Off-Grid Solar System Design Step-by-Step.

Steps of Design

  • Defining our loads.
  • Sizing inverter.
  • Sizing panels.
  • Sizing batteries.
  • Sizing a charge controller.
  • Panel connection.

Step 1: Defining our Loads

Device NumberPower/device(w)Number of HoursEnergy (wh)
Lamp118 w472 wh
Fan160 w2120 wh
Refrigerator175 w12900 wh
Total153 w1092 wh/day

Step 2: Sizing Inverter

  • An inverter is used in the system where AC power output is needed.
  • The input rating of the inverter should never be lower than the total wattage of appliances.
  • The inverter must have the same nominal voltage as your battery.
  • For stand-alone systems, the inverter must be large enough to handle the total amount of watts you will be using at one time.
  • For grid-tie systems or grid-connected systems, the input rating of the inverter should be the same as the PV array rating to allow for safe and efficient operation.
  • The inverter power should be greater than the load’s total wattage by 25% or 30%.
  • The inverter’s continuous power = 1.3* total wattage = 1.3153 W = 198.9 W.
  • If the system has motors, compressors, refrigerators, pumps, and washing machines, we need to make sure that the inverter can withstand the starting current.
  • The surge power of these devices is found on the label of them.
  • If you don’t know, you can assume the surge power = 3x – 4x the wattage of these devices.
  • The inverter surge power = Lamp + Fan + 4 Refrigerators = 378 W.
  • We need an inverter with a continuous power of 198.9 W and a surge power of 378 W.

Step 2: Sizing Inverter

Step 3: Sizing Panels

  • The total energy required by the loads is 1092 Wh/day.
  • The total energy needed from panels = total energy * 1.3 (a safety factor to accumulate for all the losses in the PV system in addition to the panels not operating at the optimum conditions) = 1092 Wh * 1.3 = 1419.6 Wh.
  • The power of panels = π‘‡π‘œπ‘‘π‘Žπ‘™ π‘’π‘›π‘’π‘Ÿπ‘”π‘¦ 𝑛𝑒𝑒𝑑𝑒𝑑 π‘π‘’π‘Žπ‘˜ / 𝑠𝑒𝑛 β„Žπ‘œπ‘’π‘Ÿπ‘ 
  • = 1419.6π‘Šβ„Ž2 β„Žπ‘œπ‘’π‘Ÿπ‘  = 709.8W.
  • We will select Sunpower SPR-200-BLK-U.
  • Number of panels = π‘‡π‘œπ‘‘π‘Žπ‘™ π‘π‘œπ‘€π‘’π‘Ÿ / π‘π‘œπ‘€π‘’π‘Ÿ π‘œπ‘“ π‘œπ‘›π‘’ π‘π‘Žπ‘›π‘’π‘™
  • =709.8200=3.549 π‘œπ‘Ÿ π‘Žπ‘π‘π‘Ÿπ‘œπ‘₯π‘–π‘šπ‘Žπ‘‘π‘’π‘™π‘¦ 4 π‘π‘Žπ‘›π‘’π‘™π‘ .
  • The power of panels = 4 * 200 = 800 W.

Step 4: Sizing Batteries

  • Assuming the lowest temperature in the location is -20Β°C. Then the nominal capacity will be 160 Ah instead of 330 Ah.
  • The temperature correction coefficient = 160π΄β„Ž / 330π΄β„Ž=0.48.
  • Ah of batteries = π‘‡π‘œπ‘‘π‘Žπ‘™ π‘’π‘›π‘’π‘Ÿπ‘”π‘¦ π‘›π‘’π‘’π‘‘π‘’π‘‘βˆ—π·π‘Žπ‘¦π‘  π‘œπ‘“ π‘Žπ‘’π‘‘π‘œπ‘›π‘œπ‘šπ‘¦ / π·π‘œπ·βˆ—π‘†π‘¦π‘ π‘‘π‘’π‘š π‘£π‘œπ‘™π‘‘π‘Žπ‘”π‘’βˆ—π‘‡π‘’π‘šπ‘π‘’π‘Ÿπ‘Žπ‘‘π‘’π‘Ÿπ‘’ π‘π‘œπ‘Ÿπ‘Ÿπ‘’π‘π‘‘π‘–π‘œπ‘› π‘π‘œπ‘’π‘“π‘“π‘–π‘π‘–π‘’π‘›π‘‘
  • = 1419.6π‘Šβ„Žβˆ—2 / 0.8βˆ—12π‘‰βˆ—0.48
  • = 616.15 Ah.
  • Number of series batteries = π‘†π‘¦π‘ π‘‘π‘’π‘š π‘£π‘œπ‘™π‘‘π‘Žπ‘”π‘’ / π‘π‘Žπ‘‘π‘‘π‘’π‘Ÿπ‘¦ π‘£π‘œπ‘™π‘‘π‘Žπ‘”π‘’ = 12/12 = 1 π‘π‘Žπ‘‘π‘‘π‘’π‘Ÿπ‘¦ 𝑖𝑛 π‘’π‘Žπ‘β„Ž π‘ π‘’π‘Ÿπ‘–π‘’π‘  π‘ π‘‘π‘Ÿπ‘–π‘›π‘”.
  • Number of parallel strings = π΄β„Ž π‘Ÿπ‘’π‘žπ‘’π‘–π‘Ÿπ‘’π‘‘ / π΄β„Ž π‘œπ‘“ π‘œπ‘›π‘’ π‘π‘Žπ‘‘π‘‘π‘’π‘Ÿπ‘¦=616.15 / 330=1.86 π‘œπ‘Ÿ π‘Žπ‘π‘π‘Ÿπ‘œπ‘₯π‘–π‘šπ‘Žπ‘‘π‘’π‘™π‘¦ 2 π‘π‘Žπ‘Ÿπ‘Žπ‘™π‘™π‘’π‘™ π‘ π‘‘π‘Ÿπ‘–π‘›π‘”π‘ .
  • Total batteries = 2*1 = 2 batteries.

Step 5: Sizing Charge Controller

  • The power of panels = 800 W and the system voltage is 12 V.

Important Note:

  • The series panel connection is dependent on the MPPT range.
  • We try to make the panel voltage at the middle value of this range.
  • If the MPPT range is not available, we will take half of the open circuit voltage value.

Step 6: Panel Connection

  • Assuming selection of the open circuit voltage at the middle of the maximum PV open-circuit voltage = 150/2=75 𝑉.
  • Number of panels in series = 𝐷𝑒𝑠𝑖𝑔𝑛 π‘œπ‘π‘’π‘› π‘π‘–π‘Ÿπ‘π‘’π‘–π‘‘ π‘£π‘œπ‘™π‘‘π‘Žπ‘”π‘’ / π‘ƒπ‘Žπ‘›π‘’π‘™ π‘œπ‘π‘’π‘› π‘π‘–π‘Ÿπ‘π‘’π‘–π‘‘ π‘£π‘œπ‘™π‘‘π‘Žπ‘”π‘’
  • =75 𝑉 / 47.8 𝑉=1.57 π‘œπ‘Ÿ π‘Žπ‘π‘π‘Ÿπ‘œπ‘₯π‘–π‘šπ‘Žπ‘‘π‘’π‘™π‘¦ 2 π‘π‘Žπ‘›π‘’π‘™π‘  𝑖𝑛 π‘ π‘’π‘Ÿπ‘–π‘’π‘ .
  • Panels in parallel = π‘‡π‘œπ‘‘π‘Žπ‘™ π‘›π‘’π‘šπ‘π‘’π‘Ÿ π‘œπ‘“ π‘π‘Žπ‘›π‘’π‘™π‘  / π‘›π‘’π‘šπ‘π‘’π‘Ÿ π‘œπ‘“ π‘π‘Žπ‘›π‘’π‘™π‘  𝑖𝑛 π‘ π‘’π‘Ÿπ‘–π‘’π‘ =4/2=2 π‘π‘Žπ‘Ÿπ‘Žπ‘™π‘™π‘’π‘™ π‘ π‘‘π‘Ÿπ‘–π‘›π‘”π‘ .
  • The open circuit voltage at lowest temperature = number of series panels * open circuit voltage of one panel at lowest temperature.
  • = 2(47.8+(0.065*(25+20))=101.45V < 150 V.
  • The input current of the charge controller = short-circuit current of the PV panel * number of parallel strings * safety factor (1.25 or 1.3).
  • = 1.2525.4 = 13.5 A < 50 A

Solar Power Systems Explained: Off-Grid, On-Grid, and Hybrid

🌞 Introduction to Solar Power Systems

As the demand for clean and reliable energy continues to rise, solar power has become one of the most popular and accessible renewable energy sources in the world. Whether you live in a city, a village, or a remote area, solar power can offer a sustainable solution to your electricity needs.

In this post, we’ll cover the basics of what solar power is, its key benefits, and the main types of solar systems available today.

πŸ”‹ What is Solar Power?

Solar power is the energy we get from the sun. Through the use of solar panels (photovoltaic cells), sunlight is converted into electricity that can be used to power homes, businesses, and even entire communities.

This electricity can be used directly, stored in batteries for later use, or fed into the national grid, depending on the type of solar power system you choose.

βœ… Benefits of Solar Energy

Here are some of the major benefits of using solar energy:

  1. Eco-Friendly
    Solar power is a clean, green source of energy that reduces carbon emissions and pollution.
  2. Saves Money
    Once installed, solar systems can significantly reduce your electricity bills. In many cases, you can even earn credits through net metering.
  3. Low Maintenance
    Solar systems require very little maintenance. Most solar panels come with a 20–25 year warranty.
  4. Energy Independence
    You no longer need to rely solely on utility companies. Solar energy gives you more control over your power source.
  5. Works in Remote Areas
    Solar is a game-changer for rural and off-grid locations where traditional electricity supply is not available.

β˜€οΈ Types of Solar Power Systems (Brief Intro)

There are three main types of solar power systems. Each one is designed to meet different energy needs and budgets:

1. Off-Grid Solar System

  • Not connected to the utility grid.
  • Uses batteries to store excess energy for use at night or during cloudy days.
  • Ideal for remote areas without access to grid electricity.

2. On-Grid (Grid-Tied) Solar System

  • Connected to the local utility grid.
  • Any excess power can be sent to the grid (often with credits via net metering).
  • Suitable for homes and businesses in urban areas.

3. Hybrid Solar System

  • Combines both off-grid and on-grid features.
  • Uses batteries for backup and can still send excess energy to the grid.
  • Offers the flexibility of power storage and grid connection.