As a typical Nigerian, one thing is common to us all, “the power problem”. If it doesn’t affect you at home, it affects you at the office. It has to come up somewhere eventually. These days the problem is even more complicated, the power units have been doubled by the IKEDC, and the petrol pump price has increased significantly. But there is a saving grace, you keep hearing people talk about solar and how it’s solving their power problems.
A big question probably keeps popping up in your head; How many panels do I need exactly? Where can I buy these from? How do I know what you consume? What are the best deals available out there?
Let’s take the questions one at a time.
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Determining how many solar panels you’ll need for your home means first knowing what your goals are. Do you want to minimize your carbon footprint? Maximize your return on your investment? Save as much money as possible? Most people want to save money while getting the best out of the solar system.
To calculate how many solar panels you need, you need to know the following:
- How much energy your household uses;
- Your roof’s usable surface area;
- The climate and peak sunlight in your area (this is generally favourable across Nigeria);
- The wattage and relative efficiency of the photovoltaic (PV) panels you’re considering;
One simple way of answering the “How many solar panels do I need” question is to visit here.
Below is a DIY (Do It Yourself) complete guide on solar panel design installation. It covers calculations about the number of solar panels, batteries rating / backup time, inverter/UPS rating, load and required power in Watts. If you follow the step below you can successfully calculate just how much you need.
Now let’s begin!
Suppose, we are going to install a solar power system in our home for a total load of 800W where the required backup time is 3 hours (this is just for a sample calculation)
LCD 42 Inches TV = 120 watts
Medium sized Fridge = 105 watts
36” Fan = 55 watts
5 100-watts light bulb = 500 watts
Decoder = 14 watts
Cell phone Charger = 6 watts
Load = 800 Watts
Required Backup time for batteries = 3 Hours
What do we need to know?
- Inverter / UPS Rating =?
- The number of batteries for backup power =?
- Backup Hours of batteries =?
Inverter / UPS Rating:
Inverter / UPS rating should be greater than 25% of the total load (for the future load as well as taking losses in consideration)
- 800 x (25/100) = 200W
- Our Load + 25% Extra Power = 800W+200W = 1,000 Watt.
This is the rating of the UPS (Inverter) i.e. We will need a 1,000W inverter for our solar panel installation according to our needs.
Required Number of Batteries
Now the required back up time of batteries in hours = 3 Hours
Suppose we are going to install a 100Ah, 12 V battery, the power it would generate is:
- 12V x 100Ah = 1200 Wh
Now to get the amount of backup time this battery will produce, we simply make this calculator below:
- 1200 Wh / 800 W = 1.5 Hours
But our required Backup time is 3 Hours.
Then we divide the backup time required by the backup time gotten.
Therefore, 3/1.5 Hours = 2 → i.e. we will have to connect two (2) batteries each of 100Ah, 12V.
How Many Solar Panels Do You Need?
A solar panel operating at 20 percent efficiency produces around 265 watts of power per hour.
Manufacturers are required to label the panels with the number of kilowatts they can power per hour during ideal conditions, i.e. direct sunlight on a cloudless and sunny day. This number is called a Standard Test Condition rating (STC) and will be for example 265 if the panel produces 265 watts of power.
If your goal is to produce 1,000 Wh, then truly you must produce 1,250 Wh to allow for loss in output efficiency.
Remember, if you are receiving an average of four hours of usable sunshine per day and your solar panel is rated at 250 watts of power, then you will need five panels to reliably
Backup Hours of Batteries
Let’s say the number of batteries and their capacities is already known, and you would like to figure out the backup time for these given batteries, then use this formula below to calculate the backup hours of these batteries:
- 2 x 1200Wh batteries
- 1200 Wh x 2 Batteries = 2400 Wh
- 2400 Wh / 800 W = 3 hours of backup time
With the UPS/Inverter rating, you’ll be able to gauge just how many panels you need from the ratings as described in the previous point.
This is a simple example of how to determine power ratings with regards to a Solar power system.
To make things easier, complete the assessment and get a free quotation on this page.
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