Whitelee powers Glasgow again

Whitelee wind farm, the biggest wind farm in Europe, is to be completed and 'switched on' this week. And
the news says that the power company is applying to extend the wind farm to increase its capacity from 322 MW to 614 MW.
I mentioned the predicted output of Whitelee in my book (page 33). Since the predictions for Whitelee were one of the sources for my estimated wind-farm-power-per-unit-area of 2 watts per square metre, I thought it was a good idea to look at Whitelee's updated numbers.
When I was writing my book in October 2006, Whitelee's predicted output was said to be "enough to power Glasgow" (Independent, Oct 10, 2006). And now, the latest news says
that, with the proposed increase in capacity from 322 MW to 614 MW, the farm will... generate enough power for [all the homes in] Glasgow!
Curious, Alice might say. We run, and we stay in the same place?
Here are the new numbers.
With two extensions, the total number of turbines would be 221, the capacity would be 614 MW, and the predicted total output is "340,000 households", which in sensible units is 184 MW (assuming that "a household" is defined to be 0.54 kW). This implies a load factor of 30%. The area of the site (according to the Sunday Herald) will increase to 75 km². So the average power per unit area of the enlarged wind farm is predicted to be 2.45 W/m².
What is the honest relationship of Whitelee to Glasgow? (I think talking about 'households' is a bit misleading.) The predicted output of Whitelee, shared between the 616,000 people of Glasgow, would deliver 7 kWh per day per person on average. That's roughly 40% of the total electricity consumption of Glasgow, and roughly 6% of the total power consumption of Glasgow (that's 'total power' including transport, heating, etc; not just electricity).

Implications for the scale of wind farms required for a substantial contribution to British power consumption

If we assume Whitelee (including its planned extension) is representative of future big wind farms that could be built in Britain, here are some more numbers.

• The government's 2020 target is for "33 GW" of wind capacity. That would require 54 more Whitelees. The area of those wind farms would be about 4000 km², about 20% of the area of Wales. The power delivered by those wind farms would be about 4 kWh per day per person, which is roughly 4% of the UK total power consumption today. (That's 'total power' including transport, heating, etc; not just electricity).
• If we wanted to get 20 kWh per day per person from wind power, we'd need 270 Whitelees, which would take up an area of 20,000 km². That's roughly the area of Wales, or 8% of the area of the UK.

If we want to get off fossil fuels using renewables, we must expect those renewable facilities to be somewhat intrusive.

End notes (in anticipation of the responses people often make)

1. Yes, the wind-farm land in between the wind turbines can also be used for agriculture or other activities.
2. Yes, the output of wind farms fluctuates, so if we build wind farms we will have to do some other smart stuff, as discussed in chapter 26 of my book. For example, ensure that lots of smart [easily switch-off-and-on-able] demand is added to the grid, for example, charging electric vehicles and running heat pumps to make hot air and hot water.
   

Hot Air Oscars nomination: GO-GREEN

We are happy to nominate for the "best GREEN advertising" Hot Air Oscar, the "Eco-Smart" organization in America who advertise "877-47-Go-GREEN" on the side of their tastefully green HUMMER.

Is David MacKay "trying to make wind sound useless"? Let's look at more data

I'm delighted to see that the response to Sustainable Energy - without the hot air so far has been remarkably positive. There's just one or two folks who have become convinced that I am anti-wind, that I am deceitfully making wind sound worse than it really is; and they have been running round leaving comments on blogs (for example, you can find one lurking in the comments on this excellent article about the financial cost of wind power (the oil drum), who asserts "MacKay has made a serious error in his calculations of on-shore wind energy resources. ... Some of the wind farms initially built were in poorer locations but close to electric transmission lines, so his calculations are not good examples of what is possible in UK.")
I've written three blog posts about this topic already, encouraging people to provide real data rather than just spreading poisonous rumours. I've now worked through the ordnance survey maps and ROC register entries for about 15 windfarms around the UK, and included the data and maps in a presentation I made at a wind energy conference in St Andrews this week. I am still working on this; what I have focussed on so far is mainly the newest windfarms for which data is available, with the largest numbers of turbines, with biggest diameters, and mainly on scottish hilltops or welsh hilltops or near to the coast. The new data starts at slide 30 and is summarised on slide 41. These onshore wind farms have powers per unit area between 2 and 4.6 watts per square metre. To indicate the rough scale of windfarms required to deliver large amounts of power, I assumed in the book a power per unit area of 2 watts per square metre. So yes, there are windfarms that have powers bigger than 2 watts per square metre. Was I deliberately "making wind power seem worse than it is"? No. I chose 2 watts per sq metre as an estimate of what we could get if we put up lots of wind farms (with the area of Wales), which is obviously going to be less than the power per unit area of the very best spots. Yes, I willingly agree that if we want wind to make only a small contribution (for example, less than 1 kWh per day per person), then it would be appropriate to assume a higher power per unit area - perhaps 3 or 3.5 W/m² instead of 2 W/m², if we keep building in the best spots.

As evidence that I am not deliberately biased against wind, take a look at the data for offshore wind farms.

In my book I assumed a power per unit area of roughly 3 watts per square metre for offshore wind. But the two offshore windfarms in my data have powers per unit area below 2.5 watts per square metre.
There are several other scientists who have used a power per unit area similar to mine when estimating wind resources. For example, Socolow from Princeton uses 2 watts per square metre when discussing his "wedges". On page 234 of my book I cite a study by Elliott et al. (1991) in which windfarms in the best locations in America, covering an area equal to that of California, were estimated to have an average power density of 1.2 W/m².
While my book is technology-neutral, the truth is that personally I am pro-wind! I think wind farms are brilliant, and I'd be very happy be within eye-shot of one almost anywhere in the ordinary countryside.
Please could the commentors call off the dogs?
Thanks! David

More or Less - the Director's Cut

I was on "More or Less"a couple of weeks ago, and wrote an article for the BBC. One topic mentioned was how much good it does to unplug phone-chargers when they are not in use.

On today's programme (8 May 2009) they are going to read out an indignant listener's letter pointing out that "if everyone unplugs their phone chargers, it adds up to a HUGE saving". More or Less asked me to write a short response, which is going out today. I'm worried that people will get the impression I am against switching anything off. So for the record, I would like to point anyone who's interested to the relevant pages of my book (p114) and Chapter 22 (p155) which should make clear that I do think that it's a good idea to find the big vampires and switch them off!
Here's what I wrote for today's More or Less, in full:
Yes, if sixty million people all make a figleaf gesture that saves half a watt (which is roughly one ten thousandth of their power consumption), then the total power saved is,
sixty million times half a watt
which is 30 megawatts, which sounds like quite a lot. It's one thirtieth of the output of a modern power station, for example. But this "if-everyone" multiplying machine is just a misleading way of making something tiny sound big:
30 megawatts is still just one ten thousandth of Britain's total power consumption.
Multiplying tiny things by sixty million to make them sound big is BAD because it distracts people from thinking about sixty million bigger things that are more deserving of our attention. [Heating sixty million buildings, and driving sixty million cars, for example.]

Hot Air Oscars nomination: biodegradable tat from 'I love planet'

I went to Edinburgh botanic garden today. The visitors' shops of such places are often nesting places for the monsters that spawn green tat.
Here I found the "biodegradable ballpoint pen". Pick it up and look at it: apart from the reassuring "planet loving" messages screaming out from its barrel, it looks and feels like a completely normal pen. And I'd be happy to bet that all its biodegradable parts are made from fossil fuels.
Is it really 'loving the planet' if you buy this fossil-fuel-plastic pen and chuck it away, rather than buying a (ten times cheaper) normal fossil-fuel-plastic pen and chuck it away?
I nominate this pen for the Hot Air Oscars consumer feel-good tat award.

Renewable planning map for the USA

One thing I've wanted to do, after the Energy book, is to make an interactive tool that conveys the scale of renewable facilities required to make a difference, and gives the user choices, subject to the "it has to add up" constraint. Here is an NRDC Google map; it's a start - it shows "where renewables have potential" in the USA; but it's not quantitative - it just shows "lowest potential" and "highest potential" on a colour scale, for one renewable at a time. The image above shows the map of Montana for Cellulosic Bioethanol. I suspect the main uses of this map will be (1) wishful thinking [about the 'HUGE' potential of renewables] and (2) NIMBYism [using the argument 'this isn't the best place for it'].
PS - when you drill down into the meaning of the map, the colour scales are given a quantitative meaning, but it's not human friendly and it does not use comparable units. For example the colour code of the Cellulosic map is explained thus:
Each county is color-coded based on total dry tons of cellulosic biomass per year, by county. [12,000; 50,000; 100,000; etc]
If I understand right, they are showing potential per county. That is bizarre. So if there are two identical regions but one happens to be divided into 10 counties and one is a single county, the single-county region will be shown as having big potential and the ten-county region will come out two notches lower.

Hot Air Oscars nomination: Tesco again!

Philip Fowler has nominated Tesco for the "Every Little Helps" lifetime achievement award, in recognition of their services to consumer awareness through labellling toilet paper with its carbon footprint - 1 gram per sheet, giving a new meaning to the motto "Cut the Crap!"

Four simple actions

I wrote an article, "We need a plan that adds up", for The Guardian and publicservice.co.uk. For the Grauniad I also created a new graphic which I thought I would show here.

Four simple actions that make significant energy savings, and one that doesn't.
The left-hand column shows five contributors to the average energy consumption of a typical reasonably-affluent Guardian reader. The right-hand column shows the reduced consumption, post-action.
Any comments? Would the figure work better if I put the phone charger in the middle instead of at the bottom of the list?

Man on radio

BBC Radio 4 has a programme called More or Less, all about numbers. On 24 April 2009 the programme opened with a conversation between me and Tim Harford, talking about energy numbers. Tim likes the book (in fact he likes it so much that he gets its name wrong!) After me, he talks to a lady from the Sustainable Development Commission who graciously dismisses my book for being full of big equations and too technical. Or something. Can anyone understand what she's on about?
If you are quick, you can listen to the podcast.
I also wrote an article for the BBC website, 'Saving the planet by numbers'.

Hot Air Oscars nomination: A Clean Use for Australian Coal

Australian Minister for Resources and Energy, Martin Ferguson, is hereby nominated for the Hot Air Oscar for highest-impact use of the words 'clean', 'ultra-clean', and 'low emissions'.


"This technology unlocks energy from Australia's significant stranded and uneconomic coal reserves."
"Technologies that convert coal and gas to ultra-clean diesel and jet fuel have the potential to replace Australia's declining oil reserves."
"The Australian Government is encouraging the development of coal-to-liquids in Australia through its election commitment to use the $500 million National Low Emissions Coal Fund to support projects generating minimal carbon emissions which utilise our extensive coal resources."


In a nutshell, they're investing government money in turning uneconomic coal that would otherwise have been left in the ground into CO₂ in the atmosphere. Brilliant! Icebergs all round!

Thanks to Alexander Ac for the nomination.

Man holding bulb

On youtube, there is a new video, arranged by the University of Cambridge, featuring someone not unrelated to me, holding a lightbulb and talking about energy plans. Hope you enjoy it! It took three days of filming to make it.

[In case the youtube video goes missing, here is the University's 'Cambridge Ideas' page.]

Every little hurts - Hot Air Oscars

There is
a superb article on Greenwash by Ed Gillespie.

Buy eco-lights, get free air miles.

Wow, Tesco has to be a strong contender for the Hot Air Oscar for best consumer-engagement

Hot Air Oscars nomination: Eco Friendly Mobile Phone Charger

Thank you to Pierre Joly for nominating The Plug In And Go Green Eco Charger for the Hot Air Oscar for Best Use of the "if-everyone" Multiplying Machine. If you've read Sustainable Energy - without the hot air or my page on phone-chargers left on standby, you'll know how thrilled I am to learn that
"The Eco Charger reduces the amount of energy needed to power a mobile phone more than any other on the market."
Fantastic news. If everyone got one of these, the ad says, the UK "could make a collective saving as a country of £85 million" (assuming, incidentally, an electricity price of 28.5p per kWh... Shurely a bit high?!).
Unfortunately the CarPhone Warehouse didn't have the space in their advertisement to apply the "if-everyone" multiplier to the price tag, but the Hot Air Oscars column is happy to help out: If everyone in the UK bought one of these "Eco Chargers" (at £22.99), it would cost us, as a country, £1.3 billion.

Greenbird wind-powered car - brilliant!

British engineering breaks wind-powered land-speed record. Wow!

Hot air Oscars nomination: most useless invention

Nick Cook has nominated the EDF Energy ideal home show, Alex Hort, and the University of Plymouth for a Hot air Oscar for "An ingenious idea that recovers useful energy from a drain pipe". "Rain water descending a down pipe is captured and stored behind an internal 'dam'... Each rush of water turns a small, plastic turbine... providing electricity which is stored in rechargeable batteries."
The raw power of rainwater on a roof of area 40 square metres, rainfall 584 mm per year, with a drainpipe of length 6 metres, is 0.001 kWh per day. This is less than one ten-thousandth of the average British person's electricity consumption. The economic value of the power captured by this contraption is roughly 5 pence per year. The energy cost of making the system and inserting it into a drainpipe must be many times greater than the energy it would ever give back.

Display energy certificates - a missed opportunity to communicate

UK legislation requires that many large buildings display a certificate, updated every few months, that shows "how efficiently the building is being used".

This mandatory certificate could have been used to communicate information to people, and to engage the building's users in the challenge of improving the building's energy consumption. However, it seems to me that the designers of the certificate have almost completely blown it: the certificate's main features looks fairly colourful, but they convey amazingly close to no information at all.

How much information can be conveyed on a sheet of paper? One of the simplest principles of communication is that the message should depend on something; the message should not be fixed in advance. For example, Lord Nelson, at sea, had a collection of a few dozen flags from which he could select some to run up his mast. Which ones he ran up his mast depended on what message he was intending to communicate. Someone looking at Nelson's ship would not know in advance what the flags would look like.

This communication principle is almost entirely lost from Display energy certificates: the look of the certificate is almost entirely determined and fixed before any building data are collected.


The most prominent feature of the certificate is the "A-to-G" scale, with its green-to-red/brown colour scheme. Almost all the numbers on this scale are fixed; the only adjustable piece is the little arrow that points at "how well this building is being used". This performance is measured in meaningless pseudo-units, with "100" corresponding to "average for buildings of this type". This number can't be compared, from building to building, since two buildings might be of different types, and the certificate doesn't say anything about the type. Nor can an ordinary person work out what the number means, nor what they should do about it, because the number can be computed only by experts using the government-approved software that churns out these certificates. (I've looked on government websites, and have been unable to find any definition of the magic formula for computing the number; I imagine I would have to pay to attend a government-sanctioned course in Display energy certificate cookery.)



The second feature of the certificate is the top-right blue rectangle. Again, this object achieves amazingly little communication. It is meant to show how much CO2 the building's use is emitting. I would like to make a prediction: I predict that, on the first certificates displayed in the year 2009 in all the thousands of buildings across the country, every single certificate will have a blue rectangle of exactly the same height!. I make this prediction because it looks to me as if the government-sanctioned standardized software auto-scales the entire blue rectangle so that it has got a standard size! Therefore the only way to find out the CO2 emissions of the building is to look really closely at the scale of the graph, which shows, in the smallest font conceivable, an absurdly long number, at the top of the vertical axis, partly overlapping the axis. This absurdly long number, I would guess, is the actual CO2 emissions. In my photo I think it shows 26095 tonnes of CO2 per year. If someone ever manages to read this number (please bring a magnifying glass!), will it mean anything to them? Is a typewritten number a good way to convey information? Is it a good idea to show five decimal places of precision? When communicators discuss how to label the axes of a graph, does anyone recommend that the six tics on the graph should be labelled (nothing), (8693), (nothing), (17396), (nothing), and (26095)?

The one interesting fact that is well conveyed by the blue rectangle is the breakdown of CO2 emissions between electricity and heating: the top (light) half of the blue rectangle shows the electricity contribution, and the lower (dark) half shows the heating.





And finally, the third prominent colour element in the display is the "Previous operational rating" graph (bottom right, orange), which shows "how efficiently energy has been used in this building over the last three accounting periods". At present (in early 2009), this colour object conveys no information at all as it shows only a repeat of the energy performance rating displayed on the left-hand side. In due course, maybe it will reveal an interesting trend, but it will depend on the choice of "accounting period". Is the accounting period going to be one year? If so, the comparison of last year with the year before will be meaningful, but is it going to engage users? Imagine if, every day when you entered your building during 2009, the porter informed you what the total energy consumption had been in 2007 and 2008. Would these facts interest you in putting effort into efficiency drives? I fear that a yearly update is too long a timescale for any useful engagement to happen. On the other hand, if the "accounting period" lasts, say three months, then the variation in operational rating from quarter to quarter would be entirely dominated by seasonal effects. My guess is that the certificates will be updated annually, so building-users will become completely blind to the certificate. The opportunity for user engagement is almost entirely lost.

What have we seen so far?

1. the main colourful numbers are in meaningless units. As it says, "the numbers do not represent actual units of energy consumed; they represent comparative energy efficiency. 100 would be typical for this kind of building."
2. the CO2 emissions are displayed in meaningful units, but these numbers are not displayed in a way that an ordinary person can understand.




Does the certificate have any useful information on it? Yes, hidden away in tiny print at the bottom left hand side are interesting numbers - at least to building energy specialists. The "technical information" shows, in a table, the energy use (heating and electrical), expressed in the meaningful units of kWh per square metre per year. And to make this energy use comprehensible, the table also specifies the "typical use" (of buildings "like this", I presume).

What could have been done better? As far as I can tell, the entire piece of paper is really conveying just two numbers:

`this building's heating consumption is: 519 kWh/m2/y';
`this building's electrical consumption is: 249 kWh/m2/y'.

The certificate hides these two numbers in the technical corner, displays some unknown munging of them on to the A-to-G scale, displays their effective carbon-ratio in the blue rectangle, and shows how the total changed compared to earlier years.

How could the certificate be better? Well, it could have been better in two ways:

1. the certificate could display the two numbers that it is meant to communicate more clearly, more accessibly, more meaningfully, and more educationally.
2. the certificate could communicate more than two numbers.

Let me spell out what I mean.

1. the certificate could display the two numbers that it is meant to communicate more clearly, more accessibly, more meaningfully, and more educationally. For example, the energy consumption (per square metre) could be displayed visually on a scale that shows the energy consumptions of a bunch of other real buildings - so as to help people visualize and aspire. Looking at the current A-to-G scale, someone in a "D"-performing building may well ask "does any building like mine ever get an A or even a B?" They don't know if it is at all plausible. If energy consumption were compared with that of benchmark buildings (eg, Whitehall, the Swiss Re tower, Freda's flower shop, Cambridge University Library, BedZed), then people would see what is possible, and could get a message such as "my building is as bad as Whitehall!" or "we're using 20 times as much as BedZed." Given real comparative data, people could aspire to meaningful goals.
2. the certificate could communicate more than two numbers. For example, there could be a duty to display and compare energy consumption every month or every week (for at least some number of consecutive weeks per year). Then the regularly-updated certificate could engage building-users in the challenge of energy-saving. If someone tries an energy-saving action, they need to get feedback within a week to tell them whether it made a difference. Without rapid feedback, no-one will be interested in energy saving ideas.

PS - To see the whole certificate in one image, follow this link

Uncontrollable burning coal-waste-heap

People often emphasize the role of uncontrolled accidental burning of fossil fuels in backward parts of the world.
I grew up in a part of the developing world called the Potteries, near the middle of England. The Potteries were rich in clay and coal, and one hill near Keele village was stuffed with little coal mines when I was a child. There were rich thick seams very close to the surface. These photos and google satellite maps show what's left there now: a great pile of rubble that is perpetually on fire. It looks rather like a Hollywood movie's improbable view of medieval England, in which every slope somehow has smoke scudding across it.

Eco super hero

Great to see that colleges are training people to be eco heroes, installing HEAT PUMPS and SOLAR THERMAL SYSTEMS!! Brilliant news.

Designers with a conscience

Graphic designers for good - looks like a useful community of people to tap into! They don't just want to promote useless consumerist tat.

Even more wind power per unit area

This is my third post giving factual data about the power per unit land area of wind farms in Britain. My first post described a farm near the coast made of small machines (27m diameter); the power per unit area was 1.4 W/m². The second post cherry-picked the best windfarm in Britain (located in Shetland); the power per unit area was 6.5 W/m². The turbines there have diameter about 50m. Now returning from mid-ocean, let's ask "what do really big land-based turbines deliver?" I picked the Glass Moor windfarm, which has eight 2 MW machines, each with a diameter 82m. (It's the biggest windfarm close to Cambridge; no special cherry-picking, here.) Looking at the OS map, I judged the area occupied by the windfarm to be 2 km². Based on one year's data, the average output of this windfarm (per unit land area) is 2.2 W/m².
These data support the view that 2 W/m² is a good ballpark figure for the power per unit area of a modern windfarm in England.

Climate-change inactivism

I enjoyed reading John Mashey on how science works, and how to critically read scientific claims such as those made by climate-change inactivists. From there, I found my way to his equally interesting analysis of Bjorn Lomborg's motivations. I actually rather like Bjorn Lomborg and don't think he's the antichrist that many make him out to be; but it is interesting to read John Mashey's analysis of the political effect of Bjorn Lomborg's arguments. In a nutshell, Lomborg's recent writings have said "yes, global warming (X) is a priority, but not as high a priority as 'A' and 'B'", where John Mashey reckons A (Eg, give lots of money to the developing world to fix things there) has been chosen not because Lomborg really wants to devote effort to A, but rather because he knows these sort of aid donations won't happen, so putting them top of a list of priorities is a good way of persuading people not to do lower things in the list (X). The space in the list between A and X is padded out with other items ("B") (eg, open up free trade more) that the neo-cons would be happy to see happen. Interesting analysis.
Myself, I had a different take on Lomborg, which is that he genuinely does care, and wants us to choose numerate policies that work; and that he comes to different conclusions from some of us simply because he tacitly chose a different objective from what we might have chosen. Specifically, the objective in his recent books seems to be something like "human economic welfare between now and the year 2100". I'd love to sit down with Lomborg and discuss what he thinks the optimal investments would be if the objective were changed to "planet still functioning well at supporting human life in the years 2200, 2500, and 3000".
I've tried to converse with Lomborg but sadly I think he's too busy being famous now.

Hot Air Oscars: Recyclemania and Eastern Washington University dining services

I'm happy to announce the launch of the first annual "Hot Air Oscars".
These awards go to the person or organization who (in the judgment of the panel) best exemplify the modern-day survival skills of greenwash and twaddle-emission. There will be awards for "most misleading advertising", for "best use of magic playing fields", for "best doublespeak", for "most creative use of the word 'zero'", for "best bogus comparison", for "best speaking with many faces", for "best supporting liar", for "best inflated difference", and for "best conparison".
Nominations may be sent to David MacKay. Shortlisted achievements will be featured on this blog over the next month or two. The winners of the Hot Air Oscars will be announced in mid 2009.

Opening nominations...
The first nomination in the "best green spin" category is the fine attempt by David McKay [no relation], director of dining services at Eastern Washington University (EWU), and Paul Kyle, associate director of dining services, to put a positive spin on their decision to use disposable Styrofoam plates and bowls in the cafeteria. "Our goal is to lessen the amount of BODs [organic pollutants in water] by washing fewer dishes," said Kyle; "The use of Styrofoam plates and bowls is an excellent energy source for the waste-to-energy plant," said McKay.
or to put it another way, Styrofoam plates are great because you can just throw them away and burn them. They claim that this initiative somehow ties in with a local initiative called Recyclemania.

I am sure the environment is thanking them for their efforts, but not everyone is so supportive. Laci Hubbard, president of the Eastern Environmental Club, said that while the group is pleased that Dining Services has been supportive of ... Recyclemania, they are "concerned about the move to use additional Styrofoam products and the logic of their subsequent explanation for why Styrofoam is a better choice for the environment."

Please keep the nominations rolling in. The judges will be happy to consider new categories for the Hot Air Oscars.

More windfarm power per unit area

Executive summary:
The windfarm with the highest load factor in the British Isles has a power per unit area of 6.5 W per square metre.

Background:
Commentors on my previous article on
the power per unit area of windfarms queried whether any cherry-picking might have happened
in the selection of Blood Hill windfarm; it was also suggested that we should work out the numbers for Burradale, the famous windfarm in Shetland with the highest load factor in Britain. The answer to the first query is "no, not at all" - Blood Hill was selected at random, and as I said, I would encourage anyone who can be bothered to look up the data for other windfarms to do so and add the results to the "withouthotair" wiki.
And now, to satisfy the request for cherry-picked facts about wind in the UK, I am happy to present...

The data: Burradale has five wind turbines: three in "phase 1" and two in "phase 2". Their capacities are 660 kW and 850 kW respectively, and their average outputs over the last few years have been 357 kW and 446 kW respectively. (That corresponds to load factors of 52% and 54%.) I judged the "area occupied" by the five turbines to be 0.3 square kilometres. The average power per unit area of this windfarm is 6.5 W per square metre.

This number can be compared with my assumed figure of 2 W per square metre for typical onshore windfarms in the UK.

So, a cracking good place for wind, Shetland! What does it need? Obviously what this place really needs is a campaign group opposed to expanding wind farms in Shetland. And The Good Lord hath provided "Sustainable Shetland".

Power per unit land area of windfarms

As I've said in SEWTHA (the book), the average power per unit land area of a typical well-located onshore windfarm in Britain is about 2 watts per square metre. (Or 2 MW per square km.) This number is my estimate of the best that can be done in Britain, and, as I explained in the appendix, the theoretical power per unit land area doesn't depend very much on the size of the turbines used, because bigger turbines are spaced further apart.

I'm always keen to check my numbers and update them if necessary. Today the the New Scientist interview with James Lovelock prompted me to write a blog article giving explicit data from a real windfarm. James Lovelock says "to spoil all the decent countryside in the UK with wind farms is driving me mad. It's absolutely unnecessary, and it takes 2500 square kilometres to produce a gigawatt - that's an awful lot of countryside." That's a power per unit area of 0.4 W/m², which is 5 times smaller than my 'best possible' 2 W/m² estimate.

Let's look at some data. I picked a random windfarm in Britain with ten 27m-diameter turbines: Blood Hill windfarm. The helpful REF website gives exact energy-generation statistics for several years. The collage at the top of this page shows the data, and a map of the site, which is very close to the sea in Norfolk. What's the area of this site? The blue grid lines are 1km squares. I'd say the ten turbines 'occupy' about 0.3 km² (including an appropriate strip of land around the turbines, where similar size turbines could not be placed). The average output of the ten turbines is 420 kW. So that is a power per unit area of 1.4 W/m².

If anyone would like to repeat this calculation for real data from other windfarms around Britain or the world, we could collate the answers in the open-source wiki for Sustainable Energy - without the hot air.

Google searches, energy cost, carbon footprint, and cups of tea

A friend asked me to confirm or deny the assertion (Harvard/BBC) that two Google searches on a desktop computer produces 14g of CO2, which is the roughly the equivalent of boiling an electric kettle.

• ``US physicist Alex Wissner-Gross claims that a typical Google search on a desktop computer produces about 7g CO2.
  
• ``However, these figures were disputed by Google, who say a typical search produced only 0.2g of carbon dioxide.''
  

My own rough back of envelope guess came out in between Wissner-Gross's assertion and Google's...

Here's how I worked it out:

1. according to a google search(!), google has about 700,000 servers.
   
2. let's guesstimate the power to run a server and all its plumbing: 250 W.
   
3. google received 90 million searches per day in 2006
   and 1200 million per day in 2007...
   
4. Hmm, this growth rate is big enough that it is going to be hard to get a trustworthy answer!
   
5. Well, let's multiply 700,000 servers * 0.250 kW * 24 hours per day / 1200 M searches per day -
   that is 0.0035 kWh per search; 0.007 kWh for a pair of searches; and 3.5g of CO₂ for a pair of searches. (Assuming that electricity has a footprint of 500 g per kWh.) [In fact I think I heard that google has lots of servers in Iceland, where the electricity footprint is much smaller.] Meanwhile, boiling a 250 ml cup of water uses about 0.028 kWh. So my estimate is that the energy cost of two google searches (measured at the googleplex alone) is about one quarter of the energy cost of boiling a cup.
   

This calculation has not included the energy cost of running your own desktop computer, wireless, and modem for the duration of the search too; nor the cost of running the internet twixt you and google. If it takes you one minute of computer time to do the search, and if your computer and peripherals use 120 W, then the cost of your computer's power in that duration is 0.120 kW * (1/60) hour, which is an extra 0.002 kWh.
Here's the bottom line from my rough guesses: the total energy cost of the pair of searches seems to be about 0.01 kWh. That's exactly the same as the energy used by leaving a phone charger plugged in for one day. Which is also the same as the energy used by driving an average car for one second.

Would electric freight vehicles be possible?

In Sustainable Energy - without the hot air, one of my main conclusions is "electrify everything" - in particular, I recommend electric vehicles. At a recent talk, someone in the audience said, yes, maybe electric cars are now viable. But surely you couldn't electrify freight? Leaving aside two possible answers (namely 1: for local freight deliveries, electric trucks are already genuinely in use, and are manufactured by a couple of companies in the UK; 2: we could make electric freight like eletric trolley buses, using overhead lines), I thought it would be interesting to investigate, using the same model I used for cars in my book, the possibility of making long-distance freight vehicles with on-board batteries.
The model assumes that energy goes into air resistance, into rolling resistance, and into brakes. The model includes regenerative brakes (assumed to be 50% efficient, round-trip), and includes energy inefficiency in the energy-conversion chains (from grid to battery and from battery to wheels). The frontal area is assumed to be 8.6 m² and the freight carried is 26 tons. The other main assumptions are the distance between stops (500m? 5000m?) and the typical speed (50km/h? 100km/h?).

The figures above and below show the theoretical energy consumption (in kWh per ton-km) for two different batteries' energy densities (corresponding to lead acid and lithium), compared with a fossil fuel truck with the same frontal area and load, versus the range (ie the distance between refuelling stops). The top figure is for the case of 500 m distance twixt stops and 50 km/h speed. The bottom figure (just above) is for the case of 5000 m twixt stops and 100 km/h speed.
The bigger the battery, the bigger the range and the bigger the energy consumption. The main conclusion of these figures is that, on energy grounds, trucks with big batteries are viable. They are superior in energy consumption to the fossil fuel truck. (The point at the top, by the way, is the fossil fuel truck benchmark from the book, which is obtained from government statistics; the lower point is the theoretical performance of a fossil fuel truck according to the model. The latter is presumably lower because the former includes a load of empty-running journeys.)
Of course many other factors need to be borne in mind - could a truck stop provide a 120-kW outlet for charging each truck parked at the truck stop, for example? And what is the capital cost of the batteries? And could they be recycled?
But I find it interesting that in principle, long-distance electric trucks would be more energy-efficient than fossil-fuel trucks. As usual, I have declared one unit of grid electricity to have the same value as one unit of chemical energy. Yes, yes, with today's electricity mix in Britain, blah blah blah, inefficiencies in conversion, ... a factor of 2.4 or some such... But as usual I am focussing attention on the future energy system we should be building, not the details of today's obsolete fossil-fuel electricity system. We want to electrify transport in order to get the whole energy system off fossil fuels as much as possible.

The FCX Clarity from Honda

On this week's Top Gear, James May called the FCX Clarity "the most important car for 100 years".
[Photo courtesy of automobiles.honda.com.] It runs on hydrogen, which "will never run out", because it is "the most abundant element in the universe". And the only emissions are water.
What twaddle!
The programme took the time to point out that the electricity to power a Tesla electric car in Britain is produced at a fossil fuel power station. Why didn't they also discuss where the hydrogen comes from?
Top Gear loves to quantify accelerations, lap times, car prices, top speeds - why couldn't they quantify the energy requirements to run "the car of the future", the FCX Clarity? And compare it with the Tesla?
Here's the answers, according to chapter 20 of Sustainable Energy - without the hot air.

The energy consumption of the FCX Clarity is 69 kWh per 100 km. (Very similar to the consumption of an ordinary fossil fuel car.) That's assuming the hydrogen is produced in the standard way, using lots of methane and a bit of electricity, and counting one unit of chemical energy as having the same energy content as one unit of electricity. Meanwhile, the energy consumption of the Tesla (according to its manufacturers) is 15 kWh per 100 km. (Of electrical energy.) Even if we penalize electricity, saying "every 1 kWh of electricity costs 2.5 kWh of fossil fuels", the Tesla is still much better than the fuel-cell car, and better than the average fossil fuel car. (And in the future, we won't be getting electricity from fossil fuels, hopefully!)
So the hydrogen car is NOT a "solution" to our problem, if our fundamental problem is an energy problem.

Why on-site renewables don't add up

Straight up, I want to say I love renewables, and I believe that we should have a massive increase in renewables as part of making a sustainable energy plan that adds up (as explained in my book Sustainable Energy - without the hot air, now available on paper).
This is an article about on-site renewables. Imagine a developer is making a new urban development. Offices or homes, perhaps. A three-floor building. Under some planning regulations, new buildings must get some fraction of their energy consumption from on-site renewables. Now, these regulations have some undeniable benefits: if it is expensive to install on-site renewables, the developer may modify the building so as to reduce its energy consumption, thus making it less costly to reach the required renewable fraction. Having local renewable energy production may also increase awareness about energy consumption among the building's users. And some local renewables are no-brainers - making hot water using solar panels, for example, makes complete sense, providing roughly half of the hot water consumption of an average home.
But here is the problem:

200 kWh per year per square metre = 23 W per square metre

On the left, 200 kWh per year per square metre is the typical total energy consumption of many homes and offices, expressed as energy per year per square metre of floor area. In terms of energy rating bands, 200 kWh/y/m² is the boundary between bands F and G. Many government buildings use twice as much as this. (The Home Office uses 400 kWh/y/m², for example.) The Passivhaus standard, at 120 kWh/y/m², is not much better than this 200 kWh/y/m² benchmark.
On the right, I've converted this quantity into watts per square metre, which are the unit in which I prefer to express renewable power production. Sadly, most renewables have powers per unit land area that are substantially less than 23 W per square metre. Wind farms generate 2 W/m². Energy crops generate 0.5 W/m². Solar photovoltaic panels generate 20 W/m². And remember, we're imagining a three-floor building. So the power required per unit land area occupied by the building is not 23, but 3x23 = 69 W/m².
On-site renewables are an interesting gesture, but if we are serious about renewables making a big contribution, they have to be big - they must occupy a land area much bigger than the land occupied by the buildings we are powering. If you want to completely power a three-floor 200 kWh/y/m² building from energy crops and wood, for example, then the land area required for the energy crops and wood must be roughly 140 times as big as the land footprint of the building.
The response of an angry green campaigner to what I have just written can be predicted: "But we could make the buildings far more efficient!" Could we? I'd love us to build more-efficient buildings, but show me data. Not wishful thinking, but NUMBERS. The Elizabeth Fry building at UEA is often held up as an example of a state-of-the-art eco-friendly building. And here are the numbers for that building (from page 299 of my book). It consumes 96 kWh/y/m², which is 11 W/m², which is only about 50% better than the Energy-Rating-Band-F/G benchmark from which I started.
The bottom line: if you want to completely power a typical building, or even an amazing eco-building, from renewables, most of those renewables have to be offsite. There isn't room on-site! And it's probably a better use of resources to accept this fact up front, rather than force developers to squeeze uneconomic figleafs (such as micro-turbines) into their developments. We should modify the planning regulations for new buildings so that developers are still required to build renewables, but are encouraged to build new renewable capacity off-site.