In a world where climate change is becoming a more important and pressing issue every day, we are actively trying to diversify our energy portfolios by increasing power generation from renewable energy sources. In the United States, wind and solar energy as well as nuclear are the hot topics in discussions, but what if we are missing out on a resource with enormous energy potential? What if generating power from ocean waves and tides could help us reach our carbon dioxide emissions reduction goals? With oceans covering over 71% of the earth, harnessing the energy of waves has the potential reduce our reliance on fossil fuels and supply us with a predictable and renewable energy source for the future.
The uneven heating of the Earth’s surface by the sun produces pockets of warm and cold air as well as high and low-pressure zones, causing circulation patterns to occur and creating wind. When the wind blows over the oceans, waves are produced. These waves have a tremendous amount of energy, and some of their energy can be harnessed for use by humans. The Electric Power Research Institute has estimated that the total wave energy potential along the outer continental shelf to be 2,640 TWh/yr, which is almost 65% of the electricity generated in the United States annually. Unfortunately, not all of that energy is recoverable, because there are competing uses for certain stretches of water (i.e shipping, commercial fishing, naval operations). EPRI estimated that 1,170 TWh/yr of wind energy potential is actually recoverable on the outer continental shelf, which is still enough to power over 25% of the United States.
Wave energy technology is far behind the technology for other renewable energy sources such as wind and solar, which is why it is a currently not viable for wide scale use. The harsh conditions that can be present in the ocean pose a significant challenge to scientists and engineers. There are currently multiple designs and systems being used to harness wave energy. There are floats or buoy systems that use the rising and falling of the ocean waves to drive hydraulic pumps which stroke a generator to produce electricity. The U.S navy has been testing out buoy systems off the coast of Hawaii since 2015 and has successfully connected the buoy to the grid via under water cables. This was the first grid-connected test site for wave energy in the United States. There are also devices called terminators or oscillating water column devices that use the in-and-out motion of the waves moving through a column to force air through a turbine. The air in the column is compressed and heats up as the waves move in and out.
In 2008, the world’s first wave farm, called was tested and operated 3 miles off of the shore in Portugal. The farm was using devices called attenuators, which are long floating structures consisting of multiple sections connected by flexible joints. Energy is generated by the friction between the sections due to the action of the waves, and it can be harnessed by hydraulic pumps and transmitted via deep sea cables. The wave farm in Portugal was $11 million to construct, and was rated a maximum capacity of 2.25 MW. The floating structures were 120 meters each.
Like all energy sources, there are advantages and disadvantages to wave energy. To start with the advantages, wave energy is renewable, because as long as the sun shines, wind and waves will be created. Second, it is a clean energy source, as it produces no greenhouse gas emissions. Wave energy also has an enormous energy potential, because our oceans are so vast and the water has a high energy density. This high energy density leads to less much smaller areas required, about 1/200 the area needed for a wind farm of equal energy potential. Finally, it is reliable and predictable. Wave activity can be predicted far in advance, and the waves will always be there.
On the flip side, wave energy has its disadvantages as well. It has proven difficult to design system robust enough to handle the extreme conditions in the ocean and the 100 year wave. The equipment must be able to withstand external conditions such as the corrosiveness of the water, the colonization of structures by marine animals and algae, and the potential for unusually large waves. Marine life can get caught up in the systems, and if placed in wrong location, the systems can disrupt migration patterns. Another con is that wave energy systems are not very visually appealing, which can effect tourism in coastal communities. There is also a lot of uncertainty in the technology, which makes large scale investments risky. We don’t have a very good idea of how long these wave energy systems will last, how often they will require maintenance or how much maintenance will cost to mention a few issues. Finally, the current systems are very expensive, and until more significant technological improvements are made, they will probably continue to stay high.
A few questions I have are: What are your thoughts or concerns about wave energy? Do you think it will become a viable source of energy in the future in the United States? Could this be a solution to powering remote coastal communities around the world?