Solar Components 101
All about Solar Racking
Solar modules are the 'face' of solar. On this page I've 'dumped' (and will continue to dump) everything I know about solar modules.
How big are they? How much do they weigh. Are they fragile? What's the difference between mono and poly? Why do some have silver frames and others are black? Can I just buy a few and then put mirrors around them? What's the warranty? Where are they made? How the heck do you get them up to the roof? How often do I need to clean them? Can I wire them directly to my pool pump? How long will they last?
If you've got a question about modules that you didn't get answered shoot me a message. Blue Skies, Jeff
Physical characteristics of modules
Ok with regards to do it yourself solar here's what you need to know. Almost all modules are ABOUT 3' x 5' (really 40" x 65") So this is ABOUT 15sqft per module. This is useful when thinking about; Will they fit? How big is my array going to be? The higher wattage panels in the 300's are usually taller like 75". They all weigh about 40-50lbs. Most of that is the glass. The glass is tempered. So if it breaks you get 100's of little pieces like when someone breaks into your side car window. You don't get big shards like a storefront window. The pieces are held together from the laminates, think of car windshield. They are pretty tough. Think about it they are installed in all the climates all over the world. You think manufacturers want to replace 1,000's of mods every year due to hail? I read somewhere they are tested by dropping a 1"steel ball from 10'. I'm not sure I could handle that.
Construction: The frame is made of aluminum it's is either anodized black or clear. With clear you get, duh, silver frames. Black is currently the pop-culture favorite, back in the 80's we'd all be McLovin the silver. You can save $ by going with silver. If looks are not important to you a high wattage silver frame is for you. If your array is going right over your front door in your track home all black is probably the best for you. "All black"? The solar cells are all placed on a backsheet (by robots not Chinese children working for $1/month). This back sheet can be either white or black. Black absorbs more heat than white. Heat causes resistance in electrical circuits. The same exact module will produce about 5 more Watts given a white backsheet. Multiply that by 30 modules and you just got yourself 150Watts. Almost another module. And you paid less. But hey we are Americans and aesthetics trump performance most of the time.
In the next section I will take about the cells.
Solar Cells -
Building blocks of modules
Have you ever noticed some modules have little white "diamonds". This is due to the shape of the ingot from which the wafer was sliced. See pictures. The white is just the backsheet that's not covered by the cell. Tada! Diamonds. As you surf the internet you'll see modules reference to as 60 cell and 72 cell. Given that each cell produces about .5 VDC (under load) or 60 cell mods all put otu ABOUT 30VDC and the larger 72 cell mods produce ABOUT 36VDC. The 60 cell mods are usually 6 x 10 and the 72's are 6 x 12. Hence the extra length of the module.
What does this all mean to you the DIY'er? Not much. There was a time when enphase microinverters couldn't accept the higher voltage and higher wattage but they're all compatible now. Another take-away is don't believe the marketing hype of some distributor claiming 72 cell are better. It's of no relevance.
Monocrstalline vs Polycrystalline
The best way I can explain the difference between poly and mono is this; do you know what OSB is? Oriented strand board. It's like plywood. It looks like the stuff off the lumber yard floor swept into a press and squeezed together. Poly-meaning 'many' is like OSB. It even resembles OSB. Mono - meaning 'one' is more like melamine wood. Very smooth. Homogeneous. Now envision yourself the size of an ant on a little tiny bicycle. Its easy to see how much extra effort would be required riding across OSB vs melamine. This is similiar to that electron that is knocked off by a direct hit from a photon traveling 93 million miles to your roof. See those two 'thick silver' lines those are the super highways for the electricity (electrons in motion) See those numerous thin silver liens? Those are the surface streets that feed the highway. First the electron must travel across the cell to get to the street. The more energy spent getting there the less energy delivered to your inverter.
So bottom line is; mono - is more efficient and poly is less. And yes, you probably guessed mono is more expensive and poly is less.
Real bottom line - Is it worth the extra cost? Should you believe the hype? I don't drink the mono juice. I look at what's the cost for the system and what's it's estimated output over the year. If you have limited space a mono may be the best choice to maximize your solar harvest. Here's a great blog post about poly vs mono from Dec 2014
NOTE: The pictures I chose here are OLD modules. Advancements in manufacturing have led to poly's that are black and hard to tell the difference between monos.
STC vs PTC
Nameplate vs PV or 'practical' rating
The performance of a solar module is related to a variety of factors with temperature and irradiance being the two biggest. When you see a module listed as 280 Watts of 320Watts, know this, it will probably never reach that level of power. The 'nameplate' rating is measured in an air conditioned factories at "max sunshine". I'm going to stop typing and let the video tell the story.
How long will they Last?
How long will they last? What's the warranty?
Solar modules have two warranties. There is a workmanship warranty that covers the craftsmanship and +95% of manufacturers will offer this at 10 years. This pretty much covers the glass separating from the frame, the j-box separating from the back side or anything else related to the assembly of the unit.
The Performance Warranty covers the ouput of the module over time. For a long time this was offered by all as 90% performance at 10 years and 80% at 25 years. A "stair step" as shown in the diagram. Slowly more and more manufacturers adopted a linear warranty of .8% per year ending at 80% in year 25. If you would like to read the Warranties visit my Solar Library
Here's some questions I've been asked
Where are they made? Most solar modules installed in US are made in China and a few here in the US. It's important to note that these are made by robots in clean rooms. There's no moving parts. I've installed 10's of thousands of modules and they simply do not fail. They are well made.
How the heck do you get them up to the roof? On a single story house one guy just hands it up to another guy standing near the edge.
On a two story one guy will carry the module in the crook of his arm resting it on his head. Then using his free hand go up the ladder. Wath the video. I did this 44 times that day! About 1,600lbs up 88 stories.
How often do I need to clean them? The short answer is 'when they are really dirty" The long answer is; It really depends. Are you located in the city or on a country dirt road. Does it rain frequently where you live? Your panels will get dirty just like anything else left outside but how fast depends on where you live. BTW, I haven't washed my modules in years. I would suggest for good performance you wash your array twice a year at each equinox. Cool weather, good irradiance, and clean panels is a great combination.
If you ever get bird droppings or something else that blocks out a portion of a module I recommend you take care of that ASAP. Sunlight blockage causes resistance which causes hot spots.
Can I wire them directly to my pool pump? No, and you wouldn't want to "wire them directly to anything. When the pump isn't running the solar panel is a waste of good silicon. Even a small 1 or 2kW kit could offset in a year more than just the pump uses. The modules are making power from sunrise to sunset. The pump runs for much less. Doesn't make sense to do this. Now water pumping froma well or running a fountain is a different story.
Can I just buy a few and then put mirrors around them? No, do not do this. The modules are manufactured to handle a certain amount of irradiance. Significantly increasing irradiance can have bad effects on the circuitry of your modules. Modules are cheap just buy 1 more.