Energy Efficiency in Solar System SS2 Solar Photovoltaic Installation & Maintenance Lesson Note

The Golden Rule of Solar

Before we even talk about batteries or panels, we have to talk about Efficiency.

In a normal house connected to the “grid” (PHCN/NEPA), people are often careless because power is relatively cheap (when it’s available). But in a Solar System, every watt counts.

The Golden Rule: > It is much cheaper to buy a low-energy lightbulb than it is to buy a bigger solar panel to power an old, hungry lightbulb.

Energy Efficiency means using technology that requires less electricity to do the same job.

Energy Conservation means changing our habits (like turning off the TV when no one is watching).

Lighting – The “Low Hanging Fruit“

Lighting is the easiest place to save energy. In Nigeria, many homes still use “Incandescent” bulbs (the ones that get very hot) or “Fluorescent” tubes.

The Comparison:

• Old Bulb: Uses 60 Watts and turns most of that into heat, not light.
• LED Bulb: Uses only 7–9 Watts to give the same amount of brightness.

Calculation Tip for Students: If you swap 10 old bulbs (60W each) for 10 LED bulbs (9W each), you save 510 Watts every hour! That is enough energy saved to power a whole refrigerator for free.

Cooling and Appliances

In a tropical climate like ours, fans and fridges are the “heavy lifters.”

1. Refrigerators: Look for “Inverter” compressors. Old fridges kick on with a huge “surge” of power that can trip a solar inverter. Inverter fridges start slowly and use much less battery at night.
2. Air Conditioners: A standard AC is a “solar killer.” If a client wants AC on solar, they must use a DC Inverter AC. It can save up to 50% of the energy used by a regular one.
3. The “Phantom Load”: Did you know a TV uses power even when it is “off” but plugged in? This is called a standby load. In a solar home, we teach people to switch off the socket entirely.

Smart Building Design (Passive Cooling)

Sometimes, the best way to save solar energy is to not use electricity at all. This is called Passive Design. If a house is cool by design, you don’t need the fan or AC as much.

• Cross Ventilation: Placing windows opposite each other so the breeze flows through.
• Shading: Planting trees or using wide roof “overhangs” to keep the sun from hitting the windows directly.
• Insulation: Using materials in the ceiling (like POP or glass wool) to block the heat from the roof.

Discussion Point: If the room is 28∘C because of good windows, the fan stays on speed 1. If the room is 35∘C, the fan stays on speed 5. That difference saves battery life for the morning!

Creating an Energy Budget

Just like a money budget, a solar user needs an Energy Budget. This is a plan of what to use and when.

The “Daytime Rule”: In solar design, we encourage people to do “heavy” work during the day when the sun is out.

• Do: Pump water, iron clothes, or grind pepper at 1:00 PM (using direct sun).
• Don’t: Wait until 8:00 PM to pump water (using expensive battery power).

Summary for the Designer: When you go to a house to design a solar system:

1. Count the old bulbs and tell the owner to change them to LEDs.
2. Check the fridge—is it an old “power guzzler”?
3. Explain that solar isn’t just “free power”; it’s “managed power.”