20 year life on Solar Panels fallacy

peakbagger

Minister of Fire
Jul 11, 2008
5,629
Northern NH
Rather than derailing another thread I thought it was worth starting a thread on common fallacy with respect the life of solar panels. This gets lot of attention in the media and every few years there are solar panel crisis articles designed to pull in eyeballs on the web. The reality is that many solar panels that date back to the beginnings of solar's early era are still putting out power despite being over the 20 year cut off. Folk tend to forget that standard affordable solar panels were not readily available until 20 years ago . As an example my 2002 era array was built with "2nd generation affordable panels which cost $6.60 per watt (note this is the cost for the panels only, the balance of system components added a lot more). First Quality panels in bulk are now in the $0.50 per watt range today and second quality are down in the $0.30 per watt range. They are now effectively commodities.

There was a market for solar panels prior to the year 2000 but the panels were in excess of $10 a watt. They were used for high value specialty applications like remote telecom and scientific (Note I am excluding satellite PV panels that are a cost is no object applications). They also were adopted by off gridders and had some popularity with off grid pot growers in Northern California. Arco Solar built a couple of early large solar plants. Due to the cost of the panels they used reflectors to boost the amount of sun on each panel. Unfortunately the coating used to laminate the panels were not designed for this use and the panels aged rapidly. As subsidies went away, the solar farms were dismantled and the panels were graded for damage and resold to mostly off gridders. These were usually relabeled as Carrizo Solar quadlams and acquired the nickname "crispy critters" as they were visibly "cooked" with a distinct burnt look to them. Despite the damage, crispy critters are still out there and they still generate usable amounts of power 40 years after. I have some later Siemens panels built in around 1990 that I still use to run my Solar Hot Water and also have some rigged up for solar water system for my garden. Yes they have lost some rating compared to nameplate but still cranking along. They also have some deterioration to the lamination coating but still work. There are several studies on the web of older PV arrays and universally the silicon based panels are still putting power out generally with less degradation that predicted and guaranteed when sold new. My original array is 18 years old and still puts out quite a bit of power and has almost no visual aging.

I am referring to the current standard which are Silicon based panels. They are thin slices of silicon laminated to a tempered glass panel that have a very small amount of other elements added to them to make them semiconductors. These chips have an electrically conductive grid attached to the chips that are connected to an internal electrical grid that eventually comes out to a junction box. The overall assembly is then sealed from the weather with coating and mounted in an aluminum frame. Overall the components are far less toxic than what is found in household electronics. On the other hand there have been other chemistry's for solar panels. The big competitors were CIGS made from a compound called copper gallium indium diselenide and Cadmium telluride (CdTe). Both were cheaper to make although both were less efficient than Silicon. Luckily the US mostly dodged the bullet as these got deployed in Europe especially Germany as they were very difficult to dispose of and had higher long term degradation rates. Since there was not a lot of history in the US on large solar deployments much of the German experience with the other chemistries was imported to the US and applied to Silicon panels.

So where did the 20 year life come from?. Its a combination of the German experience with at least three chemistries including two problematical ones and just as importantly accountants. Accountants by nature have to be conservative. In order to calculate the long term cost of the solar panels, accountants need to do a financial model over the life of the project. They don't pick those numbers out of thin air, they base them on information they have at the time and other factors and eventually the number they pick becomes a Generally Acceptable Accounting Principles (GAAP)that get adopted across the industry. The GAAP values may not be "right" but they are standardized and documented so project economics can be compared. Additionally factored in is Mean Life Between Failure of power electronics. Behind every large array is bank of inverters and they typically have a 10 year life. Most accounting models assume that there will be an initial set of inverters and one change out 10 years into the project. They are using a 20 year life so they dont have to factor in a second inverter change out into the economics so as far as they are concerned the array is beyond its economic and accounting life at 20 years. This does not mean the array is no longer functional it just means that the original investor has picked an end date and as far as their balance sheet is concerned they have an end date. Included in the economics is what it will cost to dispose of the system. Many developers do not actually buy the land, they lease it for 20 years and then let it revert to the prior owner. Generally the original developer is long gone and if the clean up is costly the project is some sort of LLC where they just walk away and let someone else clean it up.

There is also the factor of obsolescence. My original panels are still putting out power but the inverter required is no longer available as the voltage at the time is no longer supported. I hacked up a fix but a big array owner almost guaranteed will need to reengineer and possibly rewire the array to get it to meet future available equipment. What that may look like is an unknown so its easier to just write it off at 20 years.

So in 20 years what happens to the array? Most likely some entrepreneur buys it for cheap, upgrades the electronics and keeps selling power. IMHO the biggest disposal demand to date is damaged panels due to fires, wind events and defective manufacturing. These are usually damaged beyond use and whoever owns them has to dispose of them. Where they go is dependent on what laws are on the books. If mandatory recycling laws are passed some entity will deploy already developed technology to recapture the materials. There will be costs to do this and if the revenue stream does not equal the cost to break them down then whomever owns them get to pay for it. The European approach now is that the original manufacturer needs to recycle them or put in place a system to recycle them. This sounds like a good idea until someone surveys how few companies have survived in the solar business.
 
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DBoon

Minister of Fire
Jan 14, 2009
1,191
Central NY
Good points, peakbagger. To put it more simply, any corporation that invests in solar panels would depreciate them over 20 years (and perhaps inverters over a shorter period) and after 20 years they have no value left on the corporation's books.

If, after 20 years (full depreciation) something unexpected goes wrong the requires a further investment, the company might very well get rid of the items and start over, especially if on-going maintenance and expenses weren't budgeted or planned for.

It's equivalent to someone having a five year car loan and 1 month after paying off the car, needing to make a $1000 payment for new tires and a water pump, and instead just trading in the car and getting a new one and starting the payment cycle all over again, even if (more than likely), they could drive the car for another two years without further investments.
 

Stelcom66

Feeling the Heat
Nov 6, 2014
476
Connecticut
Interesting article, as I have wondered recently - do solar panels 'wear out'? The little research I've done so far reveals the standard output is 12v, I assume the author's system is of a different value.

I want to look into solar as a backup power source for smaller components like 5v USB chargers and to power a cable modem and router. I was very fortunate last time when many in the area lost power for up to a week, while I did not. I don't have the money to invest in a large solar system, it looks like for several hundred or so a 100-200 watt system could be put together.

Of course after power was restored for many, they still had no internet for a while after due to cables being down, or no power to nodes on a different electrical path. Even while electricity is being delivered from the utility solar could be used as a primary source for low wattage components. But - it would be many years to break even, if it all. Just knowing some of the sun's energy is being harnessed and put to good use could be gratifying.
 

peakbagger

Minister of Fire
Jul 11, 2008
5,629
Northern NH
Interesting article, as I have wondered recently - do solar panels 'wear out'? The little research I've done so far reveals the standard output is 12v, I assume the author's system is of a different value.

I want to look into solar as a backup power source for smaller components like 5v USB chargers and to power a cable modem and router. I was very fortunate last time when many in the area lost power for up to a week, while I did not. I don't have the money to invest in a large solar system, it looks like for several hundred or so a 100-200 watt system could be put together.

Of course after power was restored for many, they still had no internet for a while after due to cables being down, or no power to nodes on a different electrical path. Even while electricity is being delivered from the utility solar could be used as a primary source for low wattage components. But - it would be many years to break even, if it all. Just knowing some of the sun's energy is being harnessed and put to good use could be gratifying.
Sounds like you are new to it. If you look at a solar panel, its composed of many individual solar cells. Each cell puts out 0.5 to 0.6 volts at a standard temperature and standard illumination. So if you need 12 volts you are going to need around 20 cells hooked up in string. The amperage from each cell depends on how much surface area of each cell. If you need more amperage than one string of cells, then you need bigger cells or more strings of cells wired in parallel. Note I said standard temp and standard illumination, as the temperature changes and the amount of sunlight changes, the voltage changes. Most electronics want steady voltage and a solar panel is going to vary its voltage over the course of the day so a direct solar panel to drive a load is not typically a good fit. So that means you need a battery as the battery acts to fill in the gaps when the sun is not out at night when clouds pass over the solar panels. If there is extra amperage the batteries charge. So once a battery gets in the mix you need to size it so its big enough to supply the load for several days but not too big that you cant recharge it. Batteries wear out even if they are treated well and are a big part of the long term cost. A standard solar panel will last a lot longer than the batteries, as i stated in the OP, 20 plus years. Low grade flea bay or Harbor Freight panels may last a lot less time, they are made cheap and it likely they will end up in the trash.

Rarely does small solar make sense. Before you even think about using solar power for backup you need to establish a power budget which is an accurate measure how much power you need over multiple days. For 120 VAC loads there is a plug in device called a Kill a watt meter that measures how many watt hours a device will draw as long as its plugged in.

Its sad to say but you named an energy hog, cable modems are rarely energy efficient. Cats like them as they give off plenty of heat but to power them 24/7 takes a lot of power. My guess is 50 watts. So in 24 hours that is 1200 watt hours that you need to store up over the daylight hours. Its starts to add up and every day is not sunny so you need a few days in reserve in the battery. Solar USB charges can be a nice start as they skip needing a battery but obviously only charge when the sun is out.

Look around on the web for a PDF book called Solar Power Your Home for Dummies. Get a copy and read it before you spend a dime on cheap junk.

Sad to say it but for backup power a cheap harbor freight 2000 watt generator and gas can is going to be far less costly than a small solar system.
 
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Stelcom66

Feeling the Heat
Nov 6, 2014
476
Connecticut
Right, no experience with solar. The label on my Motorola Surfboard modem (cable modem only that I purchased) says .75 amps @ 12v. The Linksys router is 1 amp @ 12v, so 12 watts + the Motorola is around 20 watts. Still, it sounds like it a low wattage solar system isn't the way to go. I recently moved the cable modem so it and the router are next to each other and now on the same power strip. I may start powering it off when I'm at work as no one else would be here. Then again - if the draw is 20 watts that's not much savings. I believe I have an old amp meter, if not I may invest in the Kill A Watt meter. I'm surprised it's less than $40. If I'm going to get a generator might as well get one with enough capacity to run the well pump.
 

ABMax24

Minister of Fire
Small phantom loads sure add up. In my house between my 2 cable boxes, internet modem/wireless router, tv's, and other appliances I have a constant draw of 81 watts. Over a year that adds up to 709.5 kwh. My yearly energy consumption last year was 2489 kwh. 28% of my electrical consumption goes just to power these small phantom loads. In an off-grid setting these would be very worth while to try and reduce/eliminate. Even in my house I'd like to get rid of them, except for the fact that all of them require about 15 minutes to be usable again after having the power turned back on.
 

begreen

Mooderator
Staff member
Nov 18, 2005
85,058
South Puget Sound, WA
Phantom loads are many in a modern house with TVs on standby, streaming sticks, wireless everything. It seems a little odd to worry about an off-grid house that has a cable wire connection. Most I know are utility free. If they have internet at all it often is via a cell connection.
 

Stelcom66

Feeling the Heat
Nov 6, 2014
476
Connecticut
The other internet device I have is a VoIP Analog Telephony Adapter. That draws about 15 watts. That always takes the longest to come back on line after an internet or power outage. Another video streaming device is used about a half hour a week. I haven't had cable TV for years, local stations received via antenna. I'm not going to eliminate the internet.
 

woodgeek

Minister of Fire
Jan 27, 2008
4,256
SE PA
For backup, I'm gonna second a cheap small genny. I bought a Harbor Freight 800W unit, a Jerry Can and some spare plugs, under $200 all in, and I ran a lot of little loads for a total of 14 days over the following few years: fridge, sump pump, stove blower, not to mention cell phones, tablets, laptops, internet. and all the LED lights I wanted.

Best money I ever spent.

I have a microsolar system too, 60W PV panel and a 36 Ah 12V AGM battery. It can run a few cell phones, and charge my laptop in the summer time, but no comparison.