- Energy is transferred from cells and other sources, anything that supplies electricity is supplying energy, components transfer this energy to the environment.
- Power= tells you how fast it transfers anergy from the charge passing through it, usually measured in watts or kilowatts.
- ENERGY TRANSFERRED (J) = POWER (W) x TIME (s)
- Kilowatt hours are units of energy. Usually measured in joules but so tiny, so electricity meter records uses how much energy you use in kWh.
- KILOWATT HOUR= AMOUNT OF ELECTRICAL ENERGY CONVERTRED BY A 1kW APPLIANCE LEFT ON FOR 1 HOUR.
- Energy transferred (kWh) = power (kW) x time (hours)
- COST= NUMBER OF kWh x COST PER kWh
- High power rating= transfers a lot of energy in a short time, energy comes from current flowing through it. POWER (W) = VOLTAGE (V) x CURRENT (A)
- More efficient= wast less energy
- EFFICIENCY = ENERGY USEFULLY TRANSFERRED/ TOTAL ENERGY SUPPLIED x 100%
- Use less energy at home
- Reducing heat transfer stops energy waste- INSTALLATION, DOUBLE GLAZING, DRAUGHT-PROOFING, FIBRE GLASS HOT WATER TANK JACKET (cheap), SWITCHING OFF APPLIANCES.
- Some appliances are more cost-effective than others, payback time = how long it takes for the money saved to match original cost
- HWTJ: initial cost: 15 pounds, annual saving: 30 pounds payback time: 6 months.
- Double glazing: IC: 3000 pounds, A.S: 60 pounds, payback time: 50 years
- Energy-saving bulbs: IC: 3 pounds, A.S: 12 pounds, payback time: 3 months
- Work places: no unnecersarry printing/photocopying, car-sharing/cycling/public transport
- Government: offer grants for better insulation, trade in old boilers for new ones, imporve public transport, help control on a national scale- invest in alternative enrgy souces, improve recycling services, make laws on efficiency.
Energy sources and power stations
- Electricity= convenient way to supply energy, it's a secondary energy source because it is produced using other sources, Convenient because it can easily be transmitted over long distances via National Grid and can be used in many different ways.
- Non-renewable: fossil fuels (coal, oil, natural gas) nuclear fuels (uranium and plutonium), they'll all run out and they all damage the environment. Provide most energy currently.
- Renewable: wind, waves, tides, hydroelectric, biofuels, geothermal, solar. Never run out, damage the enironment less, can be unreliable and don't produce much energy.
- Energy sources produce steam to drive turbines in power stations: energy is released from the fuel (usually by burning in a boiler) and used to generate steam. The steam turns a turbine, generator converts the movement (kinetic energy) into electricity.
- Fossil fuels are linked to environment issues: release CO2 into atmosphere when burnt, global warming, acid rain (sulfur dioxide, coal mining- mess of landscape, oil spillages- serious environmental issues. But they do produce a lot of energy cheaply and reliably.
- release lots by splitting atoms, use nuclear fission producing heat to make steam to drive turbines- difference is the boiler. In nuclear fission, atoms in the nuclear fuel are split in two, releasing lots of energy. Water is used as a coolant to take away the heat produced by fission. Used to produce steam to drive a turbine and generator.
- Energy is released from thr nuclear fuel by fission, heat energy heats water to make steam, steam turns a turbine, generator converts the movement of the turbine into electricity.
- Advantages: a lot more energy than chemical reactions, no CO2 produced when making electricity, nuclear fuel is relatively cheap.
- Disadvantages: produce radioactive waste: - v dangerous and difficult to dispose of, emits ionising radiation and stays reactive for a long time: increases exposure= increases damage done to cells, high does tend to kill cells right out causinf radiation sickness, lower doses could ionise, causing cancer.
- People are put at risk through: IRRADIATION: exposed without coming into contact with source, damage stops when you leave the area. CONTAMINATION: picking up radioactive waste, you'll be exposed for a long time, more damage.
- Extra safety precautions needed at nuclear plants: waste disposed carefully, surrounding area check for contamination, workers= regular checks. -Take longest and cost is v. high.
Wind and Solar Energy
Wind Turbines- exposed places (moors/ around coasts) each has its own generator so electricity is directly from the wind turning the blades, which turn the generator. no pollution (except manufacturing), spoil view, noisey, unreliable (wind stops?), initial costas are high, but no fuel costs and minimal running costs, no permanent damage.
Solar Cells- generate electric currents directly from sunlight, initially expensive, best source of electricity for calculators and watches which use little electricity. Often used in remote places where there's not much choice, no polltion (except manufacturing), v. reliable source of energy-only in daytime, inital cost is high, running cost is minimal and energy is free. Solar cells- relatively small scale e.g powering individual homes. Not often practicial or too expensive to connect to national grid.
Wave and Tidal Energy
Wave Power- lots of little wave-powered turbines located around the coast, as waves come in to the shore they provide an up and down motion that can be used to directly drive a turbine, which drives a generator. No pollution, main problems are spoiling views and hazard to boats. Fairly unrelaible as waves tend to drop when wind does. Initial coats are high, but no fuel cost and minimal running costs. Wave power is ever likely to provide energy on a large scale but it can be very useful on small islands.
Tidal Barrages- use Sun and Moon's gravity- very big dams built across river estuaries with turbines in them, as tide comes in it fill it up several metres and also drives the turbines, water can then be allowed through turbines at a grdually speed. Source of energy is the gravity of the Sun and Moon. No pollution. Main problems: prevent free access by boats, spoiling the view. and altering the habitat. Quite reliable, twice a day without fail, always near predicted height. Excellent for storing energy ready for periods of peak demand. Initial costs are moderately high, no fuel costs and minimal running costs. Only used in some of the most suitable estuaries tidal power can generate a significant amount of energy.
Biofuels, geothermal and hydroelectricity
- Biofuels- made from plants and waste- renewable energy resource, used in thermal power stations. Burnt to heat up water, makes steam, drives a turbine. They can be used in some cars, can be solids, liquids and gases. Realatively quick, natural, carbon neutral(ish). But forest cleared to make room for biofuels, resulting in species losing natural habitats, decay and burning of vegetation increases CO2 and methane emissions.
- Geothermal- heat from underground. Only possible where hot rocks are close to the surface, used to drive generators in thermal power stations, free, reneable energy- no real environmental issues. Main disadvantage is cost of drilling down several km to the hot rocks. Very few places where this is an economic option.
- Hydroelectricity- uses dams to catch rain. Usually requires flooding a valley by building a large dam, rainwater is caught and allowed through turbines, driving them directly, turbines then drive generators to make electricity. No(ish) pollution, but floodng a valley has a big impact on environment: rotting vegetation releases CO2 and methane, some species will lose their habitat, look unsightly when they dry up. Location in remote valleys to reduce human impact. Immediate respsonse to increases demand, fairly reliable (except in drought), initial costs are high but no fuel and minimal running costs. Water stored in reservoir above turbines using dam, gravity causes water to rush through turbines, generator converts movement into electricity.
Comparison of Energy Resources
UK uses lots of electricity and has a increasin demand, need a reliable, affordable and environmentally-friendly source to keep us going- no single sourcecan provide all of these needs, so we need a compromise:
- Renewable sources struggle to produce same output as conventional power stations
- all our uranium and over half the coal we burn is currently imported from other countries- dependant on other countries, transport related cost and CO2 emissions.
- Supply will run out soon.
- Renewable sources are free and won't run out, but some are quite variable.
Need to consider environmental impact as well as cost:
- Economics: running costs, set up costs, engineering costs
- Environmental impact: waste and air pollution, noise pollution, carbon dioxide, dsruption of habitats, visual pollution, leisure disruption, using up resources, other problems (explosions, dams bursting).
Generators and the National Grid
- Create voltage and maybe a current in a conductor by moving a magnet in or near a coil of wire- electromagnetic induction!
- As you move magnet, magnetic field through the coil chnanges, inducing a voltage and a current flows in the wire (if it is a complete circuit)
- Generators use EM induction to turn kinetic energy from turbines in power stations into mains electricity.
- In a generator a magnet rotates in a coil of wire, as magnet turns, magnetic field in coil cahnges, induces a voltage. which makes a current fllow in the coil.
- Bigger voltage and current in the wire= faster you turn the magnet. To move it faster, you need to put more energy in to the turbine, which uses up more of the primary energy source. So the bigger the voltage and current, the more fuel we use up.
- Electricity is distributed via the National Grid, a network of pylons and cables that covers the whole of Britain. Enables power to be generated anywhere on the grid, then supplied anywhere else on the grid. To transmit alot you need high voltage or current, but you lose lots of energy via heat on cables when you use a high current, so its cheaper and better to use a high voltage which is reduced before it gets to our homes, at 230V mains supply voltage.