The proposed system uses a solar panel as the main source to get electricity. The solar panel gets the energy from the sun. It also calls the photovoltaic effect, this process causes electrons to become quite disrupted from their normal atomic orbit. This action alone creates an electrical power in the panels (also called DC), which then is sent to the battery. Then, the inverter is connected to the battery and it will automatically convert the DC into AC. Next, after the battery is fully charged or while charging we use it to charge the lamp and fan. All the component in the system is controlled by a controller.
Load Determination
In this paper, the electrical appliances that used for drawing power from the solar system are DC table fan and AC lamp. The quantity that needs to use for both electrical appliances is one but with different wattage. The wattage of the table fan is 50 W and for the lamp is 16 W and the usage of the load is 8 hours and 6 hours per day respectively.
| Item | Quantity | Wattage | Total Watt | Hours per Day | Total Watt Hours per Day |
| Table Fan (DC) | 3 | 6W | 18 | 6 | 108 |
| Lamp (AC) | 2 | 3W | 6 | 5 | 30 |
| – | – | Σ of total watt | 24W | Σ of Total Wh/day | 138 Wh/day 2.2 |
Battery Selection
The battery type recommended for using in a solar PV system is deep cycle lead-acid battery. Deep-cycle lead-acid battery is specifically designed to be discharged to low energy level and rapid recharged or cycle charged and discharged day after day for years. The battery should be large enough to store sufficient energy to operate the appliances at night and cloudy days. Hence, a 12V battery is chosen as it will be optimum for the system.
- Voltage of battery = 12 V
- Total Watt. Hour/day = 138 Wh/day
- Efficiency of battery = 80% (batteries are not 100% efficient)
Battery Capacity (Ah) = (Total Watt – hours per day used by appliances/ efficiency*nominal battery voltage) = ((138Wh/day)/(0.8*12V)) = 14.4Ah
Total Ampere-hours required is 14.4 Ah. So, the battery should be rated at 12 V, 14 Ah.
Solar Panel Selection
According to Table 2, the summation of the total watt-hours per day will be used by the system is 138 Watt-hour per day. The energy that needs to generate by the system must more than the energy that wants to use. Let assume 6 hours of effective sunlight which will generate the rated power due to the location of the sunlight which is not uniform during the 12-hour daytime.
Total power output of Panels = 12 𝑉 x 14 Ah = 168𝑊ℎ (2)
Power to be generated per hour = 168𝑊ℎ / 6ℎ =28 𝑊 (3)
Compensate for system inefficiencies. Every part of a solar-powered system has some inefficiency in it. The rule of thumb is used when there has an inverter (to produce AC) which makes the total system inefficiency become 30%. For systems that will be using the DC voltage directly from the battery bank, the inefficiency factor is 20%. So, the sizes of the solar panel need to be multiplied with 1.3.
Total of solar panel watts needed = 28 𝑊 x 1.3 =36.4 𝑊 (4)
In order to determine the number of solar panels needed, divide the total of solar panel watts needed with the rated power output (watts) of the solar generator with its solar panel that has been chosen.
Total number of solar panel needed = Total of solar panel watts needed/Solar panel rated output = 36.4W20𝑊 = 1.82 (5)
In conclusion, this system should be powered by at least 2 modules of 20 W, 12 V solar panel.
Charge controller Selection
The solar charge controller is typically rated against Amperage and Voltage capacities. So the current of the charge controller is calculated. Since this system is rated at 12V, the charge controller is also 12V.
Current rating = Power output of Panels/Voltage =28 W/12 V=2.33 A (6)
For safety factor, the size of the controller needs to be multiplied by 1.25.
New controller size = 2.33 A x 1.25 = 3 A (7)
Inverter Selection
The size of the inverter depends on the total watt of appliances. But for the safety issue, the size of the inverter should be 25 – 30% bigger than the total watt of the appliances. But it is not advisable if the watt of the inverter is too high because it will eventually decrease the efficiency of the ATO solar generator. Since the total watt for appliances is 24 W, thus the inverter size will be calculated as below:
Inverter size = (0.30 x 24 W) + 24 W = 31.2 W ≈100W (8)