ASHP with heat battery

waqasahmed

So let's say you've got a heat pump and a Sunamp battery, or similar for that matter 

Could you use Sunamps to heat the house? The rationale would be to "charge" the sunamp battery at night, connected to the heat pump.

Ie: Night time tariff = 12p/kWh 
You require maybe 80 kWh (on a bad day) worth of energy in a day, so you pull 22 kW of energy from the heat pump, with a COP of 3.5

Could you then use that stored energy, to heat the house through the radiators? And you'd probably have both a sun amp AND a heat pump cylinder ie: cylinder for water, and sunamp for pure heat. 

I'm guessing if not sunamp, then Caldera warmstone would perhaps work?  Though if you're spending 12K on a battery, surely it's worth spending that just on a GSHP instead? 

70sbudgie

I think Sunamp have a heat pump compatible version of their thermal store. I could see it being a reasonsble replacement for a gas combi boiler. Basically using cheap rate electricity stored as thermal energy, that is then released on demand for either DHW or heating. Couldn't get my head round the HP bit though - is that used to charge the thermal store or does the thermal store increase the COP of the heat pump?

Reed_Richards

waqasahmed said:

So let's say you've got a heat pump and a Sunamp battery, or similar for that matter 

Similar could be a large tank of water, that's a conventional thermal store.

waqasahmed said:

Could you use Sunamps to heat the house? The rationale would be to "charge" the sunamp battery at night, connected to the heat pump.

The phase change temperature in the standard Sunamp product is too high to work well with a heat pump.  Heat pumps require a large surface area heat exchanger.  You would have to get a Sunamp that is purpose-designed for a heat pump.  A different thermal store, such as a large tank of water with a large internal coil, would not have these issues.

waqasahmed said:

 
You require maybe 80 kWh (on a bad day) worth of energy in a day, so you pull 22 kW of energy from the heat pump, with a COP of 3.5 

This web site https://www.theheatpumpwarehouse.co.uk/shop/heat-batteries/sunamp-heat-batteries/sunamp-thermino-300-hp-sg-heat-battery/?  will sell you a Sunamp heat battery for £2800 that is said to be heat-pump compatible.  The spec says the storage capacity is 14 kWh so you would need 5 of them to get 70 kWh worth of storage.

Have you not read this thread https://forums.moneysavingexpert.com/discussion/6377030/ditching-gas-going-electric-immersion-only-a-wee-project/p1 ?  Have a look at what @Solarchaser is doing, how much heat they store and what volume of water is required to do it.       


     

waqasahmed

Reed_Richards said:

waqasahmed said:

So let's say you've got a heat pump and a Sunamp battery, or similar for that matter 

Similar could be a large tank of water, that's a conventional thermal store.

waqasahmed said:

Could you use Sunamps to heat the house? The rationale would be to "charge" the sunamp battery at night, connected to the heat pump.

The phase change temperature in the standard Sunamp product is too high to work well with a heat pump.  Heat pumps require a large surface area heat exchanger.  You would have to get a Sunamp that is purpose-designed for a heat pump.  A different thermal store, such as a large tank of water with a large internal coil, would not have these issues.

waqasahmed said:

 
You require maybe 80 kWh (on a bad day) worth of energy in a day, so you pull 22 kW of energy from the heat pump, with a COP of 3.5 

This web site https://www.theheatpumpwarehouse.co.uk/shop/heat-batteries/sunamp-heat-batteries/sunamp-thermino-300-hp-sg-heat-battery/?  will sell you a Sunamp heat battery for £2800 that is said to be heat-pump compatible.  The spec says the storage capacity is 14 kWh so you would need 5 of them to get 70 kWh worth of storage.

Have you not read this thread https://forums.moneysavingexpert.com/discussion/6377030/ditching-gas-going-electric-immersion-only-a-wee-project/p1 ?  Have a look at what @Solarchaser is doing, how much heat they store and what volume of water is required to do it.       


     

Thanks! The Caldera is £2K less? Though admittedly that thing is freaking massive along with no deal redundancy 

waqasahmed

70sbudgie said:

I think Sunamp have a heat pump compatible version of their thermal store. I could see it being a reasonsble replacement for a gas combi boiler. Basically using cheap rate electricity stored as thermal energy, that is then released on demand for either DHW or heating. Couldn't get my head round the HP bit though - is that used to charge the thermal store or does the thermal store increase the COP of the heat pump?

The idea would be to use a heat pump, get that heat energy at night and just... store it, ready to use so you've always got some 

70sbudgie

waqasahmed said:

70sbudgie said:

I think Sunamp have a heat pump compatible version of their thermal store. I could see it being a reasonsble replacement for a gas combi boiler. Basically using cheap rate electricity stored as thermal energy, that is then released on demand for either DHW or heating. Couldn't get my head round the HP bit though - is that used to charge the thermal store or does the thermal store increase the COP of the heat pump?

The idea would be to use a heat pump, get that heat energy at night and just... store it, ready to use so you've always got some 

If that is the case, I can't help but wonder whether an electric battery would be better with a heat pump? I imagine that an ASHP would have a better COP during the day, as nights are usually cooler.

Solarchaser

I also looked at the caldera warmstone, while viewing sunamp and tepeo.

Warmstone if you search long enough has a conversion loss similar to the elusive data on the sunamp, 85% rings a bell.
The caldera is huuuuge and bloody heavy too.

I dont have a heat pump, I'm not against them. 
The wife is dead against them.
However there is the consideration that to heat the house as a normal radiator set up in a timely manner, really you need something above 50C.
I have normal radiators though.
I know Reed has a heat pump and larger radiators,  and one shouldn't assume, but I do assume that with the lower temperature,  it takes the house longer to recover to a comfortable temperature after the wife has stood talking to someone at the door for 10 mins (with every other door in the house open to make sure all the heat escapes 😐🙄 )

My understanding is Heat pumps are better at lower temperatures,  like 25C ish than they are cop wise at say 60C, but to heat a cylinder of large thermal mass, you really need alot of energy and if you are storing that heat to be used, it wants to be a good bit hotter than what you need.

By that I mean, I'm generally heating my tanks to around 85C, 800L at 85C depletes to between 65C and 70C just doing the morning heat up.
And so if you were at 50C to do the morning heat up, you may end up down at 25C in the same tanks because the delta from the higher temperature will use more of your stored energy to heat the house.

Or more simply an 80C radiator will heat up a room faster than one at 50C

You would really have to look at your heating costs now, calculate what you would save by the insulation/windows etc measures you plan to take to mitigate some of the heating costs, and then look at what you would require to heat your house.
And don't make the same mistake I did, don't look at average usage and decide that will be enough, id say get your average usage for a month and add another 30% onto it to make sure you can make it work in the coldest of days when your heat pump won't be so efficient,  but you need that heat more than at any other time.

Edited to say I can find nothing referring to 85% on caldera now, they say conversion is 98-99%

waqasahmed

Solarchaser said:

I also looked at the caldera warmstone, while viewing sunamp and tepeo.

Warmstone if you search long enough has a conversion loss similar to the elusive data on the sunamp, 85% rings a bell.
The caldera is huuuuge and bloody heavy too.

I dont have a heat pump, I'm not against them. 
The wife is dead against them.
However there is the consideration that to heat the house as a normal radiator set up in a timely manner, really you need something above 50C.
I have normal radiators though.
I know Reed has a heat pump and larger radiators,  and one shouldn't assume, but I do assume that with the lower temperature,  it takes the house longer to recover to a comfortable temperature after the wife has stood talking to someone at the door for 10 mins (with every other door in the house open to make sure all the heat escapes 😐🙄 )

My understanding is Heat pumps are better at lower temperatures,  like 25C ish than they are cop wise at say 60C, but to heat a cylinder of large thermal mass, you really need alot of energy and if you are storing that heat to be used, it wants to be a good bit hotter than what you need.

By that I mean, I'm generally heating my tanks to around 85C, 800L at 85C depletes to between 65C and 70C just doing the morning heat up.
And so if you were at 50C to do the morning heat up, you may end up down at 25C in the same tanks because the delta from the higher temperature will use more of your stored energy to heat the house.

Or more simply an 80C radiator will heat up a room faster than one at 50C

You would really have to look at your heating costs now, calculate what you would save by the insulation/windows etc measures you plan to take to mitigate some of the heating costs, and then look at what you would require to heat your house.
And don't make the same mistake I did, don't look at average usage and decide that will be enough, id say get your average usage for a month and add another 30% onto it to make sure you can make it work in the coldest of days when your heat pump won't be so efficient,  but you need that heat more than at any other time.

Thanks. I guess that's why you might wanna go for a sunamp instead (or several sunamps) because of the ability to work with lower flow temps? 

Reed_Richards

waqasahmed said:

Thanks. I guess that's why you might wanna go for a sunamp instead (or several sunamps) because of the ability to work with lower flow temps? 

I think you are missing the point.  If you heat your thermal store to 60 C then volume-for-volume a Sunamp will store a good deal more heat than a tank of water.  If you heat your thermal store to 85 C then volume-for-volume the percentage difference in storage capacity between a Sunamp and a tank of water is reduced.

@Solarchaser , what's the "conversion loss" for your tanks of water?   

waqasahmed

Reed_Richards said:

waqasahmed said:

Thanks. I guess that's why you might wanna go for a sunamp instead (or several sunamps) because of the ability to work with lower flow temps? 

I think you are missing the point.  If you heat your thermal store to 60 C then volume-for-volume a Sunamp will store a good deal more heat than a tank of water.  If you heat your thermal store to 85 C then volume-for-volume the percentage difference in storage capacity between a Sunamp and a tank of water is reduced.

@Solarchaser , what's the "conversion loss" for your tanks of water?   

Why not have both? A sunamp JUST for heat, and the tank JUST for water?

Solarchaser

Reed_Richards said:

waqasahmed said:

Thanks. I guess that's why you might wanna go for a sunamp instead (or several sunamps) because of the ability to work with lower flow temps? 

I think you are missing the point.  If you heat your thermal store to 60 C then volume-for-volume a Sunamp will store a good deal more heat than a tank of water.  If you heat your thermal store to 85 C then volume-for-volume the percentage difference in storage capacity between a Sunamp and a tank of water is reduced.

@Solarchaser , what's the "conversion loss" for your tanks of water?   

There should be a theoretical zero conversion loss, or 100% conversion rate for the tanks, as the heat is applied directly to the water through the immersed heaters.
In reality there will be a bit lost in the wiring and connections to the heaters, but that said, id imagine less than 1%.

So if it was purely conversion, water tanks win hands down, however when it comes to storage after conversion,  the sunamp wins hands down as it stores it in a much smaller physical volume and we (I) think it should be inert at those stored temperatures, vs the tanks constantly losing heat. 

So if you were heating to use straight away (short time frame) then water tanks are clear winner's, but if you are storing for longer time (weeks??) The sunamp would be a clear winner, where the lines converge I've no idea.
I guess when the tanks lose 15% of their stored heat, which for me would be probably about 8C, and that would likely be just over 24 hours in their current configuration 
That's still falling back to that one instance in a video that I caught the 85% conversion,  that I've found no proof of.

Using a sunamp just for heat might work, as it would give a constant supply of a set heat for a defined amount of time.
Potentially stored for long periods of time.

I've edited my comment above, I am quite certain that 85% was mentioned for Caldera,  but I can't find anything saying that now.
Their brochure says 98-99% conversion and stsnding losses of just under 5kwh/day