Sunamp heat battery for DHW only

anon_ymous

I came across this 

https://sunamp.com/blog/a-homeowners-experience-why-i-chose-a-sunamp-heat-battery-over-a-hot-water-cylinder/

It mentions:

"So, as it turns out, by keeping hot water separate from our heating system has opened up a few different options." 

However it doesn't exactly say what those options are? Octopus do have an overnight tariff that can "heat" the battery up at 12p/kWh but surely it's not necessarily as "efficient" as a heat pump cylinder? Ie: it isn't 1 unit in, and maybe 3 units out? 

Reed_Richards

I don't think there are any "different options" that you don't get by having a DHW cylinder and an immersion heater.

waqasahmed said:

However it doesn't exactly say what those options are?

I'm afraid that seems typical of Sunamp.  They would rather present blog from a satisfied, if vague, customer than go deep into the technical details of their product.

70sbudgie

I've got the impression that the Sunamp thermal stores are most appropriate if you don't have space for an appropriately sized cylinder.

The technology application is quite exciting (imo), but I think the biggest savings are on energy density. And given that the application is relatively new, the information is vague, and what data is available doesn't necessarily demonstrate superiority over a modern version of a cylinder, I would go for a cylinder, if there is space.

anon_ymous

70sbudgie said:

I've got the impression that the Sunamp thermal stores are most appropriate if you don't have space for an appropriately sized cylinder.

The technology application is quite exciting (imo), but I think the biggest savings are on energy density. And given that the application is relatively new, the information is vague, and what data is available doesn't necessarily demonstrate superiority over a modern version of a cylinder, I would go for a cylinder, if there is space.

I'm definitely leaning more towards the cylinder. The sunamp seems cool but it lacks a COP

70sbudgie

I found it very difficult to get usable numbers off the Sunamp spec sheet I looked - everything seemed to be relative to a cylinder size.

Solarchaser

Sunamps vagueness with actial information was a part of the reason I decided against.

Despite alot of evenings searching around a year ago, actual verifiable detail was for me elusive 

anon_ymous

Solarchaser said:

Sunamps vagueness with actial information was a part of the reason I decided against.

Despite alot of evenings searching around a year ago, actual verifiable detail was for me elusive 

This does sadly seem to be the case though they could still be viable just as a heat battery alone 

Heatbatterychap

I have fitted more than 50 Sunamp batteries now, every client is very happy.
They are 3 x more efficient than a hot water cylinder - so if you heat with PV - all that heat will be there the following morning for your shower.
But critically, in a cylinder, when you draw off hot, you add cold, this reduces the temperature of all the water in the tank. In our house the boiler would turn on during a shower to re heat the mains pressure hot water cylinder as its temp.had dropped. In a heat battery the water comes out the same temperature until all the phase change material (PCM) is spent. Only the next bit of PCM heat is used, not cooling the whole battery, so you heat the battery once and have all that hot water at the same temperature until it is spent.
So it save money on heat loss and on cooling when in use - it will save you money, and space.

Martyn1981

Can I ask how it's 3x more efficient? Shirley, using resistive leccy heating they are both ~100%?

I thought the main selling point, certainly was when I sat in on a sales (attempt) at my sister's, was that you don't lose the heat that a water cyclinder does. The salesman suggested 2 or 3 kWh's per day, so up to 1,000kWh's pa. But I suggested a figure closer to 150kWh's, based on a modern cylinder losing ~1kWh per day and only the non-heating months being a full loss.*

The killer though was the enormous cost of the Sunamp units, £3k+ for a large unit for my sister's property, wheras a HPWH, with external venting, applying a COP of 3+, would use less energy. [I say 3+, as for DHW it's needed year round, rather than the winter bias for space heating.]

*Edit - I did do some maths at the time, though prices may have changed since, suggesting the cost of the losses would take ~100yrs to cover the additional cost of the Sunamp unit. But at 2% interest, investing the cost difference would earn more in interest pa, than the cost of the losses.

QrizB

Heatbatterychap said:

I have fitted more than 50 Sunamp batteries now, every client is very happy.

<snip>

This reads very much like spam, and I have reported it as such.

They are 3 x more efficient than a hot water cylinder - so if you heat with PV - all that heat will be there the following morning for your shower.

As with Martyn, I query exactly what you mean by this.

You can't mean that you get 3x as many kWh of heat out as you put in, since that would need a heat pump with a COP of 3. It seems more likely that you mean you lose 1/3rd as much heat from a charged Sunamp as you would from a HW cylinder. Considering that a modern HW cylinder loses maybe 50 watts, so 0.72kWh/day, the difference (if you are correct) is 0.48kWh/day.

0.48kWh of EPG-rate electricity is currently around 16p, of gas around 5p. That's £60 a year or £18 a year, respectively, compared to the £3k cost of a Sunamp, and would suggest a payback time of 50 years or 167 years.

But critically, in a cylinder, when you draw off hot, you add cold, this reduces the temperature of all the water in the tank.

A correctly-plumbed HW tank will add cold water from the bottom, not the top, so the cold water doesn't mix with the hot.

In our house the boiler would turn on during a shower to re heat the mains pressure hot water cylinder as its temp.had dropped.

In my house I can have a shower in the morning using the hot water left in the HW cylinder after Mrs QrizB's bath the night before.

So it save money on heat loss and on cooling when in use - it will save you money, and space.

I'll grant you the space saving. Money saving needs much more evidence than you've provided.

anon_ymous

QrizB said:

Heatbatterychap said:

I have fitted more than 50 Sunamp batteries now, every client is very happy.

<snip>

This reads very much like spam, and I have reported it as such.

They are 3 x more efficient than a hot water cylinder - so if you heat with PV - all that heat will be there the following morning for your shower.

As with Martyn, I query exactly what you mean by this.

You can't mean that you get 3x as many kWh of heat out as you put in, since that would need a heat pump with a COP of 3. It seems more likely that you mean you lose 1/3rd as much heat from a charged Sunamp as you would from a HW cylinder. Considering that a modern HW cylinder loses maybe 50 watts, so 0.72kWh/day, the difference (if you are correct) is 0.48kWh/day.

0.48kWh of EPG-rate electricity is currently around 16p, of gas around 5p. That's £60 a year or £18 a year, respectively, compared to the £3k cost of a Sunamp, and would suggest a payback time of 50 years or 167 years.

But critically, in a cylinder, when you draw off hot, you add cold, this reduces the temperature of all the water in the tank.

A correctly-plumbed HW tank will add cold water from the bottom, not the top, so the cold water doesn't mix with the hot.

In our house the boiler would turn on during a shower to re heat the mains pressure hot water cylinder as its temp.had dropped.

In my house I can have a shower in the morning using the hot water left in the HW cylinder after Mrs QrizB's bath the night before.

So it save money on heat loss and on cooling when in use - it will save you money, and space.

I'll grant you the space saving. Money saving needs much more evidence than you've provided.

After looking into this on the buildhub forums, these seem quite unreliable which is a massive shame. They're space saving at least but I don't know why they think it's somehow more efficient

It absolutely reads like spam especially given their username and given the last post before that was a while ago