Power generation system. Part 2

1. It's simple math Trevor: ............

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"
** A simpler calc is how long to pay for themselves, compared to mains
power.

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!
Click to expand...


** 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
 
** A simpler calc is how long to pay for themselves, compared to mains
power.
Click to expand...
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
 
Mark Harriss wrote:
Trevor Wilson wrote:


**All very interesting and unreasonably confusing. I did a quick search and
came up with more than 20 references to ENERGY payback for Silicon Solar
Cells. The WORST figure I came up with was 5 years, whilst the best was 1.25
years. Naturally, the financial payback time is in the order of 20-30 years,
at present energy prices.


1. It's simple math Trevor: find out how much solar energy is typical
for your location in watts per metre square, multiply that by the
efficiency for your solar cells and you get a figure for power
production for the area of solar cells you have in Watts. Assume for
simplicity that you get that wattage as long as the sun is above the
horizon so you multiply the wattage by the time to get Watt-Hours of
energy you make for a DAY.
Click to expand...
For those interested, the daily BOM solar radiation map is here:
http://www.bom.gov.au/sat/solrad.shtml
Yesterday was about 11 megajoules/m2 in Sydney which is about 3KWh/m2

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 :)
 
David L. Jones wrote:
For those interested, the daily BOM solar radiation map is here:
http://www.bom.gov.au/sat/solrad.shtml
Yesterday was about 11 megajoules/m2 in Sydney which is about 3KWh/m2

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 :)
Click to expand...

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
 
Mark Harriss wrote:
David L. Jones wrote:

For those interested, the daily BOM solar radiation map is here:
http://www.bom.gov.au/sat/solrad.shtml
Yesterday was about 11 megajoules/m2 in Sydney which is about 3KWh/m2

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
Click to expand...
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:
http://www.bom.gov.au/sat/solradinfo.shtml

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:
http://www.bom.gov.au/sat/glossary.shtml

You can get historical data here:
http://www.bom.gov.au/nmoc/archives/Solar/index.shtml

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 L. Jones wrote:
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 :)
Click to expand...
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:
http://www.jc-solarhomes.com/solar_energy_facts.htm

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
http://www.jgsee.kmutt.ac.th/exell/Solar/IntroSolar.html

This guy claims a peak of 1.1 KWH per m2
http://uqconnect.net/~zzmrobin/sunshark/thecar.html


I'm getting a bit confused here.

Regards
Mark
 
Mark Harriss wrote:
David L. Jones wrote:
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?.
Click to expand...
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.

If that's accurate dats then what are these guys on about with point 4:
http://www.jc-solarhomes.com/solar_energy_facts.htm

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
http://www.jgsee.kmutt.ac.th/exell/Solar/IntroSolar.html

This guy claims a peak of 1.1 KWH per m2
http://uqconnect.net/~zzmrobin/sunshark/thecar.html

I'm getting a bit confused here.
Click to expand...
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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