Energy Resources and the Domestic Power Equation
Renewable and Non-Renewable Resources
Every device that uses energy needs a resource to supply it. Energy resources fall into two broad categories. Non-renewable resources will eventually run out: fossil fuels (coal, oil, natural gas) and nuclear fuel are the main examples. Renewable resources are replenished continuously by natural processes and will not run out.
Non-renewable: fossil fuels (coal, oil, natural gas) and nuclear fuel. Renewable: solar, wind, hydroelectric, tidal, wave, geothermal and biofuels. The key difference is whether the resource can be replaced within a human lifetime.
Fossil Fuels
Fossil fuels were formed over millions of years from the remains of ancient organisms. When burned, they release chemical energy stored in their bonds. Fossil fuels are reliable — they can generate electricity whenever needed — but burning them releases carbon dioxide, a greenhouse gas that contributes to climate change. They also release sulfur dioxide (especially coal), which causes acid rain, and particulate pollution that harms air quality.
Once a fossil fuel reserve is used up, it cannot be replaced within any realistic human timeframe. This makes them finite resources and a long-term supply risk.
Nuclear Fuel
Nuclear fuel (commonly uranium-235) releases energy through nuclear fission rather than combustion. Nuclear power stations generate large amounts of electricity with no carbon dioxide emissions during operation — a significant advantage for reducing greenhouse gas output. The main disadvantages are: radioactive waste that must be safely stored for thousands of years, high construction and decommissioning costs, and the public perception of safety risk.
Nuclear power: advantage — no CO₂ during operation, high energy output; disadvantage — radioactive waste, expensive decommissioning. Fossil fuels: advantage — reliable, cheap infrastructure; disadvantage — CO₂ emissions, finite supply.
Renewable Resources in Detail
Renewable sources produce electricity without releasing carbon dioxide during operation, but each has specific drawbacks.
Wind: turbines convert the kinetic energy of moving air into electrical energy. Reliable where wind speeds are consistently high (offshore sites are favoured in the UK). Disadvantage: output is variable and weather-dependent; turbines can generate noise and are considered visually intrusive by some communities.
Solar (photovoltaic): solar panels convert light energy directly into electrical energy. No moving parts, very low maintenance. Disadvantage: output depends on daylight and cloud cover; less effective at high latitudes or in winter.
Hydroelectric: water stored behind a dam is released to drive turbines. Highly reliable and can respond quickly to peaks in demand. Disadvantage: requires flooding large valleys, which destroys habitats and displaces communities; limited suitable sites.
Tidal: the gravitational pull of the Moon and Sun drives predictable tidal flows. Barrages or tidal stream generators harness this movement. Highly predictable, but limited to coastal locations with significant tidal range.
Wave power: devices on the ocean surface capture the kinetic and potential energy of waves. Potential near coastlines, but reliable technology at scale remains under development.
Geothermal: heat energy from within the Earth is used to produce steam, driving turbines. Very reliable and continuous. Limited to regions with accessible geothermal activity (e.g. Iceland, parts of the USA).
Biofuels are derived from organic matter (crops, wood, waste). They are considered renewable because new biomass can be grown. However, burning biofuels does release carbon dioxide — the argument is that this is offset by the carbon absorbed by growing plants. Land use for biofuel crops can compete with food production.
Comparing Resources: A Summary
When evaluating energy resources, you should consider: reliability (can the source generate power on demand?), environmental impact (CO₂, habitat loss, pollution), cost (construction, fuel, decommissioning), and scalability (can it supply enough power for an entire country?).
Most countries use a mix of energy resources to balance reliability, cost and environmental impact. No single renewable resource is yet able to replace fossil fuels entirely without large-scale energy storage solutions.
The Power Equation: P = E/t
Power tells us how quickly energy is transferred. The equation is:
$$P = \frac{E}{t}$$
Where \(P\) is power in watts (W), \(E\) is energy transferred in joules (J), and \(t\) is time in seconds (s). One watt means one joule of energy is transferred every second.
\(P = E / t\) where \(P\) is power in watts, \(E\) is energy in joules, and \(t\) is time in seconds. Rearranged: \(E = Pt\) and \(t = E / P\).
Example 1: A wind turbine transfers 900,000 J of energy in 600 s. Calculate its power output.
\(P = \frac{E}{t} = \frac{900{,}000}{600} = 1{,}500\) W (1.5 kW)
Example 2: A 2.5 kW solar panel operates for 4 hours. Calculate the energy transferred in joules.
Convert time: \(4 \times 3600 = 14{,}400\) s
\(E = Pt = 2500 \times 14{,}400 = 36{,}000{,}000\) J = 36 MJ
Always convert hours to seconds (multiply by 3600) before substituting into the equation.
Domestic and Industrial Energy Use
Households use energy for heating, lighting, cooking, refrigeration, and powering appliances. Industrial users include manufacturing, transport and agriculture. The total demand on the National Grid must be met by the combined output of all generating sources at every moment.
The National Grid balances supply and demand in real time. Renewable sources with variable output (wind, solar) make this balancing task more complex, which is why energy storage — such as pumped-storage hydroelectric schemes — plays an important role alongside variable renewables.