DIY PV Solar Panel - encapsulation?

[Gotwind Ben]

John.
Very sorry to hear that news, It came as a bit of a shock when I read it yesterday.
I don't have children myself, but I have 2 nieces, and the thought of any loss absolutely scares the hell out of me.

Thanks Fish also, it's difficult to know what to type..

Ben & Ghurd,

Thanks to you both - I dont know what to say either - but I find the distraction of an interesting hobby helps...

I didn't get any pics of the new panel today, try again tomorrow.

I did however get a chance to measure the output of the cells from ebay. Both the poly and mono seemed to output about the same - 0.55v and around 600ma - although I had my fingers over most of the cell as was trying to hold the meter probes on the cell. These cells are incredibly fragile!!!!!! I broke one while trying to measure the output. They are wafer thin and very brittle. I have some tabbing wire so will solder some on before trying to measure output again.

Fish's eloquoent reply leaves people like me wanting.
I must have opened and closed the window 6 times before clicking 'submit'.

"the distraction of an interesting hobby helps"
Shall we all try to pretend we are not walking on egg shells?
Shall we begin the distraction and get down to business?

Mono and Poly will be about the same. Minor size difference.

Amorphous uses more space and wears out faster.
The 24V and the amps will decrease considerably over the next 3-4 months.
With luck, the rated numbers are after the break in / burn in period and will match the rated output.

"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.

I imagine the system, being high voltage, had a weak solder joint, without any bypass diodes.
A common PV, assembled in the common fashion, with common by-pass diodes as are common in high voltage systems, would most probably never experience any condition to make a fire even remotely possible.
The conditions that started the fire were a lot of unusual circumstances that came together at the wrong time and place.

G-

"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

Good point about the difference between a professional and an expert - something that I came across a lot in my time as an IT project manager. The client would always assume that everyone on the team was an expert, and I would always agree with them "Oh yes, all of the team are qualified, highly experienced etc".

The reallity was that on the team I would have a few experts and a lot of 'average' devs and a few 'below average'- all professionals, but I was the only one in a position to know who the experts were - the client had no way of knowing. I had the advantage of being able to allocate the work according the devs strengths and weakness.

On the electrical side of things, I think many electricians will struggle with the technology of RE systems. In the UK, normal household systems and wiring have become very standardised - just about every home in the UK will have ring mains, standard fuse box/RCB, stanard plugs, wiring and ratings.

In the Uk, once qualified as an electrician you can forget much of the theory and rely on experience and knowledge of which components to use. For RE, you need to understand the theory and work with components that you may have never seen before.

Well, thats my view anyway, based on my very limited experience

Progress update:

I made a start on soldering up some cells. I'm joining them into 9 sets of 4 cells for a total of 36 cells for the panel, hopefully giving around 18v. I found some reasonably priced UV stable resin, my approach so far was to paint both sides of the cells and the tabbing wire with the resin. This will give it a thin protective layer, I have decided to go for a ventilated panel. The resin coating should prevent any damage due to high humidity during the winter.

Heres a pic of the resin coated cells:



So far I've not broken any cells while soldering them. I'm going to test the output of each string of 4 cells and will replace any that perform badly. I would have done more but I've run out of tabbing wire, surprising how quickly it gets used up.

Measured the voltage and amps quickly today. Good sunshine at about 4:30pm with the cells laying flat on a table rather than direct into the sun.

Each series of four cells produced near on exactly the same output of 2.33v and 1.0 amp.

Should produce a panel of 20-30 Wp if all goes well.

I've now connected up all the cells. Ended up using 40 cells as I had made a spare set to allow for any breakages or duds, as I didn't break any I thought I may as well use them.

I've used the poly cells first to get some practice and saving the mono's for the next attempt. I've decided to try a slightly different approach for the next batch.

So I now have a 40 cells that on a day with light cloud was putting out 22v at just under 1amp. Photos and outputs in full sunshine to follow, but so far looks on track to make a 20-30wp panel as expected.

Next step is finish making the frame.

Aprox costs:

Solar cells - £20
Solder and tabbing wire - £5
Resin - £10
Panel materials - £10
Labour - £0

Total - £45 for lets say a 25w panel, just under £2 per watt. Of course, if you value your time you are much better off buying a panel ready made.