With 70% of the Earth’s surface covered by oceans, the power of waves can be one of the biggest forces we have energy resources. If you’ve ever been knocked off your feet by a big wave, you’ve felt such a force.
For decades, scientists and engineers have looked to our vast oceans and dreamed of ways to extract just a tiny fraction of that energy. In an age of climate awareness and anxiety, finding ways to do this is finally getting more attention.
Biden administration Ocean Climate Action Plan
It reveals how the ocean holds important potential for renewable energy, both from offshore wind power and less explored sources such as waves, tides, and currents. Even the cold waters of tropical deep seas can provide clean marine energy.
The plan acknowledges an ambitious endeavor nearing completion off the Oregon coast, where 7 miles of canals have been laid under the floor of the Pacific Ocean using pioneering horizontal drilling techniques. Soon, thick cables would be run through that channel to connect the mainland to it Backwavean offshore beta test set up to develop and demonstrate new technology that converts wave power into onshore electricity.
Once fully operational (by 2025), PacWave could generate up to 20 megawatts, enough to power a few thousand homes. “I get really excited about wave power because the resource is so big,” Levi Kilcher, a senior scientist at the National Renewable Energy Laboratory, told me.
Kilcher is the lead author on 2021 NREL Report
which collected available data on marine energy sources in the United States, including waves, tides, and ocean currents. The team found that the total energy potential equals more than half (57%) of the electricity generated in the United States in one year.
Although experimental sites like PacWave point to an efficient way to harvest wave energy and could facilitate breakthroughs, wave energy still has a way to go before it becomes a significant source of electricity. Although the waves are stationary, they are not identical, which poses a major challenge in designing a machine to capture their energy.
“You’re trying to adjust [the technological approach] So you can take advantage of these changing types of waves,” said Andrea Copping, senior researcher at the Pacific Northwest National Laboratory.
Various approaches to capturing wave energy include devices that ride on top of waves or those that translate pressure waves placed on the sea floor into energy. Another method involves devices called oscillating water columns, which compress air as waves rush through it. This compressed air spins a turbine and generates power.
Power from the depths
Waves are just one potential source of marine energy that scientists and officials are investigating.
Copping says there is renewed interest in another form of marine energy: Ocean Thermal Energy Conversion, or OTEC, which involves bringing in cold water from deeper parts of the ocean. This cold flow then goes through the process of heat exchange with warmer surface water, similar to the way home heat pumps exchange hot and cold air. This process drives a turbine to generate electricity.
OTEC technology was pioneered in the 1970s when energy prices soared, but it never caught on. According to Copping, climate change has led to more interest in the OTEC, which could be a good fit for islands like Puerto Rico and Guam and small nations in the South Pacific.
“There’s real interest out there, and we really think it’s going to go this time around,” Copping said.
A small OTEC factory that has been in operation in Hawaii for years. Copping believes that new commitments from the US government bode well for the future of the technology, which has also seen great interest in Japan and other surrounding countries.
It is possible that concern about climate change could open up new sources of OTEC funding. Meanwhile, building smaller facilities (10 megawatts or less) and placing them on land rather than floating in the ocean makes the technology more affordable, Copping said.
There is also the added bonus that the cold water pipes can double as a form of air conditioning in the tropics where the OTEC works best.
Go with the flow
Much of the coast of the United States, such as Alaska, the Pacific Northwest, and the rocky shores of Maine, have climates in which there is little chance of finding surface waters warm enough for the OTEC. Fortunately, some of these spots are ideal for generating energy from a source that relies on shallow waters: the tides.
Growing up in Alaska, Kilcher has always been fascinated by the power of tides. But he had no idea that nearby Cook Inlet was one of the perfect locations in the world to harness their energy. When Kilcher first started working at the National Renewable Energy Laboratory, he was surprised when colleagues told him that Homer’s hometown, Alaska, was among the best tidal power spots in the world.
When it comes to converting the ocean’s motions into electricity, tidal power technology is the most advanced—it’s as simple as placing the right turbine in the right place in the water. A number of tidal power projects have already been deployed in Europe and elsewhere, as well as in specialized applications around the world.
Tidal energy is yin relative to wave energy. Waves can be anywhere and everywhere, but they are hard to predict. Tides are a mostly known quantity that is universal, but their force potential is limited to a few very specific places. The fast flows required to generate power are usually found only in narrow channels or between islands and the mainland. However, where tidal energy works, it is a very reliable form of renewable energy.
“One thing that makes tidal energy particularly attractive is that it is 100 percent predictable,” Kilcher said.
Some smaller experiments are done with other consistent ocean properties besides tides, such as slow-moving main currents. Kilcher noted that research is underway off the coast of the southeastern United States to study how much energy can be pulled from the currents before affecting heat circulation patterns in the North Atlantic.
“You don’t want to extract so much energy that Gulfstream starts to shut down,” he said. “That’s the kind of scientific research question we’re looking at.”
Thar she blows
So far, effectively drawing energy from the ocean has less to do with the water than it does with the air above it. Offshore wind energy is by far the most productive source of energy we transfer from the ocean to land.
“Offshore wind is without a doubt the most mature technology,” Bryson Robertson, director of Oregon State University’s Pacific Offshore Energy Center, told me. “We’ve actually been working on wind power systems since the birth of civilization. We’ve been making sails [on boats]We used windmills to grind wheat.
Large, power-generating wind turbines anchored to the sea floor have become a common sight off the coast of the Northeastern states and elsewhere. Floating offshore wind turbines, Robertson says, are a promising new technology that could help increase the amount of electricity we literally pull out of thin air.
The winds are more consistent offshore, and floating infrastructure can be deployed in more parts of the world and in deep seas. And taller turbines can hit higher altitude winds at locations out of public view.
Robertson believes that the opportunities to generate more wind power from floating infrastructure are great enough to make a real dent in carbon emissions.
tough environment
Unlike developing a new mobile app or even a mobile phone, building the infrastructure to draw power from one of the most inhospitable and untamed environments on Earth can be a slow and difficult process.
“We don’t know much about the tidal heights and these big wave areas because we stay out of it,” Copping said. “That’s one of the reasons this takes time. But just look at the ocean—it’s hard not to see the energy potential.”
There are a number of other considerations as well, including the effects that marine energy infrastructure can have on wildlife, the wider environment, local people, fishing, and other industries.
“I think the biggest issue is uncertainty,” Robertson added. “We’ve never done this on a large scale before, so what would the environmental impacts be?”
He says the policy process may be slow for good reasons, but the need for offshore energy remains urgent.
“We need to find a way to deploy technology faster while being environmentally aware,” he said. “We just need to find a way to speed up this process if we have a meaningful impact on climate change.”
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