Solar panel positioning

[Naughty Cal]

On 02/05/2021 at 17:38, Alan de Enfield said:

A quality MPPT will give you ~30% more output of your panels than an MWP will, hence the price difference.

You can choose, pay a bit more and get more, or pay less and get less.

We have a CBE PRS300 Solar Controller on the van.

 

We have no idea is it is MWP or MPPT. The manuals for it are next to useless and we can't seem to find much information on it anywhere. Any ideas which it is anyone?

 

https://www.cbe.it/en/prs300/

[Higgs]

I'm not the kind of person that would bother with the problem of the flat as opposed to angled assembly. Fit and forget, with the occasional cleaning. Buy an MPPT charge controller and fit as many panels as is affordable and practical. We're not a sunny country to begin with. The solar panels are not super efficient. The power of the sun's rays are at a peak an hour or so either side of midday. The hotter your panels become, the less efficient they become. If you haven't got solar panels with bypass diodes, one cell of a panel in shade will drag the rest of a panel's output down. 

 

 

Edited May 13, 2021 by Higgs

[Tony Brooks]

5 minutes ago, Naughty Cal said:

We have a CBE PRS300 Solar Controller on the van.

 

We have no idea is it is MWP or MPPT. The manuals for it are next to useless and we can't seem to find much information on it anywhere. Any ideas which it is anyone?

 

https://www.cbe.it/en/prs300/

 

They specify 12V in put and provide two of them so I think there is a very good chance its a PWM unit. I do not recall seeing an MPPT controller with less than 100Vmaximum input. Even that 12V input is a bit odd because so called 12v panels have an open circuit voltage of around 20V+ and an PWM controller probably needs 14.5V input to provide the absorption charging voltage.

[Alan de Enfield]

8 minutes ago, Naughty Cal said:

We have a CBE PRS300 Solar Controller on the van.

 

We have no idea is it is MWP or MPPT. The manuals for it are next to useless and we can't seem to find much information on it anywhere. Any ideas which it is anyone?

 

https://www.cbe.it/en/prs300/

 

I do not know the model, and without the manual telling you, I don't know how you can tell -  but - from reports on the "Out & About" camper Van forum it may suggest they are cheap Chinese MWP.

 

Extract :

 

We recently removed a CBE PRS300 that was believed to be faulty and replaced it with a Votronic MPP165 and the charge increased by double, proving that the CBE was faulty.

Except the CBE wasn't faulty, we could find no issue at all.
On reverse engineering the circuitry and reading the manual it was clear it was just a terrible design, and we are normally fans of the CBE kit.
It even charges at lower voltages for some reason, as do some of the budget ebay units.

 

Even some of the MPPT ones sold on ebay turn out to actually be MWP. 

I think it is a case of buying a quality brand (maybe Victron ?) that you can be assured of getting what you actually want / need / order.

[Higgs]

27 minutes ago, Naughty Cal said:

We have a CBE PRS300 Solar Controller on the van.

 

We have no idea is it is MWP or MPPT. The manuals for it are next to useless and we can't seem to find much information on it anywhere. Any ideas which it is anyone?

 

https://www.cbe.it/en/prs300/

 

 

With MPPT you will generally find that, unless the sun is really weak, there will be a voltage drop reading to the battery. It is higher at the input. The controller's job would be to increase the current by reducing the voltage. With a bog-standard controller that only regulates the voltage to the battery, you will not get an increase in the current charge to the battery.  

 

 

Edited May 13, 2021 by Higgs

[Higgs]

15 minutes ago, Alan de Enfield said:

Even some of the MPPT ones sold on ebay turn out to actually be MWP. 

I think it is a case of buying a quality brand (maybe Victron ?) that you can be assured of getting what you actually want / need / order.

 

Yes, you really need to do research, to weed out the false claims of some products. Youtube is a good place to find reviews and gain a bit of insight. 

 

 

[Naughty Cal]

20 minutes ago, Alan de Enfield said:

 

I do not know the model, and without the manual telling you, I don't know how you can tell -  but - from reports on the "Out & About" camper Van forum it may suggest they are cheap Chinese MWP.

 

Extract :

 

We recently removed a CBE PRS300 that was believed to be faulty and replaced it with a Votronic MPP165 and the charge increased by double, proving that the CBE was faulty.

Except the CBE wasn't faulty, we could find no issue at all.
On reverse engineering the circuitry and reading the manual it was clear it was just a terrible design, and we are normally fans of the CBE kit.
It even charges at lower voltages for some reason, as do some of the budget ebay units.

 

Even some of the MPPT ones sold on ebay turn out to actually be MWP. 

I think it is a case of buying a quality brand (maybe Victron ?) that you can be assured of getting what you actually want / need / order.

It is what came factory fitted with the van so we have absolutely no idea about it. Most of the electronics seem to be CBE which is a brand we have never heard of and have had no dealings with.

 

Guess it is something we will get around to replacing at some point in the future 

[doratheexplorer]

 I mostly agree with those saying just leave them flat.  That's what I do most of the time.  There is one exception to this.  In early spring and late autumn when the amount of solar power is marginal, you can really boost how much you get by angling the panels toward the sun.  The days are short and the sun doesn't get very high.  On a bright february day, with flat panels I might not get more than an amp going in at midday.  When I angle my panels I'll easily get more than 5 amps for 3-4 hours around the middle of the day.  This is a significant amount and will often make the difference between needing to run the engine or not, that day.

[IanD]

1 hour ago, Loddon said:

Just add 20% more solar panels than you need and keep them flat, that's a win win situation ?

Here are the numbers:

 

https://www.viridiansolar.co.uk/resources-1-3-tilt-and-orientation.html

 

Horizontal panel annual power yield is 84% of an ideally-angled unshaded south-facing panel in the UK, so increase area by about 20% as Loddon said.

 

If the panels are not tilted facing exactly south or are sometimes partially shaded (like on a boat) the difference will be even smaller. Tilting is kind of pointless on a boat given the added mounting complexity, risk of theft and so on.

 

As far as sizing is concerned, this shows expected power yield as a function of UK location:

 

https://www.viridiansolar.co.uk/resources-4-4-performance-of-pv-solar-panels.html

 

So in Watford you could expect about 1000kWh/year (840kWh/year flat-mounted) per 1kWp of installed panels, which averages out at 2.7kWh/day (2.3kW flat-mounted).

 

This is average over the year, in summer you could expect to average about 1.7x this (4kW/day flat-mounted) and about 0.3x (700W/day) in the depths of winter.

 

Which shows why the rated panel power is not a good predictor of actual power, even in summer the real power only averages out to about 4x the rated power, equivalent to 4 hours per day of "full sunshine".

 

 

[Alan de Enfield]

35 minutes ago, doratheexplorer said:

 I mostly agree with those saying just leave them flat.  That's what I do most of the time.  There is one exception to this.  In early spring and late autumn when the amount of solar power is marginal, you can really boost how much you get by angling the panels toward the sun.  The days are short and the sun doesn't get very high.  On a bright february day, with flat panels I might not get more than an amp going in at midday.  When I angle my panels I'll easily get more than 5 amps for 3-4 hours around the middle of the day.  This is a significant amount and will often make the difference between needing to run the engine or not, that day.

 

The type of panels used can also make a big difference in early / late parts of the year.

 

I was fortunate to stumble on some panels that Bimble had for sale that were designed for 'high latitudes' in Scandinavia and were called 'low-light' panels as they were designed (not for low light levels) for low angles of incidence so they produce a better output in Spring / Autumn when the Sun is low in the sky.

 

I normally have them flattish but when possible (moored in the correct orientation) will use the triangular tilt to get a bit better angle.

[doratheexplorer]

8 minutes ago, Alan de Enfield said:

 

The type of panels used can also make a big difference in early / late parts of the year.

 

I was fortunate to stumble on some panels that Bimble had for sale that were designed for 'high latitudes' in Scandinavia and were called 'low-light' panels as they were designed (not for low light levels) for low angles of incidence so they produce a better output in Spring / Autumn when the Sun is low in the sky.

 

I normally have them flattish but when possible (moored in the correct orientation) will use the triangular tilt to get a bit better angle.

Is there a trade-off with less output in summer?

[Higgs]

Panels do vary in quality. I've just bought the cheapest I could find, for experimenting; 50w flexible panels, stuck in the windows. Two to start, but 3 more on order. £21.00 a piece. Not expecting any miracles, but it passes some time. 

 

 

[Alan de Enfield]

Just now, doratheexplorer said:

Is there a trade-off with less output in summer?

 

There doesnt seem to be  They are rated at 170w & 120v and I often get 118 volts and  have seen 12amps (at around 14v) which equates to 168 watts out of them.

 

They just seem to perform better in the early / late seasons and 'as normal' during the high seasons.

 

This was taken in February with the batteries pretty much 100% charged (charging at 14.2v) but still putting 3.3 amps into my 1200Ah battery bank

 

It was producing 46 watts at 53 degrees of latitude which is 27% of the theroretical (at midday on the equator) 170w, so I was quite happy.

Other panels I have had, I have struggled in the Winter to get even 5% of theoretical values

 

 

 

[IanD]

48 minutes ago, Alan de Enfield said:

 

The type of panels used can also make a big difference in early / late parts of the year.

 

I was fortunate to stumble on some panels that Bimble had for sale that were designed for 'high latitudes' in Scandinavia and were called 'low-light' panels as they were designed (not for low light levels) for low angles of incidence so they produce a better output in Spring / Autumn when the Sun is low in the sky.

 

I normally have them flattish but when possible (moored in the correct orientation) will use the triangular tilt to get a bit better angle.

I can't find any information about such "low-light" panels, and I'd have thought that if this was real they'd be in wide use in the UK -- and the physics of how solar panels work suggests there's no such thing as a "low-light" panel, efficiency is efficiency.

 

Are you sure this isn't just marketing fluff?

[Higgs]

Panels that are more capable than others in low-light conditions do exist. 

 

 

Edited May 13, 2021 by Higgs

[Alan de Enfield]

22 minutes ago, IanD said:

I can't find any information about such "low-light" panels, and I'd have thought that if this was real they'd be in wide use in the UK -- and the physics of how solar panels work suggests there's no such thing as a "low-light" panel, efficiency is efficiency.

 

I have no idea. Maybe their internal structure is angled to receive light at lower angles of incidence ?

You could always ask Bimble if they had some (around 5 years ago)

[IanD]

32 minutes ago, Higgs said:

Panels that are more capable than others in low-light conditions do exist. 

 

 

Please provide data -- and not just marketing claims, of which there are many which turn out to be fluff or bullsh*t.

 

IIRC there are some thin-film organic panels that claim to be better in low-light/high-angle conditions, possibly using antireflection coatings optimised for this. However the panels they're better than have around half the efficiency of high-quality mono panels, so this isn't much help...

 

Reflection from solar panels is very low anyway, the improvements we're talking about are a few percent -- and if you add AR coatings optimised for low incident angle light, they reflect more at higher angles e.g. summer/noon.

 

Physics is a b*gger, it's really difficult to get round with marketing... ?

2 minutes ago, Alan de Enfield said:

 

I have no idea. Maybe their internal structure is angled to receive light at lower angles of incidence ?

You could always ask Bimble if they had some (around 5 years ago)

See previous reply. If you're telling everyone about these great panels based on isolated marketing from 5 years ago, perhaps you're the one who should back up what you say with actual information? ?

Edited May 13, 2021 by IanD

[Higgs]

1 minute ago, IanD said:

Please provide data -- and not just marketing claims, of which there are many which turn out to be fluff or bullsh*t.

 

Sorry, don't reach anorak levels. 

 

 

[IanD]

Just now, Higgs said:

 

Sorry, don't reach anorak levels. 

 

 

Then don't make bullsh*t claims about magic fairy dust solar panels ?

[Higgs]

Just now, IanD said:

Then don't make bullsh*t claims about magic fairy dust solar panels ?

 

I don't believe it is BS. I'm just not into railway timetable scales of curiosity. 

 

 

[IanD]

6 minutes ago, Higgs said:

 

I don't believe it is BS. I'm just not into railway timetable scales of curiosity. 

 

 

Physics says it's BS, the fact that these super-duper low-light panels haven't taken over the market says it's BS.

 

If you want to do a Gwyneth Paltrow that's up to you, free speech means you can say whatever you want to. But don't expect to go unchallenged if what you say is BS...

Edited May 13, 2021 by IanD

[Higgs]

Just now, IanD said:

Physics says it's bullsh*t, the fact that these super panels haven't taken over the market says it's bullsh*t.

 

That's not very scientific. They may be costly. That would put me off. 

 

 

[IanD]

8 minutes ago, Higgs said:

 

That's not very scientific. They may be costly. That would put me off. 

 

 

Fine -- so please tell everyone where they can buy these wonder panels, so they can decide whether they're worth it or not.

 

Of course there are 4-layer multi-material rare-earth panels in labs and papers that are more than 2x more efficient than conventional mono silicon panels, but you can't buy them and even if you could they'd cost at least 100x more. And they don't work any differently at low angles of incidence to any other panel, because physics.

 

Or are you just doing your usual trick of saying something because it makes you sound knowledgeable, then finding you can't back it up (because it's not true...) so try and wriggle out of what you said?

Edited May 13, 2021 by IanD

[Higgs]

1 minute ago, IanD said:

Fine -- so please tell everyone where they can buy these wonder panels, so they can decide whether they're worth it or not.

 

Or are you just doing your usual trick of saying something because it makes you sound knowledgeable, then finding you can't back it up so try and wriggle out of what you said?

 

I know enough to think it isn't worth getting into a petty argument. Your word against another poster's. I've also read about them. I'm happy to accept it's plausible, without the use of a microscope. 

 

 

[Alan de Enfield]

15 minutes ago, IanD said:

Fine -- so please tell everyone where they can buy these wonder panels, so they can decide whether they're worth it or not.

 

Bimble are now selling similar panels to the ones I bought some years ago (but 110v instead of 120v and 165w instead of 170w)  but they are still being called 'low light' panels

 

Solar Frontier BLACK 165W CIS solar panel - higher performance in low light - No Shading Issues - SF165 - Very Rare - Last Stock in Europe - Very Limited Stocks - MPPT with input 110v above only (bimblesolar.com)

 

These panels do not have shading issues like other panels.  Shade only affects the actual amount shaded, unlike crystalline panel.  Great for boats or campers where partial shading can often happen.

These CIS thin film panels out perform Crystalline panels in lower light levels.  We have done side by side tests in winter and found that with winter sun these panels will give a decent about of additional power over crystalline panels.  In cloudy conditions they both perform the same, with very low output, but then the low powered winter sun does shine the CIS panels out perform the crystalline panels with upto double the power from the same sized array. 

 

 

 

 

Now you know, you can challenge Bimble with the 'science' if you are inclined.