Question about E/W configuration

[Satal]

Hi all,

This is probably a very noddy question, but I wanted to validate my understanding.

Recently I had solar panels installed by Solar Bureau, and one of the two sets of panels was installed in what the supplier is saying is an East/West configuration, so that the panels are in a steepled layout, so half of the panels are tilted towards the East, and half are tilted towards the West. As this wasn't how I was originally expecting the panels to be installed, I phoned Solar Bureau, who told me that the panels have been set up like this so that I get the best out of the morning/evening sun.

However, after seeing only a single cable running into the inverter and keeping an eye on the output of the panels, I decided to carry out an experiment to ensure that this was the case. So during one of our recent really sunny days, I went up to where the panels are installed at midday and covered one of the East facing panels with a blackout blind. The panel wasn't covered 100% as I was being careful while being high up, but easily 95% of it was covered.

I expect that if the panels were set up to get the most out of the morning/evening sun, this would mean that the output would be halved because the East facing panels would be limited by the one panel that was covered up, but the West facing panels would still be able to operate as usual. However, the power output of the entire set of panels went from ~1kW to 0.02kW.

I've phoned Solar Bureau a couple of times around this to try and get an understanding of thi,s but I'm being told that is expected behaviour for an East/West set-up.

Am I miss understanding this, or are Solar Bureau trying to fob me off having set up the panels wrong?

Thank you for any insights people are able to provide around this

 

[sunshine_eggo]

If the East and West panels are all in the same string, they will never perform better than the worst facing, i.e., in the morning, the east panels will perform no better than the West panels. In the evening, the West panels will perform no better than the east panels.

Your test would seem to confirm that they are improperly wired; however, there are other possibilities. By using blackout shading, you also killed the voltage from the panels. By lowering the voltage of the panels, you may have reduced their voltage to the point that they acted as a short circuit to the other facing array, i.e., by lowering their voltage, you forced the operating side of the array to discharge its current into the other side.

consider:

light produces voltage.
intensity of light produces current.

Had you simply shaded the panels such that they received enough light to generate voltage, but not current, this would have been more diagnostically useful. If you observed the same drop in production, it would confirm that all panels are in series, and this is very improper.

It is critical that all panels in a series string be facing the same direction.

The East panels should be wired in series. The West panels should be wired in series separate from the East.

If there are the same number of panels, the two strings can be wired in parallel, which would allow both to operate together independently providing their respective currents, i.e., if morning yields 10A of current from the East panels and 2A from the West panels, you would get 12A. If those panels were all in series, the East panels would be limited to the 2A of the West, so rather than 12A, you'd get 2+2A = 4A total from both facing arrays.

If in parallel at the arrays, it could mean only one pair of wires coming from the array.

You really need to determine how they are wired together.

It's is my understanding that UK sun is best described as "reluctant," so it may be very difficult to establish realistic expectations.

Something else to consider is a clamp DC ammeter. If you can get that around ONE of the wires on the East panels and ONE of the wires on the West panels, that may be diagnostically useful. If East provides more current in the morning and West provides less, when both are measured in direct sun as close to the same time as possible, that confirms the strings are in parallel. If they both measure the same current or very nearly the same current, then that suggests they are all in series.

 

[ko6kL]

would be better to have two strings feeding their own mppt inputs.
in your weather patterns are the afternoons more likely to be sunny than the mornings?
then better to have more on the west side.
if you install is not what was in the contract or not what the sale guy said focus on this and ask for some money back or to make it right.

 

[12VoltInstalls]

Am I miss understanding this, or are Solar Bureau trying to fob me off having set up the panels wrong

I think they screwed up.