P1 Energy

When energy is transferred to an object, the energy is stored in one of the objects seven energy stores.

• Magnetic , i.e 2 magnets either attract or repel
• Internal (thermal) - all objects have energy in ths store, the hotter the object the more engergy
• Chemical - engergy stored in chemical bods, such as molecules e.g. food, muscles, electrical cells
• Kinetic -  engery of moving object, eg. runners, buses
• Electrostatic - 2 charges rthat attract or reel each other
• Elastic potential - anything stretched, like compressed springs, inflated balloons.
• Gravitational potential - anything that is raised above ground level

Transferring energy

In each of these examples, energy is transferred by one of the following four types of energy transfer:

Mechanical work - a force moving an object through a distance

Electrical work - charges moving due to a potential difference

Heating - due to temperature difference caused electrically or by chemical reaction

Radiation - energy tranferred as a wave, eg light and infrared - light radiation and infrared radiation are emitted from the sun

A system is just a fancy work for a single object or group of objects.

When a system changes, energy is transferred.  It can be transferred into or away from the system, between different objects in the system r between different types of of energy stores

Closed systems are where there is no net (overal chnage) in the total energy of the system

• for example a cold spoon in s seal flask of hot soup.  Energy is transferred from thermal enegery store of the soup to the thermal energy store of the spoon, but no energy leaves, so total energy in system remains the same.

Energy Transfers

Energy can be transferred, usefully stored or dissipated (wasted) but it can not be created or destroyed.

In a closed system the energy never changes, but transferred form one store to another.

Wasted energy is caused by unwanted energy transfers.  These can be reduced in several ways

• Lubrication;  reducing th friction that produces heat
• Thermal insultaion:  reduces heat loss
• Tightening loose parts:  prevent unwanted vibration that wastes engergy as sound.

Energy can be transferred by heating

As material is heated energy is transferred to its thermal engery store, casuing its temperature to increase.

For example, in boiling a electric kettle.  Energy is transferred to to teh thermal engery store of kettles heating element.  Then energy is transferred by heating to water's thermal energy store, so temperature of water increases

Different materials have different specific heat capabilities

The amount of energy stored or relased as material changes temperature depends on the specific heat capacity of the material

Specific heat capacity is the amount of engery needed to raise the temperature of 1kg of material by 1 degC

Change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg * C) x temperature change

Power is the 'rate of work done'  - How much work is done per second

• Power is the rate of energy traansfer, i.e. the rate of gettng work done
  
• So measures HOW FAST energy is transferred or work is done
• Power is measured in watts
• One watt is 1 joule of energy is trsnaferred per second

Power W =E/T     Watts (W) = Energy transferred (joule) / Time (seconds)

or 

Power W = W/T   Watts (W) = Work doen (joule) / Time (seconds)

There will always be some energy disspated in any energy transfer.  Usually thermal eneregy stors, this is often called 'wasted' energy.  

Ways to reduced amount of energy wasted

Lubrication:  whenever something moves there is at least one frictional force acting upon it, this causes some of the energy to be dissapated. lubricants (usually liquids) can be used to reduce the friction between two objects being rubbed together so that they flow easily along each other.

Insulation - reduces the  rate of cooling. Considers materiasl with a low thermal conductivity.

• thick walls made made from a material with a low thermal conductivity will have a slower rate of energy exchange
• cavity walls- an inner and outer wall with a gap of air in between them as air is a very poor conductor of heat so less heat enters/ leaves
• loft insulations- fibreglass wool is a good insulator as it has pockets of air in it. Prevents convection currents from forming, reduces energy loss by conduction
• double glazed windows- have an air gap between the two sheets of glass to prevent conduction
• draught exluders reduce energy transfers by convection

The less energy that is wasted the more efficent the energy transfer is

The efficency of a energy transfer can be worked out as

    useful output energy transfer

efficiency = -----------------------------------------------------    x100

                   total input energy transfer

From the principle of conservation of energy : input energy = useful output energy + energy wasted

Can measure the effeicency of a device

The less energy that is wasted by device, the more efficient the device is.  The efficency of a device can be calculated using the equation, where the power input and output are known:

                    useful energy transferred by the device

efficiency = -----------------------------------------------------    x100

                   total energy supplied to the device

No device can have an efficiency that is greater than 1 (or %100).

Resources mostly used to generate electricty for transport & heating

NON RENEWABLE reources will run out one day

• fossil fuels (coal, oil & natural gas)
• Nuclear fuel

RENEWABLE will never  run out

• Sun/solar
• Wind
• Water waves
• Hydro-electricity
• Bio-fuels
• Tides

Resources used for transport

Non- renewable

• Petrol or diesal, created from oil
• Coal used in stream trains to boil water to produce steam

Renewable

• Vehicles can run of pure bio-fuels or a mix of bio fuel with petrol or diesel

Electricity also used for transport; electric ars and some trains

Resources used for heating

Non Renewable

• Natural gases burnt to heat water in a boiler & pumped around central heating system, of radiators
• Gas fires burn natural gas
• Coal is burnt in open freplaces
• Electric heaters using electricaity which cna be from non renewable energy reources

Renewable energy resources:

• Bio fuels boilers work same way as gas boilers
• Geothermal heat pumps 
• Soalr water heaters use the sun to heat water which us then pumped ino radiators in a building
• Electric heater using electricity from renwable resources

1. Each wind turbine has its own generator inside it so the electricity is generated directly from the wind turning the blades, which turn the generator.

2. There isn't any pollution (apart from a little bit when they're manufactured).

3.No permanent damage, can be removed

4. Not as reliable as other engery sources, can't produce electricty is wind stops.  Can be stopped if wind is too strong to protect turbine from becomming damanged

5. Impossible to increase supply t when there's extra demand.

Solar energy

1. Solar cells generate electricty directly from sunlight

2. Ceate no pollution once they're built, but quite consuming to built

3. Only generate electricity in daytime

4.In summy countries can be very reliable source of energy, quite reliable in cloudy countries such as UK

5. Like wind, can't increase output when there is extra demand

Geothermal 

1.uses energy from therm engergy stores of hot rocks beneath the earth's surface to heat building or generate electricity

2. Reliable as hot rocks are always hot, and geothermal power stations have minimal impact on the envronment

Hydro-ectric power uses falling water

• Usually involves flooding a valley by creating a big dam which allows rainwater through the turbines
• No pollution once running
• Large imapct on the environment - possible loss of habitat for some species , rotting vegetation releases methane and carbon dioxide
• can provide immediate response to an increase in demand
• no problems with reliability unless theres a drought
• initial costs are hign, espcailly build cost
• possible to generate electricity on a small scale in remote areas

Wave power using lots of wave powered turbines

• Advantage: No pollution.  Useful on small islands
• Disadvantage:  Disturb the seabead, habit of animals.  Unlreaibale as waves reduce when wind drops. Hgh inital cost

Use the tdes of the sea

• big dam built across river estuaries with turbines in them
• as the tide comes in it fills up the estuary, the water is allowed through the turbines at a controlled speed
• tides are produced at the gravitational pull of the sun and moon
• no pollution
• prevents free access by boats
• reliable as tides happen twice a day
• the height of tides is variable so the amount of electricity produced daily would be inconsistent
• initial high cost but cheap to run

bio-fuels-  renewable energy resources made from plant products or animal waste. They can be solids, liquids, or gases.

pros

• carbon neutral, as carbon is being used it is being reproduced so the amout of carbon it uses is equal to the amount of carbon that is produced
• reliable, take a relatively short time to grow crops and grown throughout the year.  Can be stored

cons

• costs are very high
• people fear that growing crops for biofuels will reduce the space and water used to grow food. Forests are cleared to make space to grow biofuels, so lots of species lose their natural habitats
• decay and burning vegetation increases carbon dioxide and methane emmissions, although offset

Reliable: Fossil fuels are reliable and enough for current demand.  Can be stocked and so allow power plants to respond quickly to demand.  But these are slowly running ou!

Environmental concerns:  

• Coal, oil & gase relase Co2 when burnt & leads to glocal warming
• Also relases sulfur dioxide which causes acid rain.  Acid rain makes lakes & river acidic which can kill animals and plants, and damage trees & soils
• Coal mining effects landscape, and can destroy habitate of local animals and plants
• Oil spils cause envoironmental problems and hamr sea creaturues
• Nuclear poweer is clean, but nuclear wast is very dangerous and diffcult to get rid of.  Risk of nuclear accident

Currently we still need non-renewables for much of our energy consumptiio.  There is a growing trend to be more energy efficent and move towards renewable energy resources.  Why?:

• We now know that burning fossil fuels is very damaging to the environment
• People and governments are also becoming increasingly aware that non-renewables will run out one day.
• Pressure from other countries and the public has meant that governments have begun to introduce targets for using renewable resources.
• Car companies have also been affected by this change in attitue towards the environment. Electric cars and hybrids popularity is increasing

The use of renewables is limited by reliabilty, money and politics

• There's lots of scientific evidence supporting renewables, but although scientists can only give advise

• Building new renewable power plants costs money, so some energy providers are reluctant to do this, especially when fossil fuels are so cost effective. The cost of switching to renewable power will have to be paid, either by customers in their bills, or though government and taxes. 

• Some energy resources like wind power are not as reliable as traditional fossil fuels, whilst others cannot increase their power output on demand. 
• Research on improving the reliability and cost of renewables take time and money - it may be years before improvements are made, even with funding. Until then, we need non-renewable power
•  Making personal changes can also be quite expensive.