Power generation system. Part 2 - Page 2

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.

A more realistic hours figure at 50 watts output is 1000 per year  - takes
into account winters and cloudy days.

So 50 kWH   =   $ 7.5 worth of power per year.

Break even happens at 500/7.5  =  67 years.

Shame the panels will have died after 15 to 20 years.




...........   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

"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

Mark Harriss 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

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, 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

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

"hadda hadda" <draw.hotmail.com> wrote in message


**I just performed a more detailed analysis. Urk. I will require 20 X 115
Watt panels, not 10. That is, of course, assuming I don't make any
conservation moves. At present, I get by on around 13kWhr/day. Adding Solar
hot water should drop that figure by around 5kWhr/day. Give or take.

This will require more thought.

only

What about hydrogen fuel cells?

Last forever, no batteries required.

The way of the future.

**What about consumables?



**Perhaps. However, I am searching for a practical, reasonably priced,
doable (right now) technology.

Just wondering mate, what brand of inverter are you thining of going for?




different
for
The
(<2

green

**I have yet to determine that. If anyone has a suggestion, I would be all
ears. Here is my source:

http://www.quirks.com.au /

If you want a quiet RF environment, some "pure" sinewave inverters put
out a bit of RF. Mine (SEA Voyager) puts an S5 signal on some of the
amateur bands. Can be suppressed of course - but that's more work.
It is very efficient though - even at low levels  (<50W).
Alan

What features would you look for in a "pure" sinewave inverter? what
features would you like?

Here's what I think:

- true sinewave (even at no load)
- line interactive
- fully regenerative (eats motor loads etc)
- low (ideally no) EMI. Run an AM radio sitting on top of it...
- doesnt care which wires go to the grid, which to the load
(alas, it does care about which go to the battery)
- IP66/IP68 (run the sucker underwater...)
- drop it from 1m and give it a good boot while its running (wont die)
- programmable input PF -1...+1 (IOW can do VAR compensation)
- input can act as harmonic filter
- failsafe (fully fused, thermal modelling/monitoring etc)
- no inrush current
- sub-cycle brownout/dropout detection - bumpless power transfer
- optically isolated comms link
- user serviceable cooling fan
- liquid cooling option
- 3:1 peak to average power ratio
- > 20kHz switching frequency (inaudible)
- single- & three-phase models
- wide range of battery voltages (12-24-48V)
- built-in battery condition monitoring
- simple yet useful user interface (small LCD, a few buttons)
- optional bypass contactor

Cheers
Terry

Most of those are features I am used to seeing in a commercial (i.e. not
domestic) UPS.

However review for a moment your 3:1 peak:average capability.  Peak is
determined largely by current handling in the semis.  Average is more determined
by thermal factors.

I can turn a 2:1 into a 3:1 very cheaply - by removing part of the heatsink.
One needs to be rather careful specifying such a ratio unless the average power
output capability is also defined adequately.

some of them you wont find in commercial UPS either :) Yet...


determined


yep.


ROTFLMAO! nicely put. Say Pcont = 3kW.

Cheers
Terry

Yes, I'd like all of those Terry :)
The Voyager is pretty good on most except the RFI. It's rated at 1700W
continuous, 2400W for 30 minutes and 3900W for 5 seconds. Starts all my
240v motors OK (biggest is half horse)and the 19" CRT monitor doesn't
dim the lights either at switch-on. (The 10HP/3.5 KVA petrol genny
coughs a bit under this load).
The THD is quoted at <4% but the switching freq is around 18KHz and I
get harmonics of this up to >14MHz.
Alan