Beginner here please help

Sammasalways
Sammasalways Registered Users Posts: 1
I want to buy 8kw solar system set.

How much power it will generate in a day 7 hours sunshine.


I have few more question i will shoot if iam able to get some help here.

Thanks a lot guys appreciate the work people doing here

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Beginner here please help

    Sammas,

    You are making it a little difficult here to predict--Need some more information... However, I will try and take some guesses.

    First, were are you? Beijing China? Using the solar hand book site for Beijing, fixed array, tilted 50 degrees from vertical facing south:
    [h=3]Beijing
    Average Solar Insolation figures[/h] Measured in kWh/m2/day onto a solar panel set at a 50° angle:
    (For best year-round performance)

    Jan

    Feb
    Mar
    Apr
    May
    Jun



    5.25


    5.53

    5.86

    5.97

    5.68

    5.03



    Jul

    Aug
    Sep
    Oct
    Nov
    Dec



    4.61


    4.54

    4.74

    5.12

    4.83

    4.96



    Or ~62.12 hour per year (if I added correctly). And 62.12/12 months = 5.18 hours of sun per day per month average...

    First, if this was a pure grid tied system (no batteries, solar panels+GT inverter) and you are just looking to reduce your power costs, and your utility allows "net metering" with solar power (your meter can spin backwards), an 8kW system would generate, average per day and per year:
    • 8 kW array * 5.18 hours of sun per day * 0.77 panel+controller derating = 31.9 kWH per day
    • 8 kW array * 5.18 hours of sun per day * 0.77 panel+controller derating * 30 days = 957 kWH per month
    • 8 kW array * 5.18 hours of sun per day * 0.77 panel+controller derating * 365 days = 1,018 kWH per year

    If you wanted an off grid system... Generally, i suggest tossing the bottom three months and assume a generator will make up for poor weather. The break even month would be November at 4.83 hours. A standard system (flooded cell batteries), charge during the day and use power at night (worst case), generating AC power through an inverter, such a system would generate:
    • 8,000 Watt array * 0.52 typical off grid system efficiency * 4.83 hours = 20,093 WH per day = 20.1 kWH per day of AC power in November

    The optimum size battery bank (using 5% to 13% rate of charge based on battery 20 hour capacity), using 10% as a good nominal/balanced system:
    • 8,000 watts * 0.77 panel+controller derating * 1/59 volts battery charging * 1/0.10 rate of charge = 1,044 AH @ 48 volt battery bank

    If you use 2 days of storage and 50% maximum battery discharge, the daily nominal battery usage would be:
    • 1,044 AH * 48 volt battery bank * 0.85 inverter efficiency * 1/2 days * 0.50 max discharge = 10,649 WH = 10.6 kWH per day from battery (night)

    Since you have a good amount of sun, you can use a larger battery bank (5% rate of charge) if most of your power usage is at night... If you use a lot of power during the day (water pumping, computers, working from home/office, etc.) you can keep the battery on the smaller side.

    Anyway, a really quick overview of what I guess your options may be for your region.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset