Traditional generation

Question 1

What fuel do conventional thermal stations use to generate electricity?

Answer 1

Fossil fuels such as coal

Question 2

How do nuclear stations produce steam?

Answer 2

By using heat generated from nuclear fission

Question 3

What is combined cycle gas turbine stations?

Answer 3

They combine gas and steam turbines to achieve higher efficiencies

Question 4

How do hydroelectric stations generate electricity?

Answer 4

By using natural water flows to turn turbines

Question 5

What is the function of pumped storage hydroelectric stations?

Answer 5

They use electricity to pump water into a high-level reservoir which is later released to generate electricity at peak times

Question 6

What fuels do biomass stations burn?

Answer 6

Landfill gas, sewage sludge and waste

Question 7

What are two additional renewable sources of electricity mentioned?

Answer 7

Tides and ocean waves

Question 8

How are generators arranged and located in coal-fired stations?

Answer 8

Three or four generators are typically installed near coal mines or railways and are driven by a compound arrangement of high-pressure, intermediate-pressure and low-pressure turbines

Question 9

What is the typical rotation speed of turbines and why must it remain constant?

Answer 9

Turbines rotate between 1500 to 3500 rpm usually 3000 rpm in the UK’s 50 Hz system.
It must be constant to maintain the frequency with less than about 0.5 per cent variation

Question 10

What is Carbon Capture and Storage (CCS)?

Answer 10

CCS involves capturing CO2 from large fossil fuel power plants and storing it in deep geological formations like exhausted gas fields to prevent atmospheric release

Question 11

How effective is CCS in reducing CO2 emissions and what is its trade-off?

Answer 11

CCS can reduce CO2 emissions by 80-90% but increases coal-fired plant fuel needs by over one-third

Question 12

How efficient is a gas turbine when used alone in a CCGT plant?

Answer 12

Its thermal efficiency is only about 30%

Question 13

How does a CCGT plant increase efficiency?

Answer 13

It uses exhaust gases (over 500°C) to raise steam for a secondary turbine boosting efficiency to over 50%

Question 14

What is a key construction advantage of CCGT stations?

Answer 14

They are cheaper and quicker to build than coal or nuclear stations

Question 15

What is Combined Heat and Power (CHP)?

Answer 15

CHP is the simultaneous generation of heat and electricity

Question 16

How efficient are CHP systems and what is their environmental benefit?

Answer 16

CHP systems have efficiencies over 70% reducing the use of primary energy and emissions of carbon dioxide and other combustion products

Question 17

How do nuclear power stations generate electricity?

Answer 17

They use nuclear fission reactions to produce heat for steam generation

Question 18

What distinguishes different types of nuclear reactors?

Answer 18

The working fluid and the method used to cool and conduct heat to the steam generator

Question 19

What is a major environmental challenge of nuclear power?

Answer 19

Fission products are highly radioactive and produce long-lasting nuclear waste problems

Question 20

What are the main advantages of hydroelectric power?

Answer 20

It is renewable with no fuel cost, flue-gas emissions or nuclear waste; has a predictable output; long economic life and can control floods

Question 21

What are the main disadvantages of hydroelectric power?

Answer 21

Limited economically viable sites; environmental disruption to rivers and migrating fish and potentially serious dam failures though rare

Question 22

What is capacity factor in power generation?

Answer 22

It is the fraction of the maximum possible output that is actually generated

Question 23

Why do capacity factors vary among different generation technologies?

Answer 23

Different power generation technologies have varying reliability and efficiency levels

Question 24

Why is the annual output of a wind generator usually less than its theoretical maximum?

Answer 24

Because its actual output depends on variable wind conditions rather than its nominal rating multiplied by total hours in a year (8760 hours)

Question 25

What are the main advantages of wave power?

Answer 25

It has a low environmental impact, minimal chemical pollution and poses no significant threat to marine life

Question 26

What are the main disadvantages of wave power?

Answer 26

It has high capital costs, challenges in coupling wave frequency to generator frequency and structural survivability issues in harsh sea conditions

Question 27

What causes tidal energy storage in the ocean?

Answer 27

The gravitational effect of the moon and to a lesser extent the sun

Question 28

How do tidal energy schemes generate power?

Answer 28

They rely on the twice-daily tides producing water flow and ebb

Question 29

What environmental factors affect tidal flows?

Answer 29

Ocean depth variations at different locations

Question 30

What are the two main methods of extracting tidal energy?

Answer 30

Tidal barrages and tidal stream devices

Question 31

What is biomass or biofuel?

Answer 31

It is obtained from organic matter: directly from plants or indirectly from agricultural, industrial or domestic products

Question 32

Why is biomass considered carbon-neutral?

Answer 32

Because the CO2 released during energy generation is balanced by the CO2 absorbed by plants during their growth