Macrogeneration

Question 1

What is the duty of a gearbox in a wind generator

Answer 1

The gearbox converts the rotational speed of the main shaft (rotating at the same speed of the main shaft from approx. 30-60 rpm to about 1000-1800rpm high speed shaft)These rotational speeds are required for the generation of electricity in most generators

Question 2

List the transfers of energy in a wind turbine

Answer 2

Wind energy to KE of blades/main shaft (sound and thermal loss)
KE of Main Shaft to KE to high speed shaft (Sound and thermal loss)
KE of High Speed Shaft to Electrical energy in generator (Sound and thermal loss)

Question 3

In smaller turbines, what is the purpose of a step up transformer.

Answer 3

In a smaller turbine , the step up transformer is located on the ground beside the tower. It increases the voltage from about 690 volts to several thousand volts to send it to the sub station. This is to reduce energy losses in power cables, as reducing current reduces power losses.

Question 4

In larger turbines, where is the step up transformer located

Answer 4

The step transformer is located in the Nacelle, (the housing at the top which consists of the gearbox and generators)

Question 5

Where does the electrical energy go after being generated.

Answer 5

The electrical energy is transmitted from the turbine location, to the nearest substation, some energy is loss in the form of heating the cables

Question 6

Explain the term direct and give examples

Answer 6

DIRECT- These renewable energies take energy from a renewable source such as the wind or waves in the ocean and can convert this into electrical energy directly
Eg wind, hydroelectric, wave/tidal

Question 7

Explain the term in-direct and give examples

Answer 7

INDIRECT- These take energy from a renewable source such as the sun, a physical characteristic of the material being used, convert this energy into electrical energy, eg solar PV and biomass

Question 8

Identify the energy changes involved in generating wind

Answer 8

As the wind blows, kinetic energy from the wind is transferred directly to the bladed, which rotate driving a gear system which in turn drives a generator.

Question 9

Identify the energy changes involved in generating Hydroelectric

Answer 9

The water normally comes from behind the dam built across a river valley. The water high up behind the dam acts as a store of potential energy. This transferred into kinetic energy as the water passes down through the inside of the dam. The moving water directly drives turbines blades which in turn drive electrical generators.

Question 10

Identify the energy changes involved in generating wave

Answer 10

Wave machines directly use the kinetic energy in the movement of water as it rises and falls. This method has potential but is still being developed.

Question 11

Identify the energy changes involved in generating tidal

Answer 11

Large amounts of water moved in and out each day because of the tides. A tidal barrage is built over the river to make direct use of the kinetic energy in the moving water. The barrage contains turbines which are driven by the water rushing through turning the generator.

Question 12

Identify the energy changes involved in generating Solar PV

Answer 12

Light energy from the sun is converted into electrical energy in the photovoltaic cell contained within the panel. The PV cels produce DC which can be converted to AC by an inverter if it is to be connected to the grid.

Question 13

Identify the energy changes involved in generating Biomass

Answer 13

Biomass is plant matter used either to generate electricity ( combustion same way as fossil fuel)or to produce heat (direct combustion).

Question 14

What is the national grid

Answer 14

The national grid distributes electricity across the country. It connects power stations to homes, workplaces and public buildings all around the country

Question 15

What’s the purpose of a step up transformer

Answer 15

Increases the voltage from 22,000 volts to 275000 or 400,000 volts. This reduces energy losses when the power is transmitted through the grid.

Question 16

What’s the purpose of a step down transformer

Answer 16

Decreases the voltage to 33,000 volts for industry, 11,000 volts for towns, villages and 230 volts for use in homes, schools shops and businesses.

Question 17

What is the smart grid

Answer 17

An electricity supply network that uses digital communications technology to detect and react to local changes in usage.

Question 18

What are the economic benefits of the smart grid

Answer 18

VALUE TO CUSTOMERS: Reduced requirement for expensive ‘peak fossil fuel power stations’ as this energy can be imported from more cost effective renewable energy production in member states;
EXPORTING ENERGY: France – 75% of energy from nuclear – exporting 2 billion Euro per year – Huge revenue created via this market;
Some 40% of Europe’s wind energy passes over Ireland and GB, if 29% of this practical offshore renewable resource could be harnessed by 2050 the electricity equivalent of 1 billion barrels of oil could be generated annually – making the UK a net electricity exporter, generating around 145,000 jobs and £62 billion of annual revenues for the UK.
TIME DIFFERENCES: Different regions will hit peak demand at different times, due to the time differences.
Eastern EU members such as Bulgaria and Romania are 2 hours ahead of western EU members such as the UK, Ireland and Portugal.
Thus, peak demands in Eastern regions can be supplemented by over production in Western nations, and the converse when Western nations reach their peak times.

Question 19

What are the environmental benefits of the smart grid

Answer 19

CO2 EMISSIONS: As the grid becomes more interconnected, increased utilisation of renewables in a more effective manner will result in less use of fossil fuels, eradicating the harmful gasses given off.
POTENTIAL DISASTER:
Reduced reliance on fossil fuels, and extraction and transport of fossil fuels, due to the integration of renewable production onto the grid.
This in the future leads to less oil required for cars (now electric cars, charged by the renewable energies on the super grid), so less oil to transport and obviously less chance of oil spills and the huge costs, environmental concerns with such issues. The oil spill in the Gulf of Mexico in recent years highlights the issues that are involved

Question 20

What is CHP

Answer 20

Combined Heat and Power

Question 21

What is another name for CHP

Answer 21

Cogeneration

Question 22

What’s the purpose of cogeneration

Answer 22

It can reduce carbon emissions and energy costs. A typical power system has an efficiency of about 40-50%. Cogeneration systems that combined heat and power can be up to 80% efficient.