A couple of ideas on keeping panels moisture free

[bigsmile]

It looks to me that the most important thing to prolong the lifetime of DIY panels is to keep moisture out. Here I have a couple of ideas of achieving that at relatively low cost, and I'd like to hear what you think about it.

1. Use Sylgard 184 only between the cells and the front panel glass. On the back, use cheaper silicone. The combination of Sylgard 184 and cheap silicone form the encapsulation.

2. Use cheap silicone to seal the back of the cells, but before doing this, put some silica gel along the edge of the cells so that it will absorb the moisture that's trapped between the cell and the glass.

[bigsmile]

A refinement to the second idea is that when seal the cells with silicone, leave a few holes along the edge. These holes are connected to the air chamber between the front glass and the cells. Later, put thin rigid pipes through these holes. These pipes connect all the panels in an array. Then seal the holes with silicone. This is for the purpose of connecting all the air chambers in all the panels into one connected body of air, so that it is easy to regulate later on.

A valve can be added. This valve will be opened when a day starts to get hot, then closed a few hours later when it's about the hottest. When the day cools down, the now sealed air space will create low pressure, and thus make it hard for condensation to form.

Or two valves can be added, so that the air in the panels can be forced ventilated periodically.

A potential problem is that the low pressure may crash some cells. I'm not sure how likely is this.

[bigsmile]

A little update on the idea in my previous post. I did a little calculation it seems that the reduction in pressure at night fall may not be enough to compensate for the reduction of rh and it may still fall below dew point even at low the pressure caused by cooling, and thus condensation may still occur.

[longwolf]

The problem with regular silicons is that they made with a solvent that will damage the cells, including the back side

[Sunking]

The problem you are going to run into like it or not, if you make a DIY panel, it will fail in 1 to 4 years. DIY panels are great high school science fair projects to inspire students, but on a practical scale useless and to expensive. What is the point of building a panel that will cost you around $1.50 per watt to build yourself and guaranteed to fail in a few years, when for $2 per watt or less you can buy a UL certified panel (meaning you can actually use it in your home wiring) with a 20 year warranty. I say a manufactured panel is a far superior valued and quality.

[bigsmile]

I have seen at least 2 diy projects that haven't show significant sign of failing after 1 year on this site, and I'm new here.

The problem you are going to run into like it or not, if you make a DIY panel, it will fail in 1 to 4 years. DIY panels are great high school science fair projects to inspire students, but on a practical scale useless and to expensive. What is the point of building a panel that will cost you around $1.50 per watt to build yourself and guaranteed to fail in a few years, when for $2 per watt or less you can buy a UL certified panel (meaning you can actually use it in your home wiring) with a 20 year warranty. I say a manufactured panel is a far superior valued and quality.

[russ]

I am sure some DIY panels do survive but on the whole you can expect problems over time.

Add to that the insurance problem if the unit manages to cause a fire

Add to that the present cost of panels (at or below 2 USD/watt

Is it worth it - outside of being a fun project.

Better to save money on the racks and balance of the installation if possible.

[bigsmile]

My situation is that it's either cheap DIY solar or no solar. As cheap as the $2/watt price tag may sound, that spells around a 10 year payback period, and while still OK, I don't consider it worth sacrificing all the yard space (my roof is east/west sloped). So if my research on feasible homemade solar panel ended empty handed, then I will just wait for the price to go further down before jumping in. That is why I'm thinking so hard about reducing the cost of encapsulation.

I am sure some DIY panels do survive but on the whole you can expect problems over time.

Add to that the insurance problem if the unit manages to cause a fire

Add to that the present cost of panels (at or below 2 USD/watt

Is it worth it - outside of being a fun project.

Better to save money on the racks and balance of the installation if possible.

[Sizz]

Unfortunately, there is just not enough data on how long a silicone encapsulated cell will last. It appears to be the best chance of success for diy'ers but it's still a gamble.

I don't like the idea of holes and valves. Ideally, you want to completely isolate the cells and that's going in the wrong direction. I think the best option is to encapsulate cells with silicone and add a backing layer of glass or aluminum. The only path of water vapor getting in would be from the edges which would still have to permeate through the silicone. I think if desiccant were needed to help absorb moisture, you're screwed anyway.

I believe I found a cheaper encapsulate, similar properties to sylgard but half the price. Awaiting testing to confirm.....

[bigsmile]

I read a paper titled "Control of Moisture Ingress into Photovoltaic Modules" from a link on this site. Based on what I read, moisture seeps through sealants like Slygard 184 or even EVA rather easily. Despite this fact, commercial panels still have very long lifetime. This makes me think that the purpose of the encapsulation is not to keep moisture out, since water molecules will get in after a couple of years anyway, but to prevent condensation. Water molecules in EVA won't do much damage, since, I guess, EVA with water molecules in it is still very much non-conductive.

Condensation needs a surface to form. Encapsulation deprives such a surface. Water molecules won't have the joy of forming liquid water on the surface of the cells. And no liquid water, no damage. I suspect the degradation of commercial panel comes more from delamination, which will expose the surface of the cell, than from water seepage into EVA over the years.

With this thought, I think edge sealing the panel with the hope of creating a completely airtight space should be abandoned, since that's extremely hard. Hard as you try the air within could be as wet as the outside air within a couple of days or months at best. The most important thing is to make sure the surfaces of the cells are not exposed to air.

Now I come up with another idea. How about sealing the 2 glass panels with silicone, and then fill the space with clear, non conductive liquid? There are a couple of benefits with this. First, it may be easier to remove air bubble if the liquid is very thin. Second, there will be no delamination concern. So, panel made this way may have a chance to even outlive commercial panels.

[Mike90250]

one of the Dow fluorinert types come to mind. Clear, thin, non reactive till 400F. Only about $200 per quart.

[bigsmile]

How about this

http://www.performance-pcs.com/catalog/index.php?main_page=product_info&products_id=3980

PrimoChill ICE Non-Conductive Liquid Cooling Fluid, $15 for 32 oz.

one of the Dow fluorinert types come to mind. Clear, thin, non reactive till 400F. Only about $200 per quart.

[Sunking]

Sigh, some people just do not get it like the Captain of the Titanic an hour after hitting an iceberg and saying:

Do not panic I am in charge, this ship is unsinkable.

[bigsmile]

And another candidate: good old mineral oil.

[bigsmile]

There is a point that I forgot to make when I replied Sizz. It's really unfair to blame DIY solar panels for fire hazard, considering that there were many cases of fire caused by commercial panels installed professionally. If you think about it, it really hard to imagine how doing it yourself increase fire risk, except that DIYers tend to use wood. But the thing is, if the panel is hot enough to burn wood, using wood really isn't the root of the problem. It's not supposed to be that hot in the first place.

Which part of the panel tend to be over heat? When you start to think about it, it's hard to think of any DIY factor that can be responsible, if commercial tab wires, buses, junction boxes, connectors, and so on are used. Actually, it's been reported that BP junction box may be responsible for many of the fire accidents.

When I hear such accidents, be it DIY or professional made, I tend to think about what's the cause of the fire and how it can be avoided. That's more important. A correctly installed system, no matter who does it, is not supposed to burn.