Yellow Duck Inc. (Yellow Duck) develops wave power technology that uses the rocking force of waves to turn a motor and generate electricity. The generator floats on the sea, so no large-scale initial construction is needed. It is a simple mechanism with a low environmental impact. The company is named after its symbol, a lovable device shaped like a yellow duck. CEO Shigeo Nakayama, who says the company is now running demonstration trials with the aim of use as full-scale infrastructure, talks about the journey so far and the outlook ahead.
Energy from the natural movement of a float and a weight on the sea
The technology we develop is a type of wave power generation that floats a ship-like body containing a float and a weight on the sea and extracts energy from the waves. It turns the natural movement of the floating body, as it tries to keep its balance on the sea, into energy.
Technologies for extracting energy from the sea include offshore wind power, which uses wind; ocean thermal energy conversion, which uses differences in seawater temperature; and ocean current power, which uses the flow of the tides. However, each method has advantages and disadvantages, and there is no decisive solution yet.
The advantage of our device is that “no large-scale seabed civil engineering work is needed.” The whole device is on the sea, so maintenance is easy, and it reduces the burden on the natural environment and sea life. It emits no CO2, and the entire ocean, which covers 70% of the earth’s surface, can become a power plant.
Since we started development, the road has been full of twists and turns. Before arriving at the current technology, we sometimes fell into a vicious circle: overthinking made the device too complicated, so it broke easily and its energy efficiency dropped. After those experiences, we now pursue renewable energy that stays closer to nature, based on the idea of “making the world gentler with simple ideas.”
Starting homemade experiments after the Great East Japan Earthquake
What first got me interested in energy issues was the Great East Japan Earthquake in 2011. After the disaster, the national and local governments began pushing hard to develop renewable energy.
Solar panels began to line up here and there in the area where I lived, and I sometimes felt uneasy seeing the trees on the mountains where I often played as a child cut down to install row after row of panels. In one area, mountain slopes were cut away to install panels, and every time it rained, soil washed into the rivers and muddy water overflowed onto the roads, which became a problem among local residents.
At the time I was working as an administrative scrivener, and as I saw and heard about these problems, I began to think, “Isn’t there a gentler way to produce energy?” So around 2014, I started small experiments at home while reading papers and watching videos.
The first thing I made was a generator called a “solar chimney.” It heated the air inside a black plastic bag and used the force of that air escaping through a chimney made of plastic pipe to turn a turbine. This device could generate power, but producing enough electricity for practical use would have required as much space as solar panels, or more.
Next I focused on wind. Wind power generally uses large windmills held up by tall towers, but I built a device called “kite wind power,” which attaches a windmill to a kite held by a rope instead of a tower and turns a turbine with the wind high in the sky. The big problem with this device was that its range of movement in the sky was very wide. I found that with 300 m of rope, it needed a hemispherical range of movement with a radius of 300 m, and it could get caught on things in the sky.
Development was stuck until one day, when I was walking along the coast. Seeing garbage rocked again and again by the waves, it hit me: “Maybe I can make energy from the power of waves.” So I started developing a wave power device that attached a pendulum to a swim ring and turned its motion into electricity. That was the first step toward today’s technology, around 2018.
This mechanism did not work well from the start either. Depending on the timing, the waves canceled out the pendulum’s motion, so it was unstable: sometimes it produced electricity and sometimes it did not. For about three years after I started development, trial and error continued.
Starting demonstration trials with the cooperation of local governments
The turning point came in 2022. Meeting an engineer moved the technology forward all at once. Instead of moving a pendulum, we switched to a simpler technology in which the force of the float rising to the sea surface turns the motor directly. That same year, we won the “NEDO Award” at a pitch event. After the award, more and more people from various industries reached out to us. Just then, I met Yamaoka, now one of our members, and we founded Yellow Duck in August 2023.
In 2024, we finally started demonstration trials. In experiments from 2024 to 2025 in Toyama, Osaka, and Fukuoka, using generators fixed to seawalls, we confirmed better-than-expected performance even while storm warnings were in effect. We are planning demonstration trials at five locations around Japan, with the device floating offshore.
I was working in a completely different field, and the earthquake left me with questions and a sense of unease. I feel that I was able to go from there through many small experiments to founding a company thanks to the people I met and the support of my family. That is exactly why I want more people to know about our technology and put it to use in society. With that in mind, at Expo 2025 Osaka, Kansai, Japan, we used our symbol, the yellow duck-shaped device, to show children the potential of ocean power generation.
Because our technology is on the sea, its resources are distributed, so we believe it is also effective as an emergency power source in disasters. Never forgetting our gratitude to the people who have supported us, we will keep developing toward full-scale practical use.
How We Used OIH
We have been connected with OIH since around 2022, and in 2023 we won the HeCNOS AWARD. Through that, OIH introduced us to a radio talk show by the Osaka Industrial Promotion Organization, “Zai Radio! Behind the Scenes of Business”, and we appeared on it. After that, we were confirmed for an exhibit at the Osaka Healthcare Pavilion at Expo 2025 Osaka, Kansai, Japan. On OIH’s recommendation, we also appeared in “Make Money Survive on Tour in Osaka” on “HORIE ONE,” Takafumi Horie’s show on the NewsPicks YouTube channel. Then in 2025, we were selected for the KIDOU program, which we had long hoped for. I feel that the KIDOU program is a wonderful program that is attentive to startups’ needs.
Interview date: June 18, 2025
(Interview and text: Aya Iwamura)