An alternative ‘community’ energy store

[Bugtownboy]

Another plus for District Heating Systems

https://techxplore.com/news/2022-06-ber ... inter.html

[AE-NMidlands]

You wait ages... then several come along at the same time!
https://www.bbc.co.uk/news/science-environment-61996520

Climate change: 'Sand battery' could solve green energy's big problem
Finnish researchers have installed the world's first fully working "sand battery" which can store green power for months at a time.
The developers say this could solve the problem of year-round supply, a major issue for green energy.
Using low-grade sand, the device is charged up with heat made from cheap electricity from solar or wind.
The sand stores the heat at around 500C, which can then warm homes in winter when energy is more expensive.

/snip/

"Whenever there's like this high surge of available green electricity, we want to be able to get it into the storage really quickly," said Markku Ylönen, one of the two founders of Polar Night Energy who have developed the product.
The device has been installed in the Vatajankoski power plant which runs the district heating system for the area.
Low-cost electricity warms the sand up to 500C by resistive heating (the same process that makes electric fires work).
This generates hot air which is circulated in the sand by means of a heat exchanger.
Sand is very effective medium for storing heat and loses little over time. The developers say that their device could keep sand at 500C for several months.

I'm surprised that they use air as an intermediate, as loose sand doesn't allow air to flow freely. If the hot air is in tubes, then again, water has a much higher specific heat.
I might have tried heating elements actually in the sand and then extract via tubes carrying the heat transfer fluid [edit] [but I guess that this way protects the elements from localised overheating.] Air in tubes might be attractive for extracting heat as it takes out most of the corrosion and leakage problem... [and if it is ever switched off completely, there is nothing to freeze up and split the pipework!]
(The Trombe wall had heat storage by a cellar of boulders, I think.)
A

[ALAN/ALAN D]

Few Questions.

How big sand box for play thing.
Just fit immersion heaters into sand box.
How to fit electric supply cables to heater. What type of cable.
Do they do a flexible ceramic insulated cable.
What type of sand.
What type of insulation on outside of sand box.
Sand box made of mild / stainless steel or cement.

[marshman]

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[Moxi]

On a home scale I wonder how much insulation is required to minimise heat loss to allow several months of storage ? Using air as the transport medium for the heat has some benefits but I would be weary of silicosis if there were leaks in the system after time, i would imagine the sand would after time break down in to very small particulate.

Industrial scale it would appear very attractive though.

Moxi

[ALAN/ALAN D]

Build the store box above ground. ?

Just Need Permission from the Lady Of The House to build it on the carpet. 0


Just a pity I cant get it delivered for £5
https://www.gumtree.com/p/cement-mortar ... 1436652178

concreting sand Or building sand. Whats required ?

[Marcus]

Few Questions.

How big sand box for play thing.
Just fit immersion heaters into sand box.
How to fit electric supply cables to heater. What type of cable.
Do they do a flexible ceramic insulated cable.
What type of sand.
What type of insulation on outside of sand box.
Sand box made of mild / stainless steel or cement.

Don't think your average immersion heater is designed for 5-600 deg C

Storage heater elements would be my choice. I don't know what temperature they actually get up to though - just tried googling it but drew a blank.

[ALAN/ALAN D]

How about heater inside a vented stainless steel enclosure.
House air blown into cold air side pipe.
Hot air blown into house

[marshman]

__

[openspaceman]

Using the element out of either a storage heater or possibly a fan oven would be far better

Yes or run your own nichrome wire through the box. 500C is pretty hot so safety is an issue, Also heat loss will be related to the square of the surface area and capacity will be related to the cube of the dimensions so huge is better.

If the sand is graded to one size class then the pores will be about 30% of the volume and air will travel though that well.

I still think compressed air would be a better way to store the energy for most purposes