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Are you interested in using the sun’s power to lower your electricity bills and live more sustainably? Look no further than a solar photovoltaic (PV) system! But before you jump in, understanding the basics of the solar PV system design is crucial. This guide will walk you through the key components and sizing considerations, empowering you to make informed decisions and giving you the ability to design a solar PV system for your home.
Components of a solar pv system
A solar PV system is like a mini power plant in your backyard, converting sunlight into usable electricity. The system consists of the following members:
- Solar Panels: These devices capture the sun’s rays and transform them into direct current (DC) electricity.
- Solar Charge Controller: This smart regulator ensures your batteries don’t get overwhelmed, maximizing their lifespan.
- Inverter: The translator of the system, converting DC power from panels into alternating current (AC) electricity, which is required by the appliances.
- Batteries: These are devices responsible for energy storage, they keep your system running smoothly even when the sun takes a break.
- Loads: Your appliances, from lights and fridges to TVs and computers.
Sizing the solar PV system
Now, let’s get down to the details: figuring out how much solar power you need. This involves three key steps:
- Calculating Your Energy Needs: Add up the wattage and daily usage hours of your appliances to understand your total power consumption.
- Sizing Your Solar Panels: Divide your daily energy needs by your local “panel generation factor” to determine the total wattage your panels need to produce. Based on individual panel wattage, you can then calculate the number of panels required.
- Choosing the Right Inverter: The inverter size should match your total appliance wattage, with a safety margin of 25-30%.
- Battery sizing: This depends on your desired autonomy (days you want to run on stored energy) and appliance usage. Don’t worry, we’ll provide the formulas to guide you!
The battery should be large enough to store sufficient energy to operate the appliances at night and cloudy days. To find out the size of battery, calculate as follows:
4.1 Calculate total Watt-hours per day used by appliances.
4.2 Divide the total Watt-hours per day used by 0.85 for battery loss.
4.3 Divide the answer obtained in item 4.2 by 0.6 for depth of discharge.
4.4 Divide the answer obtained in item 4.3 by the nominal battery voltage.
4.5 Multiply the answer obtained in item 4.4 with days of autonomy (the number of days that you
need the system to operate when there is no power produced by PV panels) to get the required Ampere-hour capacity of battery.
Battery Capacity (Ah) = Total Watt-hours per day used by appliances x Days of autonomy
(0.85 x 0.6 x nominal battery voltage)
Example
Let’s put theory into practice with an example. Imagine a home with a 4-hour daily usage of an 18W fluorescent lamp, a 2-hour usage of a 60W fan, and a refrigerator running 12 hours on 75W (compressor on for half the time). This system, powered by 12V, 110Wp panels, would require:
Determine power consumption demands
Total appliance use = (18 W x 4 hours) + (60 W x 2 hours) + (75 W x 24 x 0.5 hours) | |
= 1,092 Wh/day | |
Total PV panels energy needed | = 1,092 x 1.3 |
= 1,419.6 Wh/day. | |
Size the PV panel
2.1 Total Wp of PV panel capacity | = 1,419.6 / 3.4 |
= 413.9 Wp | |
2.2 Number of PV panels needed | = 413.9 / 110 |
= 3.76 modules |
Actual requirement = 4 modules
So this system should be powered by at least 4 modules of 110 Wp PV module.
Inverter sizing
Total Watt of all appliances = 18 + 60 + 75 = 153 W
For safety, the inverter should be considered 25-30% bigger size.
The inverter size should be about 190 W or greater.Battery sizing
Total appliances use = (18 W x 4 hours) + (60 W x 2 hours) + (75 W x 12 hours)
Nominal battery voltage = 12 V
Days of autonomy = 3 days
Battery capacity = [(18 W x 4 hours) + (60 W x 2 hours) + (75 W x 12 hours)] x 3
(0.85 x 0.6 x 12)
Total Ampere-hours required 535.29 Ah
So the battery should be rated 12 V 600 Ah for 3 day autonomy.
Solar charge controller sizing
PV module specification
Pm = 110 Wp
Vm = 16.7 Vdc
Im = 6.6 A
Voc = 20.7 A
Isc = 7.5 A
Solar charge controller rating = (4 strings x 7.5 A) x 1.3 = 39 A
So the solar charge controller should be rated 40 A at 12 V or greater.
Conclusion
This guide provides a solid foundation for designing your solar PV system. However, for more specific needs, consider consulting a professional installer. They can address advanced topics like shading analysis, grid interconnection, and financial considerations like cost-benefit analysis and available incentives.
With a little planning and this guide as your roadmap, you can power your home with the sun, enjoy energy independence, and contribute to a greener future. Start your solar journey today! Get a pocket friendly quote from us at https://kenyasolarinstallers.co.ke/contact/
