sea based wind farms via global citizen

Wave Hello to a Low-Cost Renewable Energy Advancement

Recent unforeseen and costly energy supply shortages have been an unpleasant surprise for Europeans, and they have spooked some of us enough to increase demands for more fossil fuel pipelines and tanker shipments. Of course, that’s exactly what the heinous carbon merchants are hoping for.

But there is a much better way to go. All of the countries that now use or are constructing offshore wind power installations—the U.K., Germany, the Netherlands, Belgium, Denmark, the U.S., China, Japan—have an opportunity to swiftly multiply non-fossil energy resources at a relatively low cost.

How? Offshore wind installations have vast propellers driving turbines atop tall columns, set out at sea in arrays. The idea is to retrofit the column base of every turbine so that it serves as the node for a cluster of water-level wave power generators. Call it Sea-Based Hybrid Power.

Intensifying the use of already allocated offshore sites would avoid the long delays required for future development sites (marine studies, national and international ocean permits, etc.), and the new units would doubtless be capable of transmitting their extra energy via cables already in place. Investigation shows that harnessing the plentiful and still fully available energy of the sea that lies between existing wind turbines would be likely to more than double the megawattage now collected in the same ocean space. Governments should now assess and support the efficient addition of wave power units within wind power farms by their existing license holders, or by selling new licenses.

Fifty years ago, as chief designer of the harbour enclosure that we built for the Brighton Marina (below the cliffs of the English Channel), I began studying waves and came to believe that, in physical principle, hydrokinetic energy is the sovereign natural power. Unlike sun and wind, wave energy is virtually uninterruptable. Seas churn constantly, with waves moving in all directions, and the sea surface itself is continually rising and falling. The painted-ocean calm of Coleridge’s description never actually occurs.

Machines designed by Pelamis Wave Power operating offshore at the Billia Croo test site of the European Marine Energy Centre (EMEC), located in Scotland’s Orkney Islands. Image via Yale Environment 360.


Moreover, while wave energy is largely a product of wind energy (and tidal motion), the forces that rule the waves often come from storms hundreds or thousands of miles away. High winds completely coincident with high waves occur randomly, and at any single wind farm node they would frequently be out of phase. So a chief attraction of sea-based hybrid power is the increased consistency of energy that collection of both wind and wave action together would produce, for a much greater security of constant supply. Which is probably constant enough to spike the folly of nuclear energy alternatives. I believe sea-based hybrid power would decisively challenge the idea that we have to put up with waiting decades and paying huge and perennial energy costs for new nuclear reactors, along with maintaining everlasting security battalions to protect the exhausted radioactive stuff that terrorists crave for dirty bombs.

The physics of water has long had human appreciation, up to a point. As Blaise Pascal investigated and described in the 17th century, water as an incompressible fluid transfers pressure undiminished. Hydraulic rams and hydraulic lifts were developed to work on this principle. Water’s density has provided the means of flotation for ships since prehistoric times, and the lowered net weight of immersed objects is greatly advantageous for the economical support of engineered structures.

A cubic meter of water weighs nearly 1,000 kg, while the weight of a cubic meter of air near sea level averages about 1.28 kg. Water’s weight—about 784 times greater than that of air—is why it’s relatively easy to withstand a 50 mph wind but get knocked over by a 3 mph wave. Wave power is figured to have a “power density” of about 25 kW/m2, compared to about 1 kW/m2 for photovoltaic glass at solar peak, and 1 kW/m2 for wind at 12 m/second. So while solar power and wind power have conversion efficiencies usually no higher than 15%, the applied forces of wave power—as Pascal’s Law suggests—are capable of converting more than 50% of received energy.

The big difference means that, with well engineered hydrokinetic conversion, the motion of water that could be harnessed in an area of ocean only 10 miles by 10 miles [LINK] “could fully power California,” as the chief engineer of a U.S. Pacific coast wave power developer has calculated. The additional footprints of wave power apparatus within wind power farms would advantageously shelter schools of fish, as environmental analysis has attested; they would not conflict with fishing trawlers that already have to keep their distance; and their maintenance and security will probably add little or nothing to existing costs.

There have been many wave power designs developed and tested, including some recent tests for wind and wave hybrids. Principle Power of the U.S. and some Danish and Norwegian companies have begun trialling structurally integrated hybrids. But for maximum speed and cost efficiency, the hot opportunity is a crash program to fit new bolt-on wave power units to already working wind power sites. A simple system used by Ocean Power Technologies has circular floating platforms that operate generators by rising and falling relative to a fixed central column. Other companies have developed hinged, clam-like mechanisms that waves can open and close, and there are even entirely underwater systems that work by means of relative buoyancies.

Since wind turbine support columns are usually built into the sea bed (some trials are testing the use of anchored floating columns), further insurance for constant energy supply could be obtained by adding storage battery chambers to the columns, for battery arrays that would charge up when winds and waves are lively and release energy when things get slow. Another kind of surplus energy bank that could be added are elevated onshore discharge basins, ideally also usable by migrating birds, that would surge back gravity-fed water through generators when the reserved power was required.

Design engineers will readily solve the questions of preferred hydrokinetic systems, the amalgamated energy units’ structural connections, and the development of their mechanical and electrical relationships. They are not very difficult problems. The industrial means of achieving the rapid and efficient production of sea-based hybrid power units will be far simpler, and should be far easier, than producing tanks and planes in World War II. And, of course, once harnessed, wave power energy, like wind power energy, will be free.

So shall we get cracking with it, or let ourselves be bullied by the carbon and nuclear merchants?

Featured image via Global Citizen. 



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