Monday, August 29, 2016

Is blue the new green? Wave power could revolutionize the renewable-energy game

Is blue the new green?  Wave power could revolutionize the renewable-energy game
Salon, 27 August 2016, by Diane Stopyra

This article discusses progress in wave power: technology to capture the energy in ocean waves, turning waves into a renewable energy source just like solar and wind power.  And there has been progress.  The U.S. Department of Energy has just announced a $40 million grant to develop an open-water wave energy test facility (the first in the U.S.), and new wave-energy systems in Hawaii and Australia have been generating energy and making headlines.  The energy potential of waves is vast; the article says that waves along the U.S. coast could power 200 million homes (a DoE estimate), and the world's oceans could supply more energy than total human energy requirements (an IPCC estimate).  Although it also cites some prominent setbacks – the closure of Pelamis, the first commercial wind farm, after only two months of operation, for example – it nevertheless says "we could be on the cusp of a tidal change", and encourages the reader to "imagine no need for coal, fossil fuels, nuclear generators, solar arrays or wind turbines" because wave power could supply all of our energy.

My take: This is complicated, so I will write a bit more than usual.  First of all, I am in favor of research on wave power.  $40 million is a drop in the bucket to research what might turn out to be an important technology.  My preferred overall energy policy, staring into the teeth of climate change, is "Forward in all directions!" (the slogan of 3 Mustaphas 3).  In other words, research every promising technology, from wave power to nuclear, fusion to CCS (carbon capture and sequestration).  That said, I am deeply skeptical that wave energy will ever be more than a tiny contributor.  It might seem straightforward – just a simple mechanical engineering problem! – but our attempts at it have failed for more than a hundred years.  As the article notes, seawater is highly corrosive, and has a way of destroying moving parts quite rapidly.  It is also quite difficult to build something designed to absorb wave energy, but that is robust enough not to be destroyed by big storms; big waves contain a truly staggering amount of energy, all directed toward mangling the wave-power device that stands in their way.  The simple, sad fact is that the new crop of wave power experiments will probably fail, just as all previous experiments have.  It's a lovely idea, but there are good reasons it has never been commercially successful.

I would also note that the potential energy stats quoted by the article are misleading.  The DoE estimate quoted is a theoretical maximum potential (if every bit of every wave's energy were captured); the same DoE document gives a technical maximum potential (how much we think we could ever conceivably capture) that is less than half as large.  Similarly, the IPCC estimate quoted includes all wave energy across the whole ocean; but they make clear that the energy available near coastlines, where it would actually be practical and economical to harvest it, is much lower and is quite unevenly distributed around the world (see the map on page 88 of the referenced IPCC report).  This means that while some coastal areas (the Pacific coast of the U.S., for example) look fairly good for wave power, other areas (the Atlantic coast, for example) are much less promising.  And of course to get the power from where it is generated offshore to all of the homes that it is supposed to power would require electrical grid capacity and technology well beyond what we have today, and would entail very large long-distance transmission losses.  These are non-trivial problems.

The other problem, which the article doesn't touch on at all, is the environmental impact of wave power.  Imagine what our coastlines would look like if we actually built wave-power generators all along them, encircling all of the continents.  What would that do to marine life – to whales, to fish, to dolphins?  What would it do to human activities that depend on the oceans, from fishing to shipping to sailing? What would it do to sediment transport, to beaches, to water clarity?  What would it do to nutrient cycling in the ocean, which is driven by waves, and what effect would that then have on marine biological productivity?  We don't have enough information right now to know, but it seems safe to guess that the impacts would be very large – one cannot fill the coasts with large mechanical equipment, and remove a large fraction of all the wave energy in coastal areas around the world, and think that there would not be a staggeringly large impact, it seems to me.  I think this is the final nail in the coffin for wave energy on large scales.  It may make sense to develop it in local areas where the potential wave energy is particularly high, however, and in any case we don't know enough about the environmental impact to pull the plug on it yet.  Just enough to be very pessimistic.

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