This paper presents a new design scheme of the pervious to light eaves. The new eaves have solved the problem that some traditional slope roofing buildings in china, with far-reaching eaves, which lead to insufficient indoor sunshine and insufficient lighting.

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SF roof (a sloping roof combined with a flat roof) is a special kind of roof existed in the Ningqiang region. SF roof isdesigned by local residents according to their experience of life. Based on experimental test, this paper discussed such roof and normal flat roofs of rural houses in the Ningqiang region of west China. It can be found that, comparing with the flat roofs, SF roof with a heat insulation transformation has better thermal insulation performance in the research region. Testing process of the research is introduced, results of the testing are discussed and conclusions are provided.

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This study examines the application of a porous model in computational fluid dynamics (CFD) analysis to simulate the effect of passive cooling method to form a comfortable outdoor thermal environment. We developed a passive cooling louver with evaporative cooling function, which can not only reduce solar radiation and provide ventilation, but also generate cool radiation and provide cool air. These functions were evaluated using CFD analysis with human scale resolution by treating the louver as an equivalent columnar porous media, to decrease the computational load.

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The electric power generation from solar powered house has tend to excess the electric consumption. This study focuses on maximizing simultaneous power consumption at grid-connected solar powered energy efficiency house from the aspect of self-consumed power. In order to evaluate the simultaneously consumption, the absolute values of the sum total of plus and minus grid power is calculated using our prototype solar powered energy efficiency house’s instantaneous measurement value for every minute of electrical power flows data. From the result, the minimum dependency of grid power and optimum install photovoltaic power capacity with the maximum simultaneous power consumption are estimated.

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Zero energy house are emerging as a solution for global climate change and energy depletion. To build a zero energy house, it is necessary not only to use passive technologies that minimize energy loss, but also use energy efficiency technologies and renewable energy technologies. Photovoltaic (PV), which is a representative renewable energy source for zero energy house, needs an energy storage system (ESS) to supply power at any time because the PV power system (PVPS) only supplies power during times of solar radiation. In addition, the ESS is used to reduce electricity prices by shifting the peak loads in Time-of-Use (TOU) rates. In Korea, a residential ESS is not available because of the high price of an ESS, a low electricity price, a progressive rate scheme (or increasing block rates), and a low penetration rate of residential with PVPS. This paper presents the conditions in which a residential ESS with a PVPS are applied using HOMER (Hybrid Optimization of Multiple Energy Resources) in Korea.

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Japanese traditional wooden houses are designed to spend cool in summer by promoting as much wind flow through the house as possible. But, these houses have low thermal insulation performance. In this paper, we proposed a partial insulation renovation for Japanese traditional house. We applied this method to Kyo-machiya and verified the effect of the renovation. Insulated sliding-doors were developed by using Japanese traditional techniques. As the results, the thermal environment in the insulated compartment was improved without changing the original interior design. The insulated sliding-doors were effective for improvement of the surface temperature and of the air-tightness.

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The purpose of this research is to study design specification toward ZEB for office building in snowy cold cities. By using the BEST program in calculation and adopting DOE, we decide the building specifications that minimize annual thermal load. Next, we examine the equipment specifications that minimize primary annual energy consumption for the minimum thermal load specifications. Finally, we aim to achieve ZEB by introducing renewable energy. As a result, as reduction rate of annual energy consumption for the standard specifications, the minimum thermal load specifications reduce 28.2%, and the equipment standard specifications reduces 54.2%. Moreover, the high-performance specifications reduce 61.6%. By the introduction of renewable energy, it is possible to realize ZEB Ready.

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The outdoor wind environment of the building is an important part of the city's microclimate, and it s also an important factor that affects the urban ecological quality. Research shows that different layout forms different flow fields. This paper takes the engineering group of Henan University of Science and Technology as an example, the ENVI-met numerical simulation software is used to simulate the wind environment in the architectural design project. According to the simulation results, the architectural layout will be optimized to achieve a good ventilation environment, so that promote the cooling of buildings and reduce energy consumption.

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Zero-energy-homes district has been developed in Kumagaya, a suburban city of Tokyo. Total of 73 houses of the district are all constructed with highly insulated wooden panels. Air-conditioners, hot water supply system, lighting equipment and ventilation system are carefully selected to minimize the energy consumption. HEMS, home energy management system, controls the windows and air-conditioners automatically so that the cooling load can be reduced without sacrificing thermal comfort even in summer. The houses are also equipped with Photovoltaic (PV) panels and city gas powered co-generation system. Electricity and gas consumption of the houses are now measured hourly. Power generations from PV panels as well as the co-generation systems are also measured. 22 out of the 73 households are now ready for evaluation since those families have lived in the district for more than a year. The data reveals that the annual energy balances of the households are “zero” on average.

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Extreme temperature occurs recently. By the end of 2017, south side of the world suffers heat while some areas in the north part endure a low, record-breakingtemperature. To cope with this situation, amount of energy for air conditioning will increase. This paper will show the possibilities of reducing energy used for heating load in annual energy cycle by using mini louvers frame. Three different mini louvers designs will be tested for eight orientations. Three different cities, located from north to south Japan, are chosen. Building simulations will executed and analyze to examine mini louvers performance of cooling load reduction.

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Thermoresponsive light attenuators, which efficiently switch between transparence and haze as a function of temperature, are a promising candidate for applications in smart windows for energy-saving buildings and vehicles. We have developed reverse-mode thermoresponsive polymer network liquid crystals (PNLCs) to be applied to smart windows. This reversible optical behavior in response to ambient temperatures is readily used because the devices do not need intricate apparatuses for operation such as an external power supply, wiring, ITO transparent electrodes, and so on. The fabrication process is simple for users and manufacturers; that is, the mixture of LCs and reactive mesogens (or LC monomers) is sandwiched a clearance of 30 micro m with antiparallel rubbing-treated transparent substrates and then is photopolymerized by exposure of ultraviolet light to induce meso-scale phase separation.

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Using a microphone array, a wind tunnel experiment for a straight-bladed vertical-axis wind turbine (VAWT) was carried out to investigate the effects of the arm’s cross-sectional shape on the power performance and aeroacoustic noise. As a result, the amount of power reduced by the ellipse arms was significantly smaller than the rectangle arms and slightly larger than the airfoil arms. In addition, the values of the overall A-weighted sound pressure level (OASPL) in the case of using the ellipse arms were significantly lower than those of using the airfoil arms and almost the same as the rectangle arms. Also, at the high frequency range, A-weighted SPL of the ellipse arm case was significantly lower than that of the airfoil arm case.

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Since the wind turbine system comprises many parts and components from various manufacturers, the facts of the Japanese wind industries had not been clear for a long time. Recently the Japanese government is considering the promotion of wind turbine industries from the view point of global warming prevention and accelerates wind turbine’s installations in Japanese severe environmental conditions. Several statics have been done about wind industries by eminent organizations. Local component suppliers and system integrators are expected to play key roles in domestic production of wind turbines suited to local environmental conditions. This paper aims at gathering information and showing analytical results of the researches performed by JSIM, JEMA, JCRE, etc. to find out proper strategy for Japanese wind turbine industries.

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In the Japanese wind turbine market there are many competitions between the number of 12 domestic and foreign larger sized wind turbine manufacturers. Recent 10 years from 2008 to 2017, there have been many drastic movements: abolishment of subsidy system, introduction of feed in tariff, liberalization of the electricity market, enforcement of environmental assessment act and change of manufacturers’ share of wind turbine. In spite of the electricity price of 22 JPY kWh-1 the market had been shrunk for several years. Japanese accumulated installation value also still much lower than what is expected by its GDP. This paper summarizes the ten-year movement of wind turbine manufacturers and suppliers in Japan to find out proper strategy for Japanese wind turbine generation business.

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Wind energy capacity has increased rapidly in recent years, and this trend is expected to continue according to various forecasts. Although wind energy can offset emissions from fossil-fueled power plants, there are potential environmental challenges associated with continued expansion of wind projects around the world that warrant scientific study to ensure they do not become critical issues. Potential environmental challenges include: lifecycle air emissions, lifecycle water use and water quality impacts, land use and wildlife impacts, end-of-life decommissioning and disposal, and human health impacts. Our literature review describes the environmental challenges related to wind energy and identifies associated research needs.

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Human-caused deaths of 10-30 white-tailed eagles (Haliaeetus albicilla, hereafter WT eagles) were reported every year in Japan. Among these, 7 or more individuals on average were killed or suspected to be killed by avian collisions with wind turbines. Importance of cumulative impact assessment is asked in Japanese environmental impact assessment (EIA) procedures. We have no guideline of methods to reduce the cumulative impact in Japanese EIAs. If the population persistence of endangered raptors is an endpoint of EIAs, potential biological removal (PBR) is probably a good indicator to decide the limit of cumulative avian collisions. In many birds, e.g., white-fronted geese or other migratory geese, the actual collisions are definitely lower than PBR. But avial collisions of the WT eagles is probably more than PBR. The PBR of WT eagles depends on scenarios; (1) including migratory eagles in wintering or not and (2) intrinsic growth rate. We propose how to evaluate PBR of WT eagles and discuss about how to utilize this indicator to future EIAs of wind farms in Japan.

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In Japan, the power grid is regionally divide by utility companies, then the wind power potential is not effectively developed. The purpose of this research is to establish the stand-alone power generation system by means of offshore wind power generation in ports and coastal area. It is necessary to know the variance characteristics of demand of electric power in port facilities. This paper shows investigated the electric power usage in two ports those are located at the west coast of Hokkaido and the northernpart of Kyushu. The time variance characteristics of electric power consumptionin a port are estimated depends on wharf operation data such as cargo handling and so on. The difference of demand in the port facilities and supply by wind energy generation by use of offshore wind turbinesis analyzed. The countermeasure to reduce the gap of demand and supply with the storage battery system is also discussed. And its reduction effect of carbon dioxide is analyzed.

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It is necessary to evaluate the economic benefit of introducing enhanced O&M technologies quantitatively as it is the key to promote such technologies to the wind power market and hence increase the occupancy rate of wind power equipment. This paper shows the way to verify and evaluate the economic benefit of enhanced O&M technology using CMS vibration acceleration sensor as an example by using "wind power generation risk assessment model". Based on the result of the evaluation, introduction of enhanced technology can be expected to raise the IRR in the scenario where a major accident occurs. From the viewpoint of risk management, evaluating the economic impact of loss and the way to minimize the influence quantitatively is good for the wind power project so improving the accuracy of the evaluation results by accumulating data.

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In this study, levelized cost of energy (LCOE) was assessed considering uncertainty in downtime and repair cost by using NEDO database. Firstly, NEDO database was implemented and validated by using METI database, which enabled reliability analysis in Japan. Then, probabilistic models of downtime and repair cost were built by using beta function for each downtime bin. The correlation between downtime and repair cost were modeled by using t copula. Predicted downtime and repair cost showed good agreement with observation in NEDO data. Finally, LCOE was evaluated by using the proposed downtime and repair cost models and cost reduction scenario was investigated to clarify the cost reduction effect of smart maintenance.

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We conducted a questionnaire research to clarify the acceptance of wind projects by people who have not disclosed their opinions. The main results are that fewer respondents could either see X Wind Farm, including the flickering or hear the noise, and fewer respondents were annoyed by X Wind Farm. Moreover, most of the respondents had a positive attitude toward X Wind Farm. Nevertheless, approval for the new wind farm was low. The study shows that having both a positive feeling toward X Wind Farm and an original positive attitude toward wind energy tend to foster positive acceptance.

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The paper deals with the transition of the Danish power system from a fossil fuel based system in 1990 to the present system with about 40 % wind power penetration. The paper describes the status of the system and the future targets. Weight is on explaining how this development has been possible while at the same time maintaining one of the highest security of supply levels in Europe. The key is flexibility provided by a strong internal transmission grid, strong interconnections to neighbors, well-functioning international markets, flexible generation units, market based system operation and integration across energy sectors.

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This paper presents a new operational strategy for a large-scale wind farm (WF) which is composed of both fixed speed wind turbines with squirrel cage induction generators (FSWT-SCIGs) and variable speed wind turbines with permanent magnet synchronous generators (VSWT-PMSGs) or VSWT with doubly fed induction generators (VSWT-DFIGs). SCIGs suffer greatly from meeting the requirements of low voltage ride-through (LVRT). On the other hand, PMSG and DFIG have sufficient LVRT capability and can also control active and reactive power delivered to the grid independently. But PMSG and DFIG are expensive due to its full or partial power rating AC/DC/AC converter. Therefore, combined installation of SCIG with PMSG or DFIG could be an effective solution. A suitable fuzzy logic controller (FLC) is proposed in the cascaded controller of grid side converter (GSC) of PMSG and rotor side converter (RSC) of DFIG to perform effective reactive power injection to the grid and improve the LVRT capability during transient period of WF which is mainly composed of SCIG. Simulation results clearly show that both PMSG and DFIG could stabilize larger rating of SCIG in a WF, but DFIG is more superior as it is inexpensive compared to PMSG.

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It has been confirmed that the voltage flicker due to the connection of a sole small wind turbine (SWT) is not so severe in general. However, the voltage flicker due to the connection of multiple SWTs is a great concern. Thus, the measurement of the output power and voltage flicker at the point of common coupling of four SWTs has been conducted. Furthermore, correlation coefficients among output power fluctuations of respective SWTs have been analyzed. As a result, it was confirmed that output power fluctuation of SWTs is almost independent on the higher frequency components than 2 Hz, and the voltage flicker by a few 5-kW class SWTs is not so severe at least.

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Output power of a wind turbine system is recognized to fluctuate more than that of a photovoltaic (PV) power generation system in general, and there is a concern that small wind turbines (SWTs) may cause severe voltage variation and flicker in low voltage distribution lines. In this paper, characteristics of output power fluctuation of a 5-kW class SWT system are analyzed, and compared with a same class PV power generation system. The result indicates that the high output power variation occurs much more in the SWT system.

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A laboratory scale testbed to demonstrate frequency regulation has been established by a reciprocating engine generator with a flywheel. The flywheel is connected coaxially to the shaft of the engine generator through the powder clutch, because it is supposed that direct connection makes starting of the engine difficult. By connecting the flywheel, both the steady state power/frequency characteristic and the per unit inertia constant of the testbed are in the range of typical Japanese power system, and frequency fluctuation in steady state is decreased to tolerable level for the frequency measurement by developed control boards.

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In the R&D project of the New Energy and Industrial Technology Development Organization, wind farm measurement network is established in eastern part of Japan and ramp forecasting technologies using the collected data are being developed. To evaluate the ramp forecasting performance of developed technologies, we select various metrics suitable for each forecast outputs. Critical Success Index (CSI) is defined as the primary metric in the project. We conduct ramp forecasting by the existing and developed technologies over the past period and compare their ramp forecasting performance. The developed technologies show better ramp forecasting performance than the existing technologies.

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We developed a methodology to unify a collection of time series predictions by a wide variety of time series prediction methods. The proposed ensemble method produces a weighted average of multiple predictions. The method is designed to be highly versatile and adaptable as it can be used for unifying time series predictions with different structures such as the time of delivery, the time resolution, the updating frequency and the prediction lead time. We implemented the ensemble method into a wind energy ramp forecasting system, where multiple forecasting methodologies including meteorological factor analysis, an ensemble forecast method, a statistical method, a machine learning based method and a dynamical systems theory based method are built in. Our method successfully produced the single prediction that results in better performance over other individual predictions.

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A forecast system to predict wind power ramps was developed and applied to evaluate the similarity between sea level pressure (SLP) patterns in global-scale model forecasts and weather patterns associated with abrupt wind speed changes. The settings of the Weather Research and Forecasting model are selected according to the SLP pattern in global-scale model forecast. Wind forecast data are converted to power output, and a principal component analysis of SLP data is used to identify and forecast wind power ramps and to compute ramp probabilities and ramp alerts.

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In the design of wind turbines, it is necessary to confirm that it has durability in various conditions assumed to be experienced in the lifetime. Among them, the state where wind turbine stops generating electricity and stands by at extreme wind speed is one of the most severe conditions. Passive yaw control is one of methods which could reduce extreme loads in the condition. In this paper, the evaluation method of load and wind turbine behavior in passive yaw control was proposed and the effectiveness of it was verified by actual measurement data. In the method, the change rate of wind direction is introduced as new input parameter and the influence of it on the load and wind turbine behavior were studied. In addition, the load reduction effect by the passive yaw control was confirmed.

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Shift to renewable energy is a nation-wide trend in Japan after 2011. Although wind power is one of the hopeful renewable energy sources, energy cost is not competitive and introduction amount is insufficient. Especially in the Northeast region of Japan(Tohoku), wind energy is strongly focused, since relatively strong seasonal wind blows. But the weather condition, industrial backgrounds, energy demand, etc. in Japanese Northeast are rather different compared to other regions in Japan. Thus, failure factor and effect on downtime should be estimated individually. This study focuses on practical failure factor in wind turbines of Japanese Northeast and carries out dynamic modeling of failure possibilities. failure modes and estimated downtimes. The result shows increasing possibility of winter thunder and some other causes are relatively important in this region and maintenance planning should respond to these failure modes. Finally, the paper concludes that proper maintenance planning corresponding to the regional situation can be a promising way to reduce energy cost and to boost installing of renewable energy.

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An investigation of an onshore wind turbine foundation was performed. The crack inspection on the top surface of footing and measurements were conducted to determine current damage state of the foundation. FE analysis was employed to predict the failure mode. The structural model including the piles and surrounding soil but excluding the tower was built. According to the static analysis with monotonic loading, the crack which had occurred from the tip of anchor plate, reached to the top surface of footing. This suggested that the failure mode of the foundation is possibly a corn-shape failure of the footing concrete.

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Hitachi, Ltd. has developed 5MW class downwind wind turbines to meet the increasing demand for larger offshore wind turbine. Using ground mounted Doppler Lidar (ZephIR 300), Hitachi has conducted power curve test at Fukashiba, Ibaraki prefecture, Japan. It was found at this site, wind shear measured with Doppler Lidar varies significantly with wind direction. Scatter in the power curve was analyzed by means of power standard deviation for different corrections applied to the wind speed including wind shear, wind veer and turbulent intensity filtering. It was found that wind shear correction has the most effect on scatter mitigation for this test. Also wind correction was found to have an adverse effect for some wind speed bins. The corrected power curve showed very similar result to simulated power curve, which is obtained by applying turbulence intensity correction to steady power curve.

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Using scanning LiDAR (Light Detection and Ranging) systems which are measurement devices to observe winds within about 10 km are a promising way to reduce technical and financial constrains for offshore wind resource assessment in coastal water. However, the accuracy of scanning LiDARs for offshore wind measurements is not well investigated. In this study, we have started an experiment campaign using a scanning LiDAR of Windcube200S at a coastal research platform in Japan. The wind condition obtained from the scanning LiDAR using a DBS (Doppler Beam Swing) method is compared with that from a sonic anemometer installed on the research platform. As a result, the wind speeds and directions from the scanning LiDAR exhibit a good agreement with those from the sonic anemometer.

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The airborne wind energy generation is in rapid progress recent years as was presented in the international conference AWEC 2017 held on 2017 October. The Japanese project is now at the 1.5 phase employing a straight blade windmill consists of two windmills. The windmill is examined its performance in a wind tunnel for the windmills of phase 1.5, 0.6m diameter and 1.2m total span, and of phase 1+, 0.3m diameter and 0.6m total span. The performance is also examined by field tests as a demonstration for of effective energy transfer through the tether. Technical key points are also in examination for the project by the coordination of professional teams.

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This paper uses a simple model to derive the governing equation for the kite motion using turn rate law. Parameter estimation technique was applied to derive the system’s parameters in real-time. The parameter estimation was used due to the uncertainty of the kite, this uncertainty comes from the change in wind speed and direction. A comparison between the governing equations and the results of the system identification was presented. Finally, a classical control was used for the stabilization of the kite. Simulation results for the model and system identification are presented to compare between the accuracy of the parameter estimation with the mathematical model.

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CFD has become the method of choice in the design of many aerospace, automotive, and industrial components and processes in which fluid or gas flow play a major role. This paper presents the performance analysis of the Horizontal Axis Wind Turbine (HAWT) using CFD modeling, comparing with experimental data obtained from the wind turbine experiments carried out by Vermeer. The 3-D CFD calculations is done for the subsonic flow over a wind turbine rotor at various values of tip speed ratio and operating at a Reynolds number of 200,000. In this analysis, three CFD turbulence models Spalart Allmaras, k-𝜔 and Transitional SST are performed to evaluate the thrust coefficient and power coefficient that agree with the experimental data of wind turbine. The work also uses the wind turbine as an example to discuss the verification of experimental results by using CFD.

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In this study, a simulation of a wind turbine wake are performed to investigate distributions of wind fluctuation by using unsteady computational fluid dynamics (CFD). In this CFD framework, rFlow3D, which was developed by Japan Aerospace Exploration Agency (JAXA) was used. Higher-order scheme (4th order) is applied in time and space respectively. Moreover, it can solve full rotor simulation and reproduce fluctuations generated by a wind turbine. Time-series data of wind velocities in wake region are obtained to evaluate distributions of wind fluctuations. The result confirmed that wind distributions in wake region are not uniform along radial positions.

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Circulation control, augmenting aerofoil lift and reducing drag using air jets is long established but little considered for wind turbine applications. This is a top-level exploration of the basic concept which involves a substantial part of the rotor blade having low solidity, elliptical sections which generate little lift and drag when passive, greatly moderating extreme storm loads when the rotor is idling. The CC rotor can then be expanded in diameter by ~ 30% within the same loading envelop of a standard rotor with gain in energy capture to compensate for added cost in the rotor systems.

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In the study wind tunnel experiments are conducted to investigate pressure distribution on a wind turbine nacelle for uniform and turbulent inflow conditions. To that end pressure field data is collected using pressure taps distributed over one side of an ellipsoid type nacelle. It was found that although the higher inflow turbulence increases the magnitude of maximum and minimum pressure in regions away from the tower, minimum peak pressure under uniform inflow in the region influenced by the tower is lower than that of high turbulence inflow case. It was further found that the maximum peak pressures are the function of inflow turbulence and can be estimated accurately using conventional approach (Eurocode). However, the negative peak pressure downstream of the tower for uniform inflow is significantly underestimated by such conventional approach. This is because the effect of tower is more pronounced when the inflow is uniform.

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Magnus wind turbine is a wind turbine that uses Magnus effect to generate electricity. The lift force was measured by using three models (cylinder with no fins, cylinder with straight fins and cylinder with spiral fins) in a wind tunnel testing and it was confirmed that the high lift force was generated by the cylinder with spiral fins. Alternatively, there was no difference in lift force between the straight and spiral fins under low rotational speed condition. It was confirmed that the vortex behavior produced by the interaction between the freestream and the fin was significantly related to lift generation.

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Brimmed-diffuser augmented wind turbines (B-DAWTs) can significantly increase the performance of the rotor. Multi-rotor 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 and five B-DAWTs placed in close vicinity have been investigated. Results show a significant increase of up to 12%-20% in total power output of the MRS with B-DAWTs compared to the sum of the stand-alone 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.

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The Wind Solar Tower (WST) is a power-generating device which can harness solar energies and wind energies simultaneously. Its turbine is driven by an updraft induced in the tower. The updraft is commonly induced by solar heating. However, we made it clear that the updraft can also be induced by wind blowing around the top of the tower. We designed the shape of the WST to generate the updraft effectively. By wind tunnel experiments and numerical simulations, we found that a diffuser-shaped tower and a vortex generator which is installed on the top of the tower produce the updraft effectively.

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The weight of the rotational axis of a VAWT with wings attached is very heavy. Therefore, VAWT is difficult to start rotating in the condition of low wind velocity. The author has new ideas. These are low friction bearings. And the assumed name is Pivot ball type. These are suitable for radial-load bearings and for thrust-load bearings. These characteristics are measured in two different ways. And the author proved the superior characteristics of these new types of bearings.

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The aim of this paper is to computationally investigate unsteady flow around an autorotating drag-type vertical-axis wind turbine which consists of three quarter circular-arc blades attached to a cylindrical core. Three values of the attachment angle of the circular-arc blades are selected as alpha (20 degree, 40 degree and 45 degree). The vortex particle method is adopted as a computational procedure. As a result, autorotation of the rotor can be simulated successfully, and it can be found that the rotor oppositely rotates between alpha less than 45 degree(forward) and alpha equal/more 45 degree(backward). In particular, the initial vortex shedding from the blades can be found to play an important role for starting up.

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In this research, we propose the development of passive pitch-stall control mechanism in order to prevent over-rotation of small-scaled wind power generation system. At first, we introduce the conventional dynamics which shock absorber (spring and damper) is utilized in the passive pitch-stall control for recovery of stalled pitch-angular by the centrifugal force of the blade. Secondly, we introduce the modified dynamics of passive pitch-stall control system that consider the thrust force when excessive rotation occurred. So far, dynamics of pitch angle and blade were considered as two simultaneous non-linear differential equations with stall coefficient in whole system. In this research, we could realize more significant result and will get the more precise dynamics by implementing the term of thrust force in the dynamics of blade and pitch angle.

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This paper studies aerodynamic noise emitted from the vertical axis wind turbine, equipped with a wing to control the vortex from the cylinder. Aerodynamic noise was investigated by changing dimensionless ratio G/D where G the gap between the cylinder and the wing, and D the cylinder diameter. Aerodynamic noise was evaluated by time derivative of pressure fluctuations on the wing surface. Consequently, the frequency analysis is performed with FFT for the pressure fluctuation on the wing surface, aerodynamic noise tends to be reduced if G/D is more than 1.5.

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This paper introduces results of a field study using the offshore observation tower system constructed Off Kita-Kyusyu City. The purpose of the study is to clear-up the influence of wave characteristics for the rational design and maintenance of offshore wind turbine support structures. For efficient maintenance of offshore structures such as wind turbines and observation towers, wave conditions were proved to be critical for accessibility evaluation and an empirical diagram was proposed. By using the diagram, it was clarified that there exists a great difference of the accessibility between for the Pacific side and for the Sea of Japan side, in both winter and summer. The characteristics of co-occurrence of high waves and strong winds were also clarified based on offshore simultaneously observed data. The results will be useful for more reasonable design condition setting.

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Added mass coefficient (Ca) and drag force coefficient (Cd) plays an essential role in dynamic response of floating offshore wind turbine (FOWT). A method is proposed to combine KC number dependency and wake effect in Morison’s equation. Firstly, wake effect on Ca and Cd of cylinders, which is caused by multimember arrangement in semisubmersible floater of offshore floating wind turbine (FOWT) is investigated by compactional fluid dynamics (CFD) simulation. Secondary, accuracy of added mass matrix of Morison’s equation is presented by comparison with global matrix of potential theory. Relationship between KC number and hydrodynamic coefficients of single cylinder is used for cylinders of semisubmersible floater. Then, global Ca and Cd in wide range of KC number is predicted based on CFD result after correction by wake effect. At last, effect of wake and KC number dependency of Ca and Cd on dynamic response of FOWT is discussed. Result indicates wake and KC number dependency is important for dynamic response.

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This paper investigated the response of semi-submersible type floating offshore wind turbine (FOWT) for different wind turbine size in order to evaluate cost reduction effect of large turbine size. Firstly, semi-submersible floaters for 2MW, 5MW, and 10MW were modeled based on the design used at Fukushima FORWARD demonstration project. Then, dynamic analysis was performed in DLC 6.1 case and it was confirmed that the floater response were almost same response and that mooring force increased with larger turbine. Finally, equipment cost per rated power was evaluated for different turbine sizes by using the weight of built model. The cost reduction effect were quantitatively evaluated for equipment cost and construction cost.

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Floating offshore wind turbines (FOWTs) can be subject to platform-pitching vibrations caused by blade pitch angle (BPA) motion. We proposed a control method for suppressing these vibrations and confirmed that it reduced the power below rated operating conditions. This report proposes an individual BPA control for FOWTs that improves the power performance below rated operating conditions. Its key function is to control rotor speed by recovering deviations of BPA from the optimal values, although the deviations are generated to suppress the vibrations. A demonstration using a full-scale 2 MW FOWT with a spar showed that the proposed control improved power performance.

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