# Latest gravity storage article (Professor Crackpot never sleeps) add a kite?

Hey I know - we could make kite-reeling more complicated and expensive!

Associating the reeling-kite (yo-yo) with the Gravitricity system makes it possible to resolve the intermittence of the yo-yo system: during reel-in phase the Gravitricity system discharges, producing electricity, and during reel-out phase the Gravitricity system charges itself thanks to the kite pull. Congratulation Professor Crackpot .

Yes sounds good Pierre, but as the comments after the article suggest, it would be way cheaper to use a small battery. I had a guy contact me about that crane-lifting-concrete-blocks gravity storage idea. He laid out a certain scenario with a certain large number of tons being lifted 40 feet. I ran the numbers for him, and it turned out to be a very small amount of kWh. His response was something to the effect he had not considered calculating how much energy it could store. Thatâ€™s the problem with so many Professor Crackpot ideas - they sound great, like energy poetry, until you do the math and go â€śuh-oh, maybe notâ€ťâ€¦ Some of these ideas look great until you run the numbers and realize how much huge, expensive structure is required, to store â€ścheapâ€ť electricity, only to convert it into unaffordably expensive energy!

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The problem is inherently that energy is so cheap. We are looking for even cheaper ways to create and store electricity. If we just increase the price of energy, there might not be a shortage of carbon neutral energy. Or - there is no shortage, just the current price.

Gravity energy storage could use less pollutants compared to batteries, being an alternative competitive edge. But I doubt that amount of steel/concrete will be competitive in that respect, as there will be energy, materials and pollution expenditure to make these. Energy storage will always be carbon positive, unlike solar or windmills, which eventually produce more energy than production cost.

At sea or on lakes using water in the place of concrete-block then a pump and a tall float. Water is available without limit on sea. Kite-reeling (yo-yo) and water gravity could be a suitable association.

With water as a medium I would immediately think pumps rather than lifting buckets. Pumps have lossesâ€¦ and water requires a strong tank. Concrete blocks are easier to handle in many ways, in particular lifting with an electric winch is near lossless. You need two conversions, one to store and one to produce energy. If electric motors are 95% efficient, and a turbine is 60% (just some random numbers from my guesses) the efficiency of the energy storage system is very different

I think about temporary storage such like to fill the gap of a yo-yo system.

I think pumped hydro is better used where the geographical conditions is right for it. So it is better to make a pumped hydro plant at a natural water reservoar in the mountains and use that to serve whatever intermittent renewable energy that is close enough to make sense with regards to powerline losses than to make a giant water tank, and a pumping installation on every wind turbineâ€¦

The problem is the limit of hydropower which fully works currently.

I often think of energy storage as first un-generating power that was already generated, then re-generating that same power. Logically, a result of the final cost of energy being at least 3x the original cost of energy would therefore not be surprising.

With such a relatively small amount of energy needed to be stored, given the cycle time of kite-reeling, batteries or even capacitors(?) might be a good choice for smoothing power. If you had several kite-pumping systems working at the same time they could be un-synchronized, to smooth the total resulting output.

Which is more expensive, digging a hole or building a tower? If we are using a big weight, why not use a flywheel energy storage device as the weight? A suspended flywheel has the advantage of not having support bearings which are strained if the device precesses. A below ground flywheel system is intrinsically safe in the case of a catastrophic disintegration of the flywheel. A flywheel-weight system combines two highly efficient energy storage devices where both systems can operate for decades without maintenance. Both systems can supply instant power adjustments for load leveling.

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Do you need to dig?
Either a frame between 2x existing city tower blocks, lifts & lowers blocks

Squashes the odd pedestrian

Or
Anchor and pulley at the sea bed and incompressible buoy pulled down to store energy.

Even simpler than pulling down a buoy is to pull up a heavy object from the sea bed, such as what http://sinkfloatsolutions.com/ proposes. The required installation at the sea bed is much simpler, essentially none.

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Welcome to the forum @AndreasEisele,

I was aware of the existence of this interesting concept, which would apply to mass storage rather than temporary storage as I mentioned earlier.

Hi @AndreasEisele welcome and thanks for the link.
Yepâ€¦ simpler still.
It now begs the questionâ€¦ Why concrete?
Canâ€™t we just fill bags with rocks? Potentially from the sea floor, thus already in place.

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Yes, I think anything heavier than water would do, and I see essentially a tradeoff between cost (financial + ecological) on one side and fluid resistance when lifting or sinking the weights on the other. Bags filled with rocks (and sand and water to fill the gaps) might be a good alternative, but I suspect the outer side of the bag should be smooth to minimise the resistance.

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A now old video (2015) explains the principle of a similar device (see at about 2:30):

The drawbacks are difficult maintenance in a very harsh marine environment (salt water, currents, etc.). Very long submarine cables and concrete blocks, as well as rocks, are particularly attractive for seashells. Finding and removing deep sand can also be difficult. And the operation itself is anything but easy, even in automatic mode: hooking and unhooking the blocks requires serious maintenance.
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My view of the future is that there will be a LOT of off-shore wind power, also in deep water, where winds tend to be stronger and less people can complain about it (currently one of the biggest problems for wind power e.g. in Germany). Maybe cables will remain too expensive, so power-to-X technology will have to be be used to bring the energy to locations where it is needed. But also power-to-X is and will remain expensive in the foreseeable future, hence whatever device will be used, it will be important to use it constantly to max out the capacity of the equipment (this argument holds even for submarine cables). In this scenario there is a big demand for cheap off-shore storage capacity, where sinkfloatsolutionsâ€™s technology and similar alternatives would be a nice fit. I do not deny there are big challenges, but I am convinced they are worth tackling.

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