Glass + Sylgard fail anyone yet?

[Mike90250]

Mike - re multiple panels - if blocking diodes aren't used on each panel, and the panels are connected in parallel - if one panel is shaded, couldn't the others discharge through it?

It could, but at a very low rate. nothing that would damage or be unsafe to the panel.

[rhjames]

Thanks. Looks like I'll settle on a Schottky diode every 9 cells (4.5V), and no blocking diodes (controller will do the job), and just connect the panels in parallel.

Mount all cells on 4mm tempered glass, wire up, and cover with Slygard.

I'll probably sit the whole thing in an aluminium frame.

Next trick is to mount a weatherproof wiring plug - any ideas?

[RifRaf]

weatherproof solar junction box with pre attached leads with mc4 connectors seem to be the easiest to deal with, they typically come with a few decent bypass diodes as well making them decent value, clip the array together with the mc4 connectors and a few longer wires to run to changer etc. the box is well sealed with silicone to attach it to panel once you connect the bus wires to it

[rhjames]

RiffRaff - thanks for the advice re solar junction box. It seems to me that this would be mounted on a backing plate behind the cells. I was planning on leaving the back open (for cooling) and having the cells and electrical encapsulated with Slygard. However, where do I mount the junction box, and how do I protect the leads from the cells to the box? Cover with Slygard up to the box?

I could just make the glass a bit oversize to allow room for the junction box mounting and glue it to the glass?

[asked]

OK fair enough So what is your point?

I am a Professional EE of 30 plus years experience and have been there and done that. If you want to play with toys to learn, more power to you, that is how you learn like I did. Fact is is you are playing with toys of not much useful application. But if you want to scale up to a useful application, the LAW of PHYSICS, ECONIMICS, REGULATIONS, and REALITY will kick your butt into shape.

OK so now you have been told, now go learn what I am talking about. It is your money and time. Prove me wrong and you will be rich beyond your wildest dreams.

Care to bet? You got 20 years to do it before i die if God blesses me with 20 more years on this earth.. Here is a good snipet of what you want to do and economics lesson.

If you want to build a battery system to generate 1 Kwh pr day of power (12 cents per day) it will cost you $3000 real money DIY for the first 5 years assuming your DIY panel last that long. Then after 5 years you will pay another $1000 for a new battery for the next 5 years.. Now do the math.

Good Luck

SK

Response to Sunking.

We know this is an old post but need to comment.

First , not to bash you as an engineer, but most innovations are not brought about by engineers. We have found that the time it takes an engineer to crunch numbers on a calculator, we can design and build an item before they are done. That is not to say they do not have their purpose. Many of the items I have created over our years in business were finalized by engineers. Some we have had working here, have problems thinking beyond their cad screen, cnc programs or paper.

Your ROI's are incomplete as well.

Electric rates need to calculated by total bill/kwh. Many places exceed 15-17 cents per kwh. And rates are going to go up.

Also in the past 6 years , we here have been w/o power for more then 3 days in 5 different instances. Two of them we were w/o for 7 plus days.

So what is that worth ?

That has to be part of the ROI.

We were running generator before we built our system. 5 gallons gas runs house for 12 hours. 10 gallons/day=$30.00 (if there is no power in your area , YOU CAN NOT GET GAS)

Also if you want to rely solely on someone else providing for you, then stay where you are, and continue to not think outside of the box.

And where are you getting your battery prices ?

We have grid tie and separate off grid system here. Total cost to build $1200.00.(solar/wind system, and yes, we as a none EE built our own circuits, chargers, dump load boards etc.). Tower, for panels and turbines, we had here, given to use by scrap company. Has been running for 38 months now. Knocked our bill down 30-35/mth. Now you do the math. Just forget about the monthly savings on the bill. Power outage would have resulted in lost freezer products if no power. To run generator just the 2 longer outages 18 days total , would have been 30*18=360.
Shorter terms would be around 120.00. That is 480.00 in gas. Our system saved our ass and runs freezer, lights, heat circulator, heating coil for hot h20 and sub pump for well.

[rhjames]

My summary is :

1. Solar energy is very expensive without government subsidy. Only in special circumstances (eg remote areas) can it be justified economically. In other areas (eg my project in Cambodia), it may be the only practical option.

2. DIY panels, designed for long term service and high reliability, are expensive, and savings over purchasing panels with a long term guarantee are not encouraging. I've seen some lower cost methods, and I wouldn't give them more than a couple of years survival.

3. Besides the panels, there's still the controllers, inverters, battery, wiring, and in many cases, logic control to swap to mains power when appropriate. Added fixed cost.

4. Building good reliable panels requires considerable skill and knowledge. There are a lot of possible errors that could render a panel useless within a short time.

5. For some of us, it's a fun (though expensive) thing to do.

[Mike90250]

Response to Sunking.

We know this is an old post but need to comment.

First , not to bash you as an engineer,

But I'll go ahead and bash anyway ?? Incomplete this.....

Good Morning, and welcome to our new member "asked".

We'd like to have you contribute positive stuff to the board, like how you saved fuel costs by using solar and such.

[russ]

I agree Mike - The post was generally trying to pat one's self on the back.

Polite posts (reasonably polite) and ones with facts to back up claims such as the 1200 USD off grid system are better.

Battery prices are battery prices and are easily available to all.

Your disregard for engineers tells much - be a bit careful there. You don't count your power failure periods in a ROI calculation - that is a separate consideration. Any bean counter can explain that.

17 cent power (mine is 19 cents) is not good but not bad and not high enough to justify a PV system on it's own.

[Sunking]

We were running generator before we built our system. 5 gallons gas runs house for 12 hours. 10 gallons/day=$30.00 (if there is no power in your area , YOU CAN NOT GET GAS)

Why on earth would anyone use gasoline to run a generator? That is foolish.

Also if you want to rely solely on someone else providing for you, then stay where you are, and continue to not think outside of the box.

I have not been without power in 15 years. I live in North Tx where tornado and ice storms are a common threat. To bad you live in a place where electricity rates are rising, mine has fallen from $.13/Kwh to $.096/Kwh in the last 3 years

And where are you getting your battery prices ?

Simple quality FLA battery cost range from $120/Kwh to $140/Kwh, very simple math.

[RifRaf]

in australia, nsw at least, power costs 24c + per kwh, in addition there is also the 30c or so per day just for availability, you pay this even if you use no power, this price WILL increase another 50% in the next few years, this is a fact. so please be mindful of this, our ecomomy has not fallen apart like the us, sure times are tougher, but please keep in mind 25c/kwh rather than 9c when doing the crazy maths.

also everyone in the bush here uses a generator to supplement power that runs from gasoline/petrol or diesel, though 10 gallons and $30 in fuel is a lot per day, though at the prices we pay of over $5 a gallon, that would be $50 a day

[BriteLeaf]

Mike, you say that 100% of cells on ebay are rejects, where would you recommend purchasing them from? I guess I got duped, i bought 36 of them..

I bought 280

[rhjames]

I bought 280

I bought 72 cells on E-bay, and all worked fine.

[Naptown]

By saying rejects doesn't mean they don't work. Kind of like buying seconds clothing at an outlet. It means that for whatever reason they did not pass inspection. i would imagine for the most part they did not pass the flash test therefore did not make it into the sorting for modules.
Have you ever wondered why a manufacturer can have 4 different modules with 4 different wattages that are all the identical size?
All cells produce differently. The best ones are put in the high watt panels and progress down from there. The ones that work but do not cut the mustard are the ones sold on E bay etc.

[BriteLeaf]

I bought 72 cells on E-bay, and all worked fine.

Mine just came in today. Still waiting for Junction boxes. Also, tomorrow I will check prices on 1/4" tempered glass and Aluminum angle pieces.

[Mike90250]

There are many tests cells can fail, end up for sale on gray market. Maybe the plating was bad, and will peel off in 3 years, or leakage was high, and a hot spot will heat up and crack your glass. PV cells are not simply little blue chips.