Renewable energy means harvesting electricity (and sometimes heat) from natural resources — the wind, sunlight, flowing water, or the heat of the Earth below its surface. All these sources are free and will last almost forever.
Yeah, we hear the nattering nabobs of negativism in the audience. “Someday the sun will explode and then where will your renewable energy come from?” Well, to you we say, “Sure, someday the sun will explode and consume our tiny little celestial lifeboat. The difference is, that won’t happen for a few billion years, whereas if we don’t solve the climate crisis in the next 8 years or so, humanity will be screwed six ways to Sunday within a century or two.”
One source of renewable energy that is seldom talked about is tidal power. Think about how vast the oceans are. Now imagine the amount of energy it takes to get those trillions of gallons of seawater to go sloshing about twice a day. If we can’t wrap your heads around such an enormous number, we can ask the folks at Encyclopedia Britannica for help. The answer? 3,000 gigawatts or 3 terawatts. That’s over 1,000 terawatts a year, which is a lot of energy waiting to be tapped.
Harnessing Tidal Power Is Hard
Recovering any of that energy is difficult. According to the Washington Post, a number of techniques have been tried, including underwater kites, but none of them has been commercially viable. Many companies have tried and gone bankrupt. The European Marine Energy Center is planning a new attempt in the Orkney Islands, which are home to some of the most powerful tides in the world.
Neil Kermode, managing director of EMEC, says tidal energy is poised to help Britain deliver on its promise to go net-zero on carbon emissions. “The R&D has shown it works and industry has shown it can do this,” he wrote in an appeal to the electricity regulators to adapt to new technologies like ocean power. “This opportunity is right here, right now.”
The Orbital O2
There are 3 tidal energy devices in operation in the Orkney Islands right now, but the most ambitious of them is the Orbital O2 from Orbital Marine, which has an output of 2 megawatts — enough to heat the tea kettles and run the lights in 2000 UK homes a year. What is Orbital’s plan? The Washington Post describes it this way: “Imagine taking an offshore wind turbine, with its rotor blades spun by moving air, and turning the thing upside down, dunking it into the sea, and letting the tidal currents turn the blades.”
The Orbital O2 is 240 feet long, weighs 650 tons, and is as big as a floating jumbo jet. “The thing looks like the Beatles’ yellow submarine,” says the Washington Post. It has a large turbine with blades 64 feet long mounted on each of its wings, which when extended are as long as those of a 747. Once anchored in place, the wings pivot downward toward the ocean floor where tidal flow turns the turbines to generate electricity. Some of that electricity is stored in batteries onboard, but most of it is sent via an undersea cable to a shore station that is connected to the electrical grid.
One of the advantages of the Orbital O2 design is that the wings can be raised when necessary to permit maintenance tasks to be performed at sea level rather than underwater, which can dramatically reduce the cost of keeping the turbines operating. Another is that the turbine blades can be reoriented to take advantage of tidal flow in both directions.
Oliver Wragg, commercial director at Orbital, knows many ocean energy experiments have come and gone. He stressed to the Washington Post that the O2 is more than a prototype. “It’s designed to produce electricity for use,” and to supply power to the national grid and to onshore experiments in producing green hydrogen. The O2 is designed to remain in the water for a period of 15 years, he said.
Wragg would like to see hundreds of the devices arrayed together in the seaway, just as offshore wind farms are today. He claims the global tidal energy market today is 100,000 megawatts, enough to provide electricity to 100 million homes. To manufacture and maintain 50,000 machines generating 2 megawatts would cost $150 billion, he says. But those costs could drop considerably once a few hundred machines get built and economies of scale start to kick in.
You skeptics out there, keep in mind that solar panels were once prohibitively expensive and LED lights were originally so dim no one thought they would ever find there way into commercial production. Never say never, in other words. Renewable energy technology is still in its infancy and huge gains in efficiency and decreases in cost are still possible.
Gareth Davies, chair of Aquatera Group in Orkney, says he had a meeting with Prime Minister Boris Johnson last year and told the PM that 25% of Britain’s total electricity could be supplied by northern Scotland’s abundant wind, tide, and solar resources if they were harnessed properly. Today, less than 1% of the potential is being exploited.
Marine Power Around The World
Tidal power may be little more than a curiosity today, but could become a significant part of the world’s energy future. The Orbital O2 is not alone when it comes to harnessing the power of the tides. Other tidal machines are in service along the coasts of China, France, South Korea, and Nova Scotia. In the United States, there are demonstration projects in Maine and Washington State. There’s even one in the East River in New York City.
One of the largest tidal power installations in the world is the MeyGen tidal stream project in the waters off the northern coast of Scotland. In 2019, that facility supplied 13.8 gigawatt-hours of electricity to the UK grid. It is owned and operated by Simec Atlantis Energy and consists of four 1.5-megawatt turbines. In the next phase of development, 49 more turbines with a total capacity of 73.5 MW are planned.
“The project will…provide an investment opportunity for commercial debt and equity providers to invest in tidal stream projects,” the company says. “In addition, Phase 1C will create an estimated 5,300 full time roles, repurposing jobs from the oil and gas sector and placing Scotland at the forefront of an estimated 25GW global export market for decades to come, as well as significantly reducing LCOE.”
Don’t be surprised if ocean power becomes a significant source of renewable energy in the years and decades to come — provided the sun doesn’t erupt into a cataclysmic final meltdown first. If that happens, talk of renewable energy will become largely irrelevant.
A CleanTechnica hat tip to Ken Anderson.
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