Language：English   Publishing type：Research paper (scientific journal)  

A multirotor system (MRS) is defined as containing more than one rotor in a single structure. MRSs have a great potential as a wind turbine system, saving mass and cost, and showing scale ability. The shrouded wind turbine with brimmed diffuser-augmented wind turbines (B-DAWT) has demonstrated power augmentation for a given turbine diameter and wind speed by a factor of about 2-5 compared with a bare wind turbine. In the present research, B-DAWTs are used in a multirotor system. The power output performance of MRSs using two and three B-DAWTs in a variety of configurations has been investigated in the previous works. In the present study, the aerodynamics of an MRS with five B-DAWTs, spaced in close vicinity in the same vertical plane normal to a uniform flow, has been analyzed. Power output increases of up to 21% in average for a five-rotor MRS configuration are achieved in comparison to that for the stand-alone configuration. Thus, when B-DAWTs are employed as the unit of a MRS, the total power output is remarkably increased. As the number of units for an MRS is increased from two to five, the increase in power output becomes larger and larger. This is because that the gap flows between B-DAWTs in a MRS are accelerated and cause lowered pressure regions due to vortex interaction behind the brimmed diffusers. Thus, a MRS with more B-DAWTs can draw more wind into turbines showing higher power output.

DOI： 10.1115/1.4042235

Language：English   Publishing type：Research paper (scientific journal)  

Brimmed-diffuser augmented wind turbines (B-DAWTs) can significantly increase the performance of the rotor. Multirotor systems (MRSs) have a lot of merits such as significant saving mass and overall cost of the wind turbine system. In the present research, B-DAWTs are studied in a MRS. In wind tunnel experiments, the power output and aerodynamics of three B-DAWTs placed in close vicinity have been investigated. The results show a significant increase of up to 12% in total power output of the MRS with B-DAWTs compared to the sum of the stand-alone (SA) same turbines. The accelerated gap flows between B-DAWTs in a MRS cause lowered pressure regions due to vortex interaction behind the brimmed diffusers and draw more wind into turbines.

DOI： 10.1115/1.4042971

Language：Japanese   Publishing type：Research paper (scientific journal)  

Power Output and Drag Characteristics of Multi Rotor Wind Turbine System Using Brimmed-Diffuser Augmented Wind Turbines (in Japanese)

Language：Japanese   Publishing type：Research paper (scientific journal)  

Improvement of Power Output of Straight-Bladed Vertical Axis Wind Turbines with Surrounding Structures (in Japanese)

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI:10.4236/jfcmv.2017.52002

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI:10.1115/1.4035754

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI:10.1051/rees/2016022

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI:10.3390/en9121077

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI:10.3390/en9060406

Language：Japanese  

Application of a Wind Acceleration Device to Vertical Axis Wind Turbines (in Japanese)

DOI： DOI:10.15017/1660015

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Four types of MRS arrangements were tested in the wind tunnel. The power output increased compared to a stand-alone turbine.
 The largest power output increase ratio was achieved on the side-by-side arrangement.
 An optimal gap and distance in streamwise direction exist in each arrangement.
 CFD flow visualization shows an accelerated gap flows as well as a generation of a low-pressure zone in the back of the wind turbines.
 Staggered arrangement CFD results shows that pressure distribution for the side turbines was remarkably lowered compared to the center turbine

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

It is important to control the wind turbine wakes for efficient operation of large wind farms. The yaw steering method can deflect wakes and is expected to contribute to the generation management of the entire wind farm. In this study, wind tunnel experiments were conducted using a model of a wind turbine to investigate the effects of the yaw steering method on the wakes and the downstream wind turbine output. The wind speed distribution of the wakes in the yaw state was measured. In addition, two wind turbine models were used to investigate the change in power output in the yaw state.

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：English  

Venue：Online   Country：Japan  

Multi rotor systems (MRS) have shown a great potential as a future application of wind energy. In this study, the aim is simulating the aerodynamic performance of a an MRS using fully-resolved shrouded wind turbine blades then validating with experimental data. MRS for wind turbine configurations have been studied using both numerical and experimental approaches. Different case studies have been studied and the power output comparison have been reported. The wind lens turbine (WLT) obviously shows a large increase in power output compared to the bare rotor case. Besides, the twin side-by-side (SBS) WLTs shows even larger power increase compared to the case of single WLT by around 20% for computational fluid dynamics (CFD) calculations at the optimum tip speed ratio s/D of around 0.2. The increase in power coefficient in close proximity can be explained by flow interference and gap flow behaviors. Previously, we used simplified models for blade modeling like actuator line method (ALM) and actuator disk method (ADM). However, currently we are improving the accuracy using CFD with full-scale blades with higher grid resolutions. As the number of units for an MRS is increased, the increase in power output becomes larger and larger. This is because that the gap flows between brimmed diffuser-augmented wind turbines (B-DAWT) in a MRS are accelerated and cause lowered pressure regions due to vortex interaction behind the brimmed diffusers. Thus, an MRS with more B-DAWTs can draw more wind into turbines showing higher power output.

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2021.6

Language：Japanese  

Venue：オンライン   Country：Japan  

Event date： 2019.12

Language：Japanese  

Venue：東京、科学技術館   Country：Japan  

The Combination Performance of Heat and Wind Created by a Wind Solar Tower

Event date： 2019.12

Language：Japanese  

Venue：東京、科学技術館   Country：Japan  

The Combination Performance of Heat and Wind Created by a Wind Solar Tower

Event date： 2019.11

Language：Japanese  

Venue：J:COMホルトホール大分   Country：Japan  

Event date： 2019.11

Language：Japanese  

Venue：J:COMホルトホール大分   Country：Japan  

Event date： 2019.11

Language：Japanese  

Venue：北海道、北海道大学   Country：Japan  

Numerical Simulation of Thermal Updraft Generated by a Wind Solar Tower

Event date： 2019.9

Language：Japanese  

Venue：電気通信大学、東京   Country：Japan  

Event date： 2019.9

Language：Japanese  

Venue：電気通信大学、東京   Country：Japan  

Event date： 2019.9

Language：Japanese  

Venue：電気通信大学、東京   Country：Japan  

Event date： 2019.6

Language：English  

Venue：University College Cork, Ireland   Country：Ireland  

Multi-rotor systems(MRSs) are defined as single structures containing more than one rotor. For more power output of MRSs, we examined staggered arrangements of MRSs with brimmed-diffuser augmented turbines (Wind Lens Turbine (WLT)). When the central turbine on staggered arrangement was moved in upwind direction, the output increase was close to a single unit’s value, while the total output of MRS did not change a lot. The changes on the individual power output increases were thought to be due to flow pattern changes of accelerated gap-flows among them. The results showed that staggered arrangements have a potential to make flows around the turbines more effective for their power output.

Event date： 2019.6

Language：English  

Venue：University College Cork, Ireland   Country：Ireland  

A wind solar tower (called WST) is one of wind-power generation plants. WST is composed of four parts; a transparent thermal collector on the ground, a tall tower at the center of the collector, a vortex-generation plate on the top of the tower, and a wind turbine inside the tower. The tower utilizes an updraft generated in the tower to rotate its turbine. Two mechanisms below exist for generating the updraft;
i) Solar energy warms the air inside the collector. Then the warm air rises in the tower with its buoyancy.
ii) Wind energy generates a vortex above the tower. The low pressure of the vortex sucks up the air inside the tower.
Although the first mechanism has already used in a traditional solar tower, the second one is our new idea. Generally, renewable-energy power plants are expected to increase their outputs per unit area. WST has a chance of becoming the most powerful device, due to its advantage over the hybrid utilization of renewable energies. Then we have tried to optimize the tower shape for the further enhancement of its power output.
Our previous study showed that a diffuser-shaped tower with a semi-open angle of 4° was efficient. The diffuser-shaped tower demonstrated about 4-5 times power output as large as a cylindrical tower. Recently, we conducted some experiments using towers in several varieties of aspect ratios (AR = h/D). We supplied heat energy to the towers in laboratory experiments and wind energy to them in wind tunnel experiments respectively. In the case of heat utilization, the tower with larger aspect ratio tended to show the high heat energy conversion efficiency (=ηH). Similarly, in the case of wind utilization, the tower with a larger aspect ratio increased the wind energy conversion efficiency (=ηW). However, the tower with the vortex-generation plate achieved high ηW regardless of its aspect ratio. This result suggests that wind energy enables us to gain a large power output with a low tower. The low tower will be built at relatively low cost and contribute to the growth of renewables.

Event date： 2019.6

Language：English  

Venue：University College Cork, Ireland   Country：Ireland  

A brimmed-diffuser augmented turbine (called Wind Lens Turbine: WLT) utilizes vortices around the brim actively to enhance its power output. However, the vortices are usually unstable and asymmetric. This study attempted to stabilize the vortices and enhance the power output of WLT. Polygonal brims were investigated in wind tunnel experiments and numerical simulations. As a result, ideas achieved 2% increase of the power output compared with standard (round) WLTs. The numerical simulation unveiled a periodicity existed in the fluctuating vortex structure on a circular brim. Polygonal brims with the same periodic scale were able to suppress the vortex fluctuation and stabilize the vortices effectively. Besides, the larger brim tended to encourage the stabilizing effects.

Event date： 2018.12

Language：English  

Venue：Korea Advanced Institute of Science and Technology, Korea   Country：Korea, Republic of  

Event date： 2018.12

Language：Japanese  

Venue：東京、科学技術館   Country：Japan  

Research on the efficiency improvement of wind lens turbines for staggered arrangement

Event date： 2018.12

Language：Japanese  

Venue：東京、科学技術館   Country：Japan  

Performance of Wind Solar Tower that utilizes solar heat and wind simultaneously

Event date： 2018.12

Language：Japanese  

Venue：東京、科学技術館   Country：Japan  

Field experiment on power output of multi rotor system using diffuser augmented wind turbines

Event date： 2018.12

Language：Japanese  

Venue：東京工業大学 大岡山キャンパス   Country：Japan  

Influence of aspect ratio of Wind Solar Tower to its wind collection performance

Event date： 2018.11

Language：Japanese  

Venue：九州大学 伊都キャンパス   Country：Japan  

Event date： 2018.10 - 2018.11

Language：English  

Venue：Hawaii Convention Center, Honolulu HI, U.S.A.   Country：United States  

Wind Solar Tower is a new power-generating device using renewable energies. A similar conventional device known as a solar chimney has utilized the solar energy alone. Besides, its generation efficiency was very low. Therefore, we largely improved the generation efficiency by arranging the shape of the tower from the cylinder type to the diffuser type. At the same time, we attached a vortex generation plate on the tower. The plate enabled the tower to utilize not only solar energy but also wind energy. The simultaneous utilization of renewable energies with one device is notable discovery. We tried the optimization of the tower shape by laboratory experiments (including wind tunnel ones) and numerical analysis. As a result, we found that the diffuser tower with 4° is the optimal shape, and we succeeded in wind-converging whose speed inside of the tower was faster than upper-wind speed, using the vortex generator. Numerical analysis contributed significantly to clarify the mechanisms. Eventually, we demonstrated the simultaneous utilization of the renewable energies in field experiments.

Event date： 2018.6

Language：English  

Venue：PACIFICO Yokohama   Country：Japan  

Event date： 2018.6

Language：English  

Venue：PACIFICO Yokohama   Country：Japan  

Event date： 2017.12

Language：Japanese  

Venue：科学技術館、東京   Country：Japan  

Event date： 2017.12

Language：Japanese  

Venue：科学技術館、東京   Country：Japan  

Event date： 2017.11

Language：Japanese  

Venue：熊本大学、熊本   Country：Japan  

Event date： 2017.11

Language：Japanese  

Venue：熊本大学、熊本   Country：Japan  

Event date： 2017.11

Language：Japanese  

Venue：熊本大学、熊本   Country：Japan  

Event date： 2017.7

Language：English  

Venue：Atlanta   Country：United States  

Event date： 2017.6

Language：English  

Venue：DTU, Copenhagen   Country：Denmark  

Other Link： http://www.wesc2017.org/

Event date： 2017.6

Language：English  

Venue：DTU, Copenhagen   Country：Denmark  

In 1989, a pilot plant of a solar chimney was erected in Manzanares, Spain, to evaluate the feasibility of the solar tower as a new source of renewable energies. Since then, the solar tower was discussed in the press and academic research, but no commercial plant succeeded the development. A reason for this could be very low efficiency, i.e., very low power output compared with other renewable energy production systems. However, a solar tower that can generate electricity in a simple structure, and enables easy and less costly maintenance, has considerable advantages. A solar tower consists mainly of three components. The collector area is a glass roof, above ground with increasing height towards the center. Attached to the center of the collector is a vertical tower inside which a wind turbine is mounted at the lower entry into the tower. When solar radiation heats the ground through the glass roof, the uprising warm air is guided to the center into the tower.
To improve the efficiency in power production for a solar tower, we focused on the shape of the tower and modified the structure from a conventional cylindrical type to a diffuser-type tower. This modification is considered to combine two mechanisms. Firstly, the mechanism to “Generate Wind” which becomes effective when solar thermal energy is available, and secondly the mechanism to “Converge Wind” which becomes effective when wind passes the top end of the diffuser even when solar thermal energy is not available. For a new power generation system using both of wind and solar energies, we named “Wind Solar Tower (WST)”. By combining these two independent concepts which complement one and another, a profitable energy availability power generation system is expected, that is capable of a larger power generation compared to the original solar tower prototype and much larger capacity factor.
As a result of fluid dynamic shape optimization, a diffuser-shaped tower shows an increase in the updraft speed of a scaled model. A remarkable improvement in the power output of the internal wind turbine as much as 4-5 times compared to the cylindrical tower is obtained (Fig.1). Based on the two kinds of laboratory experiments, we are now making a field experiment using a prototype of WST with 10m tower height (Fig.2). We have elucidated that the thermal updraft speed is proportional to the root of tower height and temperature difference between the collector inside and the ambient aloft. In the present research, we propose a new renewable energy device that can harness both sunshine and wind energies. It is now showing a high potentiality, reaching 50 times in power output compared to the Manzanares. Furthermore, almost similar amount of power output by wind aloft over the tower is expected depending on wind condition of the site.

Other Link： http://www.wesc2017.org/

Event date： 2017.5

Language：Japanese  

Venue：新潟工科大学、新潟   Country：Japan  

Event date： 2016.11 - 2016.12

Language：Japanese  

Venue：科学技術館、東京   Country：Japan  

Event date： 2016.11 - 2016.12

Language：Japanese  

Venue：科学技術館、東京   Country：Japan  

Event date： 2010.12

Language：Japanese  

Venue：東京大学、東京   Country：Japan  

Event date： 2006.7

Language：English  

Venue：Yokohama   Country：Japan  

Event date： 2005.4

Language：Japanese  

Country：Japan  

Event date： 2004.11

Language：Japanese  

Venue：科学技術館、東京   Country：Japan  

Event date： 2004.10

Language：Japanese  

Venue：九州大学、福岡   Country：Japan  

Event date： 2004.8

Language：Japanese  

Venue：名古屋大学、愛知   Country：Japan  

Event date： 2004.7

Language：English  

Country：Korea, Republic of