Solar Panel Output verse rating

[buzzstar]

Originally Posted by noelex 77

I can understand the frustration generated by solar panel specifications. They are confusing.

However, the manufacturers deserve some credit for providing a wealth of detail. They always provide the temperature coefficients so you can work out the output at different cell temperatures and most provide the power output at different illumination levels.

Some manufacturers supply a NOCT rating of the output in watts, as well as the normal STC rating. NOCT is the output at reduced illumination (800 w/m2) and elevated cell temperature. This is not commonly quoted these days, which is a pity, but the data is in the specifications so you can work out the performance under reduced illumination and elevated temperature for yourself (although the exact NOCT number needs experimental data).

In practice, the most important factor in a solar panel installation is fitting the maximum watts you can in the available space for a realistic price, so we should not get too worked up about these minor details.

If you want to accurately compare the performance of different solar panels you can work out the expected output for a couple of illumination levels and celł temperatures. Say 800w/m2 and 45°C and 200w/m2 and 35° C might be representative for a boat planning to cruise tropical waters. It is a lot of calculations and not something I would recommend as necessary, but if you are debating between a couple of different brands of panels it is interesting information.

It will also give a very realistic guide to the output of the panel under bright and dullish conditions. Factor in some losses for cabling and the efficiency of the controller, and the numbers will accurately match the real world output for those conditions on your boat, providing there is no shade.

Now I will go back to posting about safe subjects like anchors .

Aha, we are making progress pilgrim. Good info. My thanks, tarnished only by your use of a stretchy rode, rather than a properly sized chain with a kellet and a snubber.

[noelex 77]

Originally Posted by buzzstar

My thanks, tarnished only by your use of a stretchy rode, rather than a properly sized chain with a kellet and a snubber.

.

[sailorboy1]

Wish I had included a poll, maybe I would have gotten the answer

[masonc]

Solar panel specifications and test results are not confusing. They were not designed for the tiny tiny boating market. They are designed to meet the requirements of the large commercial solar installation business, where installations are designed by engineers, financed by banks and purchased by utilities. That business revolves around specifications, RFPs, contractual commitments. I doubt many boaters sue the supplier over a 1% deviation from contracted performance, but in the commercial world this is common. Major Tier 1 manufacturers such as Canadian Solar provide insurance backed performance warranties, so if the solar panel performance drifts from stated specifications, the insurance company will make good on the replacement. This is a huge deal and governs which solar panels are acceptable for financed projects. The boat industry benefits from the testing and quality assurance process inherent in solar panel manufacturing, but it is not a driving force as the market is so small.

[StuM]

Originally Posted by sailorboy1

Wish I had included a poll, maybe I would have gotten the answer

You have "gotten" the answer from several people. You are getting what is expected from your panels at your latitude at this time of year.

[sailorboy1]

Originally Posted by StuM

You have "gotten" the answer from several people. You are getting what is expected from your panels at your latitude at this time of year.

If you think so, sure on all points.

[TheThunderbird]

I laugh at people who spend 0000s $ on the assumption of AVERAGE annual output, and postponed fiscal levy.
Solarbon landbis justified only if heavily subsidized, and maintained FOR FREE by your hands :-)

That said, installations on a boat are flat.
On the average latitude 20/40° already at 11am and 2pm output is approx. 2/3 of noon's peak. Physical appreciation of irradiation is so different on our bodies! But panels see it!

I use solar for floating the batteries, and see just 60% of rated output at NOON in SICILY on early March.
I am not happy, but do not mind. Sure, i see little value in adding a third panel at current costs (flexible panels are still outrageously priced).

That said, cumulative Ah, or capacity, is the issue, not max W .

Regards

[Ding Duck]

I would tend to agree with Stu in you are probably getting what you should.
The testing standards are what they are, we don't have to agree to it, but as long as everything is tested the same, you have a benchmark. (LED lighting is another questionable comparison)
You don't need much shading to effect your panels performance. I even noticed this when the shadow of my VHF aerial in on the panels. The other issue you might like to look at the MPPT Regulator. If there is shading the MPP changes and the regulator will try to adjust to meet this new MPP. If the shadow is moving continuously, sometimes the MPPT can't find the sweet spot, shuts downs, has a reboot and tries again. The best I've seen out of my 180W panel is about 100W.
Oh, you may also want to check what length a Solar day is at your Location. This will help you in determining how many A/Hrs you should be getting. The Solar day is about 5 hours average where I am, so if charging at 10Amps, I get about 50A/hrs per day input. Value will be higher in Summer and lower in Winter.
Good topic though

[motion30]

I am in s florida as well. I have 825 watts of solar i have seen peak readings of 740 watts. This time of year i see 500 to 550 watts steady in good sun. In the summer it does much better winter averages 200-225 amps hrs per day. In the summer easily over 300 amps

[Paul L]

Originally Posted by TheThunderbird

..
.....
I use solar for floating the batteries, and see just 60% of rated output at NOON in SICILY on early March.
I am not happy, but do not mind. Sure, i see little value in adding a third panel at current costs (flexible panels are still outrageously priced).

That said, cumulative Ah, or capacity, is the issue, not max W .

Regards

Not everyone is in Sicily in March. Lots of cruisers are in the tropics where solar is king.

Flex panels are available direct from China on Aliexpress for under us$200 for 100watt panels.

[john61ct]

Originally Posted by Ding Duck

The testing standards are what they are, we don't have to agree to it, but as long as everything is tested the same, you have a benchmark.

Exactly, that's WHAT THEY ARE FOR. And only that.

Not hard to understand

[barnakiel]

Today I experimented with sun angles.

At 0 degree (no direct sun rays on the panels but plenty of reflected light from the blue sky) we got nearly 20% of the rated capacity - and this measured post regulation (pwm). I think this data gives more proper insight:

http://www.all-science-fair-projects...91/0080-b3.jpg

This much said, our panels are both tilt-able and one of them is a two axis mount. Just in case ever want to collect all there is (hardly ever our case as we have a surplus from 14:00 ST onwards)

So to each their own. We easily get nearly max rated output from our units - on a sunny day with panels angled. Our boat is 99% solar - the remaining 1% is the alt driven by the engine.

Cheers,
b.

[PacificGreen]

Originally Posted by sailorboy1

I'm been watching my solar panel output the last few days. I'm currently in Palm Beach getting lots of sun. But in the middle of the day with my 5 year old 290W panel with a MPPT controller in full sun is only putting out 170-180W and I know the batteries aren't limiting it to that amount.

What are others experience in real output verse rating?

From what I've seen in my panels so far is about a 860 watt difference in rated capacity. Factor that I've only ever seen them operate in the winter in less then stellar conditions and never in full light I'm hopeful they produce more and haven't been damaged over the winter.

Also aside from testing directly at the panel itself the different aspects of charge controllers plays a large part in the efficiency of the panel itself. If your charge controller is 97.3% efficient then likely you will see greater efficiency.

Efficiency can also be addressed in terms of voltage be that 12v, 24v, 36v or 48v panels. This is in relation to wire sizing and length of runs. Also to consider is battery chemistry in terms of how long for example an mppt controller stays in bulk mode.

Another aspect of efficiency is that many controllers limit Voc to 150v which at times requires connecting panels in series and then parallel to meed the charge controllers obligations for string optimization.

So could it then be concluded that a 600v charge controller would allow panels to be more efficient by having one large string of series connected panels? Certainly series connections are more native to STC conditions then parallel connected panels.

Also in this same forum I'm examining the use of a Morningstar 600v with disconnect box on a boat if any have thoughts on that I would welcome them.

[StuM]

Originally Posted by PacificGreen

From what I've seen in my panels so far is about a 860 watt difference in rated capacity.

That doesn't tell us anything without knowing your total installed rated wattage. (I'd guess it is in the multi KW range - far from typical)

[PacificGreen]

Originally Posted by StuM

That doesn't tell us anything without knowing your total installed rated wattage. (I'd guess it is in the multi KW range - far from typical)

Sorry Stu. I am running 2160watts of solar in a configuration like this:

String Calculator » Morningstar Corporation

But not with a tristar 60 for the controller but with a Coleman Air 440HVA shunting charge controller.