OCR 21st Century P3

Sustainable Energy
1. to ensure a security of electricity supply nationally, we need a mix of energy sources.
Sources of Electricity
1. the main primary energy sources that humans use: fossil fuels (oil, gas, coal), nuclear fuels (uranium & plutonium), biofuels, the wind, waves, and radiation from the Sun
  1. Electricity is a secondary source as it must be generated using a primary source i.e. the burning of fossil fuels
    1. power stations which burn fossil fuels produce carbon dioxide which contributes to global warming and climate change
      1. burning coal and oil releases sulfur dioxided which causes acid rain
      2. Coal Mining ruins alndscapes
      3. Oil spillages severely damage the environment
      4. Fossil fuels produce lots of energy, relatively cheaply and they don't rely on the weather. We have many foffil fuel power stations so we don't need to spend money on new technology to carry on usng them
Electrical Energy
1. when electric current passes through a component (or device), energy is transferred from the power supply to the component and/or to the environment
  1. energy transferred = power × time (joules, J) (watts, W) (seconds, s) (kilowatt hours, kWh) (kilowatts, kW) (hours, h)
    1. a joule is a very small amount of energy, so a domestic electricity meter measures the energy transfer in kilowatt hours
      1. This is the amount of electrical energy transferred by a 1kW appliance left on for 1 hour.
      2. Cost= Number of kWh x Cost per kWh
        e.g. Cost of leaving a 80W bulb on for 90 mins if one kWh costs 20p.
        Energy= 0.08kW x 1.5hrs = 0.12kWh
        Cost= 0.12kWh x £0.20 = £0.024 or 2.4p
  2. the amount of energy transferred in a process,
2. the power (in watts, W) of an appliance is a measure of the amount of energy it transfers each second, ie the rate at which it transfers energy
  1. power = voltage × current (watts, W) (volts, V) (amperes, A)
  2. the rate at which an electrical device transfers energy
Efficiency
1. Energy usefully transferred/
  1. Total energy supplied
  2. x100%
  3. Electrical Appliances
    1. E.g. An ordinary bulb is 5% efficient. If 1000J of light energy is given out, how much energy is wasted
      1. 5%= 1000J/ ? x 100%
        0.05=1000J/?
        0.05?=1000J
        ?= 1000J/0.05
        =20,000J
        20,000J-1000J= 19000J
2. Sankey diagrams summarise all the energy transfers taking place in a process. The thicker the line or arrow, the greater the amount of energy involved.
  1. This Sankey diagram for an electric lamp shows that most of the electrical energy is transferred as heat rather than light
3. Power stations
  1. Useful energy output/
    1. Energy Input
Reducing Energy Usage
1. Home
  1. cavity walls, loft insulation, double glazing, draught excluders, thick curtains etc. all reduce heat loss by conduction
  2. Energy saving appliances
  3. Washing clothes at lower temperatures, fibreglass wool tank jackets
2. Government
  1. grants for home insulation
  2. Improving recycling
  3. boiler trade ins
  4. investigating alternative energy sources
  5. Improving public transport
3. Workplace
  1. switching off appliances e.g. computers, lights, printers
  2. recycling
  3. public transport, car sharing, cycling
  4. Incentives
Generating Electricity
1. electricity is convenient because it is easily transmitted over distances and can be used in many ways
  1. mains supply voltage to our homes is 230 volts
    1. electricity is distributed through the National Grid at high voltages to reduce energy losses.
      1. The National Grid distributes electricity a higher voltage but a lower current. Because a high current=a greater number of electrons= more chance of collisions with metal ions in cables=heat produced=energy lost. So, The NG uses a high voltage, to decrease the current, saving energy
2. Nuclear
  1. A neutron causes Uranium nuclei to split into lighter atoms, releasing immense amounts of energy in the form of heat, this heat is used boil water.
    1. nuclear power stations produce radioactive waste and ionising radiation
      1. with increased exposure to ionising radiation, damage to living cells increases eventually leading to cancer or cell death
        irradiation- Being exposed to radiation from an external source
        Contamination- contact with radioactive material i.e. inside the body, skin or clothes
        Leads to long term irradiation
        Leads to mutations in DNA or the death of cells
3. Hydroelctricity
  1. renewable sources such as hydroelectric, wave and wind drive the turbine directly without the need to produce heat
4. mains electricity is produced by generators
  1. generators produce a voltage across a coil of wire by spinning a magnet near it
    1. as the magnet turns, the magnetic field through the coil changed- this change induces a voltage which makes current flow into the coil
    2. the bigger the current supplied by a generator, the more primary fuel it uses every second
      1. the faster the magnet is spun, the greater the current supplied by the generator. To spin the magnet faster, more primary fuel needs to be burnt
      2. In many power stations a primary energy source is used to heat water; the steam produced drives a turbine which is coupled to an electrical generator
Choosing Energy Sources
1. the choice of energy source for a given situation depends upon a number of factors including:
  1. waste produced
    1. carbon dioxide emissions
      1. economics
    2. environmental impact
2. Non-Renewable
  1. Nuclear
    1. Advantages
      1. >No pollutants produced
        >Nuclear fuel is relatively cheap and abundant and easily accessible
        >Nuclear reactions release a great deal more energy compared to chemical reactions e.g. burning
    2. Disadvantages
      1. >Building & Decomisioning of power stations is expensive and time consuming
        >Location- surrounding residents approval- often worried of the risks
        >Produces radioactive waste- needs specific disposal as it stays radioactive for thousands of years
        >Import uranium to UK
      2. >Contamination and Irradiation. Contamination leaves people exposed to ionising damage for a long time
        >Extra safety precautions- are tested for soil/water contamination. Safety of workers (exposure), correct disposal
  2. Fossil Fuels
    1. Advantages
      1. >Generate huge amounts at one time
        >Easy to obtain and easily accessible
        >Power stations can be constructed almost anywhere
        >Coal is affordable, easy to burn, reliable , abundant and produces high energy upon combustion
      2. Disadvantages
        >Large amount of pollution i.e. Carbon dioxide and Sulfur Dioxide (impurities) = Climate Change/ Global warming and acid rain
        >Mining endangers lives.
        >Use of finite resources that will run out
        >Ruins environments and landscapes i.e. oil spills
    2. 75% of UK's electricity = fossil fuels
3. Renewable
  1. Wave and Tidal
    1. Advantages
      1. >No fuel costs=No pollutants
        Tidal Barrages reliable- twice a day
        Minimal running costs
        Energy=gravity of the Sun & Moon
        controllable
      2. Wave power- no fuel costs
        minimal running costs
        useful for small islands
        No pollution
        Disadvantages
        >Prevents free access to boats
        >spoils the view and alters wildlife habitat
        >Variable height of the tides
        >Don't work 4 times a day when tides are level
        >Initial costs are moderately high
        High initial costs
        >Hazard to boats, spoils the view
        >Unreliable- waves die when wind drops
        >Not large scale power
    2. Hydroelectricity (Dams)
      1. A-Immediate response to increased demand
        A-reliable except droughts
        D- Flooding a valley means animals lose habitats, reservoirs look unsightly when they dry up, rotting veg releases methane and CO2
  2. Geothermal
    1. Advanatages
      1. >No fuel=No pollutants
        >Maintanence cos is low
        >Not dependent on humans or the weather
        Disadvantages
        >few sites have potential- need hot rocks near surface
        >only rural areas are suitable
        >have to drill several km into ground
        >Not economocially viable.
        >High installation costs
        >No guarantee of energy produced-dependent on mantle activity
  3. Solar
    1. >No fuel=No pollutants
      1. >Requires little maintenance
        >Silent producer-generous tax credits for owners
        >Energy is free. Running costs nearly 0
        >Good for road signs, calculators and watches
      2. Advantages
    2. Disadvantages
      1. >Dependent on weather. Not at night
        >Only 20% of the Sun's energy is converted
        >Substantial installation costs
        >Not practical to connect to NG
  4. Wind
    1. Advantages
      1. >No fuel=No pollution
        Cost effective and provides jobs
        Can be almost anywhere
        No permanent damage to nature
    2. Disadvantages
      1. >substantial costs- engeneering challenges
        >very noisy, ruins view
        Turbine blades may damage wildlife
        reliant on the weather
        Cannot increase supply to meet increasing demands
        1500 turbines to match one coal burning power station
  5. Biofuels
    1. Advanatges
      1. >lower fuel prices as the demand for FF decreases
        >Alternatives create fuel security to countries without oil reserves
        >Produces less greenhouse gases
        >Carbon Neutral
        >Low chance of particulates
        >Land is not cleared of other biomass just for biofuel
    2. Disadvantages
      1. >Loss of habitat if land is cleared
        >Larger amount of workers required
        >crops used to feed people, not for fuel-food shortages= increase food price
        >water used to grow crops leads to shortages

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OCR 21st Century P3

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