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The purpose of this paper is to conduct a comparative analysis between a straight blade (SB) and a curved caudal-fin tidal turbine blade (CB) and to examine the aspects relating to geometry, turbulence modelling, non-dimensional forces lift and power coefficients.

The comparison utilises results obtained from a default horizontal axis tidal turbine with turbine models available from the literature. A computational design method was then developed and implemented for “horizontal axis tidal turbine blade”. Computational fluid dynamics (CFD) results for the blade design are presented in terms of lift coefficient distribution at mid-height blades, power coefficients and blade surface pressure distributions. Moving the CB back towards the SB ensures that the total blade height stays constant for all geometries. A 3D mesh independency study of a “straight blade horizontal axis tidal turbine blade” modelled using CFD was carried out. The grid convergence study was produced by employing two turbulence models, the standard k-ε model and shear stress transport (SST) in ANSYS CFX. Three parameters were investigated: mesh resolution, turbulence model, and power coefficient in the initial CFD, analysis.

It was found that the mesh resolution and the turbulence model affect the power coefficient results. The power coefficients obtained from the standard k-ε model are 15 to 20 per cent lower than the accuracy of the SST model. Further analysis was performed on both the designed blades using ANSYS CFX and SST turbulence model. The variation in pressure distributions yields to the varying lift coefficient distribution across blade spans. The lift coefficient reached its peak between 0.75 and 0.8 of the blade span where the total lift accelerates with increasing pressure before drastically dropping down at 0.9 onwards due to the escalating rotational velocity of the blades.

The work presents a computational design methodological approach that is entirely original. While this numerical method has proven to be accurate and robust for many traditional tidal turbines, it has now been verified further for CB tidal turbines.

The purpose of this paper is to thoroughly investigate the aerodynamic effects of blade pitch angle on small scaled horizontal axis wind turbines (HAWTs) using computational fluid dynamics (CFD) method to find out the sophisticated effects on the flow phenomena and power performance.

A small HAWT is used as a reference to validate the model and examine the aerodynamic effects. The blade pitch angle was varied between +2 and −6 degrees, angles which are critical for the reference wind turbine in terms of performance, and the CFD simulations were performed at different tip speed ratio values, λ = 2, 3, 4, 5, 6, 7, 9 and 10.5 to cover the effects in various conditions. Results are examined in two different aspects, namely, general performance and the flow physics.

The power performance varies significantly according to the tip speed ratio; the power coefficient increases up to a certain pitch angle at the design tip speed ratio (λ = 6); however, between λ = 2 and 4, the more the blade is pitched downwards, the larger is the power coefficient, the smaller is the thrust coefficient. Similarly, for tip speed ratios higher than λ = 8, the positive effect of the low pitch angles on the power coefficient at λ = 6 reverses. The flow separation location moves close to the leading edge at low tip speed ratios when the blade is pitched upwards and the also tip vortices become more intense. In conclusion, the pitch control can significantly contribute to the performance of small HAWTs depending on different conditions.

In the literature, only very little attention has been paid to the aerodynamic effects of pitch angle on HAWTs, and no such study is available about the effects on small HAWTs. The change of blade pitch angle was maintained at only one degree each time to capture even the smallest aerodynamic effects, and the results are presented in terms of the power performance and flow physics.

Nowadays flaps and winglets are one of the main mechanisms to increase airfoil efficiency. This study aims to investigate the power performance of vertical axis wind turbines (VAWT) that are equipped with diverse gurney flaps. This study could play a crucial role in the design of the VAWT in the future.

In this paper, the two-dimensional computational fluid dynamics simulation is used. The second-order finite volume method is used for the discretization of the governing equations.

The results show that the gurney flap enhances the power coefficient at the low range of tip speed ratio (TSR). When an angled and standard gurney flap case has the same aerodynamic performance, an angled gurney flap case has a lower hinge moment on the junction of airfoil and gurney flap which shows the structural excellence of this case. In all gurney flap cases, the power coefficient increases by an average of 20% at the TSR range of 0.6 to 1.8. The gurney flap cases do not perform well at the high TSR range and the results show a lower amount of power coefficient compare to the clean airfoil.

The angled gurney flap which has the structural advantage and is deployed to the pressure side of the airfoil improves the efficiency of VAWT at the low and medium range of TSR. This study recommends using a controllable gurney flap which could be deployed at a certain amount of TSR.

This study explores the effect of CEO power on earnings quality. If powerful CEOs make the information environment more opaque, they can easily conceal information to hide self-dealing behavior through earnings manipulation. Conversely, if powerful CEOs who are well-protected create a transparent information environment, they will provide better quality earnings.

The author constructs a composite index for CEO power by combining seven CEO characteristics and employs two variables including discretionary accruals and earnings response coefficient as proxies for earnings quality.

The author’s main results show a significant negative relation between CEO power and the firm's earnings quality. In addition, CEOs with stronger structural power and expert power are more likely to generate lower earnings quality, while those with stronger ownership power are more likely to provide higher earnings quality.

The findings suggest that CEO power reduces the firm's earnings quality because CEOs with structural power or expert power may destroy governance monitoring mechanisms.

Three different configurations of vertical axis wind turbines (VAWT) were fabricated by changing the storey height and their orientations. The purpose of this study is to find the effect of storey height and orientation on the performance of wind turbines. The multistory VAWT has three storeys. The first configuration had increased middle storey height, with 0–90-0 orientation of blades. Wherein the second turbine had equal storey heights. The third configuration had increased middle storey height with 0–120-240 orientation of blades. The blades were tested numerically and experimentally.

In this research work, prototypes of innovative multistory VAWT were built with different configurations and orientations. Three configurations of three-storey VAWT were fabricated by varying the height of storey of turbines. The orientations were made by keeping the storeys orthogonal to each other. Multistory VAWT was tested numerically and experimentally. ANSYS Fluent was used for computational fluid dynamic analysis of VAWT. K-epsilon model was used for numerical analysis of wind turbine. Experimentation was carried out in a wind tunnel for different tip speed ratios (TSR).

The three configurations of innovative multistory VAWT were tested numerically and experimentally for different TSR. It has been found that the VAWT with equal storey height had a better performance as compared to the other two configurations with increased middle storey height. The power coefficient of equal storey height VAWT was about 22%, wherein the power coefficient of turbines with reduced upper and lower storey height was between 5%–8%.

The research work of multi-storey VAWT is very novel and original. The findings of the research will contribute to the existing work done in the field of VAWT. This will help other researchers to have insight into the development of multistory VAWT. The effect of storey height and configuration of multi-storey VAWT is studied numerically and experimentally, which concludes that the performance of equal storey is superior as compared to other configurations.

The multi-storey concept of VAWT was developed to counter the problem of wind direction. The blades of each storey were arranged orthogonal to each other. This helped to harness wind power irrespective of the direction of the wind. This will make the VAWT more sustainable and financially viable for domestic use.

The turbines are specially designed for remotely located housed in rural areas where the power grid is not yet reached. Users can install the turbine on their rooftop and harness wind power of 100 W capacity. This will help them to make their life easy.

This research work is very original and first of a kind. The multistory concept of the wind turbine was checked for the effect of storey height and orientations of blades on its performance. Different configurations and orientations of the vertical axis were designed and developed for the first time.

This study aims to form a new concept of power-to-gas-based virtual power plant (GVPP) and propose a low-carbon economic scheduling optimization model for GVPP considering carbon emission trading.

In view of the strong uncertainty of wind power and photovoltaic power generation in GVPP, the information gap decision theory (IGDT) is used to measure the uncertainty tolerance threshold under different expected target deviations of the decision-makers. To verify the feasibility and effectiveness of the proposed model, nine-node energy hub was selected as the simulation system.

GVPP can coordinate and optimize the output of electricity-to-gas and gas turbines according to the difference in gas and electricity prices in the electricity market and the natural gas market at different times. The IGDT method can be used to describe the impact of wind and solar uncertainty in GVPP. Carbon emission rights trading can increase the operating space of power to gas (P2G) and reduce the operating cost of GVPP.

This study considers the electrical conversion and spatio-temporal calming characteristics of P2G, integrates it with VPP into GVPP and uses the IGDT method to describe the impact of wind and solar uncertainty and then proposes a GVPP near-zero carbon random scheduling optimization model based on IGDT.

This study designed a novel structure of the GVPP integrating P2G, gas storage device into the VPP and proposed a basic near-zero carbon scheduling optimization model for GVPP under the optimization goal of minimizing operating costs. At last, this study constructed a stochastic scheduling optimization model for GVPP.

This study examines the association between Chief Executive Officer (CEO) power and the level of corporate social responsibility (CSR) disclosure, as well as the moderating role of stakeholder influence on this association.

Using a sample of 986 Bangladeshi firm-year observations, this study uses a content analysis technique to develop a 24-item CSR disclosure index. The ordinary least squares regression method is used to estimate the research models, controlling for firm-specific factors that potentially affect the levels of CSR disclosure.

The study findings indicate that CEO power is negatively associated with the level of CSR disclosure, and that the negative effects of CEO power on the level of CSR disclosure are attenuated by stakeholder influence. CEO power is documented as reducing the positive impact of CSR disclosure on a firm’s financial performance, with this negative impact attenuated if stakeholders have greater influence on the firm.

This study suggests that CEO power and stakeholder influence are important factors in determining firms’ incentives to disclose CSR information. Both CEO power and stakeholder influence need to be considered in the CSR – firm performance nexus, given the mixed findings documented in the literature.

This study makes a significant contribution to the literature on CSR practices by documenting that firms with a powerful CEO have lower levels of CSR disclosure, and that stakeholder influence affects CSR disclosure in the emerging economy context.

In less competitive markets, firms with market power are likely to exercise pricing power by setting output prices above their marginal cost, inducing welfare losses from resource misallocation, managerial inefficiency and market instability. In order to address such market imperfections, it is important for regulatory authorities to identify the sources of pricing power and devise policies to address their adverse effects. In this context, the purpose of this paper is to undertake an empirical analysis to identify the determinants of pricing power in the South African non-life insurance market.

The authors estimate the Lerner competitive index as the proxy for pricing power using annual data on 79 firms from 2007 to 2012. In the second stage, the paper employs panel regression techniques in the ordinary least squares, random effects and generalised method of moment’s estimations to examine the effect of insurer level characteristics on pricing power.

The authors find the market to be characterised by firms with high pricing power. Domestic-owned insurers are found to exercise high pricing power compared with foreign-owned insurers. The authors also identify size, cost efficiency, product line diversification, market concentration, leverage and reinsurance contracts as the significant predictors of pricing power in the market. Finally, through a quantile regression analysis, the authors find the effect of cost efficiency, business line diversification and reinsurance to be heterogeneous across different quantiles of pricing power.

The findings provide regulatory authorities with useful indicators in addressing anti-competitive behaviour in high pricing power to enhance the stability of the insurance market and improve consumer welfare and economic development.

To the best of the authors’ knowledge, this is first paper to examine the determinants of pricing power and competitive behaviour in an insurance market.

The aim of this paper is to explore the specific relationship between managerial power and enterprise innovation performance. Combined with managerial power theory and stewardship theory, financing constraints and strategic orientation, including, strategic market orientation and strategic technology orientation are included in the analysis framework to test how managerial power influences enterprise innovation performance in detail from the perspective of enterprise internal influence mechanisms.

Based on the A-share listed companies in Shanghai and Shenzhen covering the period from 2001 to 2017, this paper uses the ordinary least square method (OLS) to explore how managerial power affects enterprise innovation performance.

The results show that managerial power has a positive impact on enterprise innovation performance. Furthermore, the authors find that financing constraints, strategic market orientation and strategic technology orientation all have partial mediating effects in the relationship between managerial power and enterprise innovation performance.

This paper verifies the application of managerial power theory and stewardship theory in the relationship between managerial power and enterprise innovation performance in Chinese A-share listed companies, contributing to the literature on enterprise innovation. Moreover, by introducing the mediating mechanisms of financing constraints, strategic market orientation and strategic technology orientation, this paper builds an effective path for in-depth study to analyze how managerial power influences enterprise innovation performance and finds ways to improve enterprise innovation performance from the inside view of the enterprise.

The rapid rising of renewable energy sources particularly wind energy cannot be ignored. The numerical increase in wind energy farms throughout the world is the best example. The purpose of this paper is to assess the basic question of whether wind characteristics affect the performance and cost of energy. The importance of this question cannot be ruled out while comparing renewable energy to a conventional form of energy more specifically especially for the developing country where the cost of energy is very high.

The research design of this paper is consists of an assessment of local wind characteristics of the wind farm site using Weibull k and c parameters. The performance model is used to assess the performance of the wind turbine (WT) corresponding to local wind characteristics. The wind correlation with WT in terms of changing wind speed has been assessed to quantify the effects of wind speed on the WT behavior and failure of WT components. Similarly, the power curve of WT is assessed and compared with the International Electrotechnical Commission standards 61400-12-2. The WT power coefficient and tip speed ratio corresponding to wind speed is also investigated. The energy volume and cost of energy lost model is used to determine the cost and volume loss of energy/kWh of the wind farm.

The findings of practical wind farms showed that the wind conditions of the site are showing a strong tendency that can be determined from the results of Weibull k and c parameters. The k and c parameters are observed to be 3.44 and 9.16 m/s, respectively, for a period of a year. The standard deviation is observed to be 2.56 for a period of a year. WT shows the efficient behavior can be obtained from the power coefficient and tip speed of WT at different wind speeds. Also, wind farm observation showed that to be some increasing wind speed cause of based WT component failures. The results of energy volume and cost/kWh assessment showed that the major portion of energy volume and cost of energy is lost owing to network, voltage dip and frequency surge, electrical and mechanical components failures.

Generally, it can be concluded that the WTs are now able to cope with variable wind speeds. However, the results of this paper are showing that WT performance and availability decreased due to increased wind speeds. It can also be a reason to decreased volume and increase the cost of energy/kWh.