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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.
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.
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
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.
#DeleteFacebook
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'.
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.