Albedo 0.39

On average, the earth reflects 39% of incoming energy back into space. To use jargon for no reason other than that I like Vangelis, it has an albedo of 0.39.

Solar farms are springing up around us, incentivised by high feed-in tariffs offered so generously by the UK taxpayer.

I used to be in favour of solar farms but stressed that these should never be built in the UK, but instead in the Sahara desert or somewhere at least a bit sunny. If today’s technology doesn’t allow reasonable cable losses, then we should be waiting till we have super-cables, since there has never been any hurry, even if all the panic about CO2 levels had been correct.

A while back, I had to admit that I was maybe wrong about African solar farms. Having read the book Freakonomics, the authors point out that although solar panels look like a very green solution at first glance, they only produce a small amount of electricity (20% is considered very good for efficiency) but they are also very dark, so absorb a lot more incoming solar energy than the surface did before they were there. For a rooftop, which may have been tiled beforehand, I guess it comes down to the colour and age of the tiles. For a green field in the countryside, not only does it use up land that might have been pretty or arable, it also makes it darker. And for a desert, the change is quite marked. So it isn’t as green as it first appears.

The authors received immediate criticism because they didn’t explicitly compare the waste heat inevitable from alternative production for the same electricity, nor observe that the extra albedo of the panels would vanish once they were removed, but the key point remains true. The accounting for other means of production of the same energy, and comparisons of the overall life-cycle carbon reductions or increases are highly complex functions of the geography and climate at the location of the panel. It is a messy area full or arguments in each direction, as anything to do with climate always is. But, a solar panelled area usually will cause more of the incoming energy to be absorbed, that energy will still enter the earth’s system, and will still cause warming. Albedo might return to normal once the panel is removed, but the accumulated extra heat over its lifetime won’t vanish.

If the doom-mongers were right and warming were a really serious immediate threat and threatened to flip some environmental triggers, then we really should have been avoiding increasing it, even by solar. It would surely be far better to spend the same cash to improve energy efficiency and insulation, both of which would reduce warming, or spend it on extra research, or reducing methane…. And if the feed-in tariffs being offered to solar farmers had been offered to householders to insulate, I am sure most of us would much rather rent out our lofts for extra insulating than have ugly panels attached to the outside or pay a landowner to ruin the countryside. And if we all did that, we’d very soon realise we are all just using our own taxes to pay each other. This policy stinks.

Fortunately, it is a bit irrelevant now we know that warming isn’t as big a problem as the doom-mongers threatened. But yet another case where environmental policy seems a bit daft.

One response to “Albedo 0.39

  1. Agreed, changing the reflectivity of such massive areas would greatly negate some of the benefits of photovoltaics. But I wonder if we couldn’t incorporate dichroic filters designed for the specific frequencies needed while reflecting everything else. Theoretically, the reflectivity could be higher than that of the unmodified environment. Eventually, newer metamaterials could be even more finely tuned than optical coatings. While such a solution would add to the total cost, like so many technologies it would probably drop over time as production ramped up.


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