Energy supply and the development of society
Energy is the ability to do work: heat, light, movement, electricity. As a society develops, it uses more energy for industry, transport, cooling and heating. We measure energy in joules (J) or kilowatt-hours (kWh). 1 kWh = 3.6 million J.
- Primary energy: energy as found in nature (coal, crude oil, sunlight, wind).
- Secondary energy: energy changed into a useful form (electricity, petrol).
Global consumption has grown many times since 1950 and is still rising, mainly in Asia. Use per person is very uneven: roughly 200 kWh a day in high-income countries, about 57 kWh world average, about 19 kWh in India (approximate primary energy). About 700 million people still lack electricity.
Rising use is driven by population growth, economic growth, urbanisation and technology (more cars, air conditioners, data centres).
Renewable and non-renewable resources, fuel types and uses
Non-renewable resources (stocks) formed over millions of years and run out: coal, oil, natural gas and uranium. Renewable resources (flows) are replaced naturally: sunlight, wind, moving water, heat from the Earth, plants.
| Fuel | Main uses | Features |
|---|---|---|
| Coal | Electricity, steel | Cheap, plenty; highest CO₂, air pollution, mining damage |
| Oil | Petrol, diesel, jet fuel, plastics | Energy-dense, easy to move; spills, CO₂, price shocks |
| Natural gas | Electricity, heating, cooking (LPG/PNG), fertiliser | About half the CO₂ of coal; methane leaks; needs pipelines or LNG ships |
| Nuclear (uranium) | Electricity | Very low CO₂, reliable; high cost, radioactive waste, safety fears |
Today about 80% of world primary energy is fossil fuel: roughly oil 31%, coal 26%, gas 23%, hydro 6%, nuclear 4%, wind and solar 6%, other renewables 4% (rounded, early 2020s).
Renewable energy sources
- Solar: solar (photovoltaic) panels turn light into electricity; solar heaters warm water. Plus: free, everywhere. Minus: no output at night, needs land or roofs.
- Wind: wind turns turbine blades and a generator. Plus: very low CO₂. Minus: varies with weather, noise and visual impact.
- Hydroelectric: water stored behind a dam falls through turbines. Plus: reliable, can be switched on fast. Minus: floods valleys, moves people, harms fish.
- Geothermal: hot rock heats water into steam (Iceland, Kenya, New Zealand). Plus: steady all day. Minus: only near plate boundaries or hot spots.
- Biomass: wood, crop waste, dung or biogas. Plus: uses waste; biogas plants help villages. Minus: smoke, can compete with food crops, carbon-neutral only if regrown.
- Hydrogen fuel cells: hydrogen and oxygen combine to make electricity, and the only waste is water. Hydrogen is an energy carrier, not a source: it is clean only if made with renewable electricity (green hydrogen).
Distribution of resources and sustainability
Energy resources are unevenly spread. Oil and gas are concentrated in a few regions, such as the Middle East and Russia; coal is large in China, the USA, India and Australia; sunshine is strongest in deserts near the tropics; geothermal is near plate edges; hydro needs high rainfall and steep relief.
Current energy use is not sustainable because:
- fossil fuels will run out (reserves-to-production: oil and gas about 50 years, coal about 140 years at today's rate);
- burning them adds CO₂ that warms the climate, and causes smog and acid rain;
- extraction damages land and water (mining, oil spills, fracking).
Life-cycle CO₂ per kWh of electricity (approx.): coal 820 g, gas 490 g, solar 45 g, hydro 24 g, nuclear 12 g, wind 11 g.
Energy security, future strategies and conservation
Energy security means having enough reliable, affordable energy. Risks: wars, price shocks, depending on one supplier, extreme weather.
Strategies
- Diversify the energy mix and suppliers.
- Build renewables and storage (batteries, pumped hydro) and stronger grids.
- Use nuclear power, green hydrogen and carbon capture.
- International agreements (Paris Agreement) and shared grids.
Energy conservation
Saving energy is the cheapest new source: LED bulbs, insulation, efficient motors, public transport, star-rated appliances, switching devices off.
Try it: your home energy audit
Read your electricity bill: how many kWh did your home use this month? Divide by days and by people to get kWh per person per day. List three ways to cut 10%. Then in the 3D free play, find the low-carbon share that halves CO₂ per kWh.
Key formulas and definitions
- 1 kWh = 3.6 × 10⁶ J
- Reserves-to-production (R/P) ratio = reserves ÷ yearly production = years left
- Average CO₂ of a mix = Σ (share × CO₂ of each source)
- Energy per person = total energy use ÷ population
- Renewable = flow; non-renewable = stock
- Energy security = enough + reliable + affordable
Worked examples
1. A country has 300 billion barrels of oil reserves and produces 6 billion barrels a year. How long will it last at this rate?
R/P = 300 ÷ 6 = 50 years.
2. Electricity is 70% coal (820 g/kWh) and 30% wind (11 g/kWh). Find the average CO₂ per kWh.
0.7 × 820 + 0.3 × 11 = 574 + 3.3 ≈ 577 g CO₂ per kWh.
3. A home uses 240 kWh in 30 days and has 4 people. Find use per person per day.
240 ÷ 30 = 8 kWh a day; 8 ÷ 4 = 2 kWh per person per day (electricity only).
4. Why is hydrogen called an energy carrier and not a source?
Hydrogen is not found free in nature. We must use energy to make it (for example, splitting water with electricity). It stores and carries that energy to where it is used.
Common mistakes
- Calling nuclear power renewable. Uranium is a stock that runs out, even though nuclear is low-carbon.
- Thinking renewable means zero pollution. Making panels, dams and turbines has some impact; biomass burning makes smoke.
- Treating R/P years as an exact date when oil ends. New finds, prices and demand change it.
- Mixing up energy and power: energy is kWh (amount), power is kW (rate).