DIY PV Solar Panel - encapsulation?

Hi everyone,

My second batch of 'broken' solar cells turned up today, so I now have 50 pv cells waiting to be made into a panel. My main concern, is the damp and wet British weather.

When its raining, I want to keep the water out.
When its damp I want to stop condensation forming
When its hot, I want to keep the cells cooled.

I'm thinking that I will build a ventilated panel, if all goes as planned this will stop condensation and help keep the cells cool on the hot sunny days.

But....

The solar cells are fragile (very fragile) and I'm concerned that high humidity over the Autumn, Winter and Spring will damage both the cells and the soldered joints.

I would really like to encapsulate, or paint the cells with some sort of waterproof and UV resistant coating - some sort of acrylic laquer, or maybe a two part resin?

Anyone got any ideas on what could be used? Also is it safe to paint directly onto the surface of a pv cell?

Here's a couple of photos of the cells:

[Gotwind Ben]

microgreen.
The size and configuration of those panels look like the basis of outdoor solar LED light modules, made by the millions I suspect.
The grey ones (that may be a photographic illusion) may be suspect?

Such modules of cells can be encapsulated in a resin, but how, I have to ask others here on this, possibly Ghurd.
I can't see it being easy unfortunatly.

My advice is to simply save the cash up for a ready built panel.
It will almost certainly last longer than any DIY version and come with some form of warrantee (12 months)
Navitron have served me and others here well.

Hi Ben,

Thanks for the feedback, the grey ones are monocrystalline, see here for an example:

http://www.solarnova.de/GB_solar_cells.html

I believe that the cells I have come from larger broken units that are cut down to a uniform size.

Saving up for a ready built panel? Now where the fun be in that :)

For once its nice and sunny here, I'll pop out in the garden later and see what sort of output they have.

John

The cells do not look re-cut to me (that is a major operation).
They look more like a hodge podge assortment.

Cells collect light from different spectrum.
Best to not use a UV blocking material,
Use a UV stable (non yellowing) material.
Just because light visible to the human eye makes it seem 'clear' does not mean it is for the cells, like hi/low E glass lets through different kinds of light.

There was a GE brand substance made just for making panels. An ebay seller sold it in standard tubes with cells for a while. I do not recall the part number.

I would tend to agree with Ben about buying factory PVs.

I would tend to agree with you about ventilated.
Do not go overboard on venting. Just want the condensation to be able to 'get out'.
The problem is the solder, tabbing, etc, will corrode. I guess the cells will too, thought most fail before that.

I never saw, or heard of, a homemade PV that was actually moisture-proof, regardless of the measures employed or the costs involved.
Meaning, it must be better to let the moisture out by default?

The cost of low iron glass is not cheap. Just a stray thought.

A couple links involving homebrew PVs.
Not for the squeamish.

1st is one an unlucky gent purchased on ebay,
Just look at the photos...
http://www.fieldlines.com/story/2009/1/23/163227/642

2nd link was presented by me to show how the cells and tabbing fail.
The catastrophic failure was probably related to being a high voltage GT system.
The fire, IMHO, would not occur in a low voltage, or 12V battery system.
It certainly would not have occurred if the PVs were glass.
http://www.wind-sun.com/ForumVB/showthread.php?t=4524

I would love to see a Believable story about home made PVs still working as designed after 3 or 5 years,
and saving money at the same time,
and NOT posted by someone selling a useless overpriced ebook,
but I never did.


G-

Hi Ghurd,

Thanks for the reply and the links - very interesting reading. Quite scary that a professionally installed and inspected system caught fire like that.

I'm investigating both DIY and factory built panels - a nice shiny new 15W amorphus (spelling?) turned up today. A quick test showed it putting out a higher open voltage than I expected - around 24v. Didn't get to measure amps as fuse has gone in the meter. I'll dig out my other meter tomorrow and measure the amps.

I have a selection of old pv cells, I might experiment with a vented and unvented panel to see how they perform.

I'm a bit wary of spending lots of time soldering up all the new cells only to find they all corrode over the winter, hence lots of thinking and research before I build something up.

I'll grab a photo of the new 15w panel tomorrow - if the sun is shining :)

Just looking again at the photos of the panels that caught fire - they look very flimsy, and I think many a competent DIY'er could have done a better job.

I wonder if they will ever find out the cause? Its stuff like this that puts me off buying cheap GT invertors from Ebay.

If everything is kept at 12v with a fuse on the battery is there any way a panel could catch fire, regardless of the material its made of?

Personally I like 12v, its safer - I guess with the exception of increased risk of fire if something shorts, but then thats what fuses are for...

"Quite scary that a professionally installed and inspected system caught fire like that."
Professionally installed insinuates the installer had a clue about what he was doing, instead of simply reading ebay advertisements.
Inspected insinuates the inspector had in-depth knowledge about RE systems, and generally speaking they do not. And it is not their fault. This is new ground for most inspectors. The inspector for most places may have no idea a PV can even get a UL sticker.
G-

The problem here is that unless you have a good knowledge of PV, how is the average consumer to know if an installer is competent? Most people will assume that a professional knows what they are doing and would also assume that the system is safe as its been inspected. I suppose that like most trades, there will always be a few excellent tradesmen, many ok tradesmen and few cowboys.

Anyway, the sun is shining in Essex so I'm going to grab the new panel, camera and mulitmeter.

As soon as I had found my multimeter, the clouds had rolled in :(



Heres a pic of the panel:



Its made in China and was branded as 'TJ'. I could not find anything to indicate which factory it was made in. I have seen what appears to this exact same panel being sold/used in many places, I suspect that they are either made in the same factory, or that some are clones.

As Ghurd pointed out, from what I have read, these panels will loose a fair bit of their performance once 'broken in'.

Initial measurements, on a day with light cloud cover were: 24.6v and 528ma

I reckon they will output the full 15w on a bright summers day. I'm actually quite pleased with the output for a day with some cloud cover, considering this is a more typical UK day.

With this panel, the DIY panel and a small (educational) wind turbine I'm hoping to get somewhere around 60watts peak power and an average of around 30watts? (a pure guess). Hopefully enough to charge the 70ah leisure battery I've just bought (or at least keep it topped up) to provide lighting in the shed and garage plus some charging of cordless power tools.

Most people will assume that a professional knows what they are doing and would also assume that the system is safe as its been inspected.

I have a little "saying" concerning this very topic:

Do you know the difference between an expert and a professional?

(most people say, "no".)

A professional is anyone who gets paid to do something.

An Expert is someone who knows exactly what they are doing.

In almost every field professionals are easy to find, experts far more difficult to locate.

I am sad to say that I find myself using this little play on words quite frequently. The number of people who work as "professionals" in a capacity beyond their understanding staggers me. The last job I had other than being self-employed was in the mid-eighties while I was in college. I waited tables. Being successfully self-employed means you have to become an expert on a myriad of topics beyond your professional pursuit. Perhaps the most difficult task is making the transition from "self-employed" to "employer". This seemingly small step can have enormous ramifications. Essentially you are paying someone else to complete some tasks or portion of tasks you would otherwise complete yourself. As your business grows, this means that you can lose sight of many of the details. Larger businesses expend huge resources in an attempt to ensure "protocols and procedures" are in place for every conceivable scenario, smaller businesses tend to "trust their employees to use common sense". Both approaches are flawed.

In the particular case at hand, a contractor and an inspector OK'd a system that ultimately caused a fire. Even the most competent inspector is a government employee whose sole job is to visually inspect work to ensure it meets existing government codes. Typically these codes are guidelines established by industry experts and can be ignored or modified with an engineer's or architect's stamp or seal. It is beyond the scope of an inspector to question design. Frequently contractors rely on experience and not a fundamental understanding of a project. In general this is not a bad thing, but it can lead to trouble in emerging fields and technologies. Most electricians are unfamiliar with the challenges presented by RE technologies, but in most cases a licensed electrician will be required at some point in a professional installation. It is very easy for me to see how a licensed electrician and an inspector could fail to catch small flaws in a solar install, and these small flaws could easily place the system in jeopardy of catastrophic failure. I find it just as plausible that a contractor either knowingly or unwittingly took short cuts that led to the failure.

At the end of the day I think the fundamental problem is that RE is not ready for mainstream consumers, but media-fueled mainstream consumers are standing eagerly in line with cash. I expect this situation to get worse long before it gets better; I just hope the typical disappointment is in energy savings not structural fires!

Fish