Expected Solar Performance

tails_naf

Hi All,

I have 60 tubes which were installed some months ago, but only had them finally connected to the pump/tank this week. Tank is 300L.

I am a little dissapointed with the performance so far and was wondering if anyone here could sanity check what I am seeing -

Today - dull day, but 18C ambient - temp sensor on the panel is reporting 36-40C over the day, so not hot enough to heat the tank beyond the max of 40C.

From reading online I had expected solar to achieve temperatures of 60C even on a dull day (some even reporting 40C could be achieved throughout winter).

So can anyone relate what kind of temperatures they are seeing on the water produced by their system over the last week for example (or better still data from today). I suspect there may have been an installation problem.

celtic_oz

60 deg in my tank today!

tails_naf

celtic_oz wrote: »

60 deg in my tank today!

The 47C reported at the roof - is that because you took the picture later in the day? Do you you know what would have been reported at the roof during mid-day?

I forgot to add that my solar is pretty much south-west facing, and at an angle of about 40 degrees - which according to this calculator means its not that far from optimal (about 10% off the optimal output angle/direction).

Have you managed to hit 60C most days this 'summer'?

ccsolar

tails_naf wrote: »

celtic_oz wrote: »

60 deg in my tank today!

The 47C reported at the roof - is that because you took the picture later in the day? Do you you know what would have been reported at the roof during mid-day?

I forgot to add that my solar is pretty much south-west facing, and at an angle of about 40 degrees - which according to this calculator means its not that far from optimal (about 10% off the optimal output angle/direction).

Have you managed to hit 60C most days this 'summer'?

Hi
Check if the pipes from the oil or solid fuel are hot when not in use
I have seen this problem a few times where thermosiphining is happening
The 60 tubes should produce better results than you are showing.
Cc

quentingargan

Agree with csolar on this. Almost all cases of underperformance that I have seen with solar water heating has been heat leakage or poor insulation somewhere in the system. This can be in any pipe coming from the immersion, so leave everything off (don't run taps etc.) and see if there is heat coming off any of the pipework in the hotpress.

Ours was way over 60 yesterday and using dumps, but we also dump heat from our wind turbine into the same cylinder, so I don't think it counts...

tails_naf

Thanks for the tips.
I don't think there is any heat escaping, as none of the other pipes are hot. The only time the oil pipes were hot was when the boiler had to come on to finally heat the water when the solar didn't manage it.

I think the next step is to go up on the roof. I have my suspicions about the roof portion of the install being dodgy. The system uses copper heat pipes in vaccum tubes being connected to a manifold - and the installation guide mentioned to take care to use thermal paste and really drive the heat-pipes home into position. I'm wondering if this was not done correctly, it may explain the under-performance of the system.

I'm going to graph the temperatures every hour today and see how it goes. In any of you happen to keep an eye on what temperatures yours hit at any stage, please let me know.

tails_naf

Just an update from today -

The image is a graph of the temperature reported on the roof (collector) and the temperature at the bottom of the tank. I did not report the temp at the top of the tank, as in this case it was 60C (because the top of the tank was heated by oil as the solar yesterday was too poor) - so any heating only applies to the bottom portion of the tank (maybe 100L).

I noticed that throughout the day the pump started and stopped a lot. It usually only pumped for 5-10 mins at a go, and when it did the temp reported at the roof dropped a lot.

I believe the temperature sensor could have been installed at the 'return' end of the solar panel, but I also think the temperatures being achieved at the roof are still too low.

Does anyone else have data for today (preferably north cork/tipp region)?

Note: the drop at the bottom of the tank about mid-day was due to a shower.

championc

Check the parameters on your system. The pump should turn on when Roof Temp is > 8 deg above the bottom of the store and should turn off when only 4 deg above the bottom of the store. So the roof temp won't be going sky high.

There is obviously something badly wrong if you are basically only heating 100 L.

My guess is the shutoff temp for the pump is too low and the system is being cooled after being heated.

John T Carroll

tails_naf wrote: »

Hi All,

I have 60 tubes which were installed some months ago, but only had them finally connected to the pump/tank this week. Tank is 300L.

I am a little dissapointed with the performance so far and was wondering if anyone here could sanity check what I am seeing -

Today - dull day, but 18C ambient - temp sensor on the panel is reporting 36-40C over the day, so not hot enough to heat the tank beyond the max of 40C.

From reading online I had expected solar to achieve temperatures of 60C even on a dull day (somYou e even reporting 40C could be achieved throughout winter).

So can anyone relate what kind of temperatures they are seeing on the water produced by their system over the last week for example (or better still data from today). I suspect there may have been an installation problem.[/QwertyqUOTE]

Hope you have solved the problems with your Solar System. The attachment may be of some help to you as I keep a daily log of my system.
You might see my very first posting as well. .....JTC

John T Carroll

Since last summer was allegedly, the dullest in 25 years, I have logged my flat plate performance since its installation, the numbers in the Spreadsheet are from 01//01/2012 to 14/10/2012. I have also included calculations for a 30 tube installation, based on my figures, these may be changed to whatever anyone feels is more appropriate. I have also included estimated savings to date. JTC