What to expect ?

Re: What to expect ?

Off Grid for Little Rock Ark using PV Watts, fixed array tilted to latitude. Use 0.52 derating for AC based power usage. Say 6 panels * 250 watts = 1,500 Watts:



Station Identification



City:
Little_Rock


State:
Arkansas


Latitude:
34.73° N


Longitude:
92.23° W


Elevation:
81 m


PV System Specifications


DC Rating:
1.5 kW


DC to AC Derate Factor:
0.520


AC Rating:
0.8 kW


Array Type:
Fixed Tilt


Array Tilt:
34.8°


Array Azimuth:
180.0°


Energy Specifications


Cost of Electricity:
7.4 ¢/kWh






Results



Month
Solar Radiation
(kWh/m²/day)
AC Energy
(kWh)
Energy Value
($)


1
3.78
89
6.59


2
4.38
91
6.73


3
5.19
117
8.66


4
5.67
119
8.81


5
5.89
124
9.18


6
5.81
116
8.58


7
5.93
120
8.88


8
6.08
124
9.18


9
5.41
109
8.07


10
5.16
112
8.29


11
3.69
80
5.92


12
3.56
82
6.07


Year
5.05
1283
94.94




Toss the bottom three months and find 4.38 hours of sun minimum for "February break even month" (use generator/reduce energy usage during winter):

1,500 Watts * 0.52 AC off grid system derating * 4.38 hours of sun (Feb) = 3,416 WH = 3.4 kWH per day

That would be enough to run a "near normal" (lots of energy conservation) system with a full size energy star refrigerator, lights, laptop computer/LED TV, well pump, clothes washing machine).

We recommend around 5% to 13% rate of charge for a battery bank... And 10%+ for a full time off grid system. A 1.5kW array at 10% rate of charge would support:

1,500 Watts * 0.77 panel+controller derate * 1/0.10 rate of charge * 1/48 volt bank = 241 AH @ 48 volts (or 481 AH @ 24 volts)

That would be the basics... Largest (nominal) AC inverter on a flooded cell battery bank that would be "useful" for a 241 AH @ 48 volt battery bank would be around 2.4 kWatt rated inverter...

-Bill

Re: What to expect ?

My "typical" rating:

250 watts * 0.77 panel+controller derating = 192.5 Watt (otherwise well designed system)

In cool weather/very clear conditions, you may get more sometimes.

-Bill