Researchers are testing buoyant, wing-shaped underwater kites designed to harvest renewable energy from slow-moving tidal currents. These systems, which autonomously fly figure-of-eight patterns to generate electricity, offer a potential alternative for off-grid coastal communities currently dependent on expensive diesel generators or weather-variable solar power. While the technology remains in the pilot-testing phase, developers are working to prove that tidal kite power generators can provide reliable, cost-effective energy in remote regions.
The core concept relies on hydrodynamic lift, allowing the kites to “fly” through water much like a traditional kite moves through air. By utilizing onboard sensors and robotics, the kites can maintain speed even during slack tide, a period when fixed seafloor turbines typically struggle to generate power.
The Manta Project and Tether Technology
A notable iteration of this technology is the Manta project, developed by SRI International, a research institute based in Menlo Park, California. Unlike systems that use static tethers, the Manta design incorporates a twisted-string tether. This mechanism is designed to spin a generator without the need for complex, high-ratio gearing, potentially resulting in a more compact, cost-efficient, and easier-to-maintain system. The project is currently supported by a contract with the U.S. Department of Energy’s hydrokinetic technology program, which aims for a production cost of less than US $0.09 per kilowatt-hour at a 1-kilowatt output.
The control systems required for these kites are highly sophisticated. According to Chris Vermillion, a mechanical engineering professor at the University of Michigan, the kites must remain in constant, periodic motion to generate power, requiring an autopilot that can adjust to six degrees of freedom on the kite and three more on the tether. This “intricate dance” requires precise management of the wing’s pitch and angle of attack relative to the current as the generator load fluctuates.
Testing and Performance Metrics
In 2025, researchers led by Variano conducted tests on a 1-meter wingspan model in the San Francisco Bay. The device demonstrated the ability to power a generator rated up to 2 kilowatts, capturing over 100 watts during peak tidal flows of 1.5 meters per second. The team has since moved to a pilot-scale system featuring a 2-meter wingspan and a 15-meter-long tether. Simulations suggest this larger unit can generate an average of 1 kilowatt over a full tidal cycle, even in currents moving slower than 1 meter per second.
The testing process involves anchoring a small fishing vessel to ensure the kite’s movement is derived solely from tidal currents. During these sweeps, the generator gathers power as the kite moves away, then uses a small portion of that energy to reel the kite back in, repeating the cycle. The researchers are currently gathering data to analyze the system’s efficiency across full tidal cycles, with comprehensive results expected by the end of 2026.
Industry Scaling and Remote Applications
While the Manta project focuses on kilowatt-scale power, other companies are pursuing larger implementations. Minesto, a company based near Gothenburg, Sweden, has successfully deployed a 12-meter wingspan kite capable of driving a 1.2-megawatt generator. This system, which is currently grid-connected in the Faroe Islands, carries its generator directly on the wing. While CEO Martin Edlund notes that the company has successfully attracted capital and achieved grid connectivity, he characterizes the technology as still being in the early stages of commercial development.
For remote communities, particularly in regions like Alaska, this technology could provide a critical replacement for diesel fuel. The Manta team is preparing for future trials in Alaska’s Alexander Archipelago, collaborating with the Metlakatla Indian Community to identify narrow straits suitable for tidal harvesting. Meanwhile, BladeRunner Energy of Bend, Oregon, is testing a tethered, corkscrew-style rotor in Alaska. Their 2-meter-diameter system generates 5 kilowatts in flows between 1.8 and 2 meters per second. The company is currently planning to integrate an 11-kilowatt generator with the Napaimute microgrid, with the goal of eliminating the village’s reliance on diesel fuel.
As these projects move forward, industry observers remain optimistic about the role of marine energy in the broader renewable portfolio. Despite the early-stage nature of the technology, experts like Vermillion suggest that tidal kites are well-positioned for success, arguing that the sector is not inherently higher-risk than other established renewable energy strategies. Further updates on the performance of the Manta system are expected following the conclusion of the research team’s analysis in late 2026.
Readers interested in the progress of marine hydrokinetic energy can monitor updates from the U.S. Department of Energy’s Water Power Technologies Office for future testing milestones and pilot program reports. Please share your thoughts or questions on the future of tidal energy in the comments below.