Partially shaded solar panels

[BobK]

The lovely wife Morticia and I just spent a couple of hours with a solar energy salesperson. One thing he said strikes me as not being true.

He claims that if your roof panels are shaded by trees (all deciduous in our case), you get the same loss of power in the winter, when the trees are bare as in the summer when they are in full foliage.

I pointed out to him, that we cannot see the house behind us in the summer, but we can see it clearly in the winter, so more light is definitely getting through in the winter. But he countered with light is not the same as energy. Well, no, it is not the same but solar energy is obviously carried by light.

Then, drilling down, he claimed that a partially shaded panel loses energy in the same amount as a fully shaded panel, in other words, if any of the panel is shaded, the whole panel produces no energy. This is obviously false in a reducto ad absurdum if you consider that a single dust particle will partially shade a panel, and it certainly does not send the power output down to zero.

But what is the actual effect of shading, say 50% of the panel with the feathery shadows of tree branches? Would that reduce the power output by significantly more than 50%? I can see that as being plausible if the entire panel was one crystal, and the shaded parts had a high resistance that interfered with the non-shaded parts. But I was under the impression that the panels were many smaller cells in parallel. Is that true?

Bob

 

[debe]

The Cells are in series & any shade will significantly reduce the output. I have a 1.5Kw solar system & in the wintertime when the sun is low for about 2hours a pole creates a shadow about one foot wide. Which passes over the panels, this reduces the output to only a couple of hundred watts if you are lucky.

 

[Externet]

Hi Bob. The panels are mostly, many cells in series.

This article explains in my opinion, the partial shading behavior very well :
----> http://sargosis.com/how-shade-affects-a-solar-array/

 

[Bluejets]

The Cells are in series & any shade will significantly reduce the output. I have a 1.5Kw solar system & in the wintertime when the sun is low for about 2hours a pole creates a shadow about one foot wide. Which passes over the panels, this reduces the output to only a couple of hundred watts if you are lucky.

. Correct......even the shadow from a wc vent pipe will have a similar effect.

 

[(*steve*)]

some panels are described as having a certain number of diodes. These apparently allow part of the panel to be shaded, however Murphy will always ensure you don't have the right parts shared.

Another option is "micro inverters" where each panel (or sometimes each pair of panels) has its own inverter, capable of doing the MPPT thing on a subset of the panels.

 

[BobK]

Okay, so it does make sense that partial shade of a panel reduces the output beyond the shade percentage.

The system he was proposing does have a micro inverter per panel, but I guess most of the panels would be in partial shade from the bare trees during much of the day in the winter, severely reducing output like he said.

He still wanted to sell us a system, but the aesthics (panels on the street side of the house) and the low output makes it not worthwhile.

Damn trees.

Bob

 

[Alec_t]

Damn trees.

You could get a fair amount of energy by burning them .

 

[BobK]

Unfortunately, they are not on my property.

Bob

 

[(*steve*)]

<godfather>Such nice trees, it would be a shame if something happened to them</godfather>

 

[BobK]

But we like the shade, especially when sitting by our pond in the afternoon. Plus, the neighbor is an Italian Catholic priest. He is undoubtedly connected, to the mob or Jesus or both. Not messing with him!

Bob

 

[(*steve*)]

Is there any evidence of either?

 

[hevans1944]

Bob, your prospective solar panels simply need more elevation to place them above the shade of the trees. I could recommend suspending them with one or more tethered hot-air balloons, inflated by the solar panel salesman's breath, but this may not be cost-effective. You would probably have to use Tesla wireless power transmission technology to get the bountiful electricity harvest back down to your house without the expense of heavy cables to carry the micro-inverter current from dozens of panels. Almost everyone knows this technology has been suppressed, so such a venture would be risky. Unfortunately, this "solution" also offers no remedy for cloudy days, and is of little to no use at night.

Deep thinkers have suggested placing the solar panels in orbit about the Earth, and beaming electrical power back down with microwave transmitters exposing a significantly large "rectenna" that directly converts microwave energy to DC. This may not be affordable for the average home owner. But, wait! You have a pond! There are zillions of websites that promise to run your automobile on water! Perhaps you could jack up the wheels of the family car and drive a large alternator with such a water-fueled arrangement.

But, please, tell us what you are trying to DO rather than offer your own solutions. Some of us here may have some stock tips or get-rich-quick solutions for you to try to break free of monthly utility bills if that is your goal.

Hop

 

[BobK]

Is there any evidence of either?

Yes. A large statue of the blessed virgin, well lighted, in the back yard. Maybe what I need is a long extension cord

Bob

 

[hevans1944]

... Maybe what I need is a long extension cord ...

And save even more money by using a 1-wire extension cord.

 

[BobK]

Well, with the neutral well grounded on both sides...

Bob

 

[(*steve*)]

Yes. A large statue of the blessed virgin, well lighted, in the back yard.

If it is lit by a permanent beam of sunlight from the heavens, perhaps you can place your panels around it.

Otherwise it sounds like evidence that your neighbor is wasting electricity.

Yeah, an extension cord sounds good. You can have a Virgin powered house.