Perhaps the simpler maths would be to just look at the cost of buying panels. 50W panels used to cost about $500. How much of that is for the energy required to manufacture them? $50? How much is a KWH? Say $0.15 - then a 50W panel takes about 50/.15 or about 333KWH. So the 50W panel has to make 333KWH to break even. At 5Hrs/day, this takes 333K/(5*50) or
1333 days or 3.65 years. Alan"Alan Peake"
** Sure - but I was alluding to the silly notion that such panels could pay for themselves by generating power back into the national grid............ Phil
Yes, if you don't take into account the cost of having mains installed. I was quoted around $20,000 to get mains on here and that's cheap! Alan
For those interested, the daily BOM solar radiation map is here:
I was going to solar power a small device in a new design until I remembered that I now have sustainable "green power" mains supply anyway. So I'm effectively getting solar (among other sources) mains power now. So there was no environmental incentive, and the payback time would have been something like 100+ years Scraped that idea petty quick, mains power it is.
Dave :)
Is that figure correct, David?. From what I could find the figure is
1.2 KWH average with the best spot on the planet at 1.4 KWH.Regards Mark
Well, that's the official daily data from the Bureau of Meteorology from the GEOS-9 Satellite, so I guess it must be as correct as you can get. More info on how the data is obtained is here:
Average error on a clear day is +/-2 MJ.
1.4KWh is only 5MJ. Up North in Aus it was 4 times that figure yesterday.More interesting stuff is here:
You can get historical data here:
You can also get a really cool (no pun intended) looping map display by clicking on the "loop" link available after you search for a date range. I just did a test on some old data and it can get as high as 38MJ (10.5KWh) in many parts of Aus fairly regularly, even in winter.
Dave :)
David, is that just a peak spot reading or the entire energy per day?.
If that's accurate dats then what are these guys on about with point 4:
They claim it's 1.4 KWH per m2 above the atmosphere and about 1 on the surface.
These folks say beam solar radiation is about 0.9 KWH per M2
This guy claims a peak of 1.1 KWH per m2
I'm getting a bit confused here.
Regards Mark
Ah-ha, after closer reading it does indeed appear to be the *total* energy per day. So at the maximum reading of 38MJ on the scale, that's 10.5KWh divided by the number of hours the sun is up. That now corresponds to your figures.
Sorry for the confusion, I hadn't looked into it that far yet :->
The value does vary by a massive amount though. At 11MJ the other day that's only about 0.3KWh, a HUGE difference from the days when it peaks. So it wouldn't be wise to use just any average quoted figure when the real data is available.
Should be pretty easy to download the historical data and calculate the REAL average for your location and time of the year.
Regards Dave :)
Ah, all is made clear, it's starting to look like my initial figures were overly optimistic!.
I see some Japanese researchers have a way to electrolyse glass into silicon in a hot chemical bath, it's be interesting how much energy that route takes, though making glass takes a lot of energy too.
Ideally someone will find a way to make chep solar cells that are efficient.
Mark Harriss
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