Would wave energy devices withstand Beaufort 12? (Image is open source)
This is one of the most common observations I hear from Irish people when I mention our potential for offshore wind, wave and tidal energy: “it won’t work, the North Atlantic will simply thrash any wind or wave device in the first really bad winter storm”.
How valid is this objection?
One point to make is that the existing offshore oil and gas industry is quite used to severe storms and it is has become a standard operating procedure to simply shut down production during very severe weather events (see for example http://www.offshoreenergytoday.com/norway-cuts-in-production-possible-due-to-storm-statoil-says/).
So why should we expect offshore wind and wave to operate 24/7?
Nature and the planet don’t work like that, and we should embrace severe weather events with a more realistic approach: one cannot predict much when and where severe storms occur with more than a few days warning, and one cannot stop them, so instead they must be carefully managed and planned for, trying to build in as much resilience into the social and technical system of any offshore energy infrastructure.
It is true that the offshore oil and gas industry are worried about a greater frequency and severity of storm activity, especially in the wider Atlantic. Mel Causer*, and American Oil industry expert argued in 2006 that: “Since 1995, there has been a marked increase in the number and intensity of North Atlantic hurricanes. Climate experts point to that year as the onset of a period of heightened hurricane activity that they expect will last for decades. Indeed, in 2004 and 2005, eight U.S. hurricanes that made landfall caused insured losses to Gulf of Mexico oil and gas assets” (Casuer, 2006, p.70). He also makes the point that the commercial insurance market is acting as a powerful force on the offshore industry, and are using historic data to understand risk better.
One response has been simple: make the offshore gear much more moveable. Oil rigs can be and are moved away from the Gulf of Mexico once the hurricane season arrives. One could imagine that offshore wind and wave energy assets could be managed in a similar way, especially possible with the technical innovation of the floating offshore wind generator. Such a move could reduce premiums and indeed add to the value of the plant because it could be redeployed elsewhere if the economics and risk factors were not working out. This perspective would suggest that investing in movable and re-deployable types of wave energy devices that can be aligned to equally moveable offshore wind turbines might be one possible engineering and management approach to the problem of storm-proofing offshore ocean energy infrastructure.
A second approach is simply upgrading the engineering systems of future offshore wind and wave machinery to be able to handle category 5 storms (hurricanes), and to have this certified and verified. Already a number of well respected technically competent classification agencies have entered the market for providing a technical standard by which marine renewable devices should be built to if an adequate degree of weather keeping is to be achieved. Det Norske Veritas and Germanischer Lloyd have for example have specific written marine energy renewables standards (See Melnyk and Andersen, 2009, p. 37**). See for example: http://exchange.dnv.com/publishing/Codes/ToC_edition.asp#Offshore%20Service%20Specifications
A third approach which would build in redundancy to any offshore system would be to purposely design systems to sink-under water. See for example: http://www.stevens.edu/entrepreneurship/fileadmin/entrepreneurship/documents/REDay/SEAHORSE_TOS.pdf
This may reduce some of the nastier scope for storms to wreck havoc, but of course it does not entirely solve the problem. Nonetheless, it is not widely understood that several designs out there, have already some capabilities to take storm damage up to point of submersion and the generating plant simply shuts down and you wait till the storm lifts.
Other designs are optimized to work under the sea all the time: See http://www.atargis.com/CycloidalWEC.html and http://www.theengineer.co.uk/design-engineering/us-engineer-develops-cost-effective-wave-generator-for-harsh-environments/1007399.article. This model features in-built storm survival: “Since the cycloidal wave energy converter is entirely submerged, it is in a storm not subject to the tremendous loads imposed on surface bound devices that are exposed to wind and breaking waves. To survive a storm, the cycloidal WEC will simply feather its blades, and, if needed, submerge deeper where the effects of a storm are much smaller.” A similar approach of siting wave energy convertors under sea is used by Scottish company AWS: See http://www.alternative-energy-news.info/wave-power-scotland/
A fourth approach could be integrate some of the infrastructure of ocean energy devices into fixed coastal defences at key junctures where one will simply have to build higher, wider and perhaps multiple levee systems (such as points of key coastal infrastructure). Otherwise, one better approach to storms, surges and greater disruptive weather events is to let natural buffers such as wetlands prosper and in some case simply create buffer zones which will be allowed to flood. Politically that is tricky because usually coastal land is at a premium for recreation, farming, industry or residential use. In any event, in coastal cities where massive investments in infrastructure already have been made, it makes sense to build better, stronger and more complex coastal defences. These, mostly concrete structures one suspects, could be perfect locations for turbines, generating plant and associated machinery, leaving much lighter wave and tidal generation devices to operate on the nearby coastal floor say. Such sites would be in some cases perfect for Oscillating Water Column (OWC) devices. The British Limpet 500 systems works a bit like this (see: http://www.wavegen.co.uk/what_we_offer_limpet.htm). Moreover they would be near the large urban centres which have electricity demand. The only thing floating in the water, or under it, would be the actual wave or current energy capture device-the heavy machinery to convert or transmit that to electricity current could be onshore and under concrete protection.
The point here is that there probably are several engineering approaches which can manage the problem of storm proofing ocean energy devices, although that is not to say such measures will initially come easily or cheaply. Maybe, however, the bigger challenge will be to convert a skeptical public who might easily be persuaded that ocean energy devices are too fragile a type of energy system to invest in. Public perceptions are critical to the support of any renewable energy. Anything that can be done to tackle head-on the public’s most obvious objections is vital.
If only the public really understood the political risks associated with oil sourced from countries like Saudi Arabia, Iran, and Russia (who together account for almost 25% of global oil supply in 2011**), none of whom are exactly stable, predictable liberal democracies, and all live in war-prone parts of the world, or have a propensity to go to war.
I’d sooner take my chances with what the North Atlantic can throw at us!
*Causer, Mel ( 2006) ‘Reassessing and Addressing Offshore Post-Katrina Risks’, Contingencies, September/October 2006, pp. 70-72, available at: http://www.contingencies.org/septoct06/pdfs/Tradecraft_0906.pdf
**Melnyk, Markian M. W. and Robert M. Andersen (2009) Offshore power: building renewable energy projects in U.S. Waters. Tulsa: PennWell.