First prestressed concrete wind generator
Umiterasu Nadachi, a recreation center for the inhabitants of the city of Niigata, opened in 2000, accommodates a fitness center with swimming-pool, a venue for major sports events, a hotel and a local products center. In particular, the center was designed as a meeting point for the local population. Power generation from renewable energies such as wind power is of high importance in Japan.
This type of power generation is very much in line with the motto of the Umiterasu Nadachi recreation center, since its focus is placed on promoting the health of the population. Therefore, a wind power plant was planned for supplying power to that facility that at the same time is also a landmark for the center that can be seen from afar. In the past wind power plants in Japan were mainly built out of steel.
For the new Umiterasu Nadachi wind power plant, however, the shaft was erected using prestressed concrete for the very first time. The plants proximity to the shore was a decisive criteria for choosing prestressed concrete. The use of steel in the salty atmosphere would have been extremely expensive as a result of the cost for corrosion protection and maintenance. Due to the simpler structural design and higher service life compared to steel, the construction of a wind power plant using prestressed concrete was the best economical solution.
The tower was erected using a special formwork construction method that was developed in Austria. It consists of 12 blocks with a height of 3.90 m each. The outer diameter of the tower measures 4.0 m at its base, tapering to a lean diameter of 2.1 m at its top. For connecting the individual blocks DYWIDAG Post-Tensioning Bars were selected as they are the simplest and most secure joining method.
The 600 kW wind power plant was completed in December 2003.