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Author Topic: New member and above ground solar project  (Read 4174 times)
dhaslam
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« Reply #15 on: March 17, 2017, 10:22:57 AM »

My panels are all in series with the flat panels first.  Because the flow temperature is low this causes no problems except when there is a power cut.    It means that the system can heat even when it is raining.  Because I use plastic piping the flow has to be stopped after a power cut to prevent melting the pipes.  The pipe between the vacuum panels needs to be able to absorb expansion.  The flat panels are less likely to be very hot.

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Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
todthedog
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« Reply #16 on: March 17, 2017, 02:07:45 PM »

Agree with Desp why stop the system in winter?
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barlidge
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« Reply #17 on: March 17, 2017, 06:45:31 PM »

Agree with Desp why stop the system in winter?


That would be nice but its an above ground pool, the liner is not designed to be up during winter months so it gets packed away for the winter  Sad

« Last Edit: March 17, 2017, 08:02:33 PM by barlidge » Logged
barlidge
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« Reply #18 on: March 18, 2017, 01:28:48 PM »

Be carefull with setting up panels in parallel,I did that with out three vac tube panels because in  theory it is more efficient, but in practice it just meant one panel would always end up air/gas locked and would over heat. No matter what I did with trying to balance each panel it always ended up airlocked. Since connecting them all in series 6 years ago it has all run without fault. One EV will be fine as long as it is big enough and each circuit cannot be isolated from it, as for fluid I use water with 20% fernox X500 antifreeze, 9 years old and going strong. Surely in the winter you can just continue heating the pool but let the heat escape?

Desp

Thanks Desperate, that's definitely made me pause and give it some more thought, I'm now wondering if it would be a better idea to run that circuit with 2 banks of 2 panels with adjustable flow meters located at the pump, it would involve a little more pipework but as the pump is located directly underneath the panels its not too much.  I would run the pipework feeding the panels underneath them and the pipework exiting the panels above to help with passing any air directly through, I could also use a 5 channel temperature panel from Reuk.co.uk to help monitor and balance the panels.

As always any comments and suggestions welcome as this is a big learning curve for me.



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ringi
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« Reply #19 on: March 19, 2017, 09:39:02 PM »

To help with air locks, try to have no pipes running 100% horizontal and all running up a bit towards your air release value.   Otherwise you will find you have created a local high point somewhere in the point work, as no one can install pipes 100% level.         (Likewise with the top of panels.)

A spirotech deaerator fitted at the hottest point of the system would also help however you will need the high temperature versions so give them a phone call before ordering.
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dimengineer
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« Reply #20 on: March 22, 2017, 01:42:09 PM »

I've done the sums for you.

10mm copper - ID = 8mm.
5kW @ 0.1 l/s would give you a heat rise of 11C across the panels
10 kW, a heat rise of 22C.

For a swimming pool, neither is too high.

BUT, your pressure drop at 0.1 l/s in 10mm copper is 1 bar/10m run. Which is way too high.
If you go to 15mm copper, it drops to 0.1 bar/10m - which is much more reasonable.

Tim
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ringi
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« Reply #21 on: March 22, 2017, 02:43:31 PM »

And for most pumps a lower pressure drop will gives a higher flow rate, this will take heat out of the panels faster, and hence lower thermal loses, so the pool will heat up quicker on cold bright spring days.   (Assuming the heat exchange to the pool is sized correctly.)
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barlidge
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« Reply #22 on: February 15, 2018, 12:53:05 PM »

Thanks to everyone for the replies and my apologies for not getting back to this sooner.  I did get the system up and running in the end but it was well into July and the results were not as good as I had hoped, but we are coming into a new year and I have some tidying up bits to do on the system and I'm hopeful that I can tweak the system to improves its performance.  I will update this thread with where I got to and then post some log data on last years performance.


I've done the sums for you.

10mm copper - ID = 8mm.
5kW @ 0.1 l/s would give you a heat rise of 11C across the panels
10 kW, a heat rise of 22C.

For a swimming pool, neither is too high.

BUT, your pressure drop at 0.1 l/s in 10mm copper is 1 bar/10m run. Which is way too high.
If you go to 15mm copper, it drops to 0.1 bar/10m - which is much more reasonable.

Tim

Thanks Tim, I did run everything in 15mm, mainly solid pipe but some sections of SS flexible corrugated pre insulated.


And for most pumps a lower pressure drop will gives a higher flow rate, this will take heat out of the panels faster, and hence lower thermal loses, so the pool will heat up quicker on cold bright spring days.   (Assuming the heat exchange to the pool is sized correctly.)

The heat exchanger is 170,000 BTU, from a guide I found on the net I believe if anything the HE may be oversized.
« Last Edit: February 15, 2018, 02:03:21 PM by barlidge » Logged
barlidge
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« Reply #23 on: February 15, 2018, 01:25:35 PM »

Main panels, 80 tubes connected in two parallel banks of 40 with temperature probe on the exit of each bank so I can monitor for imbalance.





Secondary panels, two 2nd hand flat panels in series, I need to tidy up the insulation on that joint and clip that pipe up.



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barlidge
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« Reply #24 on: February 15, 2018, 02:02:28 PM »

Heat exchanger, 170,000 BTU with temp sensors placed on both flow and return for data logging.  Dedicated 10,000 lph pump and circuit circulating pool water through the HE.

I plan to insulate it this year but still deciding on the best method and repair the PVC fitting that cracked when it was fitted.  I don't think the threads are cut very well on the HE as I tried a number of threaded fittings on that spigot and they were all tight but absolutely fine on the top one which probably explains why it was sold on ebay covered in silicone sealant.




Heat exchanger specs




Pump stations and controllers, this was actually an early picture, the two controllers were changed to a Deltasol ES variable speed twin controller and a DL2 data logger, pipes have also since been insulated.  There are two butterfly valves above the left pump station that were intended to be used both for isolation and to balance the flow to the parallel panels but the panels ran at identical temperatures without the need to adjust them.  Pressure vessel pre charge set to 1.2 bar and cold system pressure at 1.5 bar.  The relays were to control the pool water pump independently from the two controllers.


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barlidge
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« Reply #25 on: February 15, 2018, 02:11:49 PM »

I wanted to monitor the pool water temperature both as it left the pool and as it returned.  I searched the net but didn't really find anything that was suitable/available/affordable so it was a good excuse to get on the lathe and turn down some brass rod into some temp probe pockets.







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barlidge
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« Reply #26 on: February 15, 2018, 02:20:49 PM »

As I was only using a small amount of corrugated SS pipe I couldn't really justify investing in a proper flanging tool and the method of tightening the nut against a circlip gave inconsistent results which I was not too happy with so I made a little tool to form my own flanges.  it worked well and did all the required joints but as the steel plate wasn't hardened it started to suffer near the end.


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barlidge
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« Reply #27 on: February 15, 2018, 02:36:33 PM »

I think that brings it up to date with where I got to with it, I just need to remember the IP address of the DL2 and download some data from it from last year, import it into excel and attempt to present it in some form of meaningful manner which could take some time. 

The DL2 was an epic battle in itself, as most of my system it was bought on a budget and it was a brand new 'old stock' unit from ebay.  It arrived and was absolutely fine but was on a very early firmware version and refused to take the update, I even spoke to Resol and they confirmed I was using the correct method and if I sent it to them they would attempt to update it back at their lab at a cost.  Well between my son Dan who's an IT geek and a helpful guy on the interweb also called Dan a github server was spawned and after a few tries the unit updated from that to a more recent version, it now happily updates from Resol's own servers.
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biff
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« Reply #28 on: February 15, 2018, 06:28:08 PM »

Well done Barlidge,!!
                 Thank you for the update and all the useful information.
                                     Biff
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An unpaid Navitron volunteer,who has been living off-grid,powered by wind and solar,each year better than the last one.
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