not quite a new b

alcatel99

have been living off grid with a NAWS system for 5 years and i am really pleased with it ,i would now like a 2nd system seperate from the rv 
have decided on 1.2 kw with 4 x 290 watt panels my latitude is 34.899 degrees my main question is does panel orientation regarding portrait or landscape make much difference my rv panels are flat on the roof but this 2 nd system will have an adjustable tilting frame,
Thanks for any advice you have.

BB.

As far as I know--There is no really issue with horizontal vs vertical panel orientation--Other than wiring between panels (see what works best for you for wiring).

You can use PVWatts and play with fixed and 1/2 axis tracking.

https://pvwatts.nrel.gov/pvwatts.php

Using Holbrook AZ, fixed array @ 34.9 degree from horizontal angle with a 1.16 kW array and 52% end to end efficiency, I get (hours of sun per day):

Month	Solar Radiation ( kWh / m2 / day )	AC Energy ( kWh )	Value ( $ )
January	5.30	86	10
February	5.96	86	10
March	7.05	107	13
April	7.62	112	13
May	7.44	111	13
June	7.37	103	12
July	6.51	93	11
August	6.65	96	11
September	7.03	100	12
October	6.70	102	12
November	6.06	92	11
December	5.06	82	10
Annual	6.56	1,170	$ 138

Note, my math would be (January for example) for AC harvest (charge battery bank during the day, discharge at night):

• 1,160 Watt array * 0.52 (typical end to end solar-batt-inverter eff) * 5.3 hours of sun per day * 30 Days =  ~95,909 WH per month of AC power

Not sure why the ~10% difference, but certainly close enough for a start here.

If you do not do 1/2 axis tracking, there is a suggestion to get "more hours per day" of sun. For example, face 1/2 the array South East and the other 1/2 South West... This usually collects slightly less WH per day, but it can give you more hours per day "on charge". Lead Acid batteries "Like" something like 4-11 hours (very roughly) on charge...

I.e., the first stage (bulk charging) from low SoC to ~80% Soc, the charging current is as much as the array/controller can deliver (current/sun limited charging). For example, 50% to 80% SoC, at 10% rate of charge is (very roughly) 3 hours of charging. Above ~80% SoC, the battery bank charging voltage is limited by the bank voltage (i.e., set point of 14.75 VDC for "Absorb Charging). The battery bank "likes" around 2-6 hours of "absorb charging". The charging current is less than maximum rate of charge (battery limits charging current at set point). 2 hours for shallow discharge, 6+ hours for deep discharging.

Splitting your array, gets more time on charge in the morning and evening times--Usually without much loss of peak charging at "noon".

You can play with PV Watts and see how this works out for you (adjust direction facing, and tilt of the array).

As always, I like to start with conservation... Find the most efficient loads you can (usually cheaper to conserve than to generate power). Next, size the battery bank to your loads (i.e., loads * 2 days of storage * 1/0.50 maximum discharge is a good starting point).

Then size the solar array to the size of the battery bank (5-13% or so rate of charge, >=10% rate of charge for full time off grid recommended). And size the array to hours of sun and energy usage (by season), and location of system (nearest major city, etc.).

Jumping in with an Array Wattage, no battery bank AH/Voltage specs, no idea of the Watt*Hours (or Amp*Hours per day) usage.

Always like to design the whole system to play nicely with your loads/needs/budget. Doing a few paper designs first, before buying/building your system case save a lot of grief.

-Bill

alcatel99

thank you for great reply