Energy Resources and Sustainability
Energy Resources
The main energy sources available on Earth fall into two categories:
• Non-renewable sources — will eventually run out. These include fossil fuels (coal, oil, natural gas) and nuclear fuel (uranium, plutonium). Fossil fuels formed over millions of years from the remains of dead organisms. They are being consumed far faster than they can form.
• Renewable sources — are replenished naturally and will not run out. These include solar, wind, hydroelectric, tidal, geothermal, wave and biomass (P6.2a).
Non-renewable sources (fossil fuels, nuclear) will run out. Renewable sources (solar, wind, hydro, tidal, geothermal, wave, biomass) are replenished naturally. Nuclear is non-renewable but does not produce CO\(_2\) during generation.
Environmental Impacts
Every energy resource has environmental consequences (P6.2b):
Fossil fuels release CO\(_2\) when burned, contributing to the greenhouse effect and climate change. They also release sulfur dioxide (causing acid rain) and particulates (causing respiratory problems). Oil spills damage marine ecosystems.
Nuclear power produces no CO\(_2\) during generation and is very reliable, but creates radioactive waste that remains dangerous for thousands of years and must be stored securely. There is also risk of nuclear accidents (e.g. Chernobyl, Fukushima).
Renewable sources generally produce little or no CO\(_2\) during operation, making them crucial for tackling climate change. However, they often have significant land use requirements (solar farms, wind farms) and can affect local ecosystems and communities. The embodied energy in manufacturing solar panels and wind turbines must also be considered, though this is typically repaid within a few years of operation.
The carbon footprint of an energy source considers the total greenhouse gas emissions across its entire lifecycle — from construction through operation to decommissioning. On this measure, wind, solar, nuclear and hydroelectric all have much lower footprints than fossil fuels. Natural gas has the lowest carbon footprint of the fossil fuels (about half that of coal per unit of energy), which is why it is sometimes called a ‘transition fuel’ as countries move towards renewables.
Energy demand varies throughout the day (peak demand in the evening) and throughout the year (higher in winter). Baseload power stations (nuclear, gas) run continuously to meet minimum demand, while renewable sources and gas turbines provide additional capacity during peaks. The growing use of battery storage and pumped hydro storage helps balance intermittent renewable supply with variable demand.
Solar: no pollution during operation, low running costs. Disadvantages: expensive to install, dependent on sunlight (ineffective at night or in cloudy weather), large areas needed for solar farms.
Wind: no pollution during operation, free fuel. Disadvantages: intermittent (only generates when wind blows), visual and noise impact, can harm birds.
Hydroelectric: reliable, can respond quickly to demand, no fuel costs. Disadvantages: requires damming rivers, which floods valleys, displaces communities and destroys habitats.
Tidal: very predictable (tides are regular), no pollution. Disadvantages: very expensive to build, limited suitable locations, can affect marine ecosystems.
Geothermal: reliable, low emissions, small land footprint. Disadvantages: only available where hot rocks are near the surface (volcanic regions), high drilling costs.
Biomass: carbon-neutral in theory (CO\(_2\) absorbed during growth equals CO\(_2\) released during burning). Disadvantages: requires land to grow fuel crops (competing with food production), still produces pollutants when burned.
Renewable sources produce little or no CO\(_2\) during operation but many are intermittent or require specific locations. No energy source is perfect — each has trade-offs between cost, reliability and environmental impact.
The National Grid
The National Grid is a network of cables and transformers that distributes electricity from power stations to consumers across the country (P6.2c). Electricity is transmitted at high voltage and low current through overhead power lines. This is because energy loss due to heating in the cables is proportional to the current squared (\(P = I^2 R\)). Using high voltage reduces the current and therefore reduces energy wasted as heat in the cables.
Step-up transformers at power stations increase the voltage (to 400,000 V) for efficient long-distance transmission. Step-down transformers near homes reduce the voltage (to 230 V) for safe domestic use.
The UK is transitioning from fossil fuels to renewables to reduce carbon emissions and improve energy security (not relying on imported fuels). The energy mix — the combination of sources used — is changing: wind and solar capacity is increasing while coal use has virtually ended.
Challenges include the intermittency of wind and solar (requiring backup from gas or nuclear), the need for energy storage (e.g. batteries, pumped hydro storage) and the cost of upgrading infrastructure. Nuclear power is being considered as a reliable low-carbon baseload source to complement renewables.
The National Grid transmits electricity at high voltage (low current) to reduce energy losses (\(P = I^2 R\)). Step-up transformers increase voltage for transmission; step-down transformers reduce it for safe domestic use.