solar panel output degradation?

Cool, thanks for sharing. I assume you are looking at the total energy of the set of cells as opposed to energy output of a single cell?

Would be interesting to correlate energy output to cell temperature.

Is the angle of the cells fixed or do they track the sun? Give the 4 years of history, what is your projected ROI? J

Hi Win, TOL* If you wanted to look at efficiency/ degradation You could make some small photo diode measurement as a comparison... (measure solar flux w/ know, good standard.) (A PD and good DMM (current input) would probably be good enough.)

On a cloudless day there'll be some pointing angle dependence, but it goes as the cosine so a few degrees won't matter much... (Hmm some diffusor in front of the PD? I guess for long term measurements, then you might be measuring the degradation of the diffusor.)

So maybe do measurements on a overcast day. Then solar panels and ref. PD see the same diffusor.

George H. (who would worry about all the connections and wonders if there is some way to measure the series resistance of the array... during the night maybe? )

It's the output from my 34-panel roof. Here's more info:

Interesting, perhaps, but as you can see from the weather variability in NE, nearly impossible with a working roof. I can't even compare "perfectly-clear" sunny days, because there's always some level of nearly-invisible haze.

I have a fixed roof angle, and in summer sometimes the sun is too high, and in winter too low. My roof cost $34k, and I expect to pay off the remaining $ 6k within 18 months. See more detail in s.e.d. thread "900 tanks of (electrons)"

I'm not confidant that I could get much better than say 3 to 5% with a home-grown roof-based approach. I've read modern solar panels may have about 0.4% / year degradation, too low to easily measure in-situ. That'd only be 1.6% for my four years.

At one point I was the winner of a one-sun system on eBay, until it turned out to be missing critical pieces. The factory was willing to help, and I had the $6k, but I was working on the x-Chapters, and my effort fizzled. A calibrated one-sun would allow for 0.5% lab-based measurements, for small panels anyway. But we'd like to know roof-top degradation.

One of my colleagues has solar panels

He states they are good for at least 25 years, if that is defined as 25% or 50% degradation at that point is blurry

Hey Win, would that not be 15% degradation since it is like compound interest?

Solar panels can also make nice space heaters...

The left panel had about 10 amps applied where the right panel had zero applied. These were sitting right in the snow so it took longer to melt the snow off the panels and more energy than it would have if it were on the roof.

Whether or not this can be done depends on how cold it is and the amount of snow on the modules of course.

boB

I've read somewhere that installations near the coast have lower failure rates/degradation. and that it's often the contact strips that loosen(unsolder?) It might be due to the lower temp differentials.

Good point, there have indeed been fires attributed to solar panel DC wiring, mostly from connectors failing and arcing from what I have seen. This is why the US NEC since 2017 has required arc fault detection and automatic disconnect of DC load; no current, no arc across loose contacts. A rapid shutdown system (RSD) is also required, when the holding circuit is interrupted by any of the NC switches in the RSD circuit, one of which must be fire company accessible, all DC wiring is disconnected at the panels. The two listed RSD systems you can use in the US also include a high temperature shutdown with a sensor in each of the panel mounted RSD switches (one per panel or 1 per two adjacent panels) which shut down the entire system when any one RSD switch senses high temperature. And obviously it behooves the property owner to insure that all wiring is done per code and with good workmanship, which includes greasing all outside electrical connections to reduce corrosion.

There is a learning curve with all new technologies, but I think we are at the point where solar system wiring can easily be as safe as any of the other wiring in your house - which has also been known to cause fires when done badly.

I don't know what the requirements are in the EU, but usually they are ahead of us in safety requirements.

Glen

glen walpert wrote in news:XA6JF.345780$ snipped-for-privacy@fx46.iad:

I would say that ANY such instance is the result of poor design engineering and possibly the installation quality as well, and the panel maker quality is to be examined too.

Some panels are made by real engineers and others are slapped together by hobbyists who happened to be lucky enough to get into it early enough to glean a profit all the while nobody noticed that there was a lot of engineering lacking in their system... and staff.

We all know that 90% of electronic and electrical failures occur at a node. A physical connection integrity issue.

We used to 'fix' PacMan at game rooms in the field by taking off and putting on the edge card connector a bunch of times to reburnish the card connection fingers on the PCB mainboard. Game fires right up. I used to fix old tube type TVs by re-socketing all such components and tubes. VOILA!

Local governance should require some city engineering inspection process before a consumer is allowed to connect up.

Little rubber caps on that too. All exposed (outside) power wiring connections should be oxidation protected regardless of AC or DC status. A regular (tri-monthly) re-examination should also be implemented.

All those protections (you mentioned)are great!

Most failures occur when the customer/owner thinks he knows alll about it, yet fails to perform a 100% QA inspection of all of his or her connections.

However, I want my solar panel to be able to do this:

(just kidding)

You found a way to wire up the solar system? How hard was it to make the connection to Jupiter? :-)

Takes some pretty long wires too. :-)

Hahaha... Over there they not only know how to tighten a connection, they know how to make sure the the folks they hire to tighten the connections knows how to, and knows the importance thereof.

That could be because it rains more often there. Towards the drier climates where I live many older solar panels look dirty all the time. They never get cleaned and then some residual dirt layer cakes in, just like it does when someone never cleans their windows. To my surprise that's even the cases on many ritzy homes where people detail their cars every Saturday.

It's similar with generators. People store them away for a year because the season is over and then next year when the power goes out they cannot get them started.

Are there any figures on how much the efficiency of a solar panel is affected by it not being cleaned? On most houses they are pretty inaccessible - the slope of the roof stopping even long window-cleaning poles from reaching the panels. And the further south they are, the flatter they are, so crud is more likely to collect and stay there.

I came across this at : " It is reasonable to assume that solar panels can loose(sic) 15-25% of their efficiency if not cleaned properly. This literally means that they will generate 15-25% less electricity, "

Why "assume"? Do they have any figures to back this up?

Who's are those ?? Not TIGO ? Are you talking PV module level or string level shut down ?

Thing about RSD or RSS is that they usually add more connectors to the system. More MC connectors can make the system less reliable and more prone to fire.... As well as connectors are not always compatible with each other and not always making a good connection.

We have had DC arc fault protection in our charge controllers since

At least a garden hose should reach. If necessary tie it to a limb saw pole for more reach. There are other tricks to increase pressure. This doesn't get it "hotel-window clean" but flushes off the worst stuff. Reducing the loss from 20% to 5% instead of 0% is worth that little effort. However, one has to keep safety in mind at all times and also should never do that during a hot day. The glass may not like such a sudden cool-off.

There have been studies on that and it should be easy to obtain scientific papers:

It depends a lot on what kind of dirt is on there. For example, we have phases where yellow clouds waft over from the area around Yosemite National Park. This is also when a lot of people come down hard with allergies. We do not have solar because our Decra metal shingle roof makes such a project prohibitively expensive. However, starting the next day our glass patio tables are so covered in brownish-yellow pollen that the sun becomes an orange glow when looking through from underneath. That's a lot of loss. A rain would wash that off but it may not rain for several months.

I wonder how these panels cope with the occasional summer cloud burst that happens while the sun is fully out? Do they all spontaneously shatter? That's a lot more common here than hail storms of any size.

Why does everyone obsess with putting solar on roofs? Solar has no need for such elevation. It works just fine being attached to the earth without a building. In fact, the many solar farms do just that without constructing buildings to put them on.

I don't want to cut down my trees by the house. So if I am going to add solar, it will be somewhere near my drain field.

It's for security of the panels, so people or animals will not mess with them. Solar farms have dedicates security teams to deal with it.

And you have free space on the roof. Not many people in residential areas like the idea of having solar panels taking up the space in the garden

te:

eed for such elevation. It works just fine being attached to the earth wit hout a building. In fact, the many solar farms do just that without constr ucting buildings to put them on.

h them. Solar farms have dedicates security teams to deal with it.

like the idea of having solar panels taking up the space in the garden

Except for roof top garden, of course. Choice between growing veg or elect ron.

te:

eed for such elevation. It works just fine being attached to the earth wit hout a building. In fact, the many solar farms do just that without constr ucting buildings to put them on.

h them. Solar farms have dedicates security teams to deal with it.

like the idea of having solar panels taking up the space in the garden

The issue is that space on the roof is not always "Free" in terms of free b eer. Someone was complaining that his roof does not provide for inexpensiv e installation on the roof. So if there is other space, which many have, i t can be used.

I may put in a detached garage which would be perfect for PV solar if I tak e down enough trees to give it a full day of sun. The solar will be the in expensive part of the deal.