Development of ducted Darrieus turbine for low head hydropower utilization

It is mentioned in front part of the present paper that how to extract an extra-low head power is one of key-solutions for problems on exhaustion of fossil fuels and greenhouse gas emissions, after explaining the present situation of micro-hydropower utilization in Japan. Since extra-low head sites of rivers are available near urban-sides with high population, where there is a demand for electricity, an appearance of suitable turbine, which has high cost-effectiveness, maximum reliability, easy maintenance and little environmental impact, is required. In rear part of the present paper, a guiding principle of design parameters of a ducted Darrieus-type water turbine for high performance is shown, based on authors' experimental results. Then the advantage and disadvantage of Darrieus turbine are reviewed and the key problems, which are settled as urgent works in future in order to diffuse the utilization of extra-low head hydropower, are finally suggested.