If you are looking to buy a solar power system and have done any kind of research on the web, then you have probably come across lots of people arguing over the pros and cons of Thin Film Solar Panels compared to the more common monocrystalline or polycrystalline solar panels. In a nutshell, there are 3 major types of solar panel technology on the market:
It seems a lot of people are firmly in either the “Crystalline” or “Thin-Film” camp. And when discussing which panel is best, they can easily lose their objectivity with arguments along the lines of “Thin Film is the only way to go” or “Mono Crystalline and Poly Crystalline are junk!”.
I like to think I’m a bit more objective that that (although by the title of this post you can probably see that I do have an opinion!) so here is my rundown of both the pros and cons of thin film solar panels.
Problem #1 Very Low Efficiency Means You Need A Huge Roof
A thin film solar panel is typically half the efficiency of a monocrystalline or poly crystalline solar panel.
Now – if you have a north facing 35 degree roof the size of a 747 hangar – no problem!
But most people have limited space on their roofs (especially their North facing roofs), so doubling the amount of space you need for a solar system will be an issue.
And I would argue that as panel prices come down to offer cheaper electricity than the grid, that roof space is going to become an even more valuable resource. I can see a lot of people who have filled up their prime roof space with enourmous thin film solar panels having to rip them off and replace them with monocrystalline panels in a few years so that they can get enough cheap solar energy to wipe out their reliance on ever more expensive electricity from the grid (officially forecast to rise 37% by 2014).
You gotta feel for those people who were sweet talked by the Solar Shop salesperson in to filling their entire roofspace with 17 huge, square, brown Kaneka solar panels only to get a measly 1kW of power!
Problem: Thin film solar panels take up twice the roof space for the same power output.
Solution: Rent an aircraft hangar?
Problem #2 Immature Technology
I get angry emails from solar installers all the time for saying this. But the truth is that the current manufaacturing process for thin film panels has not been around for more than 10 years.
But they promise you that they will last 25 years plus.
How the @#$% can they promise that?
If you are buying thin film solar panels – please be aware that the long term performance of them is not as certain as monocrystalline or polycrystalline solar panels.
Problem: Thin film panel technology is less proven in the long term than mono or poly panels.
Solution: Get a cast iron performance guarantee from the manufacturer (Not the vendor – remember those poor Solar Shop customers…)
Problem #3 Nasty Manufacturing Process
The manufacturing process to make all solar panel types uses some pretty nasty chemicals. But thin film panels require a lot more chemicals that are a lot more nasty. And, to my knowledge, no one can guarantee that the cadmium (incredibly evil chemical) won’t leak out if a panel is cracked or damaged.
I’m a pretty pragmatic guy – but I would never collect water from a roof with thin film solar panels on it for that reason.
Problem: Evil chemicals used in the manufacturing process.
Solution 1 : Only buy solar panels from a company that get a good rap from these guys who score PV manufacturers based on how they deal with toxic waste.
Solution 2: Don’t collect water from a roof with thin film solar on it.
Problem #4 They are peddled as “shade tolerant”.
I gotta be honest with you – it is not just the smooth talking, commissioned salesmen that use the oxymoron that is “shade tolerant solar panels”. I’ve heard some guys I really respect in the solar industry come out with this bull.
A shade tolerant solar panel is kind of like a sun-tolerant ice sculpture…. No such thing my friend!
Solar needs sun. If you have shade on your solar panel, you don’t get power. If you have a location with shade issues, don’t put solar there.
I think what the guys who should know better really mean to say is that thin film have better “low light performance”. This means that their power output is slightly better when the sunlight is not 100% direct due to light cloud or haze. It does not mean that they will produce power when shaded!
Problem: People get thin film solar installed in totally inappropriate areas because they’ve been told that they are shade tolerant. The result is they are very disappointed with the power output because no sun = no power.
Solution: Get a full shade analysis done if you have any shade on your roof. And only get solar if the analysis shows it is worth it. Thin film panels are not going to help.
Problem #5 Higher Install Cost
Because thin film solar panels are so much bigger than crystalline ones for the same power, you generally are going to need many more panels on your roof. This means more work for your installers and much more mounting hardware, resulting in a much higher install cost – which usually more than makes up for the slightly chapter cost-per-watt of the thin film solar panels compared to mono crystalline.
In fact Home Power Magazine (#127) compared a 3kW install done with Kaneka Thin Film Panels, to one done with Sharp Crystalline panels. They worked out the the Kaneka install would require 345 feet of racking and 129 attachment points compared to just 102 feet and 40 attachment points for the Sharp Crystalline Panels. On top of all that extra hardware, the installation labour cost for the Kaneka thin film panels would be $4600 compared to $3,400 for the solar installation using Sharp crystalline panels.
And if you are worried about the embodied energy of your system and are considering thin film panels because they use less energy to manufacture – then please consider how much energy is needed to make all that extra aluminium and steel racking and mounting hardware!
So now I’ve given thin film solar a good beating, in the interest of balance here are the advantages of Thin Film solar:
1) Slightly better performance in low light conditions (not really relevant in most of Australia due to our super strong sun)
2) Slightly cheaper than monocrystalline solar panels per Watt (in theory). However the recent huge price drops in monocrystalline panels mean that in December 2011 this isn’t true any more.
3) Lower embodied energy per panel. They need less energy to make because they contain very little silicon (which is melted sand).
4) It has the potential to be applied to flexible surfaces and even sprayed onto walls in the future.
5) Slightly better performance in high temperatures. For example if you look at our solar panel comparison tool, and filter by panel type you can see that the best performing thin film panel (First Solar FS-272) has a performance ratio of 96.28%. The best performing mono crystalline panel (Sunpower SPR-318E-WHT-D) has a performance ratio of 92.11%. The difference is down to the temperature coefficients of the panels, so you can expect your thin film solar panels to get about 4% more power in hot Australian conditions. Does 4% more power make up for the disadvantages? Your call!
Finally there are lots of new technologies appearing in the thin film space, that have the potential to fix a lot of the disadvantages I’ve listed here. These include CIGS (Copper Indium Gallium (di)Selenide) and CdTe (Cadmium Telluride) technologies, and at the rate they are progressing may soon match crystalline solar panels for efficiency.
But, in summary I’m going to keep recommending Mono or Poly Crystalline Solar Panels for residential installs, based on the current state of solar technology.
What do you think? Am I being harsh on thin film? Have I missed a huge advantage? If so please let rip in the comments below…