Talk Morgan Forums Community The Malvern Arms Electric Cars

An interesting exercise. Assuming ambient of 10C, heating 100 tons of sand to 500C puts something like 14 billion joules of energy into it, so quite a significant reserve. Then it becomes an issue of how much energy you can take out to balance the amount you can put in during the day - or how long you can get useful heat out of it if you don't put anything more in.

If the claim of 'months at a time' is translated to a slightly more believable 8 weeks, and it means we run the 'battery' back down to ambient, then we are talking about taking in the region of 11MW out, so enough to warm a reasonable number of homes even given some pretty large efficiency losses.

If we assume an average house needs 12KWh/ year for heating and use is concentrated into 200 days per year, then a village of 1,000 homes would need to draw around 60KWh/day. But we need to factor in efficiency losses, of which I have no idea. Let's assume the whole system is only about 25% efficient. That means our battery is going to have to be able to supply a steady 10KW, so well within the theoretical capabilities of a 100-tonne battery. And these things wouldn't need to be very big, 100 tonnes of sand is about 65 cubic metres, so the size of a small industrial unit/big shed would do it.

As you say though, this is just a reworking of the storage heater concept - which of course is itself a form of artificial geothermal energy. I suppose the advantage here is that it's pretty cheap to pile sand around heating coils rather than digging or boring holes to make ground source systems.

I'm sure most people would be very pleased to heat their house on 12kwh for the year ... think there might be a few orders of magnitude need added to that.

🙂

K

Oops, yes, it's MWh,not KWh

https://assets.publishing.service.g...old-Energy-Consumption-Affordability.pdf

So that would mean our sand battery would have to deliver 10MW, which might be possible given the heat capacity, but I suspect it would only really work for many fewer homes - or of course you could have a bigger pile of sand!

Yes, but how does it heat these houses? The method? Calling it a battery implies electric recovery doesn't it? Or are you suggesting blowing air through it down pipes to houses?
Nick

When I saw the term “sand battery” I thought..
How the #### is that going to work? How can sand be used in a battery?
Reading about it I realised it is a variant of storage heating. The usual media hype providing clickbait.
We’ve had storage heating for decades. Solar panels heating water that is stored in a tank/ heat exchanger, geothermal in places like Iceland, air source/ ground source heat pumps being the latest must have.
There is a lot of overselling in the media for air/ ground heat pumps. New, well insulated buildings are ok but older not so. A bit like solar in that it was a good buy with the high feed in tariffs but the maths very marginal for cost- benefits now. EV ownership and battery storage might help, though.
It is only a matter of time before fuel duty gets transferred to EV’s. smart meter variable costing too.
Covid, Ukraine have highlighted a poor long term strategy for fuel supply with self sufficiency being changed to buy it in.
It takes a “crisis” to refocus the strategic plans to stimulate development and change.

Hot water circulation. You are absolutely right, it's not a battery at all, it's a heat storage/recovery system. As many others have pointed out, hysterical and inaccurate reporting by the media is completely unhelpful.

I reckon the narrative that they are trying to push is that one day someone's going to come up with a silver bullet solution that solves all our energy problems and enables us to carry on as we are. You see it time and time again whether applied to sand batteries, hydrogen cars, fusion power or anything else.

The dangerous subtext of course is that we can therefore all carry on as we are now without making any adjustments, because the magic answer is just around the corner.

Well, my efficiency and capacity estimates were way off.

Apparently it can store 8MWh and deliver it at a nominal 100KW. So probably ok for a contribution, but you'd need to go large (or have plenty of them) to make a significant difference. Interesting approach though.

Best I can glean from the reports air is circulated through the sand and then a heat-exchanger to heat water to feed the community heating system ... presumably using water direct on 500°c sand would be a bad idea and defeat the object of being a largely passive system without the complex engineering of superheated steam turbines etc.

Makes perfect sense that if your big need is for energy in the form of heat that you don't go swapping through different energy forms .... just turn excess power into heat and store it like that, then use it direct.

Not a new idea by any means ... can remember 35 years ago when I was setting up off grid the use of stacked matt-black 50 gallon drums of water or a big thick stone wall behind a south facing glazed wall being used in the same way (heated by the sun during the day then then giving up it's heat to the house during the cooler night ... either passive or fan assisted .... worked best for the old hippies in New-Mexico ... and still seen in the 'earthship' houses there today.)

Everything else is just media hype and the poor levels of science education amongst our journalists.

K

I remember how efficient they were