An alternative ‘community’ energy store

[AE-NMidlands]

On a sunny summer day both my large water tanks and next doors water are at 80 deg C at the bottom of the tank by 08:30
Batteries get charged off a different system.
Lots of power going up the road.
I could have more batteries but they do fail over time.
Down side of Sand Shed. Needs to be not far from house. Lady of the house probably wont be too impressed when I try to explain size / location

Are you any good with a spade? The article does say they can be buried

I can't even get permission for a big rainwater tank under the patio or the top lawn!

[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

but not if you "only" want heat out - and that heat nearby rather than at a distance where generation and transmission losses would be less than the cost of a steam main. This is for district heating where it is built.

I would think that hoping for an airflow through sand is pretty hopeless unless it is a fluidised bed. The original article talks about a heat exchanger, so I would imagine electric elements buried in the sand (any old sand, it says, rather than special sharp sand or whatever to maintain an open structure) and a heat extraction airflow through dry tubes in the sand box.
That way there is no movement of the sand to break it down, nor erosion of your heat exchanger by sand grains in the airflow.
A

We don't have much district heating in UK, though there is a heating and cooling main running around the town by where I live. I still think the utility of motive power even combined with heat pumps make compressed air storage look good over turning electricity to heat and storing that, we shall see.

A fluidised bed would consume far too much power, good for rapidly freezing peas though.

Back in the days before recycling them at Machynlleth proposed collecting all the beans and soup cans and crushing them into dense blocks to circulate air past but I think that was to be solar thermal heated, they gave up on their seasonal heat stores long ago.

Good point about the possibility of sand particles getting into the flow, I have no idea how sand might degrade during numerous heating-cooling cycles.

[AE-NMidlands]

That way there is no movement of the sand to break it down, nor erosion of your heat exchanger by sand grains in the airflow.
A

We don't have much district heating in UK, though there is a heating and cooling main running around the town by where I live. I still think the utility of motive power even combined with heat pumps make compressed air storage look good over turning electricity to heat and storing that, we shall see.

it certainly does if you need electricity back out...

A fluidised bed would consume far too much power, good for rapidly freezing peas though.

Back in the days before recycling them at Machynlleth proposed collecting all the beans and soup cans and crushing them into dense blocks to circulate air past but I think that was to be solar thermal heated, they gave up on their seasonal heat stores long ago.

Good point about the possibility of sand particles getting into the flow, I have no idea how sand might degrade during numerous heating-cooling cycles.

I don't know how themal cycling up to 500C would affect sand (if at all.) I do remember being taught that wind-deposited sands could be identified because of the "millet-seed" grains, with a frosted/pecked surface. This was down to the fact that the grains impacted on each other and caused the chipping, whereas water-laid sands had shinier/smoother faces because the water lubricated and cushioned the contacts.
This doesn't show up on web search now, so maybe that theory has been superceded. I took it as evidence of the generation of much smaller particles which the body can't protect itself against if inhaled.

Anyway, moving / air-propelled or windblown sand might well generate finer dust with a silicosis risk - if it was released and available for inhalation. A bed of hot sand with electric elements and closed (air?) circuit heat extraction tubes buried in it poses no risk whatsoever - unless you are tasked with digging it back out of the silo after it has cooled down! I would hope that would be done with a vacuum suction gadget though.
A

[openspaceman]

I see Kryten has released a video today of his new boiler that appears to use just this sort of high temperature store to release it to a conventional central heating system. It weighs in at 375kg.

[Stinsy]

I see Kryten has released a video today of his new boiler that appears to use just this sort of high temperature store to release it to a conventional central heating system. It weighs in at 375kg.

Yeah, it is a storage heater that plumbs into your central heating…

[Oldgreybeard]

Yeah, it is a storage heater that plumbs into your central heating…

I remember these from the 1970s, a friend's new build house had a heating system that used a large storage heater that ran internally at several hundred degrees. Like many new builds from that time it was all-electric, using what was then "white meter" rates to charge up the heating and hot water overnight. I can't remember who made it, but do recall that it was very reliable, despite the high temperature that the core worked at. There wasn't much to go wrong, really, it was just an insulated box filled with some sort of iron bricks, a heating element and some simple electromechanical controls. I think the main downside was the same as storage heaters, it drew a heck of a lot of power when heating overnight. I think it ran off three phase, but can't be sure.

[Stinsy]

Yeah, it is a storage heater that plumbs into your central heating…

I remember these from the 1970s, a friend's new build house had a heating system that used a large storage heater that ran internally at several hundred degrees. Like many new builds from that time it was all-electric, using what was then "white meter" rates to charge up the heating and hot water overnight. I can't remember who made it, but do recall that it was very reliable, despite the high temperature that the core worked at. There wasn't much to go wrong, really, it was just an insulated box filled with some sort of iron bricks, a heating element and some simple electromechanical controls. I think the main downside was the same as storage heaters, it drew a heck of a lot of power when heating overnight. I think it ran off three phase, but can't be sure.

It'd be unusual for the house to be 3-phase. Even "all electric" resistively-heated homes were never 3-phase. It was probably 30A.

The problem with all this was the 24/7/365 coal power stations being decommissioned and replaced with ultra-flexible gas. You were lucky to get ecconomy7 off-peak for half the price of peak which was a huge social injustice because it meant the poorest with their storage heaters were paying a fortune to heat their homes.

Luckily for us lot the tide has turned and a grid with a significant proportion of wind will always have super-cheap off-peak electric.

[Bugtownboy]

I know there’s very little detail, but conceptually it could be an attractive alternative to a HP for existing homes.

Decarbonising domestic energy is, I think, only going to work with a mix of solutions to suit the mix of existing housing.

[Oldgreybeard]

It'd be unusual for the house to be 3-phase. Even "all electric" resistively-heated homes were never 3-phase. It was probably 30A.

The problem with all this was the 24/7/365 coal power stations being decommissioned and replaced with ultra-flexible gas. You were lucky to get ecconomy7 off-peak for half the price of peak which was a huge social injustice because it meant the poorest with their storage heaters were paying a fortune to heat their homes.

Luckily for us lot the tide has turned and a grid with a significant proportion of wind will always have super-cheap off-peak electric.

No, they are definitely three phase, no question about it at all. I've just found the details of these old GEC Nightstor units, they draw 19.2kW when charging and 9.6kW when boosting. I was wrong about the temperature they work at, they really work at up to 1,000°C, believe it or not. There is still a company supplying spares for them, as there are some still in use after 50 years. I think they were one of the things that came about from the supposed 1960s belief that nuclear power would give us all electricity that was "too cheap to meter". That worked out well, didn't it?

Edited to add:

Here's some photos of the Nightstor units on this website from a company that keeps them going: http://northernelectricheating.co.uk/ni ... ilers.html

[nowty]

Here's some photos of the Nightstor units on this website from a company that keeps them going: http://northernelectricheating.co.uk/ni ... ilers.html

I bet if you could see the inside of the ZEB it would look very similar to the old Nightstor. I note the video mentioned an air fed heat exchanger which looks like what the Nightstor had / has.


EDIT - I also note that Nowty Towers already has about the same 40kWh of heat + hot water storage as the quoted 40kWh capacity of the ZEB.