4 · IGCSE Physics
Energy resources
Build an electricity supply from eight energy resources and watch whether it meets demand hour by hour through a day. Compare reliability, CO₂ emissions and indicative cost as you change the mix and the weather.
Time:
Demand:
Supply:
Now:
Largest source now:
Demand met (day):
Unmet energy:
CO₂ emitted:
Carbon intensity:
Low-carbon share:
Curtailed (wasted):
Indicative cost:
Reliability:
Installed capacity
Supply must equal demand at every instant:
P(coal) + P(gas) + … + P(geothermal) = P(demand)
Energy: E = P × t (1 GW for 1 h = 1 GWh)
CO₂ = E × emission factor
(coal ≈ 0.9 t MWh⁻¹, gas ≈ 0.4 t MWh⁻¹)
P(coal) + P(gas) + … + P(geothermal) = P(demand)
Energy: E = P × t (1 GW for 1 h = 1 GWh)
CO₂ = E × emission factor
(coal ≈ 0.9 t MWh⁻¹, gas ≈ 0.4 t MWh⁻¹)
Order of use: nuclear, geothermal, wind, solar and tidal first; hydro, gas and coal are switched on to fill any gap. Costs are rough indicative averages per MWh.
Try this
- Switch from Fossil-heavy to Low-carbon and compare the CO₂ emitted and the carbon intensity. Which sources supply the evening peak in each case?
- With Renewables only, change the weather to Cloudy and calm. When do power cuts happen, and how many GW of gas do you need to add to remove them?
- Set tidal to 10 GW and everything else to zero: the output peaks about 6.2 h apart. Is tidal predictable? Does it match demand?
Exam tip: when comparing resources, comment on three things for each – whether it is renewable, whether it is reliable (available on demand) and its environmental impact – for example, wind is renewable and emits no CO₂ while generating, but is unreliable because it depends on the weather.