P3 Energy Resources

Question 1

How are most of our energy demands met today?

Answer 1

Most of the energy we use comes from burning fossil fuels (mostly oil, gas, coal)

Question 2

Why are fossil fuel and nuclear fuel non renewable?

Answer 2

They are non renewable because they cannot be replaced

Question 3

How does a power station work?

Answer 3

Fossil fuels are extracted from under the ground or under the sea bed and then transported to oil refineries and power stations.
In the power station the burning fuels heat water in a boiler. This produces steam. The steam drives a turbine that turns an electricity generator.

Question 4

What are fossil fuels and where do they come from?

Answer 4

They are coal, oil and gas. They come from long dead animals and plants.

Question 5

What is biofuel?

Answer 5

It is any fuel taken from living or recently living organisms

Question 6

What are examples of biofuels?

Answer 6

• Methane collected from cows or animal manure, from sewage works, decaying rubbish
• Ethanol from fermented sugar cane
• Straw
• Nutshells
• Woodchip
• Biodisel which comes from waste vegetable oil and plants such as rapeseed

Question 7

How can biofuel be used?

Answer 7

They can be used in modified engines for transport and in generators in power stations

Question 8

What are the characteristics of biofuel?

Answer 8

• Renewable because its source either regrows (vegetation) or is continually produced (Sewage and rubbish)
• Carbon neutral because in theory the carbon that the living organism takes in from the atmosphere as carbon dioxide can balance the amount released when the fuel is burnt

Question 9

Where does Nuclear Fuel take energy from?

Answer 9

Nuclear Fuel takes energy from atoms

Question 10

What is the fuel used in a nuclear power station?

Answer 10

Uranium or plutonium

Question 11

How does a nuclear power station work?

Answer 11

• The fuel is in sealed can in the core of the reactor
• The nucleus of a uranium atom is unstable and can split in two and energy is being transferred from the nucleus when this happens
• The core becomes very hot because there are a lot of uranium atoms
• The energy from the core is transferred by a fluid (coolant) that is pumped through the core
• The coolant is very hot when it leaves the core. It flows through a pipe to heat the exchanger then goes back to the reactor core
• The energy transferred by the coolant is used to turn water into steam in the heat exchanger; the heat drives turbines that run electricity generators

Question 12

How do Nuclear power stations compare with Fossil Fuel power stations in terms of energy released, waste and greenhouse gases?

Answer 12

• Fuel released per Kg of fuel: Nuclear PS: 300,000 MJ, Fossil Fuel PS 30 MJ
• Waste: Nuclear PS: radioactive waste which needs to be stored for many years; Fossil Fuel PS: non radioactive waste
• Greenhouse gases: Nuclear PS: No because uranium releases energy without burning: Fossil Fuel PS: yes because fossil fuels release gases such as carbon dioxide when burning

Question 13

What is a wind turbine?

Answer 13

It is an electricity generator at the top of a narrow tower. The force of the wind drives the turbine’s blades around. This turns a generator

Question 14

What is a negative aspect of wind turbines?

Answer 14

They are unreliable as if there is little or no wind they do not generate electricy

Question 15

What is Wave power?

Answer 15

A wave generator uses waves to make a generator move up and down. This motion turns the generator so it generates electricity. A cable between the generator and the shoreline delivers electricity in the grid.

Question 16

What are some negative aspects of Wave generators?

Answer 16

• They do not produce a constant supply of electricity
• A lot of cables and buildings are needed and this might spoil the coastline
• Tidal flow patterns might change affecting marine and birds life

Question 17

What is Hydroelectric power?

Answer 17

Hydroelectricity can be generated when rainwater that is collected in a reservoir flows downhill. The flowing water drives turbines that turn electricity generators at the bottom of the hill

Question 18

How does a Tidal power station work?

Answer 18

It traps water from each high tide behind a barrage. The high tide is then released in the sea through turbines. The turbines drive generators in the barrage.

Question 19

What are solar cells?

Answer 19

Solar cells are flat solid cells and use the Sun’s energy to generate electricity directly

Question 20

What are solar panels?

Answer 20

They are solar cells connected together

Question 21

How much of the energy absorbed by a solar cell is converted into energy transferred by electricity?

Answer 21

Less than 10%

Question 22

When are solar panels useful?

Answer 22

• When only a small amount of electricity is needed

- In very remote places

Question 23

Pros and cons of solar panels

Answer 23

+ do not cost anything to run

• Expensive to buy
• Lots of them are needed and plenty of sunshine for them to be useful
• Unreliable where it is clouded

Question 24

How does a solar power tower work?

Answer 24

It uses thousands of flat mirrors to reflect sunlight on to a big water tank at the top of a tower. The mirrors on the ground surround the base of the tower.

• The water in the tank is turned to steam by the heating effect of the solar radiation directed to the water tank
• The steam is piped down to ground level, where it turns electricity generators
• The mirrors are controlled by a computer so that they can truck the sun

In a hot dry climate it can generate enough electricity to power a few thousand homes

Question 25

What are solar heating panels?

Answer 25

They heat the water that runs through them

Question 26

What is Geothermal Energy?

Answer 26

It comes from the energy transferred by radioactive substances deep inside the Earth

Question 27

How does Geothermal energy works?

Answer 27

Geothermal power stations are build in volcanic areas or where there are hot rocks deep down the earth’s surface. Water is pumped into hot rocks underground and produces steam to drive turbines at the earth surface that generate electricity

Question 28

What are the issues linked to fossil fuels?

Answer 28

• When coal, oil or gas is burnt greenhouse gases such as carbon dioxide are released. Most scientists believe this is causing global warming
• Burning fossil fuels also produce sulfur dioxide. This gas causes acid rain. To overcome this sulfur can be removed before the fuel is burnt
• Fossil fuels are non renewable. Oil and gas reserves could be used up within the next 50 yrs

Question 29

What are the advantages of nuclear power?

Answer 29

• No greenhouses gases

- Much more energy is transferred from each Kg of uranium fuel than from fossil fuel

Question 30

What are the disadvantages of nuclear power?

Answer 30

• Radioactive waste

- In case of explosion of a nuclear reactor radioactive material is released is a wide area

Question 31

What are the advantages of renewable energy resources?

Answer 31

• They will never run out
• They do not produce greenhouse gases or acid rain
• No radioactive waste products
• They can be used where connection to National Grid is uneconomical (eg solar panels in remote areas)

Question 32

What are the disadvantages of renewable energy resources?

Answer 32

• They cannot currently meet the world’s demand
• Wind turbines create noise that can upset people nearby and spoil the views
• Tidal barrages affect rivers estuaries and the habitats of plants and creatures there
• Hydroelectric schemes need large reservoirs of water, which can affect plants and animals nearby and habitats are often flooded to create dams
• Solar cells need to cover large areas to generate large amounts of power
• Some resources are unreliable for example:
  Wind/ waves: too weak
  Hydroelectric: reservoirs can become dry during droughts
  Tidal: height of tide varies on a yearly and monthly cycle
  Solar: no sun at night and variable during the day

Question 33

How does demand for electricity varies during the day and in the year?

Answer 33

• It is higher in winter then in summer
• Lower at night
• Higher in the late afternoon/ evenings

Question 34

How is the variable demand for electricity met?

Answer 34

• A constant amount of electricity (or base load demand) is met using nuclear and coal fired power stations
• Daily variations and increased demand in winter are met by gas fired power stations and pumped storage schemes
• Renewable energy resources are used when demand is high and when the conditions for renewable energy are suitable
• Renewable energy resources are used when demand is low to store energy in pumped storage schemes

Question 35

What costs are involved with energy supply?

Answer 35

• Capital cost to build the facility
• Running costs to run it and maintain it
• Costs to decomission it (take it of of use)

Question 36

How do costs compare among the different energy sources?

Answer 36

• Capital costs are lowest for gas fired power stations and greatest for wind and nuclear power stations (this include decommissioning costs)
• Overall costs are the lowest for hydroelectricity and greatest for offshore wind farms
• Nuclear power stations are expensive to build, run and de-commission
• Renewable resources are cheap to run but expensive to install

Question 37

How can households save on energy bills?

Answer 37

• Low energy light bulbs

- Improved home insulation (eg double glazed windows)

Question 38

What are the different start up times of power stations?

Answer 38

• Gas power stations have the shortest start up time
• Oil
• Coal
• Nuclear have the longest start up time

Question 39

What are pumped storage schemes?

Answer 39

• Power stations tend to run all night, generating a surplus of electricity that isn’t needed.
• The additional electricity that is generated at night can be used to pump water up to a higher reservoir, which can then be released during times when demand for electricity is high - this, like hydroelectric power, generates turbines and creates electricity
• Pumped storage isn’t the same as hydroelectric power, but it allows you to store energy which has been generated previously