Free solar panel discussion

Nang

zeupater wrote: »

Hi Nang

Just looked at the site, looks good ....

An idea to fix the performance baselines could be to feed the orientation, roof angles, locations and sizes of both systems into the PVGIS model, this would give you estimated generation outputs by month for direct comparison of relative performance between the arrays.

As an aside, 20x200Wp = 4kWp .... I take it that what you really mean is 3.9999...kWp ....

Regards

I took me a little while to get your drift.

You are talking about peak output, I think.

My system is rated at 4 KW peak, and consist of 20 x 200w panels in two strings. But my inverter has a peak output of 3.81 kw. I think this is because it is not 100% efficient and so cannot convert all the DC to AC. It can never generate more than 3.81 kw, no matter how sunny it is.

But there were hot days in the summer where the system seemed to reach peak by 11:00am which suggested to me that a higher capacity inverter might have better yields.

Max has told me his is 3.81 kwp, but I think it is still rated as 4kw system same as mine.

When i originally went looking for quotes some installers were going to use a 3.31 kw inverter. So I am pleased I didnt go with those ones (a full 500w less).

Andy..

Doc_N

Doc_N wrote: »

Different roof angles perhaps? That might also explain Max's lower July figure.

Cardew wrote: »

I wouldn't have thought so - not as he had stated:

"We have a large almost completely south facing flat roof on our house and so we were told this was almost perfect for this type of installation."


In fact a 'databank' of results might alert owners about a potential problem. For instance what if there was a faulty panel - how can you tell unless you have a baseline to work from.

The picture shows a roof which looks to be at a fairly shallow angle. I'd guess this would produce poorer relative results in the autumn, winter and spring, but better in the summer because of the angle of the sun.

Certainly agree with you about the databank - a useful way of spotting if something's up with your system. I've been concerned about my October output (particularly the peak output), but it looks OK by comparison, particularly bearing in mind the 25 degree roof pitch.

Nang

Cardew wrote: »

I believe the most important monthly figure for a graph is the kWh generated.


Max's system is only 4% smaller than yours so the comparison is reasonably valid, however for a database you will have 1.44kWp systems upwards. So to compare data on different systems, the kWh per kWp is essential.

Thanks

Its the same really though he has the same inverter as me SB3800 so we both peak at 3.81 kw, the inverters cant turn all the 4000w dc to ac, so you lose a bit.

Ok I will see if I can stick KWh on the a separate graph for next month, for the people more interested in the output and less interested in the fits earnings.

Andy..

Doc_N

Nang wrote: »

I took me a little while to get your drift.

You are talking about peak output, I think.

My system is rated at 4 KW peak, and consist of 20 x 200w panels in two strings. But my inverter has a peak output of 3.81 kw. I think this is because it is not 100% efficient and so cannot convert all the DC to AC. It can never generate more than 3.81 kw, no matter how sunny it is.

But there were hot days in the summer where the system seemed to reach peak by 11:00am which suggested to me that a higher capacity inverter might have better yields.

Max has told me his is 3.81 kwp, but I think it is still rated as 4kw system same as mine.

When i originally went looking for quotes some installers were going to use a 3.31 kw inverter. So I am pleased I didnt go with those ones (a full 500w less).

Andy..

You've produced some very interesting figures. Your system is quite similar to mine (though my SB3300 inverter can only cope with 3.6 kw).

In the summer my peak output was around 3.6 kw, but lately it's been around 2.4 kw. You look to have a roof with a shallow pitch - mine's even shallower, I'd guess, at around 25 degrees. Have you found a similar dropping off of peak output in October, as against, say, August?

Nang

Doc_N wrote: »

You've produced some very interesting figures. Your system is quite similar to mine (though my SB3300 inverter can only cope with 3.6 kw).

In the summer my peak output was around 3.6 kw, but lately it's been around 2.4 kw. You look to have a roof with a shallow pitch - mine's even shallower, I'd guess, at around 25 degrees. Have you found a similar dropping off of peak output in October, as against, say, August?

Yes definitely

Right up to October it would get to 3 kw +, now it struggles to get to 2.5 all of a sudden.

Andy..

zeupater

Nang wrote: »

I took me a little while to get your drift.

You are talking about peak output, I think.

My system is rated at 4 KW peak, and consist of 20 x 200w panels in two strings. But my inverter has a peak output of 3.81 kw. I think this is because it is not 100% efficient and so cannot convert all the DC to AC. It can never generate more than 3.81 kw, no matter how sunny it is.

But there were hot days in the summer where the system seemed to reach peak by 11:00am which suggested to me that a higher capacity inverter might have better yields.

Max has told me his is 3.81 kwp, but I think it is still rated as 4kw system same as mine.

When i originally went looking for quotes some installers were going to use a 3.31 kw inverter. So I am pleased I didnt go with those ones (a full 500w less).

Andy..

Hi

Drift is/was ... if you have a 4kWp system you should only be claiming 36.1p/kWh, below 4kWp (ie 3.99999 ... kWp) the claim can legimately be the 41.3p/kWh rate .....

Measuring against the PVGIS baseline will allow you to take geographical, orientational and incline differences into consideration when directly comparing systems ......

This map (http://re.jrc.ec.europa.eu/pvgis/cmaps/eu_opt/pvgis_solar_optimum_GB.png) will give a rough idea of expected differences for optimally inclined arrays between your two locations, but it will be far more accurate to follow the PVGIS database link provided @17:21pm.

Regards

Mcfi5dhc

I think all this talk about Nangs website etc deserves a thread of its own. Anyone agree ?

If you want my October figures, 1.44kwp system , 76kwh generated, 36 of which were exported, direction SSE, roof angle 45 degrees, near Chester

Doc_N

Nang wrote: »

Yes definitely

Right up to October it would get to 3 kw +, now it struggles to get to 2.5 all of a sudden.

Andy..

Thanks for that. You've solved a mystery for me - I was beginning to think there was a problem with the panels!

ilovegreen_2

Elainemary wrote: »

Hi there and welcome to the club!! Glad I'm not alone with Homesun and their " must have's ".

Hi there, I made my submission towards the middle of September and received an email within 3 days from Krish Patel in their customer services clearly explaining why my roof was not suitable. He said in his letter that shading was an issue and therefore they were not able to install the minimum amount of panels. The good thing about this was he admitted that his decision maybe incorrect because they use "Google or Binng Maps" which may be out of date and therefore requested for me to send in more information..... so i decided to call krish patel rather than email him.....

...I contacted homesun's call centre but the agent was unable to answer my questions about why they require a roof space of 30m2 when other companies do fit large systems on slightly smaller roofs and also to inform them that the tree which appears on google maps has been completely removed by the council. They put me through to their head office and to my surprise it was krish patel who answered and from there on took full ownership of the situation and kindly explained that 30m2 is a rough measurement for a good size solar system to comfortably be installed. He then brought up my details and verbally illustrating various obstacles such as the "tree" which was causing shading on my roof on the google image which only left a small area of clear unshaded roof space and on this basis he made the decision.

Once i informed him that the tree is no longer there, he immediately advised me that a local rep in my area would be in touch and that he would personally overlook this.....he certainly did...and surely enough a homesun fella by the name of eldon contacted me and came to see me..he arranged for a survyor to come by which was followed up by a call from krish patel confirming the surveyors visit......... i'm now waiting for krish to call me with some good news...fingers crossed :-)

apologies for the long history but i felt that i should share my experience with homesun to all. If anyone would like to speed things up, let me know and i can provide you with krish patels contact number as clearly he knows what he is doing and most importantly gets things done.

Ilovegreen.

furndire

Had 3.96 system fitted 28th June.
Our roof was a steeper pitch (49 deg) than the optimum, but because of this we are hoping we may gain on the lower angle of the winter sun.
We are in Sunny Scunny.
We have discovered that the top of a bloomin great poplar tree actually shadows our panels for a short time, as the sun is lower now, but luckily its later in the afternoon - which is gutting. Its quite a distance from our roof as well.
Nang, I'll email you with figures for our system tomorrow.