Our shiny hydrogen future (rewrite)
Just a quickie as I have to catch a bus in half an hour…
That’s how I started this blog post earlier today. And I then proceeded to demonstrate exactly why you shouldn’t write and publish anything that requires fact-checking or basic arithmetic in less than half an hour. First up, it turns out that the “news” item I was critiquing was almost three years old. Way to be cutting-edge, jim.
Not content with staleness, though, I then added a healthy dollop of inaccuracy (dividing by a thousand — instead of a million — to convert square metres to square kilometres). It’s the sort of thing that wouldn’t have got published if I’d used my usual two-drafts process instead of dashing it off in twenty minutes.
Given that the maths error pretty much invalidates the second half of the blog post, it’s not something I can just amend. That said, the first half is still relevant. So I’ll leave that here as a reminder that we shouldn’t take the news at face value when they make technical-sounding statements like: “For an energy source to be commercially viable, it must reach an efficiency of 10%, which is an industry standard.” I’m going to take out the second half of the post though as it’s a bunch of arse based on a flawed calculation.
But I hope this all serves as a reminder that we shouldn’t take blogs at face value either. Thanks to Doormat for pointing out the error.
The BBC currently has an article heralding the news that Sun and hydrogen ‘to fuel future’. It suggests that a new nanotech breakthrough has made converting solar energy into hydrogen a practical method of fuelling our cars. On the surface it sounds quite interesting, but unfortunately there are serious problems with the article. It opens by telling us that:
Hydrogen Solar says it has managed to convert more than 8% of sunlight directly into hydrogen with fuel cell technology it has specially developed.
For an energy source to be commercially viable, it must reach an efficiency of 10%, which is an industry standard.
BBC News: Sun and hydrogen ‘to fuel future’
That all sounds very interesting, but it doesn’t actually make any sense. For an energy source to be commercially viable, it must reach an efficiency of 10%, which is an industry standard. Er, 10% of what exactly? I just don’t get it. The reality is that for an energy source to be viable (in practical terms, forget commercialism for a moment), it must produce more energy than is used to extract, refine and distribute it. This is measured as a ratio (sometimes known as Net Energy Ratio, NER, or more precisely as Energy Returned on Energy Invested, ERoEI) not as a percentage. So crude oil, for instance, has an NER of between 30:1 and 90:1 (depending on the well). If you were to convert this to a percentage, it would equate to a return of between 3000% and 9000%. Is that what the 10% in this article refers to? An NER of 0.1:1?
Probably not, but lest you get blinded by the intro figures claiming some sort of magical commercial threshold of 10%, please be aware that those claims make no sense as they are currently written.
[The rest has been DELETED. See above.]
Jim, you won’t like this, but… 7 square meters times 2.25 million cars is 15 750 000 square meters of solar cells, or under 16 square kilometers. I think you forgot that 1 square kilometer is a million square meters.
Now, 16 square kilometers doesn’t actually sound too bad to me! But, as you say, you’d still need a very sophisticated hydrogen distribution system. And the “10%” stuff is just bollocks!
More to the point, the fact that the article is 3 years old, and there has been no follow-up, suggests that it wasn’t quite as simple as initially suggested. What a surprise…
May 6th, 2007 | 5:15pm
by Doormat
You’re right, I don’t like that. My calculation did indeed involve dividing the km by 1,000 rather than 1,000,000. Serves me right for producing the piece to meet the bus timetable.
Damn. Undercuts the whole thing. Hmmm… I’ll probably have to rewrite it. But I’m in a bit of a rush now, and I don’t want to make the same mistake twice, so it’ll just have to wait a while.
May 6th, 2007 | 6:59pm
by Jim
Well, the second half of the blog post couldn’t be salvaged, Doormat. Thanks for pointing out the error so soon after it was put out there, though. Re-reading it, I suspect that the “seven-metre squared array” actually equates to 49 square metres. Therefore you’d need to multiply that 16 by a factor of seven. So — I believe — Solar Hydrogen are claiming that the UK’s cars could be fuelled with an array of about 112 square km.
And you’re right, in theory that’s not an insurmountable engineering challenge. Nonetheless I’m firmly convinced that attempting to make hydrogen fit the role currently played by fossil fuels in our civilisation is not only a futile task, but would ultimately be a very dangerous one (Note: the danger of misused resources, nothing to do with hydrogen blowing up or anything). Nonetheless, if it turned out to be possible to generate enough energy from a 49m^2 array to run a big car for a year, then hydrogen may indeed have a specialised role to play in a mixed-energy future.
One fairly recent solar power development does show a lot of promise though. The Spanish solar tower looks like being a great way to produce electricity in the right climate (the Australians were the first people to use solar-tower technology and they’ve had great success with it I believe). Here in Northern Europe our best bet is wind. But in those parts of the world that have more sun than wind; that’s clearly the sustainable way forward.
May 6th, 2007 | 11:35pm
by Jim
Jim, completely agreed. The reporting by the BBC is soooo bad: that whole 10% stuff is just nonsense. If I could make solar panels, with few to no environmental drawbacks, for, say, twice the price of normal roof tiles, then I think it wouldn’t matter if they were only 1% efficient, or even 0.1% efficient, they would be a massive seller. If you’re in the business of capturing a “free” resource like light, or wind, then “efficiency” doesn’t matter. What matters, surely, is some notion of “cost”: namely the monitory (and, I’d argue, the wider environmental) costs divided by what you get back.
But the BBC article makes little to no mention of costs, either in just pounds sterling, or in environment costs (how many very rare metals does their solar panel hydrogen generator use, for example).
The numbers do, in principle, work out though. For example, Wiki Picture shows that e.g. Texas gets about 200 Watts/Square Meter annually on average, while the UK gets maybe half that. So a seven by seven square array at 10% would generate annually 4900 Watts average, say 5kW. From Wiki electric car article, we see that we get about 2 miles for 1kW-hour. So an hour charge from our array will give 10 miles of driving. I don’t see that a hydrogen car would (or indeed possibly could) be an order of magnitude better than this. So as our figures are averages, we get 240 miles a day of driving. I guess that is actually really pretty good. Maybe even the figure of 7 square meters (and not 7×7) is reasonable: that would give maybe 35 miles a day, which is pretty reasonable.
Still, there are, as Jim says, massive issues of scaling all this up a society the size of the UK. You’d also need to store large amounts of hydrogen for use during winter. No-one, as far as I know, has *any* idea how to do this. It’s all just pie-in-the-sky talk which allows us to no worry about peak oil.
May 7th, 2007 | 9:23am
by Doormat