# Worksheet: Wind Power

In this worksheet, we will practice describing the advantages and disadvantages of wind turbines, and which locations are suitable for wind farms.

Q1:

A volume of air moving through a wind turbine has a mass of kg. If the air is moving at 5 m/s, what is the kinetic energy of the volume of air? Give your answer in megajoules to 2 significant figures.

Q2:

The installed capacity of a wind turbine is the maximum power output that it can produce.

What is the installed capacity of a wind farm containing 180 turbines if the installed capacity of one wind turbine is 3.6 MW?

Which of the following is the main reason why a wind farm does not achieve its installed capacity most of the time?

• AThe wind speed is not constant; thus, wind turbines are not always producing their maximum power output.
• BA lot of energy is lost to heat in the transmission of the electrical current from the wind farm to where it connects to the electricity grid.
• CA lot of energy is lost to heat in the generators in the wind turbines; thus, the actual power output of a wind farm is always lower than the installed capacity.
• DWind turbines are unreliable and often break; thus, most of the time not all of the turbines on the wind farm are operating.
• EWind turbines become less efficient over time; thus, the maximum power output that they can produce decreases over time.

Q3:

The graph shows the power output of a particular type of wind turbine against the wind speed. The table shows data for the wind speed at three different sites as measured on five consecutive days.

Calculate the average wind speed for each site over the five days on which the wind speed was measured, and use this information to determine which site will produce the largest power output if a wind turbine is placed there.

Wind Speed (m/s)
Day 1Day 2Day 3Day 4Day 5
Site A6.55.97.03.54.0
Site B1.12.83.12.44.1
Site C8.54.67.14.25.5
• ASite C
• BSite B
• CSite A

Q4:

Wind turbines convert the energy of the moving air to energy.

• Athermal, chemical
• Bgravitational potential, electrical
• Cgravitational potential, kinetic
• Dkinetic, electrical
• Ekinetic, gravitational potential

Q5:

What type of electric current do wind turbines produce?

• ARectified alternating current
• BPulsating current
• CDirect current
• DAlternating current

Q6:

The London Array is a wind farm located off the coast of Kent in the Thames Estuary. Its installed capacity is 630 MW. What is the total energy output of the London Array over the course of a year if it runs at ‎ of its installed capacity throughout the year? Use a value of 365 for the number of days in a year. Give your answer in gigawatt-hours to 2 significant figures.

Q7:

The diagram shows three possible locations where wind turbines could be placed. The average wind speed is 1.2 m/s in the valley, 5.5 m/s on the moor, and 7.9 m/s over the ocean.

Which of the three locations is not suitable for wind turbines?

• AThe moor
• BThe sea
• CThe valley

Why is this location not suitable for wind turbines?

• AThere is more space in the sea; thus, only a few wind turbines could be placed in the valley, whereas many more could be placed in the sea.
• BWind turbines spoil the view, so it is better to put them in remote places such as moors and out at sea.
• CThe speed of the wind increases linearly with height above sea level; therefore, it is better to place wind turbines in higher locations.
• DWind turbines cannot generate electricity if the wind speed is below approximately 3 m/s.
• EOffshore wind turbines are cheaper than onshore wind turbines; therefore, placing wind turbines in the valley would be more expensive than placing them in the sea.

Q8:

The table shows the average wind speed at three different sites, the power output of 1 wind turbine at each site, and the cost of building a wind farm with 200 turbines at each site.

Average Wind Speed (m/s)Power Output of 1 Wind Turbine at Each Site (W)Cost of Building a Wind Farm with 200 Turbines
Site A10.81,440 £1.1 billion
Site B12.31,640 £1.2 billion
Site C7.5690 £0.7 billion

What would the total power output of a 200-turbine wind farm located at site A be when the wind speed is at the average wind speed for that site?

Ignoring any costs involved with maintaining the wind farm, what is the cost per megawatt of building a 200-turbine wind farm at site A? Give your answer to the nearest million pounds.

• A£3 million
• B£1 million
• C£8 million
• D£4 million
• E£5 million

Ignoring any costs involved with maintaining the wind farm, for which site would the cost per megawatt of building a 200-turbine wind farm be lowest?

• ASite A
• BSite B
• CSite C

Q9:

The Hornsea Wind Farm is a wind farm being built in the North Sea off the coast of England. When completed, the first stage of the project will provide 1.2 GW of power when running at its installed capacity.

If the wind farm runs at ‎ of its installed capacity throughout the year, how much energy will it produce in 1 year? Give your answer in gigawatt-hours to 2 significant figures. Use a value of 365 for the number of days in a year.

In 2014, the United Kingdom used 302 TWh of electricity. If the United Kingdom uses the same amount of electricity over the next year, what percentage of UK’s electricity could be supplied by the Hornsea Wind Farm? Give your answer to 1 decimal place.

• A
• B
• C
• D
• E