Storing energy

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non-EV batteries and other energy storage stuff
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T1 Terry
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Storing energy

Post by T1 Terry » Tue, 29 Oct 2019, 13:26

The way we normally view storing solar voltaic energy is in a battery because this is a bit like cash in the wallet, it can be used for a number of different purposes depending on just where it needs to be used.
But energy can be stored for specific uses as well, and maybe cheaper than batteries. With second hand solar panel so cheap and plentiful on evilbay, an array could be set up to power the hot water element in the storage tank or even a few tanks and link them together in series, cold in the bottom of tank 1, hot to the bottom of tank 2 and so on ..... A lot easier than the weight of the solar tank on the roof or evacuated tubes on the roof and pumps etc, just some second hand solar racking and panels ....
Electrodacus https://electrodacus.com/ has come up with an idea using an MPPT controller set up to store heat for those cold winter nights ... might be a while before we need that sort of thing as we head into the warmer mths, but the cold is only half a yr away so being prepared never hurts.
There was another elaborate idea I read about a few yrs back where the designer was storing cold via continually running a fridge compressor while the sun was shining to pull the well insulated freezer box well down below freezing, then circulating a brine solution through his home made fridges and freezers to increase the uses for this stored cold energy.

Anyone have other ideas that could be used to store energy for use after the sun goes down?

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Re: Storing energy

Post by jonescg » Tue, 29 Oct 2019, 14:34

I have wanted to do a similar thing in the opposite direction - run an efficient heat pump for cooling water/glycol and circulating this through the home aircon system. If you went as far as making ice you can exploit the high latent heat of fusion to cool things down. Since water has the highest specific heat capacity of any material, you would still need a rather efficient Stirling engine to harness it.

Electric hot water is a clear winner, and when you use a heat pump it's even more efficient (albeit more complicated and expensive).

If you live somewhere very hilly you can set up a solar array to pump water to a tank 100 m or more in elevation. Then open the tap to run a pelton wheel for evening use. Numbers aren't so good, but if your neighbours are keen on getting in on the action you could install 300,000 litre tanks top and bottom and enjoy the gravitational potential energy. so long as you could assure a 5 litres per second flow, there's a good 4 kW of power there.
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T1 Terry
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Re: Storing energy

Post by T1 Terry » Tue, 29 Oct 2019, 15:28

Brother in law does exactly that on the side of the Huon Valley overlooking the river, but he only requires a20 mtr fall. There is a couple of springs feeding into the upper dam as well so he doesn't need to move as much of the water back up the hill. Often thought about adding a few of those billabong pumps that use the energy in the falling water to compress air in a bell chamber and that pressure pushes water up a much smaller diameter hose to fill a tank or in this case return water to the dam. They can only move about 10% of the water that passes through them, but cascading sizes down the slop would recover maybe 40%, then a mono pump driven by a solar panel could deliver the remainder back up to the dam, they can lift around 40 mtrs, so it would need a few staging dams on the way back up the hill :roll:

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Re: Storing energy

Post by brunohill » Wed, 30 Oct 2019, 00:28

I have the hill and the spare solar, I just wish I had the water.

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Richo
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Re: Storing energy

Post by Richo » Wed, 30 Oct 2019, 12:40

T1 Terry wrote:
Tue, 29 Oct 2019, 13:26
Anyone have other ideas that could be used to store energy for use after the sun goes down?
Well I believe they have all been done before.
Electrostatic, Electrochemical, Moving stuff, pumping stuff, heating, cooling...
All have their advantages and disadvantages.
Its pretty hard to beat regular batteries at the moment.

In an ideal world I'd use a gazillion MLCC caps.
They don't age as bad as electro's or ELDC's (supercaps).
When they do age you can actually re-bake them at ~160DegC which resets them.
Eternal storage... :mrgreen:
Unfortunately with the recent cap shortage and some prices going up 10x it'd cost a bazillion-gazillion dollars to buy :roll:
So the short answer is NO but the long answer is YES.
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Richo
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Re: Storing energy

Post by Richo » Wed, 30 Oct 2019, 13:04

Compressed air...
So the short answer is NO but the long answer is YES.
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Re: Storing energy

Post by HuffnPuff » Thu, 31 Oct 2019, 05:17

Richo wrote:
Wed, 30 Oct 2019, 13:04
Compressed air...
If only we could harness all the hot air in Canberra

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Re: Storing energy

Post by antiscab » Thu, 31 Oct 2019, 07:03

Richo wrote:
Wed, 30 Oct 2019, 13:04
Compressed air...
If the energy surplus were in winter, that would work out pretty well. Get heat in winter when storing and cold in summer when releasing.
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Richo
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Re: Storing energy

Post by Richo » Thu, 31 Oct 2019, 12:25

Richo wrote:
Wed, 30 Oct 2019, 12:40
In an ideal world I'd use a gazillion MLCC caps.
Just for amusement I checked on the current cost.
My estimate would be $15M per kWh.
So the short answer is NO but the long answer is YES.
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Richo
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Re: Storing energy

Post by Richo » Thu, 31 Oct 2019, 12:29

brunohill wrote:
Wed, 30 Oct 2019, 00:28
I just wish I had the water.
Well it can be anything.
I suggest someone find a way to utilise dirt.

https://www.youtube.com/watch?v=itbwXMMkBQw
So the short answer is NO but the long answer is YES.
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T1 Terry
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Re: Storing energy

Post by T1 Terry » Thu, 31 Oct 2019, 14:33

As far as the water storage generation, does the fall need to be that great? What about an https://en.wikipedia.org/wiki/Archimedes%27_screw that could lift the water via a windmill and crank arrangement that could be declutched from the shaft to allow either excess solar energy to drive the screw via motor/generator or the water run back down the screw driving motor as a generator ...... similar idea to those mentioned at the end of the Wiki link.
This system doesn't use the velocity produced by water falling over a certain distance, so is it the weight of the water that drives the screw?

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Re: Storing energy

Post by brendon_m » Thu, 31 Oct 2019, 15:32

Are screws efficient? , I feel there would be a lot of loses and I'd suspect you would lose a lot of your stored energy to leakage around the screw and the velocity of the water coming down the screw.

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Re: Storing energy

Post by jonescg » Thu, 31 Oct 2019, 16:02

Screw pumps are low flow, high pressure (head) systems which would be a good fit for sending water a long way uphill. We used one back in Emu Vale to pump about 60 m of head.
I use this calculator - https://www.engineeringtoolbox.com/hydr ... _1359.html
Put in the head and the flow and calculate the power. Then work out how big your reservoirs need to be for how long you can run it.
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Richo
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Re: Storing energy

Post by Richo » Fri, 01 Nov 2019, 12:41

T1 Terry wrote:
Thu, 31 Oct 2019, 14:33
As far as the water storage generation, does the fall need to be that great?
Ep=mgh (Joules)

1kWh=3,600,000J=m x 9.8 x h
If you have a "small" tank of 17,466L this is 17466kg of water.

3,600,000 = 17466 x 9.8 x h
h = 21.0 m (ideally)

For 1kWh :shock:
The return efficiency will be significant.
So I'd guess more like 40m with 17.5T of water for 1kWh.
So the short answer is NO but the long answer is YES.
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