Sunamp container bulging

[Jeremy Harris]

26 minutes ago, Onoff said:

Could you then...

 

Use the PV to pre heat a conventional store then use that store to feed a water heated Sunamp?

 

 

Yes, or you could try and build a hydronic unit similar to the one that sat in the top of the old Sunamp PV.  That used an immersion heater in a tube, with a variable speed Grundfos pump and a flow sensor, to take whatever excess PV was available and use it to run a charging loop at a high enough temperature to cause the PCM to change phase.  The earlier discussions around using a Willis heater and pump, plus a control system, in order to replicate this set up seemed to have merit.  One advantage of the UniQ is that these unit already have a separate charging heat exchanger circuit, so it would be possible to make a small add-on box that just used excess PV to heat a small volume of water to above the PCM phase transition temperature and pump it through the unit to charge it.  The main heat exchanger could still be used to provide DHW as normal.

 

I think there's an advantage it trying to keep the charging circuit water volume as low as possible, as that way there's less initial energy needed in order to get the temperature high enough to effectively start to charge the PCM.  A Willis heater only has a low volume, so if well insulated would heat up to the temperature needed relatively quickly, even if there was only a few tens of watts of excess PV - the lower limit would be set by the heat losses from the charging circuit when sat at required temperature (probably around 75 °C  or so, I think).

 

Turning the pump on when the temperature was at the set point, and varying the pump speed to try and maintain that temperature, seems a viable way to try to run the control system, just allowing the variable PV power level to go directly to the heating element.

[Gone West]

I've just looked at the Sunamp website and can't find any reference to the SunampPV. The only product they seem to be selling is the UniQ. So I presume all the old Stack, PV etc products have been discontinued.

[Big Neil]

I've read every word of this thread, and started another to get an understanding of what heat batteries are, so thanks everyone for the information. I'm probably never going to understand the technical in's and outs, i'm not a software engineer or a heating engineer or owt like that. However, I realise that the real core of the issue currently being discussed here is the charge acceptance level.

 

It appears like this is something they are aware of but won't have a definitive fix for some time yet. Also it seems from the phrases being used throughout the last 9 pages indicate some quite intricate if to some quite simple fixes for the issue. They would all obviously cost chunks of money. However with one eye on the key objective of saving money in the long term, would it not be best to just wait for the relevant software updates (if that is all that is required to effectively resolve the issue), and for those with these units, just turn the tap on until the charge level hits 49%. I know there's an element of waste to this, but for those of us who have the time, maybe just take another bath.

 

BY the way, none of that was meant to be patronising, i'm just struggling with why a temporary solution can't be this simple? Obviously I don't think everyone has the luxury of lolling around in baths all day...

[scottishjohn]

looking for a " work  around" an extra thermal store where you run off excess charge insunamp till it hits recharge swithcing point

or just run the hot tap a bit ?

not a solution --but could be cheaper than having E7 charging it up at night

[Onoff]

30 minutes ago, JSHarris said:

I think there's an advantage it trying to keep the charging circuit water volume as low as possible, as that way there's less initial energy needed in order to get the temperature high enough to effectively start to charge the PCM. 

 

And lower heat losses with a lower "conventional" water volume I presume?

[scottishjohn]

great +simple minds think a  like

 

[Jeremy Harris]

3 minutes ago, PeterStarck said:

I've just looked at the Sunamp website and can't find any reference to the SunampPV. The only product they seem to be selling is the UniQ. So I presume all the old Stack, PV etc products have been discontinued.

 

 

AFAIK, they have dropped the Sunamp and Stack model range completely, in favour of the UniQ range.  I presume this was because the UniQ range is a better match to whatever has turned out to be their core market, which I'm guessing isn't people wanting to maximise the storage of excess PV energy.

 

4 minutes ago, Big Neil said:

I've read every word of this thread, and started another to get an understanding of what heat batteries are, so thanks everyone for the information. I'm probably never going to understand the technical in's and outs, i'm not a software engineer or a heating engineer or owt like that. However, I realise that the real core of the issue currently being discussed here is the charge acceptance level.

 

It appears like this is something they are aware of but won't have a definitive fix for some time yet. Also it seems from the phrases being used throughout the last 9 pages indicate some quite intricate if to some quite simple fixes for the issue. They would all obviously cost chunks of money. However with one eye on the key objective of saving money in the long term, would it not be best to just wait for the relevant software updates (if that is all that is required to effectively resolve the issue), and for those with these units, just turn the tap on until the charge level hits 49%. I know there's an element of waste to this, but for those of us who have the time, maybe just take another bath.

 

BY the way, none of that was meant to be patronising, i'm just struggling with why a temporary solution can't be this simple? Obviously I don't think everyone has the luxury of lolling around in baths all day...

 

Yes, you could opt to waste a bit of hot water to ensure that the UniQ drops below the charge threshold, and that might well work as an interim measure, although it does waste energy, some of which may have been paid for during the winter months.

 

Although we've discussed alternative charging methods, using temperature-controlled water derived from a highly variable electrical power source (diverted excess PV generation), it does seem probable that a change to the control system could allow the direct electric charging system to work more effectively.  The key seems to be in the control system having enough data to make a reasonably good stab as to the state of charge of the PCM, and be able to ensure that local overheating never occurs.  I'm not entirely convinced that three thermistors down the sensor tube can give enough data to do this, but may be wrong.

[Jeremy Harris]

5 minutes ago, Onoff said:

 

And lower heat losses with a lower "conventional" water volume I presume?

 

Yes, the only slight snag is that the insulation level needs to be very good, as with a small volume in the charge circuit the proportion of heat lost, versus heat retained, increases (what's often called the "elephant and mouse effect").

 

The key to utilising excess PV generation is in allowing a very low level of power from the PV system to be able to be transferred to the PCM as useful charge.  The direct heating element will do that very well, if it can be adequately controlled.  The indirect system using a small volume heated water loop offers safety advantages, in terms of not being able to overheat the PCM, but adds losses when charging, so would be a bit less efficient.  Might not be a big enough loss to worry about, though, especially if it allows better utilisation of the heat capacity of the PCM store.

[Triassic]

13 minutes ago, JSHarris said:

Yes, you could opt to waste a bit of hot water to ensure that the UniQ drops below the charge threshold, and that might well work as an interim measure, although it does waste energy, some of which may have been paid for during the winter months.

Without a charge indicator, how would you know you’ve reached the charge threshold point?

[Triassic]

13 minutes ago, JSHarris said:

The indirect system using a small volume heated water loop offers safety advantages, in terms of not being able to overheat the PCM, but adds losses when charging, so would be a bit less efficient.  Might not be a big enough loss to worry about, though, especially if it allows better utilisation of the heat capacity of the PCM store.

I’d happily use such a system if it were available off the shelf from Sunamp. Maybe this is the answer, “oh you want to optimise PV, you’ll need the Sunamp PV optimisation add-on”.  A bit like buying a BMW, you want alloy wheels! That’ll be £x extra!

Edited December 7, 2018 by Triassic

[Jeremy Harris]

7 minutes ago, Triassic said:

Without a charge indicator, how would you know you’ve reached the charge threshold point?

 

Good point.  At the moment you'd have to rely on the mod I made to our unit (and which @Barney12 has made to his) which adds a neon indicator to show when the contactor that allows power from the PV diverter is on.  It's a bit crude, but reasonably effective, as at least it shows when the unit has dropped to either the 90% or 50% threshold (depending on how it's been set up).

[Gone West]

34 minutes ago, JSHarris said:

 

AFAIK, they have dropped the Sunamp and Stack model range completely, in favour of the UniQ range.  I presume this was because the UniQ range is a better match to whatever has turned out to be their core market, which I'm guessing isn't people wanting to maximise the storage of excess PV energy.

 

I've done a bit more digging and found this table which indicates there is a PV version, so is the UniQ dPV the version you have?

 

http://www.bublshop.co.uk/files/pdf/pdf1958b.pdf

 

[Jeremy Harris]

26 minutes ago, PeterStarck said:

I've done a bit more digging and found this table which indicates there is a PV version, so is the UniQ dPV the version you have?

 

http://www.bublshop.co.uk/files/pdf/pdf1958b.pdf

 

 

 

No, we have the eHW, as the PV version is only suitable for small PV arrays (less than 3 kWp IIRC) and only has a small (I think 1 kW) electric heating element.  Ours has a 3 kW heating element and was sold as being suitable for use with a higher capacity PV system.  The label inside our Qontroller states that it is a UniQ_SBC_01_PV, implying that it should have been set up to utilise excess PV generation, however, as supplied, it was set up with Option 1 ON, which meant that it didn't start accepting any charge until it was 90% discharged.  I changed that last Friday, in the light of information received during an email exchange with Sunamp, so that it now starts to accept a charge from 50% discharged, which should be better, but it's a long way from being ideal.

[Ed Davies]

1 hour ago, Big Neil said:

would it not be best to just wait for the relevant software updates (if that is all that is required to effectively resolve the issue),

 

Exactly. This might just turn out to be a simple software fix. Or maybe software + changed temperature sensor string, or something like that. Let's hope Sunamp give some indication soon but until they do discussion is so speculative as to be mostly a source of confusion.

[joe90]

Are Sunamp aware of this forum/thread?

[Jeremy Harris]

7 minutes ago, joe90 said:

Are Sunamp aware of this forum/thread?

 

Yes, they were pointed to it about a week ago now, I think.

[scottishjohn]

yes ,cos when i rung them to get full info  and made a comment about"bean counters" ,they suddenly knew who i  was 

and my view on that still is relevent --if they made the containers thicker they would not cause deformation of cases,

 I understand it a salt mixture ,so using metal is  not an option -but thicker thermo plastic is  as is GRP  or maybe a fibre re enforced ceramic  that could  be another heat storeage  component 

so yes they look at it

[Jeremy Harris]

OK, I've just made an interesting discovery, that I think may get around the Sunamp UniQ eHW failing to charge until 50% discharged problem.  Yesterday was quite sunny, and as luck would have it the Sunamp must have been a bit below the 50% state of charge point when we started exporting, so the unit charged up fully during the day; probably the first time it's done this from excess PV generation recently.

 

We ran two showers off this morning, which would have used around 4 kWh worth of hot water at a guess, and this wasn't enough to trigger the Sunamp to charge.  We have blue skies and bright sunshine now, and consequently we're generating  around 3 to 4 kW, yet the damned Sunamp wasn't making use of this and charging back up (this really, really annoys me).

 

So, as an experiment, I switched the power off to the Sunamp at the isolator, waited 20 seconds or so, then turned the power back on.  Lo and behold the contactor clicked on and it's now happily charging.

 

So, one bodge way around the failings in the Sunamp Qontroller may be to fit an additional time switch, that just turns the power to the controller off for a short time and then back on again, perhaps set to do this in the early morning, just after we've drawn off hot water for showers.  Not ideal, but as I have a spare time switch I'm going to wire it in to the constant power feed to the Qontroller and see if it improves the utilisation of excess PV generation.  Based on what I've just seen when I turned the power off and on again I'd say that it should make a big difference, but only time will tell.

 

The other glimmer of hope here is that if turning the power off and on again resets the Qontroller so that it works as it should, then it should be fairly easy for Sunamp to change the code to do much the same (I hope!).

[Dreadnaught]

9 minutes ago, JSHarris said:

The other glimmer of hope here is that if turning the power off and on again resets the Qontroller so that it works as it should, then it should be fairly easy for Sunamp to change the code to do much the same (I hope!).

 

Haha, it sounds like an old Windows PC .

Edited December 10, 2018 by Dreadnaught

[vivienz]

The instruction to do this was probably printed in white ink on the white paper of the instruction manual.

[scottishjohn]

 stupid question about how thisPCM actually works

is it a  reversable chemical reaction  or purely like water freezing and and melting 

and if the former how does it decide to stop 

if its the later then i am guessing  it is a latent heat situation and the energy you have taken lowers the temperature of the whole mass   and stabalizes the temp once heat has stopped being removed through the whole mass ,or is it lots of seperate cells .like batteries where some are discharged  and some still full if you did not have them all directly  connected to each other  in series 

 

[Jeremy Harris]

5 minutes ago, vivienz said:

The instruction to do this was probably printed in white ink on the white paper of the instruction manual.

 

I think the good news here is that there's nothing inherently awry with the unit itself, just the way the Qontroller firmware behaves.  My guess is that it may hold some form of state of charge (SoC) variable, perhaps not as sophisticated as this, in volatile memory.  Turning the power off, then on again, causes it to "forget" whatever it's stored to indicate SoC, so it then reads the temperatures in the sensor string and starts again, assuming a "warm start".

 

Adding a time switch to power the thing off then on again to reset it is a real bodge, but in the absence of any other fix it's an easy one to implement, and as it's external to the Sunamp should have no impact on the warranty; in essence it's no different to a short duration power cut and the unit should have been designed to deal with that scenario safely (I hope).

 

5 minutes ago, scottishjohn said:

 stupid question about how thisPCM actually works

is it a  reversable chemical reaction  or purely like water freezing and and melting 

and if the former how does it decide to stop 

if its the later then i am guessing  it is a latent heat situation and the energy you have taken lowers the temperature of the whole mass   and stabalizes the temp once heat has stopped being removed through the whole mass ,or is it lots of seperate cells .like batteries where some are discharged  and some still full if you did not have them all directly  connected to each other  in series 

 

 

Not a stupid question at all, and yes it is the same in principle as water turning from liquid to ice and back again.  One reason that lumps of ice and snow hang around for a long time after the weather warms up is that it takes a lot of energy to melt ice into liquid water.  This is much the same as melting the sodium acetate trihydrate mixture in the Sunamp, except the melting point is a lot higher, about 58 deg C.

 

There's only a single cell in the new Sunamp heat battery, whereas the Sunamp PV used two small cells fitted side by side in the base.  When partially charged I would guess that there is temperature stratification in the cell, with cooler solid PCM mixed with hotter liquid PCM.  Once cold water enters the heat exchanger the hotter liquid PCM loses heat to the heat exchanger and turns into a solid again.  We don't know for sure how this process works, but some of the papers I've read about it suggest that the formation of solid PCM within the liquid as it gives up heat may not be homogeneous, and there may be "clumps" of solid held within the liquid phase.  I've no idea if this is actually the case with the Sunamp heat cell, though.

[Nickfromwales]

8 minutes ago, scottishjohn said:

 stupid question about how thisPCM actually works

is it a  reversable chemical reaction  or purely like water freezing and and melting 

and if the former how does it decide to stop 

if its the later then i am guessing  it is a latent heat situation and the energy you have taken lowers the temperature of the whole mass   and stabalizes the temp once heat has stopped being removed through the whole mass ,or is it lots of seperate cells .like batteries where some are discharged  and some still full if you did not have them all directly  connected to each other  in series 

 

One single cell, two heat exchangers. I suppose the voodoo is a well kept secret but I think the issue is that the PCM freezes upon first activation and the heat just simply sits there waiting to be used in the super insulated cell. Based on a domestic situation, it would get recharged in any 24 hour period so not an issue. Once charged, it would just sit there until the first / next activation event.  

My thoughts, may be wrong.

I just cant see how they could stop / start the reversal tbh. Maybe they would have been better off cascading multiples of small cells, but then they'd need multiple HEx's, multiple immersions etc and the cost and complexity would be off the chart. 

[scottishjohn]

If it is as you suggest that there are lumps of solid in the liquid ,then that probably why they don,t want it be charged untill it s below this 50% level ,so you don,t end up locally heating the fluid too much  and at worst case end up with some liquid close to changing state to a gas with solid lumps which have not managed to absorb the heat from the liquid parts quick enough .

and the latent heat could cause that ,as all materials have a  latent heat range where you need to put alot of energy in to make them changetemperature + state

Ice has a larger volume than water ,then as you cool it even more it shrinks ,now not sure how much of this is to do with "free gases " in the ice ,but if same occurs  in this medium ,then theres your reason for  bulging cases,

and we all know that ice can split pipes + rock .

 So possibly the cases are just not large enough to accomodate these possible situations of excessive localised heating from an immersion heater + solution is just make more space   in the case ?

do the first type of sunamp units have same case problems?

I am not slagging the unit --just trying to get a handle on how it works  and its limitations

[scottishjohn]

I certainly feel that if sunamp made a statement as to why you cannot do what you want and the technical reason why it would actaully make people much happier 

and knowing there is technical reason why would then be accepted by most ,especailly fi they said it will shorten the life of the unit

Just like the EV cars --everyone now knows ideally you do not keep charging them up to 100% or let them drop below 20%    ,cos it will shorten battery life