Wind Energy

Reading's Wind Turbine

For months after this wind turbine was installed in Reading towards the end of 2005, I kept saying I ought to find out more about it. Visitors passing it on their way in to Reading at the M4 motorway junction 11 have asked about it, and I've been skeptical, thinking it's more of a publicity gimmick funded by the new business park there than a useful generating capacity, but it seems I'm wrong. Here's what I have discovered.

Hub on the ground I can see it from my window, but I couldn't imagine how big it is until I saw this nice night-time construction photograph (from Ecotricity) of the hub with engineers standing beside it.

Its hub is 85 metres above ground level, and its rotor blades diameter is 70 m. It's a direct-drive design, unlike most which have gearboxes, and it operates at variable speeds using an efficient AC-DC-AC conversion system to connect to the National Grid.

Its rated capacity (i.e. maximum output) is 2 MW which is typical of the biggest wind turbines being built on land at the moment. (New off-shore turbines are typically 3 MW.) Like most in Britain, it's expected to operate at around 20% to 30% of its capacity on average because of wind speed variation, and the figures given for this one indicate 20% is expected, so it will power over 1000 standard average homes requiring 375 watts (3300 kWh p.a.) each.

This wind turbine at Green Park is cited as "the UK's most visible" turbine, because of the number of people passing it on the M4. It's one of many being put up around the country by one of the "green" energy companies, Ecotricity. The average cost of installing a turbine of this scale is over a million pounds, and its operating life time should be around 20 to 30 years.

At Swaffham in Norfolk, Ecotricity has two turbines with a visitor centre.

Ecotricity has some facts and figures about it including construction photos. (They used to have a PDF "info pack" that included a diagram of the inside.)

The BWEA (British Wind Energy Association) web site has information on planning, technology, environmental impact, etc., and maps of existing and planned "Wind farms of the UK".

For FAQs about wind energy such as "Do they kill birds?" and "How long to pay back the energy used in manufacture?" you could try:

Some reasonably balanced info about birds and other environmental impacts:

So, there we are: it's useful and commercially viable, and electricity customers like us can switch to Ecotricity and pay approximately the same price as other electricity providers charge.

"Green" Tariffs

I looked in to the various "green" tariffs available from the various electricity suppliers and found a clear division between those that do what I would want and expect - invest my payments into green electricity supplies - and those that simply use the "green" badge as a marketing tool.

With most of the electricity companies, if I were to switch from one of their "non-green" tariffs to one of their "green" tariffs, in my simplistic view they would simply assign my payments to a different column on their accounting spreadsheet. At the same time, they would "guarantee" to buy that much green supply on my behalf, but that is a hollow promise. They already buy some green supply into their mix (they are required to by law, whether customers "sign up" to it or not), and by saying a particular portion of it is now "mine", that same portion of green supply must now be de-allocated from the mix that their non-green customers were already receiving. In other words, they don't buy extra green to allocate to me, they just re-allocate what they already are buying. If a huge number of customers requested their green tariff, then it might seem that they could be forced to source more green electricity than they already do - except if that started to happen and they didn't want to do it, I believe they would simply change their advertising or the types or prices of "green" tariff they offer, to manipulate "the market" of new customers into not signing up any more.

It's not as simple as that, of course. The law is changing to prevent the advertising as "green" of schemes that do not really mean what people would expect. Some of the "green" tariffs were already offering something of real green value in some of their "green" tariffs. The most common offerings were to do with ROCs (Renewables Obligation Certificates), a scheme of financial incentives among electricity supply businesses to promote green supply. However, I tried to evaluate these and found it difficult to do so.

What did I find (mid 2009)?

Ecotricityput "green" payments into "green" generation
Green Energy
Good Energy
All the major electricity suppliers,allocate "green" payments to a different column in their accounts
regional, national and international

The three good ones differ dramatically in how they use the money, but switching my payments to any of those three seems to me a Good Thing.

National electricity transmission efficiency

Local generation of electricity can avoid the energy losses that are incurred by transmitting electricity across the country. The average national transmission losses are around 6% to 9% in total in the National Grid and local distribution networks, i.e. from conventional generator connection points to the customer's meter. The amount ranges from around 9% for domestic customers down to lower levels for industrial users connected at high voltages, down to as little as 2% for high-voltage customers connected directly to the National Grid.

Source: for example, Ofgem's "Electricity distribution losses - A consultation document", 2003, section 4 "The current level of losses and the ability to control it" (and Appendix 2 table 2 has a break-down of loss into components).

UK Fuel and Energy Production and Use

Energy flowchart PDF file

I found this rather good Energy Flow Chart (PDF) on a DTI web page. It shows by the width of coloured paths how much of various fuels and electricity is imported, generated, converted, stored, lost, exported and used for various purposes in the UK. It isn't very detailed for someone concentrating on electricity, but is a very good overview of all energy use.


JAF monogram Copyright: text © Julian Foad, 2006; photographs © other people.