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Sunamp PV vs Thermal Store Heat Loss Comparison


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#21 SteamyTea

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Posted 23 November 2015 - 06:01 PM

I measure my incoming mains temperature, today it was 10.2°C, and we are still in the hot part of the year.

#22 stones

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Posted 25 November 2015 - 02:24 PM

View PostSteamyTea, on 23 November 2015 - 01:56 PM, said:

Have you given it a full work out yet.

Max flow rate
Time to depletion
Recharge time (though that is tricky with PV)

View Postjsharris, on 23 November 2015 - 02:03 PM, said:


I'll run some proper tests on it when I have a bit more time and have wired in an energy monitor so I can see just what's going in to the unit.


I'm very interested in how it performs, both with and without the ASHP preheat on.

#23 wmacleod

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Posted 25 November 2015 - 03:10 PM

View PostSteamyTea, on 23 November 2015 - 06:01 PM, said:

I measure my incoming mains temperature, today it was 10.2°C, and we are still in the hot part of the year.

I checked mine, 7.6°C today. Will be interesting to see what it drops to later in the winter.

#24 jsharris

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Posted 25 November 2015 - 03:41 PM

Ours is a pretty constant 8 deg C out of the ground, but I have ~350 litres stored out in the treatment shed, so that can cool down or heat up a bit, depending on the weather and the rate at which it's replenished.

#25 NeilW

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Posted 25 November 2015 - 04:36 PM

It's times like this when you wish you hadn't just upgraded your heating system with old tech, although I suspect my 20 litres/min flow rate requirement might be a bit difficult to reach as yet.

It's clear this unit solves the Passivhaus 'how do I warm up the water' conundrum once and for all. Electric all the way now on a green tariff.

#26 Alphonsox

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Posted 25 November 2015 - 06:23 PM

I'm thinking that it may make sense to combine a Sunamp with an ASHP preheating a 250ltr UVC cylinder to 35C. The Sunamp would provide the boost to get the DHW up to the required flow temperature. Need to do a few calcs to see if this adds up.

#27 jsharris

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Posted 25 November 2015 - 06:26 PM

View PostAlphonsox, on 25 November 2015 - 06:23 PM, said:

I'm thinking that it may make sense to combine a Sunamp with an ASHP preheating a 250ltr UVC cylinder to 35C. The Sunamp would provide the boost to get the DHW up to the required flow temperature. Need to do a few calcs to see if this adds up.

This is exactly what I'm doing in principle. It works very well indeed. No need for a UVC with the G3 hassle though, just use a hydronic unit hooked up to the ASHP.

Edited by jsharris, 25 November 2015 - 06:26 PM.


#28 Alphonsox

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Posted 25 November 2015 - 06:42 PM

My concern is that relative to your setup I have both a smaller ASHP (4KW version) and a larger house with greater water demand. I need to consider recovery times etc. However the use of a large buffer tank and heat exchanger rather than a UVC would make sense.

EDIT

In your setup is there any need for the indirect coil in the buffer tank ? (I guess this is historical).

Edited by Alphonsox, 25 November 2015 - 06:45 PM.


#29 jsharris

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Posted 25 November 2015 - 07:03 PM

No need for a coil in the buffer, it was an accident from the supplier, but it does save around 70 litres of rather expensive antifreeze!

A hydronic unit would be more sensible than a tank, take up less space and allow the full ASHP output to be continuously transferred to the water. In essence what I've done is build a home made hydronic unit with a plate heat exchanger, pump and flow switch, but several of the ASHP suppliers sell them ready made.

If you look at, say, a 10 litre per minute shower (pretty typical) at 38 deg C, with an 8 deg C cold water intake, then the 4kW pre-heat will take it from 8 deg C to 13.7 deg C. The Sunamp PV can deliver up to around 35 kW peak, which would easily take the shower temp up to the desired temperature. The energy used for a ten minute shower at 38 deg C with water pre-heated to 13.7 deg C by a hydronic unit with a 4 kW ASHP would be around 2.835 kWh, excluding the input from the Sunamp PV internal 2.8 kW heater, that I believe operates whenever water is demanded (I may be wrong about this).

So, with no allowance for recharge between showers, you could almost get two 10 minute showers from a single full charge of a Sunamp PV plus a 4 kW pre-heat from a hydronic unit on an ASHP. Seems an ideal low volume system to me, with no tanks or storage devices to worry about.

#30 Alphonsox

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Posted 25 November 2015 - 07:18 PM

Thanks - I've not looked at hydronic units before, time for some Googling

#31 SteamyTea

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Posted 25 November 2015 - 09:33 PM

If you want more flow or storage from a SunAmp, don't you just get another one?

Here is my water temperature since September.

Attached Files



#32 Fallingditch

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Posted 26 November 2015 - 06:26 AM

View PostSteamyTea, on 25 November 2015 - 09:33 PM, said:

If you want more flow or storage from a SunAmp, don't you just get another one?

(And from Jeremy "So, with no allowance for recharge between showers, you could almost get two 10 minute showers from a single full charge of a Sunamp PV plus a 4 kW pre-heat from a hydronic unit on an ASHP. Seems an ideal low volume system to me, with no tanks or storage devices to worry about."


Seems like the Sunamp unit under discussion here is designed for a single shower. In my case, we will have two showers. Only rarely will they be operating at the same time - but you really don't want to build a system which starts running cold after the 2nd shower has been running for a while, even if it happens only rarely. Sure, you can just buy a 2nd Sunamp but that does seem like a significant extra cost for a situation like this?

#33 gravelld

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Posted 26 November 2015 - 07:40 AM

I think that's when you'd use a Stack, presumably cheaper per unit.

#34 DavidFrancis

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Posted 26 November 2015 - 07:52 AM

Steamy - you water temperature has varied by more than I thought it would and also changed faster over a short period than I thought it would. Where is your temperature probe? If it's in or close to the house, do you run the water for a while before taking the temperature? Finally, do you know how deep your supply pipe is buried?

(Sorry if you've explained this before and I haven't seen it.)

#35 SteamyTea

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Posted 26 November 2015 - 08:03 AM

All I do is run the cold tap on full for a minute, put some water in a jug and then point the IR thermometer at it.
I try and do it at the same time every day (around 08:00), but sometimes forget or am doing other things/away.

I was not actually that interested in the water temperature, more the temperature under the house. I just use the water temperature as a proxy.
If I get time later I shall do a bit more charting and do a correlation with internal and external temperature. There won't be a very accurate correlation as there are not really enough data points.

#36 jsharris

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Posted 26 November 2015 - 08:04 AM

View PostFallingditch, on 26 November 2015 - 06:26 AM, said:

(And from Jeremy "So, with no allowance for recharge between showers, you could almost get two 10 minute showers from a single full charge of a Sunamp PV plus a 4 kW pre-heat from a hydronic unit on an ASHP. Seems an ideal low volume system to me, with no tanks or storage devices to worry about."


Seems like the Sunamp unit under discussion here is designed for a single shower. In my case, we will have two showers. Only rarely will they be operating at the same time - but you really don't want to build a system which starts running cold after the 2nd shower has been running for a while, even if it happens only rarely. Sure, you can just buy a 2nd Sunamp but that does seem like a significant extra cost for a situation like this?

For us, with a 70 litre buffer store at 35 deg C then we can easily get two ten minute showers from it if there is at least half an hour or so between them(and in our case this is normally the case). Our pattern of use also means that one shower is rarely longer than 6 minutes, often only 4 or 5, which helps.

#37 DavidFrancis

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Posted 26 November 2015 - 09:08 AM

Steamy - your October water temperatures look only about 1 degree less than the mean daily MAXIMUM temperature for October recorded at Camborne. How far are you from Camborne?

#38 SteamyTea

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Posted 26 November 2015 - 09:18 AM

I am about 4 miles from the Kehelland weather station.

If I get time later today, I shall try and get all my household data together and see what is happening.

I could see that the water temperature coming into my house is close to the maximum temperature as the pipe may not be very deep under the house.
I shall try and work out the flow rate and estimate the volume in the pipe when I get really bored.
It is a bit of a rough and ready methodology, but I initially start data collecting this way, then I can see if it is worth spend some money on getting a decent logger onto things.

#39 stones

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Posted 26 November 2015 - 09:41 AM

View PostFallingditch, on 26 November 2015 - 06:26 AM, said:

Seems like the Sunamp unit under discussion here is designed for a single shower. In my case, we will have two showers. Only rarely will they be operating at the same time - but you really don't want to build a system which starts running cold after the 2nd shower has been running for a while, even if it happens only rarely. Sure, you can just buy a 2nd Sunamp but that does seem like a significant extra cost for a situation like this?

The SunampPV as I understand it was created as an add on for a gas combi system so that households with PV could reduce their gas useage. It just so happens that the very low heat loss is lending itself to the application Jeremy is using it for. Combined with a gas combi, running cold wouldn't be an issue.

Clearly pattern of usage (length of showers taken) is going to have a big impact. This is the very concern I have about using a SunampPV as a standalone product.

The interesting news, having asked the question of Andrew @ Sunamp in the course of discussing the Stack, is that demand is driving them to create a bigger 4 cell version or perhaps even a 6 cell version depending on final unit dimensions and racking system within. If they were to go down this route, the ability to buy a 4 cell unit that has the flexibility that allows you to add one or two additional cells (as being considered with the Stack) would be very attractive.

I should make clear I have no connection with Sunamp other than being an interested potential customer.

#40 Volcane

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Posted 26 November 2015 - 04:27 PM

If I ever get planning, I would need at least a 4 cell version. I could not live down a 'no hot water' incident