Lesson 7 – O: Orient Your Learning: How Do We Match Solar Supply to Energy Demand in a Mini-Grid?

O: Orient Your Learning

Planning a Mini-Grid System by Knowing the Energy That Is Needed

Power tells what is happening now. Energy tells what happens over time.

You already know that power is measured in watts. Power tells how fast electrical energy is being used or produced at one moment.

Energy includes time. If you want to know how much electricity a load uses in a day, you need both:

How much power it uses
How long it runs

Key Formula

Daily energy = power × hours of use

Example

Infographic titled "Power vs. Energy: Understanding the Difference" comparing electrical power (watts) and energy (watt-hours). The left panel explains that power (W) is the rate at which electricity is used at a given moment, illustrated by a glowing 10-watt light bulb labeled "10 W." The right panel explains that energy (Wh) is the total electricity used over time, using the example of the same 10-watt light bulb operating for 5 hours, shown with a sequence of clocks. A calculation demonstrates 10 W × 5 hours = 50 Wh/day. A key formula at the bottom states: Daily energy (Wh) = Power (W) × Hours of use (h/day).

Engineers estimate solar supply in a similar way. If a panel is rated at 200 W and the site gets about 5 hours of strong sunlight, the panel produces about:

Infographic titled "Solar Panel Example: Power and Energy" explaining the difference between power (watts) and energy (watt-hours) using a solar panel. The left panel shows a solar panel under the sun labeled "Panel power: 200 W," explaining that power (W) is how fast electricity is produced at a given moment. The right panel explains that energy (Wh) is the total electricity produced over time, illustrating 5 hours of strong sunlight with a sequence of sun-and-clock icons labeled 1 through 5 hours. A calculation shows 200 W × 5 hours = 1,000 Wh/day. A key formula at the bottom states: Daily energy (Wh) = Power (W) × Sun-hours (h/day).

Key Idea

To know whether a mini-grid can meet a need, engineers compare daily demand to daily supply.

Think About It

Which uses more daily energy:

A small device that runs all day
A larger decice that runs for only a short time