4 cell SunampPV

[Stones]

Along with others, I'm interested in using a SunampPV for my DHW.  The units currently on offer contain 2 cells which equates (roughly) to 4.4kWh worth of energy storage.  Having done my sums, I came to the conclusion that this wasn't going to meet our requirements and that I needed additional capacity.

Having previously had discussion with Andrew @ Sunamp in respect of the Sunamp Stack, I asked if it would be possible for them to supply a larger (4 cell) SunampPV, which would give a capacity of circa 8.8kWh.  He agreed that technically, there was no reason why a 4 cell unit wouldn't work, and indeed when Andrew got back to me after speaking to his technical team, advised that his chief engineer had unknown to him, been running a 4 cell system himself.

However, to supply a finished and tested unit, he advised that further development work and testing would be required, and that he was unable to give any fixed timescale on how long this would all take.

Fast forward a few weeks, and with no further news, I contacted  Andrew on Friday evening and had a very productive conversation. He remains happy to offer SunampPV's on a buy one get the second half price offer as one way to get around the issue (until they have added a 4 cell unit to their product line).  

However, accepting that I (and others) don't require a doubling up of the charging capability, only the storage capacity, he is  willing to offer forum members (being the pioneers we are) additional capacity in the form of 'spare parts' which we could add to a single SunampPV to increase its capacity.  

Sunamp would supply a case/cabinet, additional cells, and vacuum insulation panels, along with full instructions in respect of how they should be plumbed in. The cells in the existing SunampPV are plumbed in series.  Andrew advised that any additional cells would be plumbed in series with each other, but would be plumbed in parallel to the main SunampPV unit.  

Two SunampPV cabinets, side by side, equates to a washing machine sized unit.

The only issue in fashioning a larger capacity unit using this arrangement is one of pressure release.  The cells in the existing SunampPV are plumbed to a PRV, and have a safety release via tundish to a drain. Andrew advised that if we decided to plumb in the cells without the additional work involved in putting in an additional PRV and safety release via tundish, we should be fully aware of the consequences of the very unlikely risk of cell a failing, and that we would be doing this at our own risk.

Andrew said he would have a formal quote to me this week which I will update the forum with on receipt.

 

 

[DeeJunFan]

This sounds interesting,

I can almost hear the sharp intake of breath from my plumber!

[Jeremy Harris]

Thanks for pursuing this, as we're seriously interested in the same setup (and I've registered an interest with Andrew a while ago).

It seems to me that the cell pressure release issue is very minor, as the volume is low and the likelihood of it ever happening is miniscule, a far, far lower risk than with a conventional sealed water heater.  It wouldn't surprise me at all to find that, with time, there might be a change to the regs to accommodate systems like this and remove the need for the cell PRV altogether.  The consequences of an over-pressure event are not serious, either.  My view is that it's mainly a case of regulations that are worded (very wisely) for conventional unvented systems, but that really aren't wholly appropriate for this system.

Nice to hear that Andrew's view is the same as mine, that an additional pair of cells should be in series/parallel with the existing pair of cells.  When I was looking at the hydraulic diagram this seemed the logical way to increase the capacity, to me.  It looks like feeding a flow and return from the cell circuit out of the case and connecting to the flow and return of the new series connected pair of cells should be quite straightforward.  The only issue would be dodging the vacuum panel insulation and it would probably be necessary to include an additional air vent to bleed air from the new pipe loops. 

Another possibility that comes to mind would be to fit a ball valve (hand operated or motorised) to select whether or not the additional cells were to be used.  For example, in winter, without much PV, I'd probably want to cut the storage down to just that which I could heat with a mix of PV and a timed boost.  In summer, or if we had guests and needed more capacity, I could turn on the additional storage and allow that to be charged.  As far as the Sunamp controls are concerned nothing would change, as it uses temperature as the indicator of state of charge and for control.  I need to have a bit of a think about this, but my gut feeling is that it could be useful to be able to switch the capacity easily.

 

[Guest Alphonsox]

Thanks for the info, I'm very interested in this set up please keep us updated.

[readiescards]

Ditto - looking forward to learning more

[Stones]

21 hours ago, JSHarris said:

It seems to me that the cell pressure release issue is very minor, as the volume is low and the likelihood of it ever happening is miniscule, a far, far lower risk than with a conventional sealed water heater.  It wouldn't surprise me at all to find that, with time, there might be a change to the regs to accommodate systems like this and remove the need for the cell PRV altogether.  The consequences of an over-pressure event are not serious, either.  My view is that it's mainly a case of regulations that are worded (very wisely) for conventional unvented systems, but that really aren't wholly appropriate for this system.

In fairness to Andrew, he listed all of the testing the cells have undergone to indicate how low the risk is, but ultimately, he had to make anyone considering this route aware and make it their decision.

Once I have my formal quote back, I'll try and have a chat with their engineer to firm up on how it will be configured and whether there the units could be stacked (assuming suitable support structure was in place), or installed facing each other, rather than a side by side arrangement.

[JamieM]

Hey stones did you get your formal quote yet?

[Stones]

Yes, although i do have to get a couple of things clarified.  Will post when I have done that (on the to do list for this week).

Edited July 5, 2016 by Stones

[JamieM]

Cool, cheers

[Stones]

Update -  Sunamp asked me not to give the figure they have quoted, but I don't think it unreasonable to say more than a single unit but less than their current buy one get one half price offer (basically what they are proposing to supply is a complete 2 cell unit, and a second without the hydraulic components).  They suggested anyone interested contact them directly to discuss their requirements.

I still have to speak to them about some technical queries.  Further info to follow in due course.

Edited July 8, 2016 by Stones

[Guest Alphonsox]

Thanks - I've been meaning to get in contact again. Who have you been dealing with ?

[Stones]

I was speaking to Joan, but was having a bit of difficulty in pinning down what they could and when, so I ended up speaking directly with Andrew.  That conversation clarified what they could supply and a price, but I will be following up with Joan now.  As above, I have a couple of technical queries to run through with them before I commit (as well as the considerations of my DHW indecision topic).