solar panel power loss

3.2Kw from a 5Kw solar system does not seem too bad to me from what i have seen. I am in the planing stage of getting a Solar energy system installed and now know the rating the solar panel makers list is the absolute max power the panel can produce. In the real world, 60-70% of rated power is not bad.

Regards

 

It depends how you are measuring your power. For starters, you may not have 'one sun' insolation conditions, even though you think it is pretty sunny. Yes you loose a bit of power in the dc cables, and in the grid-connect inverter. Also, the pv panels reduce their output as their temperature rises - they can get pretty hot - which is why they are usually mounted where fresh air can cool their rear side. You may also not be at a time in the year, or day, where the panels are perpendicular to the sun. And they may be a bit dusty!

Ciao, Tim

 

Another thing that people don't talk about, probably because it's not politically correct in today's 'go green' mentality; is that solar panels have a limited life expectancy.
How old are your panels, their output degrades with time. 13 to 15 years is peak efficiency. Considerable degredation after that.

 

As darkman says, unless the inverter is "intelligent" and keeps searching for the maximum power knee point then you get substantially less power than the panel label.

 

shrtrnd - crystaline silicon (single and multi) are fine for well past 20yrs for well made panels - amorphous Si continuously degrades but cycles - not sure about more recent Cd tels and others?

MPPT algorithms are pretty good nowadays - they probably stay within a percent or two of max, as long as the insolation level is constant - otherwise they have a short delay effect if radiation level is bouncing around a lot.

 

Hmmm, ok Trobbins, who are these 'well-made' panels?
I'd like to investigate this.
I live in the Arizona desert, the sun kills 'em quick here.
I'd guess they might survive longer in less hostile environments, but not by much.
I keep reading the technology is getting better, but that's kind of a subjective claim.
I'd sure like to know who makes 20+ year solar panels that can output anywhere near
their newly manufactured specs. I want me some.

 

Manufacturers back in the 80's were able to get it pretty right (links below), showing an acceptable drop of measured output after 15 yrs. I note BP Solar are claiming 0.4% degradation per annum nowadays - however care is required comparing difference between field and accelerated test results - but I would suggest that those manufacturers using time proven techniques and quality materials would get it right, which may not be the case for all manufacturers. But, a larger percentage of panels are being sold into large PV installations, where warranty is extending out to 20 years.

uaelani.jeeran.com/uae/PVCAR2.doc
http://www.telepower.com.au/PVsec96a.PDF
http://www.telepower.com.au/Solar96.PDF

 

You can calculate the DC loss if you can determine the average length of cable between the panels in the string, and if you can estimate the MPP current, and if you know the gauge of wire used (I2R).

The power measurement in the grid inverters has an error tolerance that you have to add in too - SMA have a doc on that aspect.

 

Why do I have a problem believing BP's claims, when they're pushing 'going green' in publicity ads? Looking for government subsities. And what are they going to say after 20 years? Oops, we made a mistake, but oh well, those claims are 20 years old, and we didn't have all the data?
Actually though. I have been reading claims about the cells getting better, so I'll be looking into them. Arizona heat is probably a worst case scenario (the cell output is greatly diminished, the hotter the cells get).
A lot of people here got suckered in, buying rooftop sheets with tax breaks. It takes 15 years to get your money back in energy savings, and that's about the time it takes
before their present efficiency dropped so far as to make them require replacement or removal.
I'll be checking into this again with newer models. But everything I've seen lately, still makes the cost effectiveness of solar cells for power, a losing proposition.
Thanks for the input. If trobbins is still out there, I'd be interested in hearing what companies (by name) are putting out the best gear lately.

 

Most of the big names have a range of panels - they all know how to make top notch stuff - it's just that you need to sell panels, so they all have a variety of more budget oriented panels - you have to sell to keep in business, and competition drives the price point for sales down. The likes of BP Solar were a major source for the panels in use in Australia telecom and have had huge experience on what ages and deteriorates.

Davenn, the text is obviously a contextual typo error - if you read the rest of the article you may better appreciate that. There were product from a few manufacturer's tested, some of the panels exhibiting degradation down to the low BP Solar levels talked about nowadays.

Steve, they understand English, and mathematics, very well. The quote comes from the links I put in earlier.

Shrtrnd, it is reasonable to extend the economic lifetime of panels out past the 80% rated output timeline, there is often no disadvantage to letting them continue producing power in this mppt age. Like finding 52 matchsticks in a box marked with a quantity of 50, all the produced panels have to exceed their rated levels (aka battery capacity).

There can also be an aesthetic bias against old panels - it was not unheard of that techo's were replacing 'old looking' panels for new panels after 15-20 years, only to be told to put them back again because they had in fact only degraded to 90 odd %.

 

Ok trobbins, I'll have to look into the latest and greatest.
Hey, Hope Johnny 5 got the answers he wanted.

 

Steve, many people wanted to remove Telstra's PV panels - it got so bad that Telstra tried many different techniques over many years to ebb the flow of panels into the hands of others - the one I thought most innovative was using an orange coloured backing to the cells (tedlar layer). Orange was the corporate colour of Telstra, and very niticable from the road and the air at long distances!

Ciao, Tim