Calculating for the use of sand for a thermal store.

[Nickfromwales]

  On 02/01/2023 at 20:30, SteamyTea said:

Right, rather than trying to store energy at elevated temperatures, for months  why not just use a heat pump.

Then all you need to work out is the power needed to run it, and your potential to generate that power.

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A crane to lift an immensely heavy weight a very short distance seems a good idea. That stored energy will last until you release the brake.

Airbag powered lift under a summer patio via a compressor.

Electrical energy into storage, then returned via a HP to multiply x4 on the return.

Or;

Other such lunacy?

 

 

 

 

 

 

 

 

Am I a Boffin yet?

[Marvin]

  On 02/01/2023 at 20:46, pdf27 said:

If you're trying to store heat, no reason to use PV - solar thermal captures about 3x the energy per unit area, and you're going to need a liquid system to get the heat out again.

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Hi @pdf27

 

Another great idea, however there is no roof left that can be used for solar anything.

 

We have PV and an ASHP. 

Yes we produce about 2000kWh excess in the summer.

 

4m3 was the guess of the size as I still have to calculate the heat loss.

 

No we are not going to put the thermal storage in the building. It must remain outside the building thermal envelope.

 

We are looking to use about 500kWh of heat during the 6 months of the year. The maths is complicated because even on some days in January like today we produced more energy than we could store or use (there's just less days like this in January).

 

Any idea how much a Sunamp system is per 100kWh? 

 

M

 

[RobLe]

  On 02/01/2023 at 22:49, Radian said:

 

 

When it comes to lossless energy storage you can't do much better than bunch of rocks minding their own business. It takes approx. 50,000 Joules to lift 1000 kg 5 meters (roughly 14kWh) so around 35 tons to see you through the winter.

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Sadly I think 50,000J is only 14Wh, not 14kWh.  That’s a big old weight you’ll need.

[Marvin]

  On 02/01/2023 at 21:41, Roger440 said:

 

My new house is smaller than my old one, but less thermally effiecent. Early indications are an oil consumption rate similar to the old one. Which was about 1700 litres of oil a year, so circa 16000kwh annually.

 

Ok, im going to improve the current situation, so lets say im really good and halve it 7500.

 

Just rough numbers its going to need over 1000kwh per month in mid winter, or 33kwh per day. 

 

Feel free to point out what bit ive got wrong, maths isnt my strong point, or how much PV i need in december / january. But its going to be an awful lot?

 

 

 

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This December we produced 169kWh from 5.12kW system in the sunniest part of the country which means you would need about a 30kW system.  However we produced no PV some days and today 12kWh which means your system would produce about 70KWh. The panels would cover some 27m2. And so on. Your right. An awful lot.

M

[Marvin]

  On 02/01/2023 at 21:58, SteamyTea said:

 

 

I sometimes think that the people that run these schemes don't know what they are doing, rather than actively trying to rob people.

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Are you referring to any one in particular? SBF?

[Marvin]

  On 02/01/2023 at 22:11, MikeSharp01 said:

That's an interesting read - 23T of  water and you cannot make it pay.

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They should of done the maths and not waste the time.

[Marvin]

  On 02/01/2023 at 22:49, Radian said:

 

 

When it comes to lossless energy storage you can't do much better than bunch of rocks minding their own business. It takes approx. 50,000 Joules to lift 1000 kg 5 meters (roughly 14kWh) so around 35 tons to see you through the winter.

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Yes @Radian I have seen systems like that. What's that? 20 cubic meters?

 

The costs would be exstoronate. 😂

[Iceverge]

The annoying thing about this is that if proper nett metering was a thing no silly complex domestic mechanisms would be called for. 

 

Excess solar could be used in summer to offset any carbon based power generation. When all that headroom was used up we could use the power for electricity hungry industries like steel making to boost capacity. 

 

Maybe @Marvin you could install an industrial electric arc furnace in the back garden and use the spare power that way😂

[Nickfromwales]

  On 03/01/2023 at 00:05, Marvin said:

Any idea how much a Sunamp system is per 100kWh? 

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Only good for a day or so of storage. The unit bench tests well, but add the connective pipework and the losses soon shoot up.

[Onoff]

@Marvin, can you lose a 4m diameter, 7m tall cylinder at your place? If so you're onto a winner:

 

https://www.renewableenergymagazine.com/storage/first-commercial-sandbased-thermal-energy-storage-is-20220707#:~:text=Polar Night Energy and Vatajankoski,in a district heating network.

 

(I think I've posted this before).

[SteamyTea]

  On 03/01/2023 at 00:29, Marvin said:

Are you referring to any one in particular? SBF?

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No.

I have been to a couple of local Dragon's Den type events where local businesses are trying to raise money.

The ignorance is staggering sometimes.  One of the Dragons, someone I know quite well, and does have his head screwed on as he checks concepts with people that do know, likes to see the other investors loose money.

[jack]

  On 02/01/2023 at 21:09, Roger440 said:

Thats why i looked at milk tankers, buried if need be. But its simply economic madness.

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I considered this before we built our house as well. 10 mins of research to conclude there was no way it could make economic sense!

[Roger440]

  On 03/01/2023 at 03:51, Onoff said:

@Marvin, can you lose a 4m diameter, 7m tall cylinder at your place? If so you're onto a winner:

 

https://www.renewableenergymagazine.com/storage/first-commercial-sandbased-thermal-energy-storage-is-20220707#:~:text=Polar Night Energy and Vatajankoski,in a district heating network.

 

(I think I've posted this before).

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Can it be on its side? If so, i could.

 

Whats the payback? About eleventy billion years?

[MikeSharp01]

  On 03/01/2023 at 08:10, jack said:

I considered this before we built our house as well. 10 mins of research to conclude there was no way it could make economic sense!

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YES...but the basic physics is sound, which is probably why people keep banging away at it, you can, after all, store a lot of energy in a ton of sand (most things really) in a variety of forms, kinetic & heat for instance, and energy availability shifting is the holy grail, its just getting it there, keeping it there, getting it in & out efficiently and all for a reasonable sum that are the problems! The reasonable sum gap might be closing a little as energy costs rise and so close it. 

[Marvin]

  On 03/01/2023 at 03:51, Onoff said:

@Marvin, can you lose a 4m diameter, 7m tall cylinder at your place? If so you're onto a winner:

 

https://www.renewableenergymagazine.com/storage/first-commercial-sandbased-thermal-energy-storage-is-20220707#:~:text=Polar Night Energy and Vatajankoski,in a district heating network.

 

(I think I've posted this before).

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Hi @Onoff

 

Yes Thanks. I don't need 80000kWh of power..... and might need planning permission.

[Roger440]

  On 03/01/2023 at 08:10, jack said:

 

I considered this before we built our house as well. 10 mins of research to conclude there was no way it could make economic sense!

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Sadly, as this thread shows, there dont appear to be any economically sensible solutions to storing energy for extended periods. Even on a DIY basis, and even if you have unlimited space.

 

I think we have concluded i "can" install a solar array big enough to heat my house all year, but the costs of doing so, again, make no sense, even DIY with second hand kit.

 

The real difficulty, as discussed before, is not knowing what the price of electricity is likely to be going forward. On a supply/demand basis, very much higher than it is now seems "likely". But not with enough confidence to spend a 5 figure sum on the necessary PV installation. 

[Marvin]

  On 03/01/2023 at 08:43, Roger440 said:

 

Sadly, as this thread shows, there dont appear to be any economically sensible solutions to storing energy for extended periods. Even on a DIY basis, and even if you have unlimited space.

 

I think we have concluded i "can" install a solar array big enough to heat my house all year, but the costs of doing so, again, make no sense, even DIY with second hand kit.

 

The real difficulty, as discussed before, is not knowing what the price of electricity is likely to be going forward. On a supply/demand basis, very much higher than it is now seems "likely". But not with enough confidence to spend a 5 figure sum on the necessary PV installation. 

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Hi @Roger440

 

The other cost challenge would be upgrading your connection to the grid but I didn't mention because as you say the cost turns out to be silly. 

[Radian]

  On 03/01/2023 at 00:20, RobLe said:

Sadly I think 50,000J is only 14Wh, not 14kWh.  That’s a big old weight you’ll need.

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That'll teach me to do sums when still hung over!

[Roger440]

  On 03/01/2023 at 08:47, Marvin said:

Hi @Roger440

 

The other cost challenge would be upgrading your connection to the grid but I didn't mention because as you say the cost turns out to be silly. 

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But thats not actually necessary is it? Or am i missing something?

 

My plan was to connect my solar direct to heating water for heating the house. That way it can be completely stand alone and avoid all the unnecessary complications of interfacing with the grid supply.

 

Sure, in summer, ill have a bunch of power i dont need. Does that matter? 

 

Sorry, not direct to heating water, put with a heat pump. But stand alone all the same.

Edited January 3, 2023 by Roger440

[Marvin]

  On 03/01/2023 at 08:51, Roger440 said:

 

But thats not actually necessary is it? Or am i missing something?

 

My plan was to connect my solar direct to heating water for heating the house. That way it can be completely stand alone and avoid all the unnecessary complications of interfacing with the grid supply.

 

Sure, in summer, ill have a bunch of power i dont need. Does that matter? 

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Hi Roger. No it doesn't matter apart from being able to get paid for any excess. I think the system would generate about 30,000kWh a year.

[SteamyTea]

  On 03/01/2023 at 08:43, Roger440 said:

is not knowing what the price of electricity is likely to be going forward.

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We do have a fairly good idea.

https://www.gov.uk/government/publications/contracts-for-difference-cfd-allocation-round-4-results/contracts-for-difference-cfd-allocation-round-4-results-accessible-webpage

Apart from Tidal Stream and floating turbines, I think they are all around $45/MWh.

Energy from waste, which still has a fair way to go is coming in at the same price as PV and onshore wind.

Natural Gas is now at August 2021 prices, but still volatile.

 

Over the last 40 years, domestic energy prices has been around 5% of median household income, no reason to think it will be much different in the medium to long term.

EDF dropped my night rate by 3p/kWh, though the day rate did go up by 8p/kW.  ~85% of my usage is at night, with my day usage pretty consistent at 1.3 kWh/day.

It may possibly be worth me getting a kWh of storage to run the hob and oven.  Or I could stop using the oven as much (used it more in the last year than I did the previous year).

 

Edited January 3, 2023 by SteamyTea

[Marvin]

Thank you everybody for your input. Very informative.

 

I think we all basically agree that sand can hold a lot of energy. 

 

What I want to calculate is the losses incurred from a particular design.

 

This is not simple and related only to our property. I have calculated, and recorded the fact, that even in November and December there are days when despite all the household equipment, heating, electric vehicle and battery storage, we still send energy to the grid. In fact every month of the year there are days when this happens.

 

The point is: IF  we had a thermal store this energy could be used to reduce the loss from the already energised (is that the right word?) thermal store. A sort of top up.

 

I will now be trying to define what thermal losses would be expected ( and will probably need @SteamyTea's help) from example designs of a store. 

 

 

 

 

 

 

[Roger440]

  On 03/01/2023 at 09:02, SteamyTea said:

We do have a fairly good idea.

https://www.gov.uk/government/publications/contracts-for-difference-cfd-allocation-round-4-results/contracts-for-difference-cfd-allocation-round-4-results-accessible-webpage

Apart from Tidal Stream and floating turbines, I think they are all around $45/MWh.

Energy from waste, which still has a fair way to go is coming in at the same price as PV and onshore wind.

Natural Gas is now at August 2021 prices, but still volatile.

 

Over the last 40 years, domestic energy prices has been around 5% of median household income, not reason to think it will be much different in the medium to long term.

EDF dropped my night rate by 3p/kWh, though the day rate did go up by 8p/kW.  ~85% of my usage is at night, with my day usage pretty consistent at 1.3 kWh/day.

It may possibly be worth me getting a kWh of storage to run the hob and oven.  Or I could stop using the oven as much (used it more in the last year than I did the previous year).

 

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Correct me if im wrong, but the link you provide is the "buy" price, not the selling price?

 

[SteamyTea]

  On 03/01/2023 at 09:04, Marvin said:

I will now be trying to define what thermal losses would be expected ( and will probably need @SteamyTea's help) from example designs of a store. 

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Model a 'cartoon' store i.e. basic shape and whole number dimensions.

Then get working on a spreadsheet.

Always pick the worse numbers, rather than the most likely.

[Roger440]

  On 03/01/2023 at 09:04, Marvin said:

Thank you everybody for your input. Very informative.

 

I think we all basically agree that sand can hold a lot of energy. 

 

What I want to calculate is the losses incurred from a particular design.

 

This is not simple and related only to our property. I have calculated, and recorded the fact, that even in November and December there are days when despite all the household equipment, heating, electric vehicle and battery storage, we still send energy to the grid. In fact every month of the year there are days when this happens.

 

The point is: IF  we had a thermal store this energy could be used to reduce the loss from the already energised (is that the right word?) thermal store. A sort of top up.

 

I will now be trying to define what thermal losses would be expected ( and will probably need @SteamyTea's help) from example designs of a store. 

 

 

 

 

 

 

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Do keep us updated. The principle is fairly simple. Its just the practical application.