Module 2 • Duration: 55 Minutes • Format: Video Demonstration + Practical Guide

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Learning Objectives

By the end of this lesson, you will be able to:

• Conduct a professional on-site electrical energy audit for residential and commercial clients
• Calculate daily energy consumption in Watt-hours (Wh) and kilowatt-hours (kWh)
• Differentiate between resistive and inductive loads, factoring in motor inrush surge currents
• Construct a precise 24-hour load profile to size inverter and battery capacity

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1. The Importance of a Professional Energy Audit

The single greatest mistake made by amateur solar installers in Nigeria is guessing the system size based on property size (e.g., "A 4-bedroom duplex always needs a 5kVA system").

Every home and business has distinct energy consumption habits. Over-sizing inflates capital expenditure needlessly, while under-sizing leads to inverter overloads, battery deep-discharge, and client dissatisfaction.

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2. Conducting the Load Audit Step-by-Step

Step 1: Equipment Inventory & Nameplate Inspection

Walk through every room with an audit clipboard or digital tablet. Inspect the manufacturer nameplate on each appliance to record rated wattage ($W$) or rated voltage and current ($V \times I$).

Step 2: Establish Realistic Operating Hours

Interview the client to determine how many hours each appliance runs during:

• Daytime (Solar hours: 8:00 AM – 5:00 PM): Powered directly by solar PV.
• Nighttime (Non-solar hours: 5:00 PM – 8:00 AM): Powered exclusively from the battery energy storage system.

Step 3: Appliance Classification (Resistive vs. Inductive)

• Resistive Loads: Light bulbs, flat screen TVs, computers, electric kettles, soldering irons. Unity power factor ($\text{PF} \approx 1.0$). Negligible start-up surge.
• Inductive (Motor) Loads: Refrigerator compressors, air conditioning units, submersible water pumping machines, washing machine motors, power tools. Low power factor ($\text{PF} = 0.7 - 0.85$).
  • Inrush Surge: Inductive loads draw 3 to 6 times their rated running power for 1 to 3 seconds during compressor startup. An inverter must be sized to endure this instantaneous surge.

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3. Practical Energy Audit Calculation Sheet

Consider a typical 3-bedroom residential client in Abuja:

Appliance	Quantity	Rated Watts (W)	Total Watts	Daily Run Hours	Daytime Hours	Night Hours	Daily Energy (Wh)
LED Lighting	12	15 W	180 W	6 hrs	1 hr	5 hrs	1,080 Wh
Smart TV (55") + Decoder	2	120 W	240 W	8 hrs	3 hrs	5 hrs	1,920 Wh
Standing Fans	4	60 W	240 W	10 hrs	2 hrs	8 hrs	2,400 Wh
Inverter Refrigerator	1	150 W (running)	150 W	24 hrs (duty 50%)	6 hrs	6 hrs	1,800 Wh
Laptop Computers	2	65 W	130 W	6 hrs	4 hrs	2 hrs	780 Wh
WiFi Router & CCTV NVR	1	50 W	50 W	24 hrs	9 hrs	15 hrs	1,200 Wh
1.5HP Inverter Air Conditioner	1	1,100 W	1,100 W	6 hrs	4 hrs	2 hrs	6,600 Wh
Total Simultaneous Load			2,090 W
Total Daily Energy							15,780 Wh (15.78 kWh)

From this table:

• Nighttime Energy Demand: $(180\times 5) + (240\times 5) + (240\times 8) + (150\times 6) + (130\times 2) + (50\times 15) + (1,100\times 2) = 8,390\text{ Wh (8.39 kWh)}$.
• This audit forms the exact numerical baseline for sizing our solar panels, battery bank, and inverter.

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Knowledge Check & Self-Assessment

Lesson 2 Knowledge Check Test your understanding before proceeding to the next lesson:

1. What is the minimum recommended tilt angle for solar panels installed in Nigeria to ensure natural self-cleaning?

A) 0° (Flat)

B) 10° – 12° (True South orientation)

C) 45°

D) 90° (Vertical)

2. In a hybrid solar installation, why should standard AC circuit breakers never be used on the high-voltage DC solar circuit?

A) AC breakers are too expensive

B) DC current has no natural zero-crossing point, causing continuous destructive arcs inside AC breakers

C) AC breakers reduce the wattage of the panels

D) They cause battery charging to reverse

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Hands-On Lab Assignment (GTE Practical Workshop)

1. Practical Exercise: Using your digital multimeter and clamp meter, perform the full pre-commissioning testing sequence demonstrated in this lesson.
2. Documentation Task: Fill out the GTE Field Commissioning Inspection Form with your measured values, verifying that all readings match theoretical design calculations within a 5% margin of error.
3. Submission: Upload your completed inspection sheet and photo of your multimeter test reading to the GTE Academy portal for instructor evaluation.

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