Energy resources · Grade 8
We generate electricity and power transport from many energy resources. Some, like coal, oil and gas, will run out and release carbon dioxide; others, like wind, solar and hydroelectric, are renewable but depend on the weather or the landscape. Choosing a mix means weighing up cost, reliability and environmental impact.
Key facts
- Non-renewable: coal, oil, natural gas (fossil fuels) and nuclear (uranium).
- Renewable: solar, wind, hydroelectric, tidal, wave, geothermal, biofuel.
- Burning fossil fuels releases CO₂ (global warming) and sulfur dioxide (acid rain).
- Nuclear power releases no CO₂ while running but produces radioactive waste.
- Wind and solar are unreliable (weather, night); gas, nuclear, hydro and geothermal can supply on demand.
- Power from wind ∝ v³; hydroelectric power = efficiency × (mass of water per second) × g × h.
Worked examples
Example 1
Solar panels of area 10 m² receive 800 W/m² and are 20% efficient. Find their electrical power output.
Answer: 1,600 W
Example 2
In a hydroelectric station, 50 m³ of water falls 80 m each second. It is 90% efficient. Find the power output. (ρ = 1,000 kg/m³, g = 9.8 N/kg)
Answer: 35.3 MW