Starting off small scale

**Sunking** · 07-11-2010, 07:37 PM

Originally posted by Steve

I'd like to construct the panels to last a long time. Is there any problem with plexiglass turning cloudy with age?

So would everyone else who has tried to make them. So far no one has done it. I wouldn't worry too much about the Plexiglas turning cloudy on you. Most likely water will penetrate causing the panel to fail long before the Plexiglas turns cloudy and causes it to fail.

**Sunking** · 07-11-2010, 07:46 PM

Originally posted by Steve

I hope to start off small, experimenting what works and what doesn't. My first project after building the panel is a solar powered alarm clock.
My clock currently runs off 120v but like most every small appliance uses an internal step down transformer to drop the voltage to low levels. It would take me a very short time to cheaply modify it for low voltage low current DC.

There are a lot of DIY charge controller circuits I'd like to experiment with.

Maybe I am way off base here, but I'd like to convert as many appliances (lights, fans etc) in a single room for efficient DC, eventually feeding the entire room.
Once one room is finished, I'd begin with the next expanding my PV system... and so it goes.

Steve as long as you are just experimenting things are OK as long as you keep it outside the house like a detached tool shed. The problem comes when you cross the line into your home and integrate into your premises wiring (house wiring). Once you cross that line everything by law has to be UL certified. Anything you make cannot be UL certified. If you ignored the laws and something were to happen like burning down your home or someone getting hurt, you rare fully liable and no insurance will pay any claims. I guarantee you cannot connect for a grid tied system because that takes permits and pass inspections which anything DIY will not fly.

**Steve** · 07-11-2010, 10:28 PM

Thank you all, looks like I need to stay very small indeed.

**Steve** · 07-17-2010, 10:09 PM

Both me and my wife are getting pretty jazzed about solar power.

We've been looking around the net and located a couple local professional companies and will probably go with one to install a grid tie system. We can't afford the system right away but hopefully within 5 years do the dip. Our June KWH usage was about 1.8KWH according to our power bill.

My solar cells arrived this morning and only after a couple hours I had them all tabbed and ready for the frame which I will probably assemble next week.

I have a some questions if you don't mind.

1.
Do the PV frames need to be vented for passive cooling or can they be sealed airtight?
I plan to use treated marine grade plywood for the back, a bordering frame and center member out of more treated wood all painted white. Silicone caulking everywhere, a plexiglass face, more sealer, aluminum tape around the border edge, Sealing it again with UV resistant polyurethane covering everything except the acrylic plexiglass. Maybe put an aluminum L channel around the edge to finish.
So you see it would be almost impossible to add a vent once finished.

2.
What type of battery?
We plan to make 8 panels in all, each should deliver around 65W for a total of around 500W. We hope to power some small appliances (Low voltage clocks, fans etc) lights etc.
I've taken the insurance consideration Sunking mentioned seriously and will stay out of the house wiring, although I haven't yet worked out my solar power distribution method.

Like everyone I am looking for lowest cost. I know I'm looking for a deep cycle battery. Are these the same as a marine deep cycle battery? I've found some within my project budget online, however their RC value isn't usually posted on the web.

I am not building this project thinking I'm going to save big $$ on energy bills. I consider it more of an extension of my electronics hobby building panels, trying weatherproofing techniques, making controllers for a practical and useful but limited utility.

3
Does a professionally installed grid-tie system add to a home's resale value like almost all advertisements claim? I'll also check with some local realtors because we will probably move to a new location in around 10-15 years.

Note:
I will be retiring in around 10-15 years to the island of the Philippines. We'll probably live in a small home somewhere on the beach on a private lot and the experience I gain with my PV experiments here and now may well be used there for our primary electric utility. The grid there presently isn't reliable and we don't expect there to be a lot of municipal improvements. We may even choose a remote location without a grid.

Thanks for your consideration

**MarineLiner** · 07-17-2010, 10:19 PM

Originally posted by Steve

I'm not a licensed electrician but have done a lot of large scale commercial/residential wiring projects working along side professional electricians.
I have a more than usual knowledge of electronics in general but also respect and aware of my own limitations.
.....

There are a lot of DIY charge controller circuits I'd like to experiment with.

**Mike90250** · 07-17-2010, 10:51 PM

Originally posted by Steve

Both me and my wife are getting pretty jazzed about solar power.

We've been looking around the net and located a couple local professional companies and will probably go with one to install a grid tie system. We can't afford the system right away but hopefully within 5 years do the dip. Our June KWH usage was about 1.8KWH according to our power bill.

My solar cells arrived this morning and only after a couple hours I had them all tabbed and ready for the frame which I will probably assemble next week.

I have a some questions if you don't mind.

1.
Do the PV frames need to be vented for passive cooling or can they be sealed airtight?
I plan to use treated marine grade plywood for the back, a bordering frame and center member out of more treated wood all painted white. Silicone caulking everywhere, a plexiglass face, more sealer, aluminum tape around the border edge, Sealing it again with UV resistant polyurethane covering everything except the acrylic plexiglass. Maybe put an aluminum L channel around the edge to finish.
So you see it would be almost impossible to add a vent once finished.

If you are going to use plywood, understand you will never be able to seal it and use enough paint to make it water vapor tight. May as well plan for some venting along the bottom and top edges to keep the condensation down.

Clean the inside glass absolutely spotless, wipe down with rubbing alcohol, and the same with the front side of the PV cells and their edges. Moisture gets in there and causes leakage currents to flow (too small to measure, but enough to start electrolysis happening, and as that removes the front surface metal, the cells stop working.)

Paint the inside and let it bake in the sun for a few days, so the paint outgassing does not collect on the inside glass or the PV cells.

--

Batteries.. 6V golf cart batteries are a good starter set, get 2, place in series to get a 12V system. They generally are 200ah for the small ones.

You will need a charge controller and need to add water (distilled only) to the batteries on a monthly basis.

--

Any "permitted and inspected" systems you add to the house, add to the value. PV systems, with a design life of +25 years for the panels, will add a significant portion of their cost, to the value. I'd guess 80% of what you install

Try to install ASAP, before the tax breaks are gone. Even Solar Thermal for your hot water is good.

**Steve** · 07-18-2010, 12:44 AM

Thank you for the replies.

Regarding the plywood, do you have any other recommendations? If possible, could you point me in the direction to what you (Any reader here) consider the best built DIY PV frame you've seen for continuous outdoor duty? Possibly a link?

I understand the consideration of what is a "better" design is probably arbitrary from person to person, but the designs I've found on the web are mostly for very temporary installations, like panels hinged in the middle for easy fold-up and storage.

The battery tip was most helpful.

**Mike90250** · 07-18-2010, 11:27 AM

Another battery tip - Rubbermaid large storage containers, or garden benchs with underseat storage, are GREAT battery boxes.

**Steve** · 07-19-2010, 12:59 PM

I've been spending a lot of time on the web searching for different ways to construct a panel. I consider this the most promising:

Me and the Mrs. is going to a local glass company and price out four pieces of glass of 32 x 26" dimensions. Two sheets of tempered low lead glass and two regular window glass to construct two panels. I'll also see if they can get a large "O" ring seal just smaller than the diameter of the glass. The O' ring would be about 1/2" thick, watertight (Maybe rubber covered sponge). Also some aluminum U channel from the hardware store.

This is the plan:
1. Glue the string of panels onto the window glass with the usual dab of silicone.
2. Place the O ring on top of the window glass close to the edge and place the tempered glass on top.
3. Further adjust the seal into a proper position between the glass, just inside the edge.
4. Press the two panes of glass together, compressing the spongy O' ring seal between them and slide the aluminum frame on the edge.

Once the aluminum frame is in place it will retain the seal compression.

I may need to make a construction frame out of scrap wood and a simple lever to achieve proper compression between the two panes of glass while maintaining an even pressure, depending on the elasticity of the seal while assembling the frame on the edge.

Here's a simple graphic looking at a cut-away view of the glass edge:
Black = Aluminum channel
Cyan = Tempered glass
Red = rubber and foam seal
Green = Window glass

..........|//////////////////////|/|
/////////////////////////////////|/|
..............oOOOo.......|/|
...........OOOOOO.....|/|
.......OOOOOOOOO.|/|
...........OOOOOO.....|/|
..............oOOOo.......|/|
/////////////////////////////////|/|
..........|//////////////////////|/|

I could also put a small packet of moisture absorbing silica beads inside in case of humidity.
Also, maybe put a thin mylar strip in the aluminum channel to keep the glass off the metal.
I could completely disassemble it in the future if needed.

I think it might work.

**Mike90250** · 07-19-2010, 01:13 PM

usually, the seal is a flexible membrane fused to the back of the cells/front glass.

While an O ring will be OK, you will have pressure build in the sun, and suction in the cold winter nights. (as the air trapped inside expands and contracts) This will bow and flex the glass, and while that's fine with glass, the thin PV wafers and their wire leads will be flexed, and this is where breaks will occour. And, different O ring material is permable to water vapor, so I'd be inclined to use a nitrogen purge, and a dessiccant to help keep moisture down. Eventually, if water vapor gets in, it will condense, and drip and that will ruin the cells. Ever see a waterproof watch crystal get fogged up with water ?

**Steve** · 07-19-2010, 02:17 PM

Thanks for the expansion/contraction breakage tip. I didn't consider that.
Maybe the expansion/contraction (Bowing) will be minimal enough to facilitate a few years worth of operation.

I've tabbed all my cells but not soldered the string yet. The tabbing material is basically solid core wire. I've learned in past unrelated projects that when mechanical flex is to be expected on a solid core wire to leave the wire as long as possible and create an "S" pattern into it where the flex can be absorbed through several even bends, instead of all the mechanics focused on one particular spot which would form the breaking point.

I'll be sure to follow the same rule when I solder the string, leaving the tabbing wire long as possible to the back side of each cell and form several "S" shapes in the small space between the cells. Maybe form the curve of the S's around a small nail brad.
Two brads spaced about 1/8" apart put on the end of a stick would make a perfect forming jig.
It's a lot of work- but I have a lot of time at present and if it might extend their utility I'm willing to do it.

Batteries:
I found some golf cart batteries online- two 6 volt 200ah cells average around $300 each. I was able to find one vender with a marine type deep cycle gel cell rated 12v/200ah for cheaper. However it weighs 110lbs and I imagine shipping cost would be considerable.
I live near a major lake recreational resevoir so maybe I could find one locally.

I tested all my cells today in bright sunlight outside and all are 0.56v +/- a couple 0.03V.
This is a project me and the Mrs. is doing together. It's been a while since we've enjoyed a project so much.

**Mike90250** · 07-19-2010, 02:31 PM

Sounds like you have a realistic handle on the situation.

Golf cart batteries (6V 200A) are a good starter battery. 2 in series will give 12V, and they can take abuse, marine deep cycle batteries are not true deep cycle, because they are a 50% compromise of starter battery & deep cycle.

You never want to discharge below 80% (20% remaining) and seldom below 30%. (70% remain) That's why battery banks are generally large, the deeper the discharge cycles, the shorter the battery life.

You should be building your panels to produce about 18V, so that the charge controller can regulate it down to 16V for battery charging, and as they heat up, their voltage will drop a couple of %.

**Steve** · 07-24-2010, 12:47 PM

Things are moving right along with my project after a bit of a snag.

I've been looking online for batteries with the rating suggested here. I searched online and was getting disappointed- it seemed I'd need to spend around $500 to obtain 12V 200Ah deep cycle. I asked around town and found exactly what I've been searching for.

We bought two 6V 220Ah deep cycle golf cart batteries at Sam's Club, $79 each. Just perfect and within our solar budget.

I also found what is probably a good discovery.
We have a local glass company which specializes in stained glass products. We purchased 4 sheets of clear tempered glass 33x26x.25 to make two panels. I was having trouble finding a rubber seal and asked the glass company for suggestions.

In his usual business, he creates the stained glass assemblies and sandwitches it inbetween two regular clear glass panels. The panels are hermetically sealed using a special rubber compound which removes all moisture from the air between the glass. He says it's completely air tight, permanent and has no problem doing the same for me. He showed me an example and it appears to be exactly what I need.

He had to order the glass for pickup in a couple days and does the sealing in his shop. Four sheets of tempered glass with .25x.25 hermetic seal came to about $220. I don't mind the extra cost, I expect this tempered glass system to outlast a plexiglass and plywood box and won't have to do all the painting/sealing/caulking/gluing. I will only need to add an aluminum U-channel frame.

In the mean time I've put a strain-relieving tripple curve into every cell's tab wire to try and avoid the breakage problem previously posted. I've soldered the strings of 9 cells each and temporarily laid them out on a wooden board.
I've wired them as they would two panels in parallel. Output is 19.5v unloaded and 7amps shorted in full sunlight. I expect it to be less once they are sealed within the glass.

I got one of those 750-1100(P) amp AC inverters for a test run last night.
I was able to run these devices for around 4.5 hours using only battery power:

1. Inverter rated at 10% power loss
2. Fan 50W
3. Desktop computer 60W
4. 20" Gateway CRT monitor 72W
5. Yamaha audio amp playing music 18W

It was drawing about 1.6 amps for everything combined using one of those plug-in consumption meters.

The inverter has a low level alarm which went off @ 11.7 volts measured with my digital VOM at the battery and that's where I ended my experiment last night.

Today I put my cells back into sunlight and have them recharging the batteries. I'm still looking for a good deal on a charge controller so I'll need to monitor the progress. The batteries delivered 12.5v when they were full from the store while running the inverter with a 50w load so that's where I'll stop charging until I get the controller.

I had some time last night to mess around on the computer, trying to figure out a cheap and easy way to mount the panels outside.
We have some outside light posts we hope to power along with my back yard workshop building which is now powerless. I have a number of typical power tools (Drillpress, grinders etc) within the workshop. The building itself is positioned inside the woods and not suitable to put the PV system there. We also hope to have the power available in case of grid outage.
If my system proves workable, we hope to expand to 6-8 panels.

After brainstorming a number of (Sometimes ridiculous) mounting schemes this is what I came up on the computer last night:

The battery box would be a rubbermaid container next to the door on the deck. (Not shown) I'd cover the support framing with vinyl lattice for appearance.

The lower side of the panel supporting frame would be hinged, and the upper side is supported by a pair of almost vertical wood (2x4) beams which can be adjusted up/down to adjust the panel angle. (Not easily seen in these renders)
The panels would be easy to clean while standing on the deck.

This is moving right along.

**Steve** · 07-25-2010, 03:34 PM

I've had some successes and some major drawbacks.

The successes are learning as much as possible about lead acid batteries. What they're made of, how to charge, what "Floating" means and understanding internally what happens if abused by under or over charging. I spent the whole day yesterday reading about this for a good understanding along with Amp hour calculations and what I can expect out of my batteries and how to test them.

I expect my glass to be ready tomorrow and I did a major blunder trying to get prepared beforehand.

I watched countless YouTube videos about how to tab solar cells before doing so myself. When it was my turn, I ended up making lots of annoying fingerprints on the cells from the flux. I don't think the flux was harmful but unsightly.

I recall a couple videos where it was suggested rubbing alcohol safely removes fingerprints from the cells. So I cleaned one cell out of my array with alcohol to test. The cell lost it's deep blue tint and any gloss was removed. Thinking I destroyed the cell, I tested it and still delivered the normal 0.6v.

So I cleaned all 72 of my cells in the same manner.

Me and the wife used the batteries last night to run two CFL's and drained the batteries down to 11.8v before disconnecting. This morning I put my board of cells out into the sunlight and took a reading.

They deliver 19V as expected like they did yesterday but only deliver 4 Amps shorted instead of 6.
That's about 33% power drop!

DON'T DO STUPID THINGS LIKE CLEAN MULTI CRYSTALLINE CELLS WITH ALCOHOL!

Now I am contemplating whether or not to toss the lot out or keep them. It represents a lot of time (and money) and once they're sealed within the glass it's done. They still deliver the correct voltage, and if I can be sure they won't further degrade I'll probably still use them. We will be adding another 2 panels next month. I have learned a lot, and how to avoid the fingerprints all together next time.

Ever done something you wish you could scroll back time and yell at yourself? This is one of those "Kick yourself in the head" moments for me.

In the mean time I've improved my panel mounting design. I was also studying the correct panel N-S panel angle and was shocked that my angle will vary between 30 and 80 degrees according to this and other sources for Atlanta Georgia:
Solar angle calculator

80 Degrees seems so radical it's hard to believe. But I changed my mounting design accordingly, making the center of the panel hinged at the center balancing point instead of the end. All the weight would then be transferred to the two vertical posts and easy to adjust angle for the season. It's a more solid design.

The picture below represents 30 to 80 degrees movement. I never realized N-S sun position was so extreme.

Starting off small scale

Starting off small scale

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