The Department of Energy is attempting to tap into this resource by sponsoring 11 initiatives aimed at harnessing the energy of flowing water in rivers and ocean tidal currents.
The long-term goal, according to Mario Garcia-Sanz, the program's director, is to have renewable energy sources that can function 24 hours a day, seven days a week.
In an interview, he added, "That puts our technology in a very favorable position with other renewables."One reason, he noted, is that other forms of sustainable energy are constrained. The unavailability of solar energy occurs on a nightly basis. In storms, wind power is unpredictable and can be destructive. Underwater currents, on the other hand, are rather consistent, trustworthy, and predictable.Using rushing water to generate energy isn't a novel idea. Hydroelectric dams, on the other hand, come at a high expense and have a significant environmental impact. As a result, the latest generation of scientists and engineers is attempting to enhance the concept while minimizing the disadvantages.
Underwater turbine design and control, which is required to transform energy into electricity, is still in the experimental stage. For one thing, cost is a consideration — it is still far too expensive for commercial use. This qualifies it for the Advanced Research Projects Agency-Energy (ARPA-E) of the Department of Energy, whose aim is to "change what's possible" through taking risks.
In this example, ARPA-E is awarding a $38 million funding package to 11 initiatives put together by a collection of firms, colleges, and organizations in November 2020. SHARKS means for Submarine Hydrokinetic And Riverine Kilo-megawatt Systems, and it refers to the group of projects as a whole.
SHARKS is assisting in the deployment of devices such as the "Manta" and the "Tidal Power Tug."The Tidal Power Tug is designed to start with a machine on a white tubular buoy that juts out of the water. It is tethered to the seabed, but beneath it is a pylon that houses a turbine powered by what appears to be a big airplane propeller. The current spins it, and the spinning powers a generator. It connects to a shore-based power grid with the electricity it generates.
The Tidal Power Tug's purpose is to harvest electricity from the Gulf Stream as it moves from Florida to North Carolina along the US east coast. It generates a slew of gyres, or circular currents. According to Aquantis, the inventor of the Tidal Power Tug, the strategy provides the United States with "a tremendous strategic renewable energy resource in close proximity to significant population centers."
Several other experimental turbines work in the same way that kites do. The Manta, for example, is named after the way a manta ray swims. It was created with assistance from the University of California, Berkeley, by SRI International, a nonprofit scientific research institute based in Menlo Park, Calif.It has a small generator attached to the seabed that spins a spool of rope tied to a kite-like polymer-coated foam-filled inflated object as the tide drags it out. The spinning of an associated generator generates electricity, which can be fed into a local grid connection. It also has a small motor that may be used to divert the Manta, pull it back in, or deflate it if it comes into contact with a storm or a large ship.
Manta is intended to provide power to small, remote villages near rivers or tidal inlets. "There are terawatts (1 trillion watts) of untapped energy ready to be transformed into clean and renewable energy in the world's oceans, rivers, and estuaries," SRI's lead research engineer Roy Kornbluh said in a statement.
The National Renewable Energy Laboratory's group manager of water power research and development, Michael Lawson, said the lab is collaborating with four SHARK projects to develop a computer model that can forecast the performance of underwater turbines based on data from wind turbines.
According to the National Renewable Energy Laboratory (NREL), there is enough potential energy to generate 94 terawatt-hours of energy each year. That's enough to power about 9 million homes. A substantial percentage of it will come from tidal inlets. They can be waterways between the coast and barrier islands, or divides in the coast large enough to allow tidal forces to work. Cook Inlet, in Anchorage, Alaska; Puget Sound, near Seattle; and inlets in northern Maine are just a few examples.
He noted that a vast number of turbines may provide "utility-scale resources" to power large communities. He also suggested that single turbines or small groups of turbines may provide power to smaller or more remote areas. Lawson pointed out that small towns usually rely on diesel generators, which are generally costly and subsidized by the state or federal government. Underwater turbines, according energy proponents, might be both cleaner and less expensive.
So far, Europe has led the way in developing underwater turbines, but China and other Asian countries are following suit, according to Lawson. According to Garcia-Sanz of ARPA-E, the primary hurdle for undersea turbines will be the same as it was for wind turbines in the 1990s: cost.In tidal locations, the underwater turbines currently being tested can create electricity for roughly 25 cents per kilowatt-hour. To remain competitive, the projects will need to reduce the price to roughly 4 cents."At this point, it's difficult to say who will be more successful. "We only started a year ago," he explained.
