Limitless solar?

One of the things I have been almost continuously talking about in the realm of renewable energy is the need to diversify our sources of energy. Another is the need to beware of people who preach that there is One True Solution. It was thus with great interest that I read about an upcoming paper in the Proceedings of the IEEE.

In this paper, Derek Abbott of the University of Adelaide argues that solar, and in particular, solar thermal, is the Ultimate Answer to the world’s energy problems.  In fact, according to Physorg, he claims that solar thermal can last us for “the next billion years.”

Despite this claim, the quoted numbers in the article and the conclusions are actually pretty reasonable in general. Solar thermal is the most cost-efficient (although certainly not the most space efficient) renewable technology in terms of energy yield.  However, stating that solar thermal by itself is sufficient for the next “billion” years is rather unreasonable.

Either Abbott presumes that the rate of growth of energy usage on the planet will slow down to nearly nothing or that we will eventually fill near-Earth space with solar collectors and ship either hydrogen or microwaves back down to Earth. No other possibility can justify his statement. As I calculated some time back, at modest growth rates, there is a much-closer horizon of about 500 years before we start running up against the limits of solar power.

There are also other issues in the article that should be addressed. The first is the cost, both capital and variable, of transmission lines in his scenario. If, as he suggests, we convert 8% of the desert land in the world to energy production, we are faced with the challenge of either building transmission lines to the hinterlands, which are on average about 30% efficient, or according to his scenario, generating hydrogen, liquefying it, and shipping it. I don’t know the efficiencies of electrolysis of water, or of hydrogen liquefaction, but in any case, there are three lossy steps here, before that hydrogen is either burned or passed through a fuel cell to make electricity.

Don’t get me wrong: in large part I agree with Dr. Abbott. Both my numbers and his point to the same conclusion – that solar must be a part of any renewable future. My primary concern about this article and others like it is that they will serve to skew the funding and research environment in renewable energy the same way that the biofuel craze has. We have a good way to go before we can replace fossil fuels in their entirety and it seems clear to me that as we transition away from a fossil fuel energy monoculture, we would do well to avoid another one.

One thought on “Limitless solar?

  1. My background is not in geophysical science, but rather in the biological sciences. I agree with this blog very much. Monoculture isn’t healthy in most any way I’ve ever seen it present itself. Whether we’re talking about genetics and consanguineous health issues, or money and the myriad of issues with globalization, having huge amounts of one thing done one way never seems to be a good answer in the long run. I would add to your argument that mono-geography is also problematic: all those solar panels in huge patches covering up environmentally sensitive desert, the problems with moving the energy from the “hinterland”. Why can’t we put solar panel arrays in small units at the source of need with little or no environmental impact, ie – rooftops? Each business, each home….power right there, excess to the grid? And no having all of everyone’s power go out because some huge cable gets cut, or some other catastrophe occurs that takes out a whole city’s power source? Add a geothermal heat pump with hot water with an exercise bike designed to power the pump when solar’s out, and you’ve got great energy independence!

    Small and local works for more than CSAs!!!

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