Thermal Stores

ASavvyBuyer

I have been looking at possible alternatives to replacing our gas boiler, if & when it fails and is not worth repairing.

Instead of ASHP's or GSHP's, a thermal store looks like a possibility.

Found the Tepeo’s Zero Emission Boiler

Are there any others that people have experience of ?

Reed_Richards

Well it's basically an updated form of night storage heater.  Lots of bells and whistles but the principle is the same, heat something up using cheap night-rate electricity and then use the heat during the day.

Coastalwatch

Hmmm! 40 kWh's of heat store is certainly tempting in winter, however with resistance heating would there will be any COP ratio to take advantage of.

Not sure if that amount of heat would be too much use in summer over a daily shower or two, but I could well be wrong.

Couldn't find anything about efficiencies or what losses may occur over a 24hour period. As a guide our well insulated thermal store has a heat loss of 68 W's.

They seem to make a big thing about zero emission but hasn't that been the case with electric immersions since time began.

Mind you, if they can warm Theresa May up then they may well be on to something!

Reed_Richards

On a dual-rate electricity meter, the only meaningful COP I can think of would be the cost of your day rate electricity divided by the cost of your night rate electricity.

ASavvyBuyer

Coastalwatch said:

As a guide our well insulated thermal store has a heat loss of 68 W's.

What thermal store are you using?

shinytop

Will 40kWh be enough for heat and HW for a whole house ? Isn's a single NSH 7 hours at 2-3 kW?  We've got 8 plus an immersion so wouldn't even come close.  

Coastalwatch

Hi ASB, Advance Appliances, 210 Litre version. They also do a 160L ish version which is no doubt quite adequate for just the two of us but got the larger for when we have anyone else stay. Actually the heat loss for the 210L version is 1.92kWh/24hrs, so 80W's not 68 which is for the 160L version.

We purchased the Hot water only, electric version, although they also do one combined with heating also. As well as other combinations. It has a ten year guarantee.

michaels

Hmm - we use 87kwh per day - on average over the year.  Given that the boiler is probably only 90% efficient lets call it 80kwh.  But that is the average, obviously on a cold winter day we might use 3 or 4 times as much....

I wonder how the economics compare to using a battery store and heat pumps to achieve a COP uplift?

matelodave

TBH 40kwh isn't a lot to provide your heating and hot water - all you need to do is read your gas meter daily for a couple of weeks to see how many kwhs you use in a 24hr period and then work out how many 40kwh thermal stores you'd need to match it.(you should do it when it's everso cold outside rather than now the weather is getting a bit warmer. 

If you run out of stored energy at the off-peak rate then you'd have to top it up at the peak rate.

As leccy at the off peak rate is around 3-4 time the price of gas and 5-6 times at peak rates then I really cannot see any benefit whatso ever in changing a gas boiler to use leccy. TBH if you are going to use a thermal store you'd probably be better off by using proper storage heaters placed where you need the heat. You could store more than 40kwh in just 2 x 3kw storage heaters.

BTW it appears that the sort of Thermal store that coastalwatch is using is a big hot water tank rather than a pile of bricks with a heat exchanger as suggested by Asavvybuyer.

In fact the Tepeo's ZEB appears to be a flow boiler with a pile of bricks inside which allows it to store up to 40kwh during off-peak periods and deliver it as required during heating and hot water periods in conjunction with peak rate energy. It's interesting to see that their "demo" was done in October rather than December, January or February when its significantly colder and you are most likely to run out of stored heat by the afternoon and evening. 

Martyn1981

Coastalwatch said:

Hi ASB, Advance Appliances, 210 Litre version. They also do a 160L ish version which is no doubt quite adequate for just the two of us but got the larger for when we have anyone else stay. Actually the heat loss for the 210L version is 1.92kWh/24hrs, so 80W's not 68 which is for the 160L version.

We purchased the Hot water only, electric version, although they also do one combined with heating also. As well as other combinations. It has a ten year guarantee.

I guess between cheap rate leccy and PV, you can mostly get by now, or perhaps another week or two into March?
Actually, today was decent for us here, with both A/C units powered all day, so on average, do you expect PV to cover heating and hot water through the Spring, during the daytime?

ASavvyBuyer

Thanks for all the comments so far. Interested to see what other makes are available. Regarding the 40kWh/day, that would easily be enough to replace the typical amount of gas we now use, since having the 2 Air 2 Air ASHP's. This winter, our average gas use per month has been less than 200kWh. In fact this month it is likely to be less than 75kWh. Therefore, potentially, by a bit more fine tuning of the settings on the ASHP's and circulating the warm air more, they could reduce it to 0kWh/month.