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Having a morning cuppa,before heading down to Monday Market and a thought hit me.

Isn't a hotwater storage tank and solar diverter the cheapest form of energy storage we can have? There is a definite growth in lifepo4 battery take up yet the HWT surely trumps it in cost and kWh storage capacity?

I wonder what the retrofit costs are for those with combi's? Or if possible?

For reference, we store around 12kWh of power per day in our hwt when home is in use with the two of us.
This tank.
https://www.cityplumbing.co.uk/Oso-Delt ... iel=Mobile
Solar I boost diverter £250
Plus fitting costs as required, call it two grand all in for 12kWh stored solar power. Just a thought...

It depends on what your goals are. It might be more useful to turn that PV into something else (abit at less efficiency) and store that - especially if you can store that for say 3 to 4 months.

The underlying driver is the cheapness of PV, which generally 1. Gets cheaper over time 2. More production of panels increases demand for them.

except the only thing you can store is heat and it is not really available in winter when you need it most. In summer when it is "full" you can't fill it again a second day, but I can see that it would save using power to heat more water on a subsequent cool /poor generation day.

Maybe in the shoulder season it could be used to supplement the central heating if the plumbing was suitably arranged?
A

Swwils wrote: ↑Mon Jul 25, 2022 7:47 am It depends on what your goals are. It might be more useful to turn that PV into something else (abit at less efficiency) and store that - especially if you can store that for say 3 to 4 months.

The underlying driver is the cheapness of PV, which generally 1. Gets cheaper over time 2. More production of panels increases demand for them.

The only way I could store for 3 to 4 months and not use would be in the EV (then not drive it). I'd love to build a passivhaus and store a vast amount in the concrete mat for Winter. Huge fan of more panels. Just thought this idea should be floated again for guys in pre purchase stage that pass through.

AE-NMidlands wrote: ↑Mon Jul 25, 2022 7:50 am except the only thing you can store is heat and it is not really available in winter when you need it most. In summer when it is "full" you can't fill it again a second day, but I can see that it would save using power to heat more water on a subsequent cool /poor generation day.

Maybe in the shoulder season it could be used to supplement the central heating if the plumbing was suitably arranged?
A

We actually use the full 12kW each and every day. It only goes up if the kids are back! Recharging it each day is not a problem. I was surprised to see how much our gas use fell back in the day when we turned on the solariboost. CH was quite a small part of it. The wax and sand store with immersion coils and HW coils is very appealing but I don't have the space. Can store at higher temps instead of cutting off at 80 deg c in a HWT.

Thats why i bought this ....Just Need the time to fit IT


We had a laugh about heat pump hot water ideas years back , but for me i needed a hot water storage anyway and the surplus costs of a heatpump ontop where small

Aye and a well insulated thermal store doesn't lose efficiency with age or deep discharge. With heating and DHW being your greatest energy demand it makes sense to store surplus as hot water rather than electrons

I think this makes more difference for those with larger solar arrays and even more so if they have a TOU tariff so that they are able to offset all of their electrical use first.

Whilst is it is true that a solar diverter install will be much cheaper than batteries (my own install is going to be around the £750 mark - although I already had a hot water tank) the amount of savings will be less than the savings I make with the batteries and being able to use electricity generated during the day at night.

This is probably amplified by the fact I cannot get a TOU electricity tariff until I we get some form of EV. So every KW I can store in the battery is worth 22p more to me than 1KW of energy stored in the HWT.

Obviously this is offset by the install cost of the batteries - so I think people need to balance the view with the other potential services / facilities they have.

Its another storage tool in the box, I store 15 kWh of heat in this 300 litre tank for our domestic hot water. It can be heated by my GSHP, or via twin immersions powered by a solar diverter.

And it also runs through the gas combi which is now only used in an emergency, so if we ever ran out of hot water, switch the combi on and instant hot water again.

£500 from a bankrupt plumber, brand new and still strapped to a pallet.

How Doooo the electrons get into the immersion heater. Are you using Nuclear Fusion. ?

I cant seeee any cable wired to it.