Hi Florin !!!
One method of calculating the energy need is using amperes instead of
watts. This is because the panel can produce power at 17 volt or less, but
the difference in volts between battery voltage and panel voltage is
wasted. (maybe very advanced chargers with dc/dc converters exist, but i
do not know).
I would select a 24 volt nominal voltage system, you have less
current and the wire can be thinner. You can use 24 volt panels or 12 volt
connected in series.
In my calculations, for 1313 wh /day, at 24 volt you need 164 ah
battery for 3 day autonomy.
In average, you must produce at least 1313 wh /day -> at 24 volt
55 ah /day. But count battery efficiency, so you must produce more. I
suppose it is 85% so you must produce 55/0.85 = 64.7 Ah
For that, if you have 6 hour equivalent full sunshine you need a
panel that produces 11 A at full power. I would try to find a 180watt 24
volt nominal power panel and use two in parallel. Or combine your 110 w 12
V panels putting in parallel two groups of two panels in series.
I hope this helps, i would appreciate any corrections if i am
oversizing the system.
Best regards,
Jon Aramendia
At 10:08 23/05/2004 +0000, you wrote:
>Hi guys,
>
>I'm very confused related to the PV energy production. I don't
>understand where is the truth.
>
>I need for example to use Daily PV Energy Budget � 1313Wh/day from a
>solar energy system, at 12 V/220V. (Only a TV set + lights)
>
>- Bright Sunshine � 6 Hours
>- 3 days of autonomy
>
>Based on my calculation the results are:
>
>- Total Rated Battery Capacity calculated 729 Ah
>- Using batteries at 6V/450Ah I need 4 batteries connected in
>series/parallel
>
>And if I'm using Siemens PV � SP110 with the following
>characteristics, 110W - 6.47A/17V
>
>Based on this then I need 3 modules on parallel. Am I right? But�here
>is the confusion that I have.
>
>Those panels produce according with Siemens specs at 6 h bright
>sunshine � 6x110W = 660W per day !�. but my system works with 12 V
>not 17 V!! �. So the results should be 6h x6.47A x12V = 465W ! � well
>my question is :
>
>Where are 200W?� because as far as I understand the max current
>generated will be 6.47Amps .. and not more?
>
>I hope you guys can help me !
>
>Thanks,
>Florin
>
>
>
>
>
>
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