Cluster-Type Wind Turbines: A New Approach to Renewable Energy
A Japanese university and startup are developing an array of small wind turbines to replace the huge traditional turbines now in use.
Wind power has become one of the most effective methods of producing large-scale renewable energy. Solar energy accounts for 28 percent of the world’s renewable energy generating capacity, according to The International Renewable Energy Agency (IRENA). Wind energy is effectively the same at 27 percent. In 2021, wind and solar accounted for 88 percent of all electricity generation capacity additions worldwide. By 2035, renewable energy will account for 60 percent of the electricity generated worldwide.
Cluster-type wind turbines. Image used courtesy of Riamwind
By 2030, the hopes to deploy 30 gigawatts (GW) of offshore wind power, much of it from wind farms located along the Atlantic coasts of New Jersey, New York, and New England. Offshore sites in the Gulf of Mexico, on the West Coast, and in Hawaii will contribute to the total.
The ever-increasing demand for renewable energy has led to designs for bigger, more powerful wind turbines. Offshore wind turbines are typically between 300 feet and 500 feet high, while the largest, the 15-megawatt (MW) Vestas V236-15,0 MW turbine, has a rotor diameter of 714 feet and a height of 919 feet, making it also the world’s tallest wind turbine.
Because the output of a wind turbine is proportional to the swept part of the turbine blade, wind turbines with larger rotor diameters can produce more power but also results in more noise generation. Also, because bigger rotors interact with each other, 60 percent fewer of the bigger turbines can fit into the same space. As the rotor spins, the speed of the tips of the large blades of a traditional turbine can travel at more than 100 meters per second—a speed high enough that raindrops can damage them.
Offshore wind turbine. Image used courtesy of Pixabay
Cluster-Type Wind Turbine Advantages
Researchers at Kyushu University's Research and Education Center for Offshore Wind have developed a system that uses a cluster of up to 100 smaller wind turbines placed in a grid, allowing them to work together to capture more wind energy. This results in a more efficient and reliable system that generates more power and produces less noise than a traditional wind turbine.
The cluster approach has shown some advantages:
- The turbines in a cluster-type system are typically smaller than traditional wind turbines, making them less expensive to build and maintain.
- In the event of the failure of one of the smaller turbines, it can be repaired while the others are still operating.
- The turbines in a cluster-type system are often arranged in a grid pattern, ensuring they capture as much wind energy as possible.
- Cluster-type wind turbine systems can be used in various locations, including offshore and onshore.
- Cluster-type wind turbine systems are still in the early stages of development, but they can potentially become a major renewable energy source.
Demonstrating the Cluster Concept
Japan’s Kyushu University and Riamwind, a Fukuoka-based company spun from the university, will build a demonstration system in 2024 comprised of two turbine arrays, each with a diameter of 25 meters (82 feet). The system will generate data used to build another consisting of a “matrix of beams” to support 100 turbines arranged in a 10-unit by 10-unit array that is 230 meters (754 feet) high and 280 meters (918 feet) wide. This system is predicted to produce 20 megawatts of power.
Wind Turbine Lens
In addition to clustering smaller turbines, the system will feature Riamwind’s diffuser shroud at the circumference of its rotor used to concentrate wind energy. This results in a smaller turbine, called a wind lens, that can generate power more efficiently.
Wind hitting the shroud of the lens creates a vortex. The vortex forms a lower pressure area behind the turbine that increases the wind flow through the turbine, increasing the effective wind velocity. The vortices created by the blades within the lens area cancel each other, reducing noise. Riamwind says the new turbine's energy-capture efficiency per unit of the swept area is higher than any other wind turbine in the world, generating less noise than a traditional turbine with the same output.
Because the lens catches wind along with the blades, it can be subjected to more wind pressure than traditional systems. Excess wind pressure can risk damage in extremely strong winds, and this is one of the factors that will be examined in the testing program. One solution the company suggests is to consider installing the turbine blades horizontally to reduce wind pressure.