity.
What if - and stay with me here for a second, but what if we pumped the water into the clouds? It works for data, surely it would work with water.
I believe we have a pump for that: the sun (not to be confused with sun microsystems). The problem with that is a bunch of environmentalists won't let us build turbines to recover that energy, so we are stuck with these balls...
After a certain height, the hanging weight of the water at the bottom causes the pressure at the top of the water column to drop below the vapor point, and all you get is near-vacuum water vapor going into the pump.
Death trap for whom ?
By death trap do you mean 'non-zero' risk similar to the people who live below a hydroelectric dam, or near a nuclear power plant, or who mine coal, or who live downwind from a dirty coal plant ? I suspect the human risk is pretty low comparably.
if you mean the critters living nearby, we eat around 100M tons of fish / year, so that might be a better place to focus in terms of 'death trap'.
It makes me wonder if anyone has considered a turbine generation system for storm water runoff.
My back of the envelope math says that our local stormwater system handles something like 40,000 acre-feet of water per year, which is the current flow rate of the Mississippi river at St Paul for a month.
That's potentially a lot of water flow that hasn't been tapped, and a lot of it is all downhill with no pumping (because it goes into the river itself).
You've just reinvented hydroelectric power stations ;)
The practical problem to extracting a useful amount of energy from water is that you have to restrict its flow. You'd end up with a giant lake like every other hydroelectric system, except it would flood the city.
There's no getting around the fact that extracting kinetic energy from water makes it slow down. When it slows down it backs up. Its level raises as upstream flow is converted to gravitational potential energy in the form of increased head height while it is "waiting" to flow through the restriction.
If you want to allow the water to flow mostly unimpeded, you could only extract a fraction of a percent of the available kinetic energy.
If they plan to use it in salt water, they should be testing it in salt water. The problems aren't the same. It may still be a good idea, but testing it in fresh water worries me. Of course, this may be an early prototype...but they damn well better be testing the pilot in salt water...if it were near where I live I'd say they also need to be testing it in winter storms, but perhaps they're planning on using it in a sheltered area.
I think we've pushed this "anyone can grow up to be president" thing too far.
It seems like you're assuming that the sphere is pumped full of air when the water is drained out, but that is not a necessity. In fact, doing so would needlessly complicate the design significantly as it is scaled to greater depths while simultaneously compromising its power generation potential by reducing the pressure differential between the interior and exterior of the sphere.
What your're looking at is more like an implosion of a ~14,000m^3 vacuum chamber which might not even be obviously noticeable from the surface when the sphere is placed at greater depths.
Normal hydro-storage depends on pumping water uphill - and that means you can only use it where there are hills or mountains nearby. But this only requires pressure, which is available in many places where drops aren't. It could certainly add to the options for large-scale storage.
It's big and expensive to build of course - but I'm not sure it's actually bigger and more expensive than a coal or solar plant. So it may still be a win.
Unicode killed the ASCII-art *
>In what ways is this better than simply pumping water uphill into a holding tank or artificial reservoir?
It can be done in places where there are no handy hills to pump up. Potential energy storage by height is directly determined by just how high you go - and the volume you store - the higher you can make the water fall - the more acceleration you get, and the faster your turbine can be turned). You can only get a little storage from a tank on a tower (at least one built at reasonable cost). Such systems can and have been used as home-energy storage for people on solar (for decades actually) but they don't scale well because the construction cost goes up exponentially as you increase volume and height - because water is pretty heavy stuff.
It's a lot easier if you can use a dam on a mountain - or couple some pumps to an existing hydro-electric generator.
But those rely on geographic features that aren't available everywhere. Most notably they tend to be hard to find in places where wind power is at it's best. Mountains and hills are wind-breaks, so they tend to make wind power less effective (but pumped storage is often great for solar). On the other hand the meeting-point of land and sea is a natural wind-generator (due to the heat-storage differential between rock and water) - so a lot of wind-farms are on the sea-shore already. Using the nearby ocean's pressure as a storage technology could make perfect sense.
Part of the trick with renewables, unlike fossil fuels, is that they are far less one-size fits all. Your local geography has a huge influence on your options. Hydro is great - but only if you have the kind of rivers you can build the kind of dams in that generate it well. Geotherman is fantastic - but it's only available if you have active volcanoes. Solar and wind can be great (often in different places) but they need lots of storage to provide good baseload. All these factors influence what is the "best" combination in a specific region. And even when it comes to storage technology there is no one ideal answer, the best choice depends on what the local geography offers.
Unicode killed the ASCII-art *
The killer to these projects is you have to recoup your cost before the system wears out while also covering maintenance costs. We do this on land pumping water up hills and doesn't make economic sense. The systems require to much maintenance. In North America the ones that are already build are used as insurance. Utilities pay for the ability to draw several MW from these systems while they wait for a coal system to come on line. Coal takes a while, while hydro is close to instant. The utilities pay for this insurance every month whether they use the electricity or not and when they do use the electricity they pay in the multiple dollars per KWh. The system in the article will be charged with unwanted electricity, cost 0, but will sell the electricity only at peak and shoulder prices. It's not going to viable.
Keep Calm and McNugget on.
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Industry in salt water is, indeed, well established. Also well established is that it takes a LOT of on-going maintenance. Oil platforms that are abandoned rapidly decay, e.g. This is intended for residence on the floor of the ocean (well, sea) so maintenance is likely to be a real problem. That means they need to test the pilot well and thoroughly before they build the real one. And I'd think they'd also want to test the prototype in the real environment also, but perhaps it's already got so many untested features that they wanted a safer environment to test it in.
I think we've pushed this "anyone can grow up to be president" thing too far.