Is Solar Thermal the Way to Go?

The most recent issue of Proceedings of the IEEE was devoted almost entirely to its cover subject: Computational Anthropomorphic Anatomical Models. Fascinating, no doubt, but not necessarily my cup of tea for extended reading. Much more to my interest was the “point of view” column from Derek Abbott, an IEEE Fellow from Australia who penned a short but dense article prefacing the issue that described his vision for the future: a solar-hydrogen economy in which solar thermal collectors are preferred to solar cells. He says that pure hydrogen in liquid or gas form—generated via the Carnot cycle and combusted in normal IC engines—is a much better energy solution than electric batteries, hydrogen fuel cells, and photovoltaics.

It’s an interesting argument, and not because Abbott finds way to shoot down the various energy generation and storage alternatives on offer: lithium supply is limited; fuel cell membranes are expensive; highly-ordered PV structures are impractical and fragile; and poor expected reliability of fusion reactors if we do build one). The compelling piece of Abbott’s story is his argument for simplicity: the only way we can achieve the economy of scale for ecologically-sustainable energy needs is to go low-tech.

How low-tech? Simple parabolic or trough-shaped mirrors direct light to water, creating steam to drive a turbine (basically a Rankine cycle engine). His reasoning is that this is the only solution that is friendly to the elevated temperatures required to get the most out of solar energy (reflectors can build to thousands of degrees Celsius, melting normal PV structures). Water isn’t the only solution for concentrated solar, of course. Oil, molten salt, or even graphite, are popular alternatives. But it’s hard to deem any of these as environmentally-friendly as water.

But solar thermal, even of the water-based kind, isn’t very cheap yet. The biggest installation, the PS20 Solar Power Tower in Seville, Spain, still produces power that’s three times as expensive as power from conventional sources. That should change over time as production for components builds, but for now it’s not cheap enough for widespread use. Plus, water itself is an environmentally-loaded medium; the ideal closed-loop system that prevents the creation of wastewater is still under development.

Abbott’s ideas have merit—solar thermal is clearly his solution for basic load requirements, while PV solar, wind, batteries technology, and other energy solution serve to provide portable or localized power requirements. I can certainly live with a car running on hydrogen, especially if I can produce hydrogen with my own wind turbine or solar collector on the rooftop. But I would like to see solar thermal also go portable: perhaps someday we can build an ocean-going vessel that operates on the same principle, bringing back the age of sail.

What do you think? Drop me a line at