# Flexible Solar Cells



## IamIan (Mar 29, 2009)

PZigouras said:


> Has anyone tried those new "flexible" solar cells?
> 
> And how do they make the panels flexible? If they are crystaline cells, then won't they crack as well?


There are some variations in the 'how' question .. but in short , some are not crystalline ... these can be very durable ... some will not crack ... they can still be damaged and stop working ... but some of them can take allot of flexing and allot of punishment.

Don't forget the roll the adhesive will play as well ... the adhesive will also have to allow for flexing ... if the adhesive cures ridged, it will impair the ability of the flexible cells to flex.

Now for the bad ... 
The flexible cells are significantly more expensive $ per watt of power.

The flexible cells are significantly less efficient and will produce less electrical energy under the same conditions and coverage. 

Many of the flexible cells degrade much faster over time than the crystalline variations do... so 20 or so years from now don't expect the same kind of 80% initial power output many of the crystalline style cells offer.

So there will be a trade off.

Are there specific flexible cells you are looking at?


----------



## PZigouras (Jun 5, 2010)

Here's what I don't understand...

I know that thin film cells can easily be made into flexible materials, because they are essentially sprayed on (there's more to it than that, but...)

The problem is that thin film isn't worth using on cars because the efficiency is extremely low (maybe 7% ???) and would not even make a difference for your batteries. Now take a look at these:

http://cgi.ebay.com/NEW-80W-Flexible-Mono-Solar-Panel-12V-Battery-Charge-/130486935588

These are monocrystaline cells, but they are flexible. Now, from what I see, they are basically the same type of crystaline cells that I have on my car. How come those give a little, and mine wont? I tested the epoxy, and it gave a lot more than the cells did. It didn't snap until well after the cell did.


----------



## zaxxon (Jul 11, 2009)

How well were they sealed. Is it possible water seeped in under the cell and froze breaking out the cell area? Also wonder if the issue could be the uneven application of a hard epoxy and thermal expansion of the under laying metal that caused the cells to crack. 

I would be skeptical of the flexibility implied in the picture if the cells used are Monocrystalline. The majority of flex would be between the cells not the actual cells. I think they mean they are encapsulated in a flexible medium.


----------



## IamIan (Mar 29, 2009)

PZigouras said:


> The problem is that thin film isn't worth using on cars because the efficiency is extremely low (maybe 7% ???) and would not even make a difference for your batteries. Now take a look at these:
> 
> http://cgi.ebay.com/NEW-80W-Flexible-Mono-Solar-Panel-12V-Battery-Charge-/130486935588


From the pictures ... it looks to me like the cells are ridged , and the panel flexes at the joints between cells... so the panel is flexible but not the cells themselves... But some of the usual details are missing ... like power warranty information ... craftsmanship warranty information ... amount of flex tolerance , etc ... You can always write them and ask for more details... but without additional details I would not risk the ~$433 for 80 Watts ... ~$5.41 / watt is not particularly good.

I agree the true flexible cells are low efficiency , high cost , high degradation.... but high flexibility and high durability... it is a trade off.


----------



## PZigouras (Jun 5, 2010)

IamIan said:


> From the pictures ... it looks to me like the cells are ridged , and the panel flexes at the joints between cells... so the panel is flexible but not the cells themselves... But some of the usual details are missing ... like power warranty information ... craftsmanship warranty information ... amount of flex tolerance , etc ... You can always write them and ask for more details... but without additional details I would not risk the ~$433 for 80 Watts ... ~$5.41 / watt is not particularly good.
> 
> I agree the true flexible cells are low efficiency , high cost , high degradation.... but high flexibility and high durability... it is a trade off.


From what the ebay picture shows, the cells are actually bending with the lamination.... which seems strange, because crystal cells do not bend very much (without braking).

I could try to do the same thing... put a very thick coat of clear on. The urathane auto enamel I used is very thin..... I think if I had used a heavier enamel and applied it thicker, they may have flexed with the hood instead of cracking. 

I think what really killed it was that it rained after the 1+ foot of snow we got that day. The snow, soaked with rain, was extremely heavy... there must have been at least 400 pounds of snow on that hood -- no joke. Normally, it either rains or snows, but not both.


----------



## IamIan (Mar 29, 2009)

PZigouras said:


> I could try to do the same thing... put a very thick coat of clear on. The urathane auto enamel I used is very thin..... I think if I had used a heavier enamel and applied it thicker, they may have flexed with the hood instead of cracking.


That would help distribute the force over the cell better ... but will still give at the weakest point

Probably best to test a bit on some of your broken cells to see how much improvement you can get... before investing in the idea to any large amount of $.

I don't see significant flexing of the cells themselves in their ebay pictures or on their main web site page ... but that is just my point of view.


----------



## JRP3 (Mar 7, 2008)

The answer may be to put reinforcing under your hood to stiffen it.


----------



## PZigouras (Jun 5, 2010)

JRP3 said:


> The answer may be to put reinforcing under your hood to stiffen it.


I know, I though of that but it's a shame that you have to stiffen a stock hood.... you think they would have built it to withstand the elements from the factory 

Although you can't really tell in the pictures, the hood itself DID get permanently warped from the weight of the snow. Dang shame.

On the flip side, the cells are pretty cheap... about $2 each. I've broken them before (by accident), but never that many at the same time! I think a really, really, really heavy coat of clear may help.


----------



## Kelmark (Oct 26, 2009)

PZigouras

I like the idea of incorporating solar cells to my project and interested in how this turns out as far as the best way to install and seal the cells on top of a car.

I was thinking of just running them to the 12v aux battery to reduce the power through dc to dc conversion and in affect draw less power from my main pack. I would be interested in the results you have seen in real world application and where you purchase your cells.


----------



## Snakub (Sep 8, 2008)

> PZigouras
> 
> I like the idea of incorporating solar cells to my project and interested in how this turns out as far as the best way to install and seal the cells on top of a car.
> 
> I was thinking of just running them to the 12v aux battery to reduce the power through dc to dc conversion and in affect draw less power from my main pack. I would be interested in the results you have seen in real world application and where you purchase your cells.


Are your solar cells powering your 12 volt battery or traction pack?


----------



## PZigouras (Jun 5, 2010)

I use 48 cells (24 x 2 in parallel) in this car to charge my 12V accessory battery. I actually never have to plug in the 12V charger, because it gets almost 100 watts continuously when I park it outside. 

My Explorer has 150 cells (about 80 volts total) that charge my 144V primary battery pack. I push the 80V into a low frequency 2;1 transformer then rectify it to get about 160V worth of charge. There's no charge controller so, in theory, it could someday overcharge the pack, but that'll take weeks.... so I'm not worried about it. Plus they are flooded batteries, so I don't think they really care too much about a few extra volts.

- Paul


----------



## Harold in CR (Sep 8, 2008)

There are flexible panels that roll up, like a roll of paper. 

Also, New design of Roofing Shingle have cells in them. Plug and play so I am told. No links, no proof. Do a Google.


----------



## spdas (Nov 28, 2009)

Harold in CR said:


> There are flexible panels that roll up, like a roll of paper.
> 
> Also, New design of Roofing Shingle have cells in them. Plug and play so I am told. No links, no proof. Do a Google.


These flexible rollups are very low efficiency. And actually using any solar cell is not really worth it for a car. EXCEPT the bragging rights as you can very easily convince passersby that the solar cell contributes A LOT to running the EV and they also will assume you are running for free.

Francis


----------



## PZigouras (Jun 5, 2010)

spdas said:


> These flexible rollups are very low efficiency. And actually using any solar cell is not really worth it for a car. EXCEPT the bragging rights as you can very easily convince passersby that the solar cell contributes A LOT to running the EV and they also will assume you are running for free.
> 
> Francis


I disagree that they have no practical uses. It my case, it eliminated the need for a DC-DC converter, and I never really have to plug in the 12V vehicle battery.

As far as range goes, an extra 100 watts obviously will not help any... but for some people, it can help in other ways. For example, if you keep your car parked outside while you're at work, even 100 watts will help... especially if you are parked there all day (9 hours, for me). 

Speaking of range, I will soon be upgrading my friend's 1998 Suburban with solar cells, in hopes that it will boost his range. Our goal is to install 1 kW worth of cells on the truck. We did the math and we cannot hit that figure with just the roof (not enough surface area), but I am hoping that if we add in the hood, we may just hit 1000 watts. The hood on that truck is massive, so I'm hoping we can get at least close to that. I'm also hoping that we can match the array's voltage with his battery pack, to eliminate the need for a transformer.

This is my biggest project yet, and I will post pictures as we go along. If this works, I'm sure that the 1kW of continuous power will at least boost the range a little.... but there's only one way to find out!


----------



## rfhendrix (Jan 24, 2011)

PZigouras said:


> I disagree that they have no practical uses. It my case, it eliminated the need for a DC-DC converter, and I never really have to plug in the 12V vehicle battery.
> 
> As far as range goes, an extra 100 watts obviously will not help any... but for some people, it can help in other ways. For example, if you keep your car parked outside while you're at work, even 100 watts will help... especially if you are parked there all day (9 hours, for me).
> 
> ...


Keep us informed. I can fit 1000 watts on the rack of my Ranger so I know it is possible. I bet that Suburban is heavy.


----------



## spdas (Nov 28, 2009)

Don't get me wrong, I am a solar guy and off the grid and have 109 x 195Watt panels, 9 charge controllers, 3 inverters, running my welding/fabricating shop and plan to charge my EV Yaris with solar. 

But for me my 144v pack charges up the Aux Battery through the Dc/Dc converter and I will have a small solar panel on the dash to keep the Aux battery feeding electrons to the clock and misc stuff when parked. I figured it was such a trade-off sacrificing the Aerodynamics of the EV by mounting large panels and so little to gain.

Francis


----------



## rfhendrix (Jan 24, 2011)

Here is something that seemed to work for short trips:

http://evalbum.austinev.org/838

According to their website:

"From June to November 2000, 2001 and 2002 the SBB traveled an average of 50-80 miles per week using only energy gained directly from the sun (about 10-15 miles of free driving per day). It cost literally nothing to drive and produced virtually no air pollution for a period of six months each year."


----------



## Peterp (Mar 7, 2011)

flexible solar cells are a great new technology. Im loving how the solar energy generation technology just keeps advancing, and not only getting better but getting cheaper too. For starters it was the regular solar panel, then its the solar concentrators, then also the portable solar panels, for camping and such, and now thin film panels that can be moulded to fit all sorts of interesting new applications. Whats next?


----------



## aeroscott (Jan 5, 2008)

I was thinking of a 1kw array on my ranger . at 5.9 hours/day yearly average sun at full power . 10 days would be a full charge (50kwh). better in summer and much less in the dead of winter . thinking of glued on clear coated monocrystalline cells with a fold-out set to augment output . cell weight is not much with out glass .


----------



## rfhendrix (Jan 24, 2011)

aeroscott said:


> I was thinking of a 1kw array on my ranger . at 5.9 hours/day yearly average sun at full power . 10 days would be a full charge (50kwh). better in summer and much less in the dead of winter . thinking of glued on clear coated monocrystalline cells with a fold-out set to augment output . cell weight is not much with out glass .


 I didn't think of a fold out set. I live in southern California so I hate to see all that sun go to waste. With my 5 mile commute 4 days a week I think that I would be (mostly) self sufficient even if the power goes out.


----------



## aeroscott (Jan 5, 2008)

fold out might not work in a crowded parking lot , unless going vertical . I was heating the glass on a broken solar panel comes loose at about 250f. and noticed how incredible the cells look . The color shifting iridescence are so cool .Just need a way to protect them as in clear coat that lasts or is easily replaced .


----------



## CFreeman54 (Jan 14, 2009)

Look into a thin coat of epoxy resin.....I don't remember what efficiency loss you will get from this....of course the thinner the coat the less light is blocked.


----------



## JRP3 (Mar 7, 2008)

Many epoxy resins break down in sunlight without another protective coating over them. There may be better alternatives.


----------



## aeroscott (Jan 5, 2008)

UV epoxy would have better sun life but may loose to much power. Tefzel is what they coated the Prius cells with .


----------



## PZigouras (Jun 5, 2010)

JRP3 said:


> Many epoxy resins break down in sunlight without another protective coating over them. There may be better alternatives.


 
I don't think the epoxy in the back was an issue, because the cell itself blocks almost all the sunlight from hitting the epoxy. I think the encapsulation (top coat) was a bigger issue.

I only sprayed the equivillant of ONE layer of clear coat over the cells, so they were not encapsulated really well. I have a feeling that if I had sprayed a very thick layer... maybe 3 to 4 coats, they may have flexed with the hood and not broken. 

I tested this out today by putting several layers of clear tape on both sides of a cell, then bending it. Although it did eventually crack, it flexed MUCH more than a regular cell, which crumbled almost immediately. I am going to re-coat the rest of my cells after I replace the broken ones.

One more thing... if anyone is going to try this, be aware that MOST automotive clear-coat has UV protection built-in, and I think that you should NOT use those. They do make non-UV clear coat, but it's hard to find... make sure you ask. I'm sure the UV-protection blocks out a good chunk of the spectrum, not just UV.


- Paul


----------



## JRP3 (Mar 7, 2008)

Yes I was talking about the top coat. As to auto clear coat, the clear coat without UV inhibitors may also yellow and break down. Look into that before you apply it. I would not expect a thin layer of resin of any type to add much strength to the cells, thicker coats tend to be less flexible, not more. Bottom line is if the cells don't respond well to flexing the answer is to reinforce the substrate to reduce the amount of flexing. Stiffen up that hood.


----------



## aeroscott (Jan 5, 2008)

just found Tefzel $$ 36" x 300" (25') .001" for $437.00 . also called ETFE and A CLZ treated for bonding one side . how about rattle can of clear lacquer non uv .


----------



## JRP3 (Mar 7, 2008)

If it's non UV it will probably break down. It also won't add any strength.


----------



## PZigouras (Jun 5, 2010)

Since the snow actually collapsed part of the hood itself, strengthening the hood goes without saying. 

Funny thing is, when I stood on my old 1984 Firebird's steel hood, I caved it in. When I replaced it with a fiberglass hood, believe it or not, I could actually stand on it just fine. I think I may wind up going with a glass hood and then stiffening it up a bit... it will still weigh less than the stock hood, with less flex.

I believe it was a GlassTek hood... very well-made


----------



## rfhendrix (Jan 24, 2011)

What do you all use for a charge controller? I was going to build an array of six 24V panels but how do you control that into the battery pack? Do you have to convert it to AC?


----------



## Ziggythewiz (May 16, 2010)

rfhendrix said:


> What do you all use for a charge controller? I was going to build an array of six 24V panels but how do you control that into the battery pack? Do you have to convert it to AC?


You shouldn't need a controller unless you plan to park with a full battery. Is your pack 144V? If so are these 24V nominal panels or 24V open circuit?


----------



## rfhendrix (Jan 24, 2011)

Ziggythewiz said:


> You shouldn't need a controller unless you plan to park with a full battery. Is your pack 144V? If so are these 24V nominal panels or 24V open circuit?


I haven't bought the panels. Still shopping. The pack will be 144 volt. So do you just wire the panels in series to get 144 and then directly into the battery pack?


----------



## Ziggythewiz (May 16, 2010)

rfhendrix said:


> I haven't bought the panels. Still shopping. The pack will be 144 volt. So do you just wire the panels in series to get 144 and then directly into the battery pack?


Just like your charger puts out more than than 144 to charge to that level, you'll need more than that for your panels, plus even more to accout for less than peak sun. Standard is to size it at 16-18V for 12V nominal, so in your case that would be 192-216V. Can you fit that much?

That's one of the tricky parts I haven't figured out for mine yet, my pack is 120V, but I only have a VW Bug's roof and hood space to work with. I need some smaller cells (I have 3x6's) or high voltage flexibles.


----------



## aeroscott (Jan 5, 2008)

I hooked up 700watts of 32v panels to my charge controller ( trace C40 DVM) on the 12v system . The panels just pull down to the battery voltage . In this case you loose the amperage of splitting the voltage and doubling the amps . Back to the point all you need is a low voltage and high voltage cutout .


----------

