Off-grid calculation-Pakistan

[Saad194]

The client aims to power various loads using the solar PV system during both day and night.

The day is divided into three time periods:

Off-peak time: 8 AM to 5 PM
Peak time: 5 PM to 10 PM
Off-peak time: 10 PM to 8 AM
The load distribution throughout the day includes the following:

AC 1.5 ton (a) inverter Gree company: 1800 watts (1.1 KW on average per hour when running) run 24 hours.
Fridge: 350 watts run 24 hours.
2 fans: 100 watts each run 24 hours.
10 LED lights: 12 watts each (operating for 12 hours)
AC 1.5 (b) running from 5 PM to 6 AM run 13 hours.
AC 1.5 (c) running from 9 PM to 6 AM run 9 hours.
The system will be installed in Lahore, Pakistan.

Grid charges:

Off-peak time: 57 PKR per unit (KWh)
Peak time: 62 PKR per unit (KWh)
The proposed inverter is Nitrox 8 KW Hybrid, and the solar panels will be either Longi or Jinko 580 watts mono Perc. The quantity of solar panels will be determined through calculations.

Three types of batteries will be considered:

Lithium-ion (Narada brand, 48V 100Ah, efficiency 80%)
Gel type (Narada brand, 220Ah 12 volts, efficiency 70%)
Tall tabular (Exide brand, 220Ah 12 volts, efficiency 65%) require calculation how much solar PV , inverter, and battery bank

 

[BentleyJ]

We can start by totaling up an estimated usage for a 24hr period. We will assume the AC runs 50% of the time ( For example:15min ON and 15min OFF) or a 0.5 duty cycle.
1) A/C(a): 1.1kW x 24hr x 0.5 = 13.2kWh
2) A/C(b): 1.1kW x 13hr x 0.5 = 7.2 kWh
3) A/C(c): 1.1kW x 9hr x 0.5 = 5.0kWh
4) Fridge: 0.35kW x 24hr x 0.5 = 4.2kWh (350W seems high for a standard refrigerator)
5) Fans: 0.1kW x 24hr x 2 = 4.8kWh
6) LED: 0.012kW x 12hr x 10 = 1.4kWh
Total = 35.8kWh per day.

Solar production is based on the STC size of the array and average number of solar hours per day. Solar hours are based on geographic location, Azimuth and tilt of the panels as well as shading from nearby buildings or trees. Since we don't have all of this info we will estimate Solar Hours to be 5.
35.8kWh/5 solar hrs = 7.2kW Which is the MINIMUM size of the solar array needed.

Inverter is sized based primarily on Max & Continuous kW output capability. Since all 3 A/C units and other items will be operating at the same time during part of the 24hr period, the output requirement is approx. 4kW. That doesn't take into account any momentary surges. If we assume the A/C units are inverter type mini-splits, they have minimal surge. However, any type of conventional fixed speed compressor with an induction motor has tremendous inrush current and will need soft starters installed and an upsized inverter.
If a HF frequency, transformerless inverter is to be used I would recommend a 6kW model or larger. If a good, LF inverter is used a 5kW model should be sufficient. (see note above regarding A/C being inverter type mini-split)
Secondary consideration for the inverter is the number and capacity of MPPT inputs (if its going to be an All-in-One type) to accommodate the PV array.

Battery sizing is based on storage capacity needed for your stated 24hr period x the number of days you wish to have back up in case of an outage and/or poor solar days due to clouds and rain.
Since your highest usage is going to be at night when there is no sun light and all 3 AC units are running. You will need about 20kWh of USABLE storage. Since batteries should be cycled to only 80% DoD, a 25kWh battery is required for overnight operation. If additional back up time/days is desired then more battery storage is needed.
Lastly, I would strongly recommend against Li-ion as they can be a fire hazard. LiFePO4 is much safer.