All biofuels are equal, but some biofuels are more equal than others.

In the British Governments bonfire of the quangos last year the Renewable Fuels Agency (RFA) was abolished and had it’s functions transferred to the Secretary of State for Transport. The RFA was responsible for running the Renewable Transport Fuels Obligation (RTFO). The RTFO was set up to obligate fossil fuel suppliers to supply a specified percentage of road transport fuels as bio-fuel. The fuel suppliers are given certificates for bio-fuel they supply (or gain them through trading with other suppliers) and at the end of the year they use the certificates to show that they have complied with their obligations. In practice what this means is that the fuel that you buy at the forecourt will have a small percentage of bio-fuel blended with it. Currently the target is that approx 3.6% of road transport fuel by volume should be bio-fuel. This is all well and good, and modern vehicles can happily make use of 5% blends without modification. But the main driver for the use of bio-fuel is that of carbon abatement and sustainability. This is where the relevance of the title of the post should become clear.

The problem is that in order for the use of bio-fuels to make sense from a sustainability/environmental point of view, the bio-fuels need to be sourced sustainably. In order to make sure that this is the case,  obligated fuel suppliers  are meant to report on the “carbon and sustainability” of the fuel they supply.

The RFA has just published its Year 2 report on the RTFO and in this they detail the information supplied to them by the obligated fuel suppliers on carbon and sustainability. It turns out that only 31% of the bio-fuel supplied in the UK over 2008/2009 met the environmental qualifying standard. Now this is an improvement over the previous year (20%) but still some way below the government target of 50% for the year. Of the balance, the fuel suppliers either didn’t meet the standard or perhaps worse, failed to submit data regarding the sustainability of their bio-fuels.

BP, Chevron, INEOS, Morgan Stanley, Murco and Total failed to meet any of the Government targets set. These were meeting the environmental qualifying standard, greenhouse gas emission reduction targets, and data reporting of fuel characteristics.

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Lies, damn lies, and statistics.

In his 1954 book “How to lie with statistics,” Darrell Huff devotes a chapter to the “Gee-Whiz” graph. He shows that by truncating figures and altering the proportions between axis that it is possible to create a misleading impression without falsifying any data.

For people who would like you to belive that climate change isn’t a big problem this approach can sometimes be too tempting to avoid. A prominent think tank has a figure similar to the following on their homepage.

I have used data from the UEA Climatic Research Unit to reproduce the figure. There doesn’t seem to have been much in the way of global warming over the last decade, right? But if we want to see if “Global Warming has Halted,” we can use the same data source to take a look.

Borrowing an idea from Tamino, in the below figure I have plotted global mean yearly temperatures from 1975 up to 2000, using the same data source as for the figure above. I have also plotted a trend line (0.0174 °C∙yr-1) estimated by linear regression and dashed lines representing ± twice the standard deviation of the residuals. The idea is that aproximately 95% of the yearly values should fall between the two dashed lines. (Actually, to get things completely right, I need to account for autocorrelation of the residuals, but it shouldn’t make too much difference for our purposes.) By extending the dashed lines forward in time to the present we should be able to see if warming has halted or not.

If when the data points for 2001 – 2009 are included they sit within the two dashed lines, then claims that global warming has halted would seem to be premature. In fact as the below figure shows, the global mean  yearly temperatures for 2001 – 2009 are right where we would expect them to be if global warming were continuing without pause.

 

Posted in Climate Change, Statistics | 5 Comments

Yes, but how many Jumbo Jets is that?

In the Guardian yesterday they announced a Gamesa led project to develop the “worlds largest offshore wind turbine.” It will be a 15 MW machine that would be “even bigger” than the 10 MW Britannia turbine also under development by Clipper Windpower. Unfortunately they neglect to tell us how much bigger it would be. Even more importantly they neglected to tell us how many Jumbo Jets that is. Fortunately, they provide an estimate of the size of the Britannia turbine that we can use to make a guess at the size of the Gamesa led turbine as long as we make some reasonable(?) assumptions.

1: Both turbines are horizontal axis types.

2: Both turbines have the same rated windspeed.

3: Both turbines have the same power coefficient.

4: Air density is a constant.

This means we can use the ratio of the rated powers of the two turbines to find the ratio of their swept areas and from there the diameter of the Gamesa turbine.

So: 15/10 = 1.5

From the link the Britannia would have a rotor diameter of 150 m. This gives a swept area of about 17672 m2. Therefore the swept area of the Gamesa turbine would be 26508 m2, it’s rotor diameter would be about 185 m and the turbine would be about 220 m high.

A Jumbo Jet (747-8) has a wingspan of 68.5 m so this means the Gamesa turbine would have a diameter equivalent to 2.7 Jumbo Jets. Thats half a Jumbo Jet larger than the Clipper.

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