‘Sun in a box’ would store renewable energy for the grid

Posted: December 6, 2018 by oldbrew in Energy, innovation, research
Tags: ,

This may or may not have its uses, but any idea that the whole world could get electricity mainly from the sun and the wind is not credible, with today’s technology at least.

MIT engineers have come up with a conceptual design for a system to store renewable energy, such as solar and wind power, and deliver that energy back into an electric grid on demand, says TechExplore.

The system may be designed to power a small city not just when the sun is up or the wind is high, but around the clock.

The new design stores heat generated by excess electricity from solar or wind power in large tanks of white-hot molten silicon, and then converts the light from the glowing metal back into electricity when it’s needed.

The researchers estimate that such a system would be vastly more affordable than lithium-ion batteries, which have been proposed as a viable, though expensive, method to store renewable energy. They also estimate that the system would cost about half as much as pumped hydroelectric storage—the cheapest form of grid-scale energy storage to date.

“Even if we wanted to run the grid on renewables right now we couldn’t, because you’d need fossil-fueled turbines to make up for the fact that the renewable supply cannot be dispatched on demand,” says Asegun Henry, the Robert N. Noyce Career Development Associate Professor in the Department of Mechanical Engineering. “We’re developing a new technology that, if successful, would solve this most important and critical problem in energy and climate change, namely, the storage problem.”

Henry and his colleagues have published their design today in the journal Energy and Environmental Science.

Record temps

The new storage system stems from a project in which the researchers looked for ways to increase the efficiency of a form of renewable energy known as concentrated solar power.

Unlike conventional solar plants that use solar panels to convert light directly into electricity, concentrated solar power requires vast fields of huge mirrors that concentrate sunlight onto a central tower, where the light is converted into heat that is eventually turned into electricity.

“The reason that technology is interesting is, once you do this process of focusing the light to get heat, you can store heat much more cheaply than you can store electricity,” Henry notes.

Concentrated solar plants store solar heat in large tanks filled with molten salt, which is heated to high temperatures of about 1,000 degrees Fahrenheit. When electricity is needed, the hot salt is pumped through a heat exchanger, which transfers the salt’s heat into steam. A turbine then turns that steam into electricity.

“This technology has been around for a while, but the thinking has been that its cost will never get low enough to compete with natural gas,” Henry says. “So there was a push to operate at much higher temperatures, so you could use a more efficient heat engine and get the cost down.”

However, if operators were to heat the salt much beyond current temperatures, the salt would corrode the stainless steel tanks in which it’s stored. So Henry’s team looked for a medium other than salt that might store heat at much higher temperatures.

They initially proposed a liquid metal and eventually settled on silicon—the most abundant metal on Earth, which can withstand incredibly high temperatures of over 4,000 degrees Fahrenheit.

Last year, the team developed a pump that could withstand such blistering heat, and could conceivably pump liquid silicon through a renewable storage system. The pump has the highest heat tolerance on record—a feat that is noted in “The Guiness Book of World Records.”

Since that development, the team has been designing an energy storage system that could incorporate such a high-temperature pump.

Continued here.

Research article: Secular decrease of wind power potential in India associated with warming in the Indian Ocean

  1. cognog2 says:

    Interesting technology. Plenty of grant money potential; but hardly practical when scaled up. Think of the footprint area required for all those mirrors and those poor birds getting an in flight roasting.

    Harvesting low grade energy will always be an expensive process; mainly because you are swimming against the thermodynamic laws.

  2. Bloke down the pub says:

    I think that for the time being, I’d stick with these guys.

  3. Bloke down the pub says:

    cognog2 says:
    December 6, 2018 at 11:26 am

    It doesn’t have to be heated by concentrating solar, it could use electricity from the grid.

  4. JB says:

    Instead of a 60 minute test, they need to perform a 6000 hour test. Feasibility studies should always include failure modes, in this case including sabotage and acts of god.

  5. hunter says:

    Another example of how the climate kooks will destroy the Earth in order to indulge their CO2 obsession.
    “Vast” arrays of mirrors means “vast” areas of open land turned into bird frying uninhabitable mirror farms, displacing native life, when not killing it.
    Industrial blight “vastly” larger than anything else to date.
    And all to melt down silicon…and then convert the glow of the liquid silicon electricity?!?
    How many huge efficiency losses will occur in this self-parody scam?
    How even MIT is being damaged by the climate change obsession.

  6. hunter says:

    The one application that a super reliable liquid silicon system could possibly make sense would be in the nuclear power field.
    But the risks and dangers of basically using molten glass as a primary coolant seems to be much higher than any benefits.
    Can you imagine a hard shut down?
    And think of how to do a restart.
    Leaks would be literally fatal to the touch.
    This is just grant fishing, as cognog2 points out.

  7. ivan says:

    Another solution looking for a problem to solve, the problem being how to supply reliable dispatchable power. That problem was solved with the building of coal fired boilers that powered very large alternators (coal can be replaced by nuclear power).

    What they should be concentrating on is improving the efficiency of the coal or nuclear generators but since both of them are on the green black list there is no grant money available for that.

    As usual they have only done this as a lab experiment. They assume it will scale but don’t give any indication of how big this storage system would need to be to supply power to a small town, for example10000 people,for a full night when the wind isn’t blowing or if solar panels can restore the lost energy and power the town during the day. One can only assume that real power generators to do that which means a grid connection. The need for a grid connection raises the question ‘what is the use of this system, other than striking the egos of the academics and greens?

    I am waiting for some academic to read some old science fiction (it has to be old because modern SF is nothing more than doom and gloom rather than looking to the possible future) and so come up with the idea of collecting sunlight out in space, with correct positioning, available 24/7/360, and then beaming the generated power down to earth using microwaves – think of the research money they should be able to get for that.

  8. vuurklip says:

    The current contribution of “renewables” is close to zero – so imagine how many more turbines and mirrors will be required to not only cover current use, but to also store enough for those rainy days.

    So, it’s double up on wind, double up on solar – but still keep coal/nuclear/gas in reserve!

    Thus double up on subsidies as well.

    Here in South Africa we can’t even keep the lights on WITH coal (even with billions in subsidies) …

  9. Jim says:

    It’s not downscalable. You could not leave it in a backyard with children playing around it. Or send it into space as part of a usable power source. ” Things break” liquid glass is not a healthy item to store in living spaces. Or be used as a battery.

  10. Gamecock says:

    Renewables need backup because they are not . . . renewable.

    Orwellian doublespeak.

    Storage will be finite; outage potential infinite. Storage is a fool’s errand.

    ‘The new design stores heat generated by excess electricity’

    Oh, yeah. When we’re on 100% renewables, there’ll be excess electricity everywhere.

  11. oldbrew says:

    Germany already has excess electricity from renewables at certain times, and has to ‘sell’ it even at negative prices i.e. pay to get rid of it. Obviously with yet more wind and solar such problems can only get worse.


  12. spetzer86 says:

    Ivanpah happily burns gas to get its molten salt system up and running. Ivanpah is working better today than it did originally, not it’s still burning gas. As mentioned above, how you’d go about liquifying a silicon pumping system from a cold start is a daunting proposition.

  13. Kip Hansen says:

    Interesting idea — but still in Pie-In-The-Sky territory.

  14. oldbrew says:

    such a system would be vastly more affordable than lithium-ion batteries

    About those lithium-ion batteries…price rise imminent due to cobalt content.


  15. Bitter@twisted says:

    Yet another expensive pie in the sky “solution” to a non-problem.
    These so-called academics need to get out a bit more often.

  16. Stephen Richards says:

    if you are going to put vats of molten metal in the public domain it might as well be Liquid Thorium or Sodium in a nuclear reactor. That way you won’t need windmills and solar panels which are dirty technology

  17. BoyfromTottenham says:

    I heard recently that CSIRO here in Oz was given A$25 million by BHP to develop a hydrogen-powered mining truck. I asked where they would get the hydrogen from, they said ‘ammonia, which is much cheaper then diesel fuel’. An ex-BHP engineer who specialises in truck fleets heard it and laughed – we don’t need exploding trucks, he said. Another waste of good money, but it will keep a load of ‘researchers’ in funds for several years and out of the real world. Reminds me of the old joke about the scientist who asked ‘I know it won’t work in practice, but will it work in theory?’.

  18. Graeme No.3 says:

    We have a company here in South Australia planning to use such technology called 1414 degrees after the melting point of silicon (℃). That means a good deal of energy has to go into the storage to make it usable and is unavailable for use. Certainly you could in theory heat the liquid silicon to 2400℃ and get better efficiency as per Carnot but….
    I would appreciate someone translating the following
    “a module with 200MWh storage capacity would use the equivalent of 400 tonnes of silicon, “capable of charging at up to 40MW” and could supply 10MW of base load electricity plus heating for more than eight hours.”

  19. Gamecock says:

    THORIUM ?!?!

    HOW 1960 OF YOU!

  20. Stuart Brown says:

    Graeme – I suspect you know more than me about such things, but you asked..

    Assuming the 200MWh is heat energy, then you boil some water and get 80MWh electrical energy back out – or 10MW over 8 hours. That’s an efficiency of 40%, which is plausible, I suppose, if you want the output temperature to be something higher than barely usable for district heating. Since the input temperature is at least 1414℃, you could probably get up to 60% efficiencies using a combined cycle gas/steam turbine? But with nothing much useful in the way of heat at the end.

    And the input is electrical energy? So at 40% efficiency we need to overprovide our renewable power capacity by a factor of, say, 3 to overcome intermittency, and another factor of 2.5 to overcome the inefficiencies in this storage scheme, without considering the heat energy that leaks out of the thing. Maybe that’s insignificant, but 10MW is a tiny power station. Scaling up we need 40,000 tonnes of molten silicon to give 1GW output for eight hours, or 800,000 tonnes of white hot material to keep you going through a windless week with an equivalence to a decent coal/gas fired or nuclear power station? Sound about right?

  21. BoyfromTottenham says:

    This whole idea smacks of the old line ‘Last week I couldn’t spell Enguneer and now I are one’!

  22. Graeme No.3 says:

    Stuart Brown says:
    December 6, 2018 at 10:42 pm

    I was being sarcastic. I don’t think they have gone as far as a practical method of turning the high temperature into usable electricity. I am not sure how much 800,000 tonnes of molten silicon cost but I wouldn’t want it in my neighbourhood.
    Yes, they plan to use ‘excess’ wind turbine output as the energy source. The folly of seasonal smoothing of renewable energy is explored in

    The combined wind + solar LCOE without storage was $50/MWh
    with battery storage capital costs included
    LCOE Case A: $699/MWh
    LCOE Case B: $1,096/MWh

    Possibly they may be thinking of a Drayton cycle where inert gas is heated and drives a turbine before being cooled and recycled. Overall efficiency claimed is about 59% conversion.

  23. oldbrew says:

    Is there a prize for thinking up expensive high-tech ways of producing/storing small amounts of electricity? It seems to be a crowded field 😎

  24. Stephen Richards says:

    Gamecock says:
    December 6, 2018 at 10:22 pm

    Or sodium

  25. stpaulchuck says:

    I’m glad to see they are thinking up variants to our power systems, but this one is just a non-starter. Perhaps parts of it can be reused in other experiments. For now, we’ve got 1,000 years of nuclear, oil, gas, and coal base load fuel that is reliable and relatively cheap. I’ll go with a proven winner thank you and skip the Satanic Gases nonsense.

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