Wind Power, Without Wind

[cashinmattress]

link

Offshore wind could provide abundant electricity — but as with solar energy, this power supply can be intermittent and unpredictable. But a new approach from researchers at MIT could mitigate that problem, allowing the electricity generated by floating wind farms to be stored and then used, on demand, whenever it’s needed.

The key to this concept is the placement of huge concrete spheres on the seafloor under the wind turbines. These structures, weighing thousands of tons apiece, could serve both as anchors to moor the floating turbines and as a means of storing the energy they produce.

Whenever the wind turbines produce more power than is needed, that power would be diverted to drive a pump attached to the underwater structure, pumping seawater from a 30-meter-diameter hollow sphere. (For comparison, the tank’s diameter is about that of MIT’s Great Dome, or of the dome atop the U.S. Capitol.) Later, when power is needed, water would be allowed to flow back into the sphere through a turbine attached to a generator, and the resulting electricity sent back to shore.

One such 25-meter sphere in 400-meter-deep water could store up to 6 megawatt-hours of power, the MIT researchers have calculated; that means that 1,000 such spheres could supply as much power as a nuclear plant for several hours — enough to make them a reliable source of power. The 1,000 wind turbines that the spheres could anchor could, on average, replace a conventional on-shore coal or nuclear plant. What’s more, unlike nuclear or coal-fired plants, which take hours to ramp up, this energy source could be made available within minutes, and then taken offline just as quickly.

The system would be grid-connected, so the spheres could also be used to store energy from other sources, including solar arrays on shore, or from base-load power plants, which operate most efficiently at steady levels. This could potentially reduce reliance on peak-power plants, which typically operate less efficiently.

The concept is detailed in a paper published in IEEE Transactions and co-authored by Alexander Slocum, the Pappalardo Professor of Mechanical Engineering at MIT; Brian Hodder, a researcher at the MIT Energy Initiative; and three MIT alumni and a former high school student who worked on the project.

The weight of the concrete in the spheres’ 3-meter-thick walls would be sufficient to keep the structures on the seafloor even when empty, they say. The spheres could be cast on land and then towed out to sea on a specially built barge. (No existing vessel has the capacity to deploy such a large load.)

Preliminary estimates indicate that one such sphere could be built and deployed at a cost of about $12 million, Hodder says, with costs gradually coming down with experience. This could yield an estimated storage cost of about 6 cents per kilowatt-hour — a level considered viable by the utility industry. Hundreds of spheres could be deployed as part of a far-offshore installation of hundreds of floating wind turbines, the researchers say.

Such offshore floating wind turbines have been proposed by Paul Sclavounos, a professor of mechanical engineering and naval architecture at MIT, among others; this storage system would dovetail well with his concept, Hodder says.

In combination, floating turbines and undersea storage spheres could provide reliable, on-demand power, except during extended calm periods. Meanwhile, a siting many miles offshore would provide the benefit of stronger winds than most onshore sites, while also operating out of sight of the mainland. “It provides a lot of flexibility in siting,” Hodder says. The team calculated that the optimal depth for the spheres would be about 750 meters, though as costs are reduced over time they could become cost-effective in shallower water.

Jim Eyer, a senior analyst with energy consulting firm E & I Consulting of Oakland, Calif., who was not involved in this research, says the concept “addresses some important challenges associated with wind generation in general, especially the temporal mismatch between production and demand, and generation variability, especially rapid output variations that lead to excessive ‘ramping’ of dispatchable generation.” While he calls the idea “somewhat novel and potentially significant,” he adds, “Obviously we’ll need a proof-of-concept pilot to take the next development step.”

Slocum and some of his students built a 30-inch-diameter prototype in 2011, which functioned well through charging and discharging cycles, demonstrating the feasibility of the idea.

The team hopes to extend its testing to a 3-meter sphere, and then scale up to a 10-meter version to be tested in an undersea environment, if funding becomes available. MIT has filed for a patent on the system.

The researchers estimate that an offshore wind farm paired with such storage spheres would use an amount of concrete comparable to that used to build the Hoover Dam — but would also supply a comparable amount of power.

While cement production is a major source of carbon-dioxide emissions, the team calculated that the concrete for these spheres could be made, in part, using large quantities of fly ash from existing coal plants — material that would otherwise be a waste product — instead of cement. The researchers calculate that over the course of a decade of construction and deployment, the spheres could use much of the fly ash produced by U.S. coal plants, and create enough capacity to supply one-third of U.S. electricity needs.

The work was supported by a grant from the MIT Energy Initiative.

Pumped storage is the best solution for intermittent power sources.

It's such a simple solution what MIT proposes, but very obvious to anybody that's ever seen a dam.

No need for a penstock per say, and definitely no surge tower; just a big valve, a turbine and pump.

The cycle will need to be proven, both as cost effective and repeatable with the water depths and statistical prevailing wind characteristics.

[jareth]

There are others thinking along the same lines: Compressed air energy storage has bags of potential

The basic idea of CAES [Compressed Air Energy Storage] is that excess power on the grid is used in an electric motor to drive a compressor. The compressed air is cooled and stored at pressures of typically 60-70 bar. At times of high electrical demand, air is drawn back from the store, heated and then supplied to a modified gas turbine. The energy from this high-pressure air, together with some thermal input, drives the turbine stage. The energy is then converted by an electrical generator and re-supplied to the grid.

...

’The overall process for adiabatic compression sounds simple, but the difficulty is how you handle the heat when you compress the air to 60 and 70 times atmospheric pressure,’ said Edward Barbour, a researcher in CAES at Edinburgh University. ’There are two main problems. One is that the heat is generated very quickly and that’s difficult for the machinery to handle, and the second is that your energy density suddenly becomes very low.’

At these pressures, the heat from compressed air can reach temperatures of 650°C. Seamus Garvey, a professor of dynamics at Nottingham University, believes he has come up with a solution that will allow for cost-effective heat storage. Garvey’s idea is to compress air in containments called Energy Bags held down on the sea bed in deep ocean water. ’Underwater bags are an attractive option because the sea acts as the pressure vessel,’ he said. ’You don’t have to pay for the full structure, just the structural material required to hold the bag down. No matter how full or empty your container is, the pressure stays the same, and that’s lovely for the machinery at the sea surface.’

Imo wind turbines should have been required to be linked to an energy storage system from day one.

[cashinmattress]

There are others thinking along the same lines: Compressed air energy storage has bags of potential

Imo wind turbines should have been required to be linked to an energy storage system from day one.

Yeah, I've heard of such before.

Problems with any non-static structure are life cycle and of course the usual, barnacles, sea life, dragged anchors, fishing nets.

I've used similar air bags for the oil industry, for sub-sea lifting purposes.

A big concrete sphere is a much better solution, as is using water as the working fluid due to it's energy density, plus getting air down there would be a bitch for service.

Still, good to see solutions coming to the fore, and hopefully on line soon.

[happy_renting]

Interesting, but in the example, 1000 30m-diameter spheres would cover a whole square km of sea bed, each requiring concrete equivalent to about 3m thick. That's a lot of concrete to be laid down by whatever ship is eventually built to be big enough to do the job.

Maintaining the turbines might be an expensive job too.

One for the environmomentalists:- What if a dolphin gets squished when they drop one of these things onto the sea bed?

[cashinmattress]

Interesting, but in the example, 1000 30m-diameter spheres would cover a whole square km of sea bed, each requiring concrete equivalent to about 3m thick. That's a lot of concrete to be laid down by whatever ship is eventually built to be big enough to do the job.

Maintaining the turbines might be an expensive job too.

One for the environmomentalists:- What if a dolphin gets squished when they drop one of these things onto the sea bed?

I'm rusty on my hydrodynamic stress analysis, and material properties of concrete; leave it for you civil engineers out there.

But it's hardly an issue if they are installed with the intent to become habitat for wildlife.

One bank bailout would serve to create this infrastructure for the whole of Britain if it was managed correctly.

Environmentalists, unless they are actually living sustainably off the land, are generally a bunch of unenlightened hypocrites.

[corevalue]

I have a small niggling doubt that the energy required to burn lime to make the concrete, will be more than the attached turbine delivers in it's lifetime. And burning lime is a major contributor to CO2 emissions.

[cashinmattress]

I have a small niggling doubt that the energy required to burn lime to make the concrete, will be more than the attached turbine delivers in it's lifetime. And burning lime is a major contributor to CO2 emissions.

CO2 CO-schmu. We need it to live; without it this world would be a hellish fire-storm.

There is no win-win situation when it comes to energy production.

However, it's the legacy costs that are most important to life.

We're going to continue having children, and seeking to use energy as heat to cook, and to manufacture.

C02 can be sorted out, with relatively simple technology and mantra; war, famine, disease or just plain old trees.

Spent nuclear fuel is permanent and dangerous to human life for our tenure on planet earth.

No simple solution.

[Kurt Barlow]

There are others thinking along the same lines: Compressed air energy storage has bags of potential

Imo wind turbines should have been required to be linked to an energy storage system from day one.

Why saddle the technology in its early phase with such a needless requirement? The UK is nowehere near the point where it needs to think of additional storage of the type proposed.

There is at least 4GW of pump storage capacity that could be built plus another 2GW of conventional hydro in the UK.

[Kurt Barlow]

CO2 CO-schmu. We need it to live; without it this world would be a hellish fire-storm.

There is no win-win situation when it comes to energy production.

However, it's the legacy costs that are most important to life.

We're going to continue having children, and seeking to use energy as heat to cook, and to manufacture.

C02 can be sorted out, with relatively simple technology and mantra; war, famine, disease or just plain old trees.

Spent nuclear fuel is permanent and dangerous to human life for our tenure on planet earth.

No simple solution.

Forget about Co2 then what about the economics? At the prices quoted it would be hopeless. These structures would store say 6000kwh - on a daily basis they might make £500 on taking advantage of the best times to generate. That isn't going to pay for an £8m up front investment.

[cashinmattress]

Forget about Co2 then what about the economics? At the prices quoted it would be hopeless. These structures would store say 6000kwh - on a daily basis they might make £500 on taking advantage of the best times to generate. That isn't going to pay for an £8m up front investment.

I don't know who actually came up with the original idea of monetising CO2.

Brilliant bit of wealth extraction and marketing. Does nothing for your health and well being however.

[happy_renting]

I think that burning whale-blubber is the solution.

And whales are sustainable - they breed.

Environmentalists will love the idea.

[fluffy666]

I think that burning whale-blubber is the solution.

And whales are sustainable - they breed.

Environmentalists will love the idea.

You've been watching too much Futurama.. although I'd point out that the sustainable harvest of whale blubber isn't that high.

I'm personally dubious about all energy storage schemes, they are basically spending a lot of time and effort to solve the wrong problem. It has to be repeated : Shifting demand is always more efficient than storage. At the moment we are trying to fit a square peg to a round hole.

Indeed, there is a general principle here. If a system has low losses (i.e. pumped hydro) it's because there are no chemical changes, which means the energy density will be poor, and the resultant size of the structures vast.

If a system has a high energy density, on the other hand, that's almost certainly due to chemical changes which will involve significant energy loss (say making hydrogen, or ammonia). Which again often leads to impractical expense and/or sizing.

It goes without saying that a fleet of new nuclear plants would make this problem go away (mostly, anyway). But who would want to combine relatively cheap and reliable power with zero CO2 emissions?

[Kurt Barlow]

You've been watching too much Futurama.. although I'd point out that the sustainable harvest of whale blubber isn't that high.

I'm personally dubious about all energy storage schemes, they are basically spending a lot of time and effort to solve the wrong problem. It has to be repeated : Shifting demand is always more efficient than storage. At the moment we are trying to fit a square peg to a round hole.

Indeed, there is a general principle here. If a system has low losses (i.e. pumped hydro) it's because there are no chemical changes, which means the energy density will be poor, and the resultant size of the structures vast.

If a system has a high energy density, on the other hand, that's almost certainly due to chemical changes which will involve significant energy loss (say making hydrogen, or ammonia). Which again often leads to impractical expense and/or sizing.

It goes without saying that a fleet of new nuclear plants would make this problem go away (mostly, anyway). But who would want to combine relatively cheap and reliable power with zero CO2 emissions?

True but then the UK has another 2GW of potential conventional hydro capacity, 4GW of additional pumped storage on top of the existing 4 GW of PS and and conventional hydro which seems to work pretty well. Pump storage is 75-80% efficient so doesn't entail big system losses.

[Riedquat]

True but then the UK has another 2GW of potential conventional hydro capacity, 4GW of additional pumped storage on top of the existing 4 GW of PS and and conventional hydro which seems to work pretty well. Pump storage is 75-80% efficient so doesn't entail big system losses.

Pumped storage still works best (AFAIK) with predictable load variations. Whilst it'll smooth out some of the irregularity of wind it's too irregular to be reliable (you'll sometimes have days to cover). Using it to balance generation that can't easily be throttled up or down but is consistent, by storing excess offpeak generation seems the better use of it to me. It would also work well with tidal power.

[Guest eight]

Pumped storage still works best (AFAIK) with predictable load variations. Whilst it'll smooth out some of the irregularity of wind it's too irregular to be reliable (you'll sometimes have days to cover). Using it to balance generation that can't easily be throttled up or down but is consistent, by storing excess offpeak generation seems the better use of it to me. It would also work well with tidal power.

Should I just wire up the exercise bike to the computer?

[europbaron]

If a system has a high energy density, on the other hand, that's almost certainly due to chemical changes which will involve significant energy loss (say making hydrogen, or ammonia). Which again often leads to impractical expense and/or sizing.

That energy isn't lost. We're just not smart enough to use it.

[cashinmattress]

You've been watching too much Futurama.. although I'd point out that the sustainable harvest of whale blubber isn't that high.

I'm personally dubious about all energy storage schemes, they are basically spending a lot of time and effort to solve the wrong problem. It has to be repeated : Shifting demand is always more efficient than storage. At the moment we are trying to fit a square peg to a round hole.

Indeed, there is a general principle here. If a system has low losses (i.e. pumped hydro) it's because there are no chemical changes, which means the energy density will be poor, and the resultant size of the structures vast.

If a system has a high energy density, on the other hand, that's almost certainly due to chemical changes which will involve significant energy loss (say making hydrogen, or ammonia). Which again often leads to impractical expense and/or sizing.

It goes without saying that a fleet of new nuclear plants would make this problem go away (mostly, anyway). But who would want to combine relatively cheap and reliable power with zero CO2 emissions?

Dude. Your petrol tank is a stored energy scheme.

What's your point?

[jareth]

Why saddle the technology in its early phase with such a needless requirement? The UK is nowehere near the point where it needs to think of additional storage of the type proposed.

There is at least 4GW of pump storage capacity that could be built plus another 2GW of conventional hydro in the UK.

Will more pumped storage and hydro get past NIMBYs and the Government? It is difficult enough just to build reservoirs for water storage because the government has decreed that we must instead use less water.

Insisting that wind turbines have some form of energy storage would allow them to integrate seamlessly into the national grid - they would operate like any other producer storing energy (though physically instead of chemically as with coal for example) and then putting it into the network when there was demand for it. At present wind energy gets dumped on the grid when it is there and other producers have to cut back on their output. That variability could have been avoided.

With the benefit of hindsight the introduction of nuclear power should have been followed by building significant pumped storage capacity - to make use the off-peak power. If that had been done wind turbines could now be making use of the pumped storage as well.

[Kurt Barlow]

Pumped storage still works best (AFAIK) with predictable load variations. Whilst it'll smooth out some of the irregularity of wind it's too irregular to be reliable (you'll sometimes have days to cover). Using it to balance generation that can't easily be throttled up or down but is consistent, by storing excess offpeak generation seems the better use of it to me. It would also work well with tidal power.

The irregularity of wind is gradually being reduced by the introduction of large wind turbines, larger wind farms, and better distribution (it used to be Scotland now its the whole UK inc maritime areas) which makes the job of balancing that irregularity easier.

Tidal power would be good too.

[Kurt Barlow]

Will more pumped storage and hydro get past NIMBYs and the Government? It is difficult enough just to build reservoirs for water storage because the government has decreed that we must instead use less water.

Insisting that wind turbines have some form of energy storage would allow them to integrate seamlessly into the national grid - they would operate like any other producer storing energy (though physically instead of chemically as with coal for example) and then putting it into the network when there was demand for it. At present wind energy gets dumped on the grid when it is there and other producers have to cut back on their output. That variability could have been avoided.

With the benefit of hindsight the introduction of nuclear power should have been followed by building significant pumped storage capacity - to make use the off-peak power. If that had been done wind turbines could now be making use of the pumped storage as well.

There was a proposal to build a second Dinorwic on Exmoor but that got shelved when it was realised that we wouldn't be going down the same route as France.

On the planning front who knows.

Here is a sizeable proposal for Scotland (600MW scheme)

http://alansloman.blogspot.com.au/2012/02/loch-choire-ghlais-pumped-storage.html

The nimbys are out in force against this small 50MW proposal

https://www.thebmc.co.uk/llanberis-power-plant-proposal

[Kurt Barlow]

This Strathclyde Uni report analyses potential pump storage capability at existing hydro sites in Scotland

Apparently 514GWH of storage which is enough to power the Uk on an average day for 12 hours.

http://www.esru.strath.ac.uk/EandE/Web_sites/03-04/wind/content/storage%20available.html

Over 12 hours that would be 21GW which is probably unlikely so take a figure of 36 hours thats 7GW of instantaneous supply or demand.

[swissy_fit]

This Strathclyde Uni report analyses potential pump storage capability at existing hydro sites in Scotland

Apparently 514GWH of storage which is enough to power the Uk on an average day for 12 hours.

http://www.esru.strath.ac.uk/EandE/Web_sites/03-04/wind/content/storage%20available.html

Over 12 hours that would be 21GW which is probably unlikely so take a figure of 36 hours thats 7GW of instantaneous supply or demand.

I doubt if any big projects will get off the ground in Scotland until after the independence vote.

[swissy_fit]

link

Pumped storage is the best solution for intermittent power sources.

It's such a simple solution what MIT proposes, but very obvious to anybody that's ever seen a dam.

No need for a penstock per say, and definitely no surge tower; just a big valve, a turbine and pump.

The cycle will need to be proven, both as cost effective and repeatable with the water depths and statistical prevailing wind characteristics.

Would these concrete spheres be easier to build and deploy than massive tidal pools?

[fluffy666]

Dude. Your petrol tank is a stored energy scheme.

What's your point?

I would ask you to elaborate but quite frankly I suspect that sandpapering my own todger off would be a more enjoyable and productive use of my time.

[wherebee]

I would ask you to elaborate but quite frankly I suspect that sandpapering my own todger off would be a more enjoyable and productive use of my time.

Calling ccc!