Heat Battery 20 October 2019 at 9:55PM edited 30 November -1 at 12:00AM in Green & Ethical MoneySaving 21 replies 5.3K views

Solarchaser

I've been researching the sunamp.
Possibly looking at two of the 6kwh models as they will fit in void at the cupboards in my kitchen, and the combi I have will run a 55c input, so pipe runs etc will be way simpler than a tank in the loft.

https://midsummerwholesale.co.uk/buy/sunamp-heat-batteries/sunamp-uniq-6
6kwh is around £2k, and the 12kwh is around £2.8k. But it's over a meter tall, so wont fit under kitchen worktops.

Wondering if anyone has actual experience of using these, and any pluses or minuses to these.

Planning on running them from surplus pv, and cheap rate leccy in winter to reduce gas use, hopefully in time expanding to cover heating too.

mwinlow

Bit of an old thread, now but...

I see at least one other company is selling a heat battery - Fischer 'Auqufficient' but I couldn't find any prices on-line.  I would think this is defo the water HW storage will go in the near future, obviating the need for last volumes of hot water storage and the expensive copper to contain it.  I have read recently that Sunamp's control system has some serious issues but should be fairly easily fixable.  It's very early days yet.

Maybe the biggest market for this tech (as alluded to in an earlier comment) is huge heat batteries either 'charged up' using waste heat from industrial processes and then transported elsewhere to be used or (just one example) a Scottish distillery hosting one or more wind turbines to generate the electrical energy to heat the battery and then help provide the heat for the distilling process during calm weather.

The costs of the units is pretty minimal and I would guess the Aerogel insulation (I'm assuming this is what is used as it is the best available) is the most expensive constituent in the box.  The 'active ingredient' ie the phase-change material is sodium acetate (yep, as used to make crisps) and is relatively inexpensive - probably about the same cost as the copper in an equivalent (heat energy) sized cylinder.  So, I would expect [rices to tumble significantly in time and with greater acceptance in the market.

For those with long runs of pipework, consider small bore plastic pipe for your next installation - as long as the pressure is good - and assuming you have mains pressure hot and cold water - this will minimise 'dead water',  massively reduce heat transfer through the pipe wall and hugely increase the hot water delivery time.  Copper's thermal conductivity is very good, plastic not so much... by a factor of getting on for a thousand!  Not much use for bath filling, perhaps, but sinks, washing machines and showers, perfectly fine.  

michaels

This sounds interesting to me if paired with a very cheap overnight electricity tariff, we use about 33kwh of gas every day just heating hot water but presumably heating this heat store using leccy at 4p a unit overnight would work out at a similar cost?  I wonder if they could choose a storage medium with a transition temperature more accessible to heat pumps and you could then 'charge it up using a heat pump at a higher COP than just a resistive heater?

isvana

These sound like an interesting option... for hot water heating with spare solar energy. I am planning an extension and was thinking of a “heat battery” in terms of an underfloor set of bricks or blocks. A bit like these guys do... thermaray dot com

Hot_Toddy

I had 2 UniQ 6 heat batteries fitted in my flat 12 months ago to provide heat and hot water. Previously used electric heaters and immersion heater. Was told they were efficient would save money, blah, blah blah. I now pay twice as much and the radiators never get warm. Wouldn't recommend. Fischer only use Sunamp for heating water and so does the guy who fitted the batteries which so as I now know they are no good for heating

Pile_o_stone

Crikey, Hot_Toddy, you've been a member of MSE for over 10 years and this is your first post. Thanks for making it on the Ethical board!

Solarchaser

Thanks for sharing your experience. 
Its good to know this technology is not useable for heating, saves me some money and some hassle

Reed_Richards

Hang on a minute.  Your only hope to derive any running-cost savings from a heat battery if all-electric (and without solar PVs) is to use Economy 7 (or similar) to charge the battery at night with cheap-rate electricity.  You might just as well have a hot water cylinder and night storage heaters.  The only advantage that the heat battery offers over those is that it is more compact.  You would not expect any savings unless the old electric heaters that @Hot_Toddy replaced were instantaneous.  Also the standard heat battery heats water to 60 C.  That is too hot for Domestic Hot Water but colder than a typical boiler-driven radiator which aims for an average temperature around 70 C. 

Martyn1981

Reed_Richards said:

Hang on a minute.  Your only hope to derive any running-cost savings from a heat battery if all-electric (and without solar PVs) is to use Economy 7 (or similar) to charge the battery at night with cheap-rate electricity.  You might just as well have a hot water cylinder and night storage heaters.  The only advantage that the heat battery offers over those is that it is more compact.  You would not expect any savings unless the old electric heaters that @Hot_Toddy replaced were instantaneous.  Also the standard heat battery heats water to 60 C.  That is too hot for Domestic Hot Water but colder than a typical boiler-driven radiator which aims for an average temperature around 70 C. 

Yes. The selling point though is that they are more efficient as they don't leak heat. This was the approach the salesman used to 'sell' the idea to my sister and BiL, but when he suggested a price of about £2k, I explained it would take around 100yrs to get your money back against a high quality water cylinder with excellent insulation leaking about 1kWh per day. He really didn't like me only classing loses for 6 months of the year, as I said the 'loses' during the heating months are within the thermal envelope, so not an actual loss. When I pointed out that the price difference invested at 1% was greater than the annual 'saving' he really got pee'd off ...... then suggested these new super duper storage heaters from Germany ...... I asked if they had the 'magic clay' in them, and he gave up!

Reed_Richards

Actually you could fill your night storage heaters with a phase change material like they use in a heat battery to make them more compact.  Possibly they would also perform better because all the heat is released at the phase change temperature.  So there you are, @Martyn1981, 'magic phase-change clay'.