PROS AND CONS OF OCEAN WAVE ENERGY
Ocean wave energy has fascinated inventors and engineers for centuries but no practical method of harnessing this resource has been developed, until recently. _________________________________________________________________ The Real Goods Homepage
Wave power systems typically channel the movement of ocean wave energy through a turbine generator. There are a number of interesting approaches to accomplish what, at first glance, would appear to be a deceptively simple looking task. A number of ideas being tested look promising as shown in this World Energy Council Wave Energy Report , which is the primary reference for this page. Some ocean wave energy designs are land based while others use buoys anchored to the seafloor. Because wave power is scattered and the size of individual waves is limited, all designs are necessarily modular. Harnessing wave energy probably won’t be done with a few, very large generators. Large-scale use of wave energy will likely involve thousands of small generators of 1MW and less. Wave power is more energy dense than wind power, but it is still diffuse. National Renewable Energy Laboratory Ocean Wave Energy Data shows that even in high wave energy dense areas such as the Pacific Northwest, we can expect energy production rates of about 1.5 MW for every 100 feet of shoreline occupied by generators. By comparison, a large fossil fuel plant of 1,000 MW capacity would occupy about two hundred acres. Installing a similar capacity using on shore wave power would occupy over 12.5 miles of shoreline; and that’s in the best areas like the Pacific Northwest. _________________________________________________________________ ENVIRONMENTAL FRIENDLINESS - While all forms of hydropower are pollution free, they still have environmental impacts. Ocean wave energy is still in the development stages but it is already apparent that its impact on the environment could be relatively high compared to other renewable energies. Because it is a diffuse energy source we can expect to see environmental impacts on par with those experienced by large power dams or wind turbines. It is noteworthy that even these environmental impacts are far less than those of most fossil fuel plants. Off shore ocean wave generators need anchors to hold them to the sea floor. These generators may actually be beneficial to sea life because of the subsurface structure they provide. But, on shore ocean wave energy generators will occupy extended lengths of coastline. And most of the coastlines of the world that have significant wave activity are either highly desired residential areas, or they are pristine wilderness. It doesn’t take a genius to see that any proposal to line these shores with ocean wave energy generators will be met with stiff resistance. Whether or not a case can be made that on shore generators would, in addition to being air pollution free, help preserve our shorelines from endless erosion remains to be seen. And there are ways to install these generators with minimal impact on the shoreline; but all of the methods will involve cost overruns. _________________________________________________________________ COST - World Energy Council wave power cost data suggests that wave energy is very close to being competitive with installed costs that suggest electrical charges of less than $.05 per KWh; which makes it competitive with fossil fuel generators. But that figure doesn’t take into account the fact that wave energy is intermittent and variable. Even in the most active wave areas, there are many days with little wave activity. On days that have good wave activity, wave levels can vary. As explained on the Pros and Cons of Wind Power page, resolving intermittency problems to attain reliable energy output can double and even triple the cost of power. The key to reliability and economy of operation is site selection based on good site research. _________________________________________________________________ AVAILABILITY - While waves cover virtually every mile of water on the planet, economically accessible wave power is found only in coastal areas. Some areas are better than others and the best resources tend to be found on the west coasts of our continents.
Economically usable worldwide resources add up to a significant amount of power. The NREL site noted above shows that we have economical global ocean wave energy resources of about 2,000 TWh annually, roughly 12% of world electrical output, if we can find acceptable ways to utilize it. The NREL site also gives an overview of the technologies used to harness wave energy. _________________________________________________________________ AESTHETICS - Whether we are discussing onshore or offshore ocean wave power we have to deal directly with aesthetics problems in someone’s back yard. Onshore systems of any significant size will use miles of coastline and involve massive structures to channel waves and convert ocean wave energy into usable power. Wherever these systems are placed they will almost certainly have to be designed with regard to visual impact. It comes down to a choice of designing something that has a natural appearance, or having thousands of miles of barren concrete seawall on all of our coasts. Offshore installations have a different kind of problem. If we expect to harvest significant amounts of energy from off shore waves, we can expect to see thousands of them bobbing around within eyesight of shore. There are some systems being tested that are underwater and out of sight. But time will tell whether or not they can stay that way. If they are shallow enough such that they are navigation hazards, they will have to have marker buoys – lots of marker buoys. There are other, deep water systems that actually work more efficiently than those closer to shore. But efficiency gains on these systems is given up to power losses through long distances of expensive underwater transmission lines that have to be ran to bring the power to shore. So they may not prove to be competitive in the energy marketplace. Beyond any visual impact we must be aware of the fact that storms will cause ocean wave generators to occasionally dislodge from their anchors and become serious navigation hazards. _________________________________________________________________
Ocean wave energy looks like an iffy proposition. There are a few areas where wave power may prove desirable. But environmental and aesthetics concerns combined with expensive intermittency problems will be serious obstacles to significant wave power use for some time. _________________________________________________________________ _________________________________________________________________
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