Section 4: Energy resources and energy transfer Flashcards
Solar cells
Pro:
- Free and renewable
- No pollution
- Can generate electricity from photovoltaic cells
Con:
- uk sunshine unreliable and limited
- confined to daylight hours
- relatively expensive to manufacture
Wind
Pro:
- renewable
- emission free and quick to build
- no fuel costs
Con:
- noise and visual pollution
- more expensive than fossil fuels
- wind levels fluctuate
Tidal
Pro:
- renewable
- emission free
- predictable
Con:
- development costs
- harmful to aquatic life
- very few ideal locations
Hydroelectric
Pro:
- renewable
- no CO2 emissions
- very cheap once dam has been built
Con:
- natural flow hydro reliant on rainfall and vulnerable to droughts
- pump storage relies on off peak electricity to pump water back uphill
- environmental and social impact of large dams
Oil
Pro: -reliable -cheap to extract -well established Con: -CO2 emission -non-renewable -price instability -reliance on politically unstable countries
Nuclear
Pro: -reliable and efficient -minimal CO2 emission after construction -not vulnerable to price fluctuations Con: -danger of nuclear waste, safety -huge cost of building/ decommissioning reactor -planning/building takes years
Biofuels
Pro:
-carbon neutral(carbon released balance carbon absorbed)
-suitable crops can be grown in UK
Con:
-space required to grow crops
-greenhouse gases in harvesting/transporting crops
-inefficient compared to fossil fuels
Coal
Pro:
- cheap and reliable
- abundant, UK has large reserves
- decline of SO4 (acid rain) emissions last 29 years
Gas
Pro: -reliable -cleaner than coal -lower CO2 emission -uk North Sea reserves Con: -significant CO2 emissions -reserves running out fast so growing independence on imports and rising prices
Landfill gas
Pro:
-burning it reduces methane(contribution to climate change)
Con:
-releases CO2 and nitrogen oxide gases
Define work done
Work done = force applied x distance
(in joules) (Newtons) (metres)
W = F x d
Work done is when energy is transferred from one from to another. e.g lifting an object
Gravity potential energy
- Equation
- change in GPE
GPE = m x g x h
(J) g) (10N/kg) (m)
When we do work to give an object GPE we are lifting it above Earth’s surface.
△GPE = m x g x △h
Kinetic energy
-The amount of energy possessed by a moving object
-This depends on the mass and speed of the object
KE = 1/2 mv ²
KE = 1/2 mass x velocity ²
(J) (Kg) (m/s)
Power
The rate of which work is done
P = W/t
Power = work done/time
watt) (J) (s
1 watt = 1 joule transferred/second
Law of conservation of energy
Energy cannot be created/destroyed, only transferred from one form to another.
e.g Electric motor
electric→KE +( heat + sound)
wasted-dissipates into atmosphere
Efficiency
Efficiency = useful energy output/ x 100
total energy input
Can be represented by a Sankey diagram
Work done/GPE example:
- Calculate the WD lifting a 5 kg brick 10m into the air
- What’s its GPE?
W = F x d
The force we need is the weight of the object
force = 5 x 10 = 50N WD = 50 x 10 = 500J
When i ve done the work the brick has GPE
△GPE = mg △h
5 x 10 x 10 = 500J
So the gain in GPE = WD
What happens to wasted energy?
Every energy transfer produces heat which is dissipated into the atmosphere
(spreads out in air)
Energy changes:
- electric motor
- recharging battery
- speaker
- microphone
- diving
- electric motor: electrical → kinetic + heat + sound
- recharging battery: electrical → chemical + heat
- speaker: electrical → sound
- microphone: sound → electrical
- diving: GPE → kinetic
Note: heat is always a product of energy transfer
Energy in different forms
- Sound energy (particles vibration)
- Heat energy
- Light energy
- Chemical energy (burning fuels and food)
- Kinetic energy (moving objects)
- Nuclear energy (stored in the nucleus of an atom)
- Gravitational potential energy (objects above ground)
- Electrical energy
- Elastic potential energy/strain energy (stretched objects)
Renewable fuel
Fuels produced from renewable resources that we have an infinite supply of
Non-renewable fuel
Fues produced from non-renewable resources that we have a finite supply of
What is a fuel
A concentrated source of energy
Where are nuclear power stations built? Why?
Near a constant supply of water, in an isolated area
Because of their immense size and safety considerations
What happens after 40-50 years to a nuclear power station?
It ends its productive life, and needs to be shut down in a process called decommissioning. This takes years and costs billions of pounds
Demand for electricity
Varies from day to day. This can be predicted to an certain extent.
Examples of a predictable demand for electricity
- surge in early morning/evening
- greater demand in winter than summer
Examples of an unpredictable demand for electricity
- a storm
- break in-between a football match
Start up time of different energy resources
Nuclear power station: Weeks (not stopped unless absolutely necessary )
Coal, Oil and Gas : typically a few hours
Hydroelectric: seconds (particularly good for supplying at peak demand times )
Wind: depends on wind
Tide: predictable when available
Sankey diagrams
Check iPad
What is energy?
Ability to do work
