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A2 Science In Society 3.5
Teacher Notes
Introduction
Resources
This activity is designed to help students prepare for the Unit 4
assessment. Note however that this is a learning task and not an
assessment task and so should not be regarded as being typical, in all
respects, of Unit 4 exam questions and no mark scheme is provided
though answers to all the questions are suggested.
Source A: ‘Warwick leads way on
wind trials’ (The Courier:
Leamington Spa)
www.leamingtoncourier.co.uk/greenstories/Warwick-leads-way-onwind.3654148.jp
In this case study the newspaper articles and press release are all
related to a technical study of small-scale wind generators which
culminated in a final report published early in 2009.
Source B: ‘Wind turbines like David
Cameron's don't provide much
electricity' (Daily Telegraph)
www.telegraph.co.uk/earth/environm
ent/4224513/Wind-turbines-likeDavid-Camerons-dont-providemuch-electricity.html



Source A (January 2008) helps to set the scene and provides
some of the background to the study.
Sources B – C are responses to the presentation of the final report
a year later in January 2009.
Source D is a selection of pages from the final report. Students
only need to review other pages quickly on a shared print-out, or on
screen.
Students should review all the sources before they start to answer any
of the questions.
If your students live well away from the Midlands, it may help if they
look at a map to see how close Warwick and Leamington are to each
other (www.streetmap.co.uk).
Source C: ‘Location, location:
proper turbine placement key to
viability’
Press release from the British Wind
Energy Association
www.bwea.com/media/news/articles
/location_location_proper_turbi.html
Source D: Selected pages from the
Warwick Wind Trials final report
which can be downloaded as a pdf
file. All students need these pages
1-2, 19-22, 24, 29, 30,33, 35, 36
www.warwickwindtrials.org.uk/2.html
Part A
1
Refer to source A
(a) What, according to the journalist, was the main question that the trials were aiming to answer?
Are the benefits that manufacturers claim for small turbines justified in practice?
(b) What distinguished these trials from previous studies of wind turbines?
The trials were designed to test turbines when installed, not in test sites, but in a variety of typical,
practical situations on homes, offices and factories. In other words, the trial was designed to reflect
the realities of the market.
(c) Why does the district around Warwick (which includes Leamington) have one of the highest
concentrations of domestic wind turbines in the country?
Encraft (the company carrying out the trials) is based in Leamington. Setting up the trials meant that
more people and small businesses were encouraged to install wind turbines as part of the trials.
Page 1
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A2 Science In Society 3.5
Teacher Notes
(d) Judging by the tone of the article, what can you say about the expectations of the journalist for
the outcomes of the trials?
The very positive tone of the article suggests that the staff journalist was expecting a positive
outcome which would justify the pioneering examples in Warwick and Leamington being taken up
much more widely.
2
Refer to sources B and C
(a) How is it possible for a wind turbine system to use more electricity than it generates?
The turbines have an electronic control system to manage the connection to the local electricity
circuits and to the mains supply. This system uses some power. If the turbine performs very poorly it
can supply less power than that needed by the control system.
(b) Why were the engineers who carried out the trials so surprised by the findings?
The performance of wind turbines, especially in urban areas, was so much worse than the claims
made by manufacturers.
(c) How does the British Wind Energy Association (BWEA) explain these disappointing findings
whilst still strongly supporting small wind turbines?
The BWEA tries to play down the significance of the findings. It argues that they are not
representative but does not quote any evidence (other than general experience) to justify the claim.
Although it accepts the importance of correct siting for small turbines. The BWEA seems unwilling to
accept evidence that could have a negative impact on the uptake of small wind turbines.
(d) B&Q say that most of their customers come from urban areas. Why do the reported findings of
the trials justify the decision by B&Q to stop selling wind turbines?
The Encraft study suggests that micro-turbines of the kind sold by B&Q may not perform well enough
to satisfy the expectations of customers because turbines on homes in urban areas were the least
likely to perform well. See this article for more detail.
www.guardian.co.uk/business/2009/feb/06/windpower. B&Q made the decision after many months of
customer feedback
3
Refer to the specified parts of source D.
(a) The design of the study and the features of the report
(i) In the acknowledgements at the end of the Executive summary, on page 2, the authors mention
the value of funding “to enable the trials to maintain their independence”. Explain why this might be
important.
If the trials had been funded by a group with a vested interest in the sales of wind turbines there
would have been a suspicion of bias.
(ii) Explain the importance of including the detailed information on each site and turbine on pages 6 –
18 in the report. (You do not need to read this.)
This information describes the turbines that were the basis of the study and allows readers of the
report to assess the extent to which the study was based on a representative group of turbines
installed in realistic situations.
Page 2
©The Nuffield Foundation, 2009
Copies may be made for UK in schools and colleges
A2 Science In Society 3.5
Teacher Notes
(iii) Why would it not be appropriate to relate the findings of the study to larger-scale wind turbines, or
to freestanding wind turbines mounted on masts well away from obstructions? (pages 1 and 2)
The turbines tested were in urban environments and mounted on building. The buildings upset the
airflow and cause turbulence and mean that wind speeds are much lower and less consistent.
(b) The data (page 19)
(i) The researchers collected the data from the turbines during regular visits to the turbine sites rather
than collecting the data remotely. What were the advantages and disadvantages of doing this?
Advantage: regular visits to the sites meant that the scientists could collect information from the
turbine owners in addition to the electronic date.
Disadvantage: faults were only identified at monthly intervals and then might take another month to
put right.
(ii) The researchers were not able to collect long-term performance data from as many wind turbines
as they had expected. Give some reasons for this.
Many of the wind turbines were unreliable and broke down while others were badly installed and had
to be switched off. A further set of turbines were noisy and had to be turned off because of
complaints.
(c) Modelling the wind speed data (see pages 20–22, 35 and 36)
Before deciding to install a small wind system it is essential to have a good knowledge of wind speed
at the site. This can be predicted using modelling. The national wind speed database (NOABL)
contains estimates of the annual mean wind speed throughout the UK.
(i) Refer to Figure 1 page 21 and comment on the discrepancy between NOABL predictions and the
measured wind speeds.
Measured wind speed always lower than that predicted by NOABL, more than 60 % lower in some
cases.
(ii) The NOABL predictions can be modified using a scaling factor as devised by the Microgeneration
Certification Scheme installers standard (MIS). This is necessary to correct for the effect of local
land features and buildings on the basic NOABL model.
Comment on the effectiveness of this scaling factor for the prediction of mean wind speed, using
Figure 1.
Agreement was better for some sites but still did not give good agreement at others.
(iii) The distribution of wind speeds is as important as the mean wind speed. This is modelled using
an equation which includes a shape factor ‘k’. The measured distributions of wind speed for two
sites, Lillington Road and Hill Close
Gardens are shown on pages 35 and 36 compared with the predictions using the widely accepted
value k=2 and with modifications using different values for k.
In what way does using k=2 in the model lead to a poor estimate of average wind speed for Lillington
Road or Hill Close Gardens?
Page 3
©The Nuffield Foundation, 2009
Copies may be made for UK in schools and colleges
A2 Science In Society 3.5
Teacher Notes
Average would be too high. Distribution shifted to higher wind speeds, for example Lillington Road
showed 2.5m/s for 35% of time. In fact 2.5m/s measured for only 18% of time
(iv) What do these plots and the data in Figure 1 show about how the researchers used and modified
the models to predict wind speeds?
vital to check against measurement
measured mean speeds much lower than predicted by NOABL model by as much as 20%-60%
model must be modified to suit local conditions with a local scaling factor
local shape factor also needed, the widely used value did not give good agreement
local modification does provide a reasonable fit.
some sites fit the standard model better than others
even with local scaling factors there are differences between predictions from the model and
measured values which can be in the range ± 20%
(d) Energy
Manufacturers provide power curves for the wind turbines. (page 29-30)
(i) What is a power curve for a wind turbine?
A power curve is a plot showing how the electric power (in Watts) from a turbine varies with wind
speed.
(ii) Use Figures 8, 9 and 10 to discuss how manufacturers predictions compare with measured power
outputs.
The red line shows that manufacturer’s power curve is significantly higher than the observed values
shown by the blue dots. This means that the manufacturer’s curve overestimates the output.
Agreement better at low wind speeds.
(iii) How does this overestimate of power relate to the comparisons between predicted and measured
energy outputs shown for the two sites on pages 35 and 36?
Energy output is power x time
If power output less then overall energy supplied will be less
Output always lower than that predicted, at all wind speeds
(e) Imagine you have friends who lives at the Lillington Road site. They bought the wind turbine
because they were advised that it would provide them with about 800kWh each year.
Explain to your friends why the prediction was so seriously wrong using Table 1 on page 24 and
other facts you have learned from this activity.
Three factors determine annual output.
The wind speed – NOABL data seriously overestimate this. This accounts for most of the loss of
energy, 88kWh rather than the predicted 819kWh.
Page 4
©The Nuffield Foundation, 2009
Copies may be made for UK in schools and colleges
A2 Science In Society 3.5
Teacher Notes
The relationship between wind speed and power output from the turbine, shown as a power curve –
the manufacturer’s power curve overestimates the power at all wind speeds
The time the turbine is out of action for maintenance in this case major repairs were needed.
Part B
Imagine that you work for a company that manufactures small wind turbines. You have been asked by
your boss for a memo summarising the key findings of the Warwick Wind Trials and spelling out the
implications of the findings for the design and installation of new products and the marketing of existing
and new products in the UK. The length of your memo should not exceed 400 words.
Some of the points that might be made in the memo are listed below.

Findings: The trials show that small wind turbines are only appropriate in urban areas in exceptional
circumstances. The reputation of companies like ours is at risk if we continue to promote wind
turbines in areas where they do not offer value for money.

Design, production and installation: Noise can be a major problem and needs to be taken into
account during design and testing. Turbines need to be tested rigorously in realistic conditions to
ensure that they are reliable. Installers need rigorous training.

Marketing: We should not be marketing our turbines aggressively in urban areas. We need to be
educating our customer base about the circumstances in which the turbines work well. The NOABL
wind speed data base should not be relied on when advising customers.
July 2009
Page 5
©The Nuffield Foundation, 2009
Copies may be made for UK in schools and colleges
A2 Science In Society 3.5
Student sheets
Introduction
In February 2009, B&Q, the DIY chain, withdrew wind turbines from sale because of a survey by energy
consultants Encraft which showed that home turbines generated only a fraction of the energy promised
by manufacturers, and in some cases needed more electricity than they made.
In this case study you are going to study parts of the final report on the Warwick Wind Trials carried out
by Encraft. You are also going to read some of the responses by the press and interest groups to the
findings. You should read all the sources before you start to answer the questions. It is important that
you have read the key parts of the final report before you start answering questions about the other
sources.
Resources
Source A: ‘Warwick leads way on wind trials’ (The Courier: Leamington Spa)
www.leamingtoncourier.co.uk/green-stories/Warwick-leads-way-on-wind.3654148.jp
Source B: ‘Wind turbines like David Cameron's don't provide much electricity' (Daily Telegraph)
www.telegraph.co.uk/earth/environment/4224513/Wind-turbines-like-David-Camerons-dont-providemuch-electricity.html
Source C: ‘Location, location: proper turbine placement key to viability’
Press release from the British Wind Energy Association
www.bwea.com/media/news/articles/location_location_proper_turbi.html
Source D: Selected pages from the Warwick Wind Trials final report which can be downloaded as a pdf
file. All students need these pages 1-2, 19-22, 24, 29, 30,33, 35, 36
www.warwickwindtrials.org.uk/2.html
Questions
Part A
1
Refer to source A
(a) What, according to the journalist, was the main question that the trials were aiming to answer?
(b) What distinguished these trials from previous studies of wind turbines?
(c) Why does the district around Warwick (which includes Leamington) have one of the highest
concentrations of domestic wind turbines in the country?
(d) Judging by the tone of the article, what can you say about the expectations of the journalist for
the outcomes of the trials?
Page 1
©The Nuffield Foundation, 2009
Copies may be made for UK in schools and colleges
A2 Science In Society 3.5
2
Student sheets
Refer to sources B and C
(a) How is it possible for a wind turbine system to use more electricity than it generates?
(b) Why were the engineers who carried out the trials so surprised by the findings?
(c) How does the British Wind Energy Association (BWEA) explain these disappointing findings
whilst still strongly supporting small wind turbines?
(d) B&Q say that most of their customers come from urban areas. Why do the reported findings of
the trials justify the decision by B&Q to stop selling wind turbines?
3
Refer to the specified parts of source D.
(a) The design of the study and the features of the report
(i) In the acknowledgements at the end of the Executive summary, on page 2, the authors mention
the value of funding “to enable the trials to maintain their independence”. Explain why this might be
important.
(ii) Explain the importance of including the detailed information on each site and turbine on pages 6 –
18 in the report. (You do not need to read this.)
(iii) Why would it not be appropriate to relate the findings of the study to larger-scale wind turbines, or
to freestanding wind turbines mounted on masts well away from obstructions? (pages 1 and 2)
(b) The data (page 19)
(i) The researchers collected the data from the turbines during regular visits to the turbine sites rather
than collecting the data remotely. What were the advantages and disadvantages of doing this?
(ii) The researchers were not able to collect long-term performance data from as many wind turbines
as they had expected. Give some reasons for this.
(c) Modelling the wind speed data (see pages 20–22, 35 and 36)
Before deciding to install a small wind system it is essential to have a good knowledge of wind speed
at the site. This can be predicted using modelling. The national wind speed database (NOABL)
contains estimates of the annual mean wind speed throughout the UK.
(i) Refer to Figure 1 page 21 and comment on the discrepancy between NOABL predictions and the
measured wind speeds.
(ii) The NOABL predictions can be modified using a scaling factor as devised by the Microgeneration
Certification Scheme installers standard (MIS). This is necessary to correct for the effect of local
land features and buildings on the basic NOABL model.
Comment on the effectiveness of this scaling factor for the prediction of mean wind speed, using
Figure 1.
Page 2
©The Nuffield Foundation, 2009
Copies may be made for UK in schools and colleges
A2 Science In Society 3.5
Student sheets
(iii) The distribution of wind speeds is as important as the mean wind speed. This is modelled using
an equation which includes a shape factor ‘k’. The measured distributions of wind speed for two
sites, Lillington Road and Hill Close Gardens are shown on pages 35 and 36 compared with the
predictions using the widely accepted value k=2 and with modifications using different values for k.
In what way does using k=2 in the model lead to a poor estimate of average wind speed for Lillington
Road?
(iv) What do these plots and the data in Figure 1 show about how the researchers used and modified
the models to predict wind speeds?
(d) Energy
Manufacturers provide power curves for the wind turbines. (page 29-30)
(i) What is a power curve for a wind turbine?
(ii) Use Figures 8, 9 and 10 to discuss how manufacturers’ predictions compare with measured
power outputs.
(iii) How does this overestimate of power relate to the comparisons between predicted and measured
energy outputs shown for the two sites on pages 35 and 36?
(e) Imagine you have friends who live at a site similar to the Lillington Road site. They bought the
wind turbine because they were advised that it would provide them with about 800kWh each year.
Explain to your friends why the prediction was so seriously wrong using table 1 on page 24 and other
facts you have learned from this activity.
Part B
Imagine that you work for a company that manufactures small wind turbines. You have been asked by
your boss for a memo summarising the key findings of the Warwick Wind Trials and spelling out the
implications of the findings for the design and installation of new products and the marketing of existing
and new products in the UK. The length of your memo should not exceed 400 words.
Page 3
©The Nuffield Foundation, 2009
Copies may be made for UK in schools and colleges