Renewable & Non-Renewable Energy Resources and Power Stations

1

Non-renewable energy resources

Finite resources that cannot be replenished on a human timescale and will eventually run out: 1. Fossil fuels (Coal, Oil, and Natural Gas): reliable, high energy density, and existing infrastructure, but release CO₂ (global warming) and SO₂ (acid rain, especially coal). Gas has the shortest start-up time and emits the least CO₂ per MJ of the three. 2. Nuclear fuels (Uranium and Plutonium): zero CO₂ or SO₂ emissions during operation and huge energy released per kg of fuel, but produces dangerous radioactive waste (expensive to store for thousands of years) and carries high decommissioning costs and accident risks.

Save

2

Solar & Wind Energy

Renewable resources with zero fuel costs and zero greenhouse gas emissions during operation, but both are unreliable (intermittent). Solar cells (photovoltaic panels) convert sunlight directly into DC electricity (or solar thermal panels heat water), but generate nothing at night and less in cloudy winter weather. Wind turbines use wind kinetic energy to turn a generator directly, but produce nothing on calm days (or must shut down in storm-force winds) and cause visual/noise pollution.

Save

3

Hydroelectric & Pumped Storage

Rainwater trapped behind a dam in a high-altitude reservoir has a large gravitational potential energy (GPE) store. When sluice gates open, water flows downhill (GPE -> kinetic energy), turning turbines connected to generators. Very reliable with an immediate start-up time to meet power surges (pumped storage pumps water back up at night using cheap surplus electricity), but flooding valleys destroys habitats, displaces communities, and rotting submerged vegetation releases methane.

Save

4

Tidal & Wave Power

Tidal barrages are built across river estuaries: as the tide comes in and goes out (caused by the gravitational pull of the Moon and Sun), water flows through turbines in the barrage. Extremely predictable (tides happen twice a day at known times), though not continuous, and alters estuary habitats for wading birds and blocks shipping. Wave power uses floating generators rocked up and down by surface waves (driven by wind); renewable and pollution-free, but unreliable in calm seas and easily damaged by storms.

Save

5

Geothermal Energy

Uses thermal energy from the Earth's interior (generated by the radioactive decay of elements in the crust/mantle). Cold water is pumped down to hot rocks and returns as steam to drive turbines (or heats buildings directly). Extremely reliable (doesn't depend on weather), low environmental impact, and renewable, but only geographically viable in volcanic/tectonic regions (e.g., Iceland, New Zealand).

Save

6

Biofuels (Biomass)

Renewable fuels derived from biological material (fast-growing plant crops like sugar cane/oilseed rape, woodchips, or methane biogas from animal manure/sewage). Reliable (can be stored and burned on demand like fossil fuels) and theoretically carbon-neutral (CO₂ released on burning = CO₂ absorbed during growth by photosynthesis), but requires vast areas of farmland, which can cause deforestation, habitat loss, and higher food prices.

Save

1. Q1

   The UK government plans to replace retiring coal-fired power stations with a mix of offshore wind farms and a new nuclear power station. Evaluate the use of offshore wind turbines compared to nuclear power stations for generating the UK's electricity. [6 marks]

   Check Mark Scheme

   Click “Check Mark Scheme” to compare your answer, 1. Renewability: Wind is a renewable energy resource that will never run out, whereas nuclear power uses uranium/plutonium which is a finite, non-renewable resource [1 mark]. 2. Reliability: Nuclear power is highly reliable and provides a continuous, steady baseload output 24/7 regardless of weather, whereas wind power is unreliable because turbines generate zero electricity on calm days (or must be switched off in gales) [1 mark]. 3. Power output density: A single nuclear power station generates a massive electrical power output (~3,000 MW), so thousands of offshore wind turbines covering a huge area of sea are needed to match one nuclear plant [1 mark]. 4. Waste and pollution: Neither wind nor nuclear emits carbon dioxide or sulfur dioxide during operation, so neither contributes to global warming or acid rain; however, nuclear power produces high-level radioactive waste that is difficult and expensive to dispose of safely [1 mark]. 5. Safety and habitats: Nuclear power carries a small risk of a catastrophic radiation leak/meltdown, whereas wind turbines pose zero radiation risk (though they can harm seabirds and affect marine habitats/views) [1 mark]. 6. Costs and timescales: Both have zero fuel cost (wind) or very low fuel cost (nuclear), but nuclear power stations take over 10 years to build and have extremely high construction and decommissioning costs compared to wind farms [1 mark].

2. Q2

   Explain how a pumped-storage hydroelectric power station operates, and explain why it is essential for helping the National Grid cope with sudden surges in electricity demand (such as at the end of a major televised football match). [4 marks]

   Check Mark Scheme

   Click “Check Mark Scheme” to compare your answer, 1. A pumped-storage hydroelectric station has two reservoirs at different heights: an upper reservoir and a lower reservoir [1 mark]. 2. When there is a sudden surge in demand, sluice gates are opened and water flows rapidly downhill from the upper reservoir through turbines connected to generators (transferring gravitational potential energy to kinetic energy to electrical energy) [1 mark]. 3. It is ideal for sudden surges because opening the valves takes only a few seconds (extremely fast start-up time), whereas thermal coal/nuclear power stations take hours or days to ramp up [1 mark]. 4. At night, when electricity demand is low and there is cheap surplus electricity on the grid, water is pumped back up from the lower reservoir to the upper reservoir ready for the next day [1 mark].

3. Q3

   Explain why biofuels are often described as carbon-neutral, and give two reasons why replacing all petrol and diesel with crop-based biofuels could harm the environment or society. [4 marks]

   Check Mark Scheme

   Click “Check Mark Scheme” to compare your answer, 1. While the biofuel crops are growing, the plants absorb carbon dioxide from the atmosphere for photosynthesis [1 mark]. 2. When the harvested biofuel is burned, it releases the exact same amount of carbon dioxide back into the atmosphere, so there is theoretically zero net increase in atmospheric CO₂ [1 mark]. 3. Harm 1: Growing enough biofuel crops to replace all petrol and diesel would require clearing huge areas of natural forest (deforestation), destroying habitats, reducing biodiversity, and releasing stored carbon [1 mark]. 4. Harm 2: Using prime agricultural farmland to grow fuel crops instead of food crops reduces global food supply and drives up food prices for poorer populations [1 mark].

4. Q4

   A wind turbine receives 2.5 MW of kinetic power from the wind and generates an electrical power output of 900 kW. Calculate the percentage efficiency of the wind turbine and explain where the wasted energy is transferred. [4 marks]

   Check Mark Scheme

   Click “Check Mark Scheme” to compare your answer, 1. Convert both powers to the same unit (Watts or kilowatts): Input power = 2.5 MW = 2,500 kW; Useful output power = 900 kW [1 mark]. 2. Efficiency = (Useful power output / Total power input) x 100 = (900 / 2,500) x 100 [1 mark]. 3. Efficiency = 36% (or 0.36) [1 mark]. 4. Wasted energy: Work is done against friction in the turbine bearings and electrical resistance in the generator coils, dissipating energy to the thermal energy store of the surroundings, and some kinetic energy remains in the moving air leaving the blades [1 mark].

Related study guides