Izumi Ushiyama

An experimental study of the two-staged wind turbines

In order to improve the torque performance of the propeller type wind turbine, and to increase the relative rotational speed of the generator, two-staged wind turbines were proposed. The experimental results of a wind tunnel test showed that self-starting characteristics of two-staged co-axial type were improved by attached front wind turbines for two bladed main wind turbine, and the relative rotational speed of counter-rotating type was increased.

Renewable energy strategy in Japan

Japan has few indigenous energy supplies, and imports the bulk of its energy, so it is hardly surprising that, following the oil crises of the mid 1970s, it has taken renewable energy seriously. Moreover, increasing constrains on energy and the environment, especially the global environmental consequences of energy use, are causing a rising concern world wide, giving a warning that such constraints may be limits to sustaining our future development.

A demonstrative study for the wind and solar hybrid power system

In March 1995, a small scale wind and solar hybrid power system was installed at Ashikaga Institute of Technology. Until now, the authors have acquired the data of the output of the hybrid power plant along with wind speed, wind direction, and the solar radiation, in order to demonstrate a complementary relationship between solar energy and wind energy.

Wind energy activities in Japan

This paper describes recent activities on wind energy in Japan. The national “Sunshine Project” conducted by the Ministry of International Trade and Industry, was reviewed in 1990 to map out a new energy strategy in the Age of Global Environment. As a result, a new 500kW WECS R&D project has started in FY1991 and the operation started in FY1996. A number of basic and applied studies have been undertaken at the NEDO, the MEL and many universities. Interests in utilization of wind energy have spread gradually among power company. From FY1991, the Tohoku Electric Power Company has operated a 2,875kW Windpark(5 units of 275kW machine and 5 units of 300kW machine) at Tappi, where the annual wind speed is as strong as 10m/s.

Straight Wing Vertical Axis Wind Turbines: A Flow Analysis

This research examines the flow velocity characters around lift-based straight-wing vertical-axis wind turbines (SW-VAWT) by numerical simulation. The precision of the prediction technique was confirmed. Furthermore, we estimate the flow behaviour during the wind turbine rotation by using this numerical simulation technique, and evaluate the flow around the SW-VAWT. This paper presents an outline of the work and gives the results of the calculations.

A Feasibility Study for Floating Offshore Windfarms in Japanese Waters

This paper reports the results of technical and economic feasibility studies of floating offshore wind farms under typical environmental conditions in Japanese Waters. Outline designs are considered, with economic assessments. Both horizontal and vertical axis wind turbines are considered, although it is realised that horizontal axis machines now dominate.

Experimental Determination of Optimum Design Configuration for Micro Wind Turbines at Low Wind Speeds

This paper reports experiments and theory on some small wind turbines of rotor diameter 100 cm and less. Discrepancies in power performance have been found from predictions of blade element theory. Wind tunnel experiments showed that performance depends on the solidity of the fixed diameter rotor due to the dependence of Reynolds number on chord length. In particular, power output is lower than theory predicts on wind speed less than about 10m/s. For turbine rotors of constant diameter, output depends on solidity. In general, at low wind speeds, rotors with greater solidity give a higher output than with less solidity. This is due to the difference in Reynolds number, which itself is associated with chord length. The optimum value of Reynolds number for such small turbines is 100,000.

Experimentally determining the optimum design configuration for savonius rotors.

The Savonius rotor was proposed in the early 1920s. Until now, there has been no systematic work on the optimum design configuration of Savonius rotors. Therefore, in the present work, various model tests were carried out in a wind tunnel, in order to ascertain the optimum design configuration of Savonius rotors. The effects of six design parameters on the aerodynamic performance of the rotors were experimentally determined. These were the rotor aspect ratio, the overlap and the separation gap between rotor buckets, the profile of the bucket cross-section, the number of the buckets, and the presence or absence of rotor endplates. In addition, the flow around the rotor was investigated by the flow-visualization method. From this study, the influence of important design parameters of the Savonius rotor have been investigated and the rotor configuration giving the maximum torque and power has been determined.

Yaw Behavior of Horizontal-Axis Small Wind Turbines in an Urban Area

This paper reports the experimental study on passive yaw behavior of a horizontal axis small wind turbines. The yaw angle velocity in a small wind turbine is one of the significant design values and IEC61400-2 Ed.2 prescribes its maximum value should be less than 3 rad/s. However, in practice, in the case of small wind turbines with diameters under 2 m, the yaw angular velocity may exceed the limit of 3 rad/s. The authors conducted a theoretical evaluation as well as a wind tunnel test to examine the possible maximum yaw velocity. The model wind turbine has a diameter of 1 m, blade number of 5, solidity of 0.26 and 2 types of tail fins (large and small). For each tail fin size, the yaw behavior was studied for a range of rotational speeds and wind speeds. The results show that the yaw angular velocity becomes larger with increasing wind velocity and tail fin area. The larger the rotor rotational speed, the smaller the yaw angular velocity. Furthermore, a maximum yaw angular velocity of 3.84 rad/s was observed at a wind speed of 10 m/s, which exceeds the conventional design value of 3 rad/s.

Prospect of offshore wind energy development in Japan

In Japan, the cumulative capacity of wind turbine generation systems on land has increased steadily in recent years. To install a large number of wind turbines has inherent problems such as shortage of suitable land, and inadequate infrastructure such as power cables and roads. The necessity for development of offshore wind turbine generation systems has been recognised based on the above backgrounds. An expert committee to survey the prospect of offshore wind turbine generation in Japan was organised last year. In this paper, the prospect of offshore wind energy development in Japan is reported based on the discussion in the committee. As a result, it was found that there are some undesirable circumstances for offshore wind energy utilisation in Japan. For that reason, we need technological innovation as well as an increase in scale of wind farms in order to achieve an economical profit. The difficulty in realising of offshore wind farms in Japan relates to Japanese inshore conditions, various legal regulations and fishing rights issues.