DT Edexcel GCSE: 1.2-3: Energy sources & evaluating new tech

Solar

Photovoltaic panels: sunlight → electricity using 2 layers of doped silicon to allow electrons to flow when photons fall on them

Solar thermal: sunlight → heat fluid circulated through pipes → transfers heat to water → steam → turbine → generator → electricity

Advantages:

- Renewable, and no pollution

- Useful for low-power

- Useful in remote areas

- Solar thermal reliable in warmer countries

Disadvantages:

- Take up lots of space

- Inconsistent (energy must be stored)

- Expensive set up

- Low efficiency - depends on location

- Unaesthetically pleasing

- Could change ecology when large solar farms replace traditional farms

Hydroelectric

Flowing water due to gravitational potential energy turns a turbine and generator as it descends the dam

Advantages:

- Consistent

- Can be used for pumped storage

- Can increase to full power quickly and turn off quickly

- Cheap to run

- Can have secondary function as water reserve

Disadvantages:

- Can cause floods and trap wildlife

- Very expensive to build

- Hard to find suitable site

- Water quality + quantity downstream can be affected

Pump storage

Upper reservoir's water can be quickly released and due to GPE, it will turn a generator. When demand is low, lower reservoir's water can be pumped back up to store the energy

Advantages:

- No emissions/fuel

- Very quick

- Very useful to cope with spikes in demand

Disadvantages:

- Expensive to build

- Environmental issues regarding building of dams

Wind

Thermal energy from convection currents → kinetic energy in wind → spins propeller blades → turn a shaft → turbine + generator to produce electrical energy

Advantages:

- Freely available

- Renewable, and no emissions

- Land beneath is still usable

- Useful for remote areas

Disadvantages:

- Not consistent

- Few suitable coastal areas

- Could restrict shipping traffic when placed in the sea

- Kill wildlife & disturb migration patterns of birds

- Wind farms = unsightly

Geothermal

Water heated underground when in contact with hot rocks and the earth creates steam that drives turbines to generate electricity. (Heat retained in the earth created by radioactive rocks & solar radiation absorbed at the surface)

Advantages:

- Renewable, and no emissions

- By-products are often minerals which can be sold or are re-injected

Disadvantages:

- Not many suitable locations

- The area may run out of steam

- Hazardous substances may come up from underground which are hard to safely dispose of

Tidal

Turbines within barrages (dams) constructed across tidal rivers, bays, and river estuaries can use rising and falling tides to generate electricity. Water is trapped and then released through the turbines as water levels change

Advantages:

- Renewable, and no emissions

- Cheap to maintain and operate

- Can produce lots of energy

- Is very predictable & stable (so you can plan)

- Barrages can serve a secondary function like a bridge

Disadvantages:

- Very few suitable sites (coastal areas only)

- Only works for 10 hrs tide flows ∴ lower energy output than fossil fuels

- Very expensive to build

- Environmental impacts for fish, birds

Biomass

Organic matter derived from wood, crops, rubbish, landfill gas, alcohol fuels etc. burnt to produce heat (which can then be converted to electricity)

Advantages:

- Renewable waste reduction (e.g., from farming)

- Reliability

- Availability

Disadvantages:

- Not completely clean (combustion still causes emissions)

- Possible deforestation

- High cost & space requirements

- Requires lots of water

Biodiesel

Made from plants/vegetables/fermented waste/cooking oil and can be used in diesel-powered vehicles without modifying engine

Advantages:

- Renewable waste reduction (e.g., from farming)

- Reliability

- Availability

Disadvantages:

- Possible deforestation

- High cost & space requirements

- Requires lots of water

Coal

Burn → heat converts water into steam → turns turbine → generator → electricity

Smaller amounts used as domestic heat source

Advantages:

- Stable, large-scale, and high-power electricity generation

- Cheap to extract & use

- Reliable

Disadvantages:

- Emit CO₂, particulates, NOₓ, SOₓ, Sulfur, Mercury, Selenium, Arsenic (is the dirtiest fossil fuel)

- Technologies to reduce coal power plant emissions are expensive

- Coal mining impacts landscape & produces toxic dust

Oil

Crude oil processed & split into petroleum products: petrol, paraffin and diesel

Burn → heat converts water into steam → turns turbine → generator → electricity

Advantages:

- Stable, large-scale and high-power electricity generation

- Cheap to extract & use

Disadvantages:

- Oil power plants are highly polluting

- Oil exploration impacts on the landscape

- Oil extraction risks environmental disasters (fracking)

Gas

Burn → heat converts water into steam → turns turbine → generator → electricity

Natural gas used in homes for heating or cooking

Advantages:

- Stable, large-scale and high-power electricity generation

- Cheap to extract & use

- Cleaner than coal or oil (emits half the CO₂ as coal)

Nuclear

²³⁵U used in fission to heat water to steam turning turbines → electricity

Advantages:

- No air pollution, therefore fewer health impacts

- High energy density

- Safe

- Very low fuel cost

- Useful for the base load of the UK

Disadvantages:

- Non-renewable

- Affects marine life as cooling water systems used to maintain temperature are taken from a river or ocean. Fish and other organisms are unintentionally captured in the cooling system are killed. After the water is used to cool the power plant, it is returned to the ocean/river, but the water returned is 25° warmer than it was originally.

- Long start-up time

- Safety measures are expensive

- Accidents would be catastrophic (although new tech using thorium reduces this)

- Radioactive waste, so disposal is difficult, and leaks are hazardous (although thorium reduces this)

- Some say it causes nuclear proliferation (although thorium as fuel makes it harder to make nuclear weapons)

How a company can reduce carbon footprint

- maximising energy efficiency

- analysing their supply chain

- recycling

- using renewables

- identifying suitable carbon offsetting methods

LCA:

- raw material extraction & processing

- product/part manufacture & assembly

- product/part transportation & distribution

- product use

- product disposal/recovery

Power system

a network of components that supply, transfer and use electric power, including batteries and cells, wind, solar, and mains electricity

Things to consider when selecting power systems for products

portability of power source, environmental impact (including creation, transport, and disposal), power output & consistency, circuit/system connections, cost

Mains electricity supply

AC 50Hz 230V

Description & disadvantages of batteries and cells in general

Chemical reaction produces electrons that collect at the negative terminal and when connected in a circuit flow to the positive terminal

Expensive source of electricity

Can lead to chemicals leaching into water & soil if not disposed of correctly

Advantages of cylindrical cells (D, C, AA, AAA, AAAA)

- Easy to manufacture

- Small

- Inexpensive

- Have good mechanical stability and long life

Advantages/disadvantages of prismatic cells (ones used in mobile phones + tablets)

Advantages:

Prismatic cells are flexible, easy to recharge

Disadvantages:

Prismatic cells are expensive, have a shorter life than cylindrical batteries