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PV system sizing and cost calculations

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Posted by Steve Spence on August 9, 2003, 12:39 pm
 
In complement to our PV sizing tutorial (
http://wedconx.green-trust.org/2003/pvsizing/  ), I have put together a
spreadsheet that helps you calculate the costs and output of a Photovoltaic
Power System. Follow these four steps to determine your loan payments,
output, and costs.
http://webconx.green-trust.org/2003/pvsizing/pvcalc.htm

--
Steve Spence
www.green-trust.org



Posted by Steve Spence on August 9, 2003, 12:39 pm
 
In complement to our PV sizing tutorial (
http://wedconx.green-trust.org/2003/pvsizing/  ), I have put together a
spreadsheet that helps you calculate the costs and output of a Photovoltaic
Power System. Follow these four steps to determine your loan payments,
output, and costs.
http://webconx.green-trust.org/2003/pvsizing/pvcalc.htm

--
Steve Spence
www.green-trust.org



Posted by Grant Beuchel on August 9, 2003, 7:27 pm
 good job steve, but what about us wind turbine users?



Photovoltaic


Posted by George Ghio on August 11, 2003, 12:44 pm
 

Well Steve they say that imitation is the sincerest form of flattery.
But I have got to say you have made quite a mess of my spreadsheet.

1) When will you learn that the best way to do an Energy Audit is on a
daily basis, weekly is a joke as you only have to divide by 7 (row 46).

Also all items in the energy audit should be listed separately including
all lights. The reason for this is that when you set up a system you can
fine tune your load item by item.

2) Row 16, Daily Watt hours divided by inverter efficiency expressed as
.9 for 90 percent or .8 for 80 percent etc. will give you the inverter
correction. Sure beats the hell out of your 83.4 percent guess.

3) Row 22,  Daily AC Watt hours (corrected for inverter loss) divided by
system voltage i.e. 12, 24 ,48, will give you the daily Amp hours used
by the AC side of the system.

4) Row 27, Another time waster. Daily loads, listed separately for fine
tuning of the DC
 load.

5) Rows 34, 37, 43, DC weekly Amp hours. Bugger that for a lark.

6) Row 46, Divide by 7. Point to George It all comes back to your daily
load.

Battery Sizing

7) See, Daily load in Amp hours. And after only 51 rows in the
spreadsheet. Of course the SS you cobbled this mess from only requires
31 rows to be finished.

8) After another 24 rows you get the battery Amp hours needed (adjusted
for temp) with the added embarrassment of getting the wrong answer.

9) After another 15 rows you find out that yes you really do need two 6
volt batteries. And after only 59 rows past the point that the original
SS has answered it all right down to the last panel

10) Row 92, The Array sizing. Long time coming.

11) Row 94, There is no AVERAGE here, if you did your energy audit
correctly you Know what you use. Leave average systems with average
performance for Nick. Strive for exultance.

12) Row 97, See item 2 above.

13) Row 100, If you size your system according to summer sun light it
will start to fail around mid fall and will require lots of generator
time for the next six months or so. Never use Average sun hours. If you
dont know what PEAK SUN HOURS are learn now and check the NASA surface
meteorology web site to find out the peak sun hours for your location.
Also missing is the panel angle.

Sorry Steve but your attempt to rewrite my spreadsheet is but a pale
imitation of the real article. I am glad you found it worth the effort
but you should have just used it as is. I would not have minded in the
least.

George L Ghio
Solar Power Consultant


Posted by Nick Pine on August 11, 2003, 3:37 pm
 


Good idea, but probably not the one you intended :-)

Nick


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