Energy Efficiency, Renewables and Careers

Introduction

Power is how fast energy is used. Energy is what you pay for and what changes the climate. This lesson links the physics you know to everyday decisions, the changing energy system and careers.

Energy, power and cost

• Power (watts) is the rate of using energy.
• Energy is power over time. The unit on your bill is the kilowatt-hour (kWh): using 1000 W for one hour.

Energy (kWh) = power (kW) × time (hours)

Example: a 2 kW heater running for 3 hours uses 2 × 3 = 6 kWh. If a unit costs 0.25 in your currency, that is 6 × 0.25 = 1.50. A 10 W LED bulb running for 5 hours uses 0.01 × 5 = 0.05 kWh.

Practical efficiency

• Know the big users: heating, cooling, water heating, cooking and old appliances. Check ratings.
• Efficient lighting: LEDs give the same light for far less power than old incandescent bulbs.
• Standby power: many devices use a little all the time. Switch off at the wall where sensible.
• Insulation and draught-proofing reduce heating and cooling needs.
• Efficient motors and appliances with good energy ratings.
• Heat pumps move heat rather than creating it, and can deliver several units of heat per unit of electricity.
• Behaviour: controls, timers and sensible settings.
• Measure: a plug-in energy monitor shows real use, so you can find surprises.

Renewable electricity

• Solar photovoltaic (PV): panels turn sunlight directly into DC. An inverter converts it to AC for the grid or home. Output varies with sun, season and weather.
• Wind: turbines drive generators. Output varies with wind speed.
• Hydro: flowing or stored water turns turbines, and can be fairly controllable.
• Others include geothermal and biomass.

These sources vary. Capacity (the maximum power) is not the same as the energy actually produced over a year, which depends on conditions.

Storage and the changing grid

Because supply and demand must match, the grid is changing:

• Batteries store energy for hours, in homes and at grid scale.
• Pumped hydro and other storage handle larger amounts.
• Smart meters and demand response shift use to times of plentiful supply.
• Interconnection between regions shares variation.
• Electric vehicles add demand, and can sometimes feed back.
• Smarter grids use sensors and software to balance supply and demand.

Home installations such as solar panels and batteries involve mains-voltage wiring, structural work and regulations, so they must be done by qualified, registered installers.

Careers in electrical work

• Electrician: installs and maintains wiring in homes, buildings and industry, through apprenticeship and registration.
• Electrical technician: tests, repairs and commissions equipment.
• Electrical engineer: designs power systems, machines and controls, usually with a degree.
• Power systems and grid engineer: transmission, distribution and operations.
• Renewable energy technician or engineer: solar, wind and storage.
• Maintenance and controls engineer: keeps industrial plants running, with automation and motors.
• Energy auditor and consultant: helps reduce energy use.
• Safety and inspection roles: testing and certifying installations.

Routes include apprenticeships, vocational college courses and university degrees. Safety competence and registration matter greatly, and rules differ by country, so check your local requirements.

Try it yourself

Pick five appliances. Estimate each one's power from its label, and how long it runs per week. Calculate each one's weekly energy in kWh, and rank them. Then choose one change that would save the most.

Summary

• Energy in kWh is power in kilowatts multiplied by hours, and it sets your bill.
• Efficiency, heat pumps, LEDs and measuring use reduce energy needs.
• Solar, wind and storage change how the grid works, and electrical careers need training, competence and registration.