Assessment of utilization of wind energy resources in Nigeria

The study critically reviews the prospects and challenges of utilizing wind energy resources for power generation in Nigeria. The various initiatives by governments and researchers were surveyed and the nation is found to sit in the midst of enormous potential for wind harvest for power generation. The far northern states, the mountainous regions and different places of the central and south-eastern states were identified as good areas for wind harvest together with the offshore areas spanning from Lagos through Ondo, Ogun, Cross-Rivers to Rivers states along the Atlantic Ocean in the south–south. Despite this great potential and huge prospect, the country is found to still suffer from serious energy crises due to her over dependence on hydropower which also is susceptible to seasonal variation in the amount of water levels at dams. There is yet to be committed wind energy project for power generation on-going in the country. Several challenges bedeviling the development and utilization of wind energy resources were identified and suggestions highlighted to help pull the nation out of this lingering energy crisis.     

Impact of public policy uncertainty on renewable energy investment: Wind power and the production tax credit

It is generally understood that the pattern of repeated expiration and short-term renewal of the federal production tax credit (PTC) causes a boom–bust cycle in wind power plant investment in the US. This on–off pattern is detrimental to the wind industry, since ramp-up and ramp-down costs are high, and players are deterred from making long-term investments. It is often assumed that the severe downturn in investment during “off” years implies that wind power is unviable without the PTC. This assumption turns out to be unsubstantiated: this paper demonstrates that it is not the absence of the PTC that causes the investment downturn during “off” years, but rather the uncertainty over its return. Specifically, it is the dynamic of power purchase agreement (PPA) negotiations in the face of PTC renewal uncertainty that drives investment volatility. With contract negotiations prevalent in the renewable energy industry, this finding suggests that reducing uncertainty is a crucial component of effective renewable energy policy. The PTC as currently structured is not the only means, existing or potential, for encouraging wind power investment. Using data from a survey of energy professionals, various policy instruments are compared in terms of their perceived stability for supporting long-term investment.     

Large scale wind power integration in China: Analysis from a policy perspective

Between 2006 and 2010 the installed capacity of wind power in China has doubled and by 2010 China's cumulative installed capacity of wind power ranked the first in the world, surpassing the United States. However, the rapid expansion of installed capacity has not been matched by grid connection, and this deficiency has aroused the concern of both policy makers and scholars. Unlike most of the current studies which focus on technical strategies in China's wind power industry, this paper analyzes the problem from a policy perspective. The paper analyzes the four challenges that large scale wind power integration in China faces: the uncoordinated development between wind power capacity and power grids; the lack of suitable technical codes for wind power integration; the unclear nature of the grid companies’ responsibility for grid connection; and the inadequate economic incentives for grid enterprises. To address these problems, the paper recommends that the government: formulates policies to better coordinate the development of wind power and the planning and construction of power grids; establishes grid codes that reflect in particular the requirements to be met by users of power transmission and distribution networks; and integrates administrative intervention and economic incentive policies to stimulate the grid enterprises’ enthusiasm to absorb wind power generation.     

Economic assessment of the engineering basis for wind power: Perspective of a vertically integrated utility

If wind park configurations are globally coordinated across the service area of a power utility, then electricity can be generated for the grid with substantial cost advantages. Based on this premise, the paper introduces a model by which large scale assessment of grid connected wind based power generation may be undertaken for a utility service area. The model can be useful to the policy maker for decisions regarding suitable wind portfolio standards (WPS) definition. The utility on the other hand, may use the model to study its service area for prospective wind based generation. Aspects of the problem modelled include cost-of-energy from individual generating units, daily load variations for the utility with emphasis on limited penetration, features of wind at prospective installation sites, makes of wind energy conversion systems (WECS) available, and recovery of expenditure through revenue. Application of the model to an assessment exercise for the state of Andhra Pradesh (India) is presented as an example.     

Between fragmented authoritarianism and policy coordination: Creating a Chinese market for wind energy

The Chinese grid-connected wind energy sector has undergone a number of fundamental changes during its 20 years of existence. The scope of this article is to track the reforms of the energy bureaucracy and its policy approach on the one hand and changes in wind energy installations on the other. By comparing three historically distinct phases of wind energy in China it is shown how policy reforms have changed largely from a state of “fragmented authoritarianism” towards policy coordination. In the initial phase (1986–1993), wind energy was expanding very slowly with disjointed policy making and in the incremental phase (1994–1999), the energy authorities were in dispute over the strategy and launched conflicting policy initiatives with poor results in wind energy output. The latest coordinated phase (2000–2006), however, developed a coherent renewable energy agenda and policy regime for the wind power sector. It is found that this phase with coordinated market regulations and incentives has helped give birth to a take-off in Chinese wind energy installations and substantial cost reductions, although the latter is threatening the profitability of wind farms. The article contributes to the academic debate over the role of policy making in renewable energy development and argues that China should continue, and improve, the coordination of regulations and incentives.     

Modelling of energy systems with a high percentage of CHP and wind power

This paper presents the energy system analysis model EnergyPLAN, which has been used to analyse the integration of large scale wind power into the national Danish electricity system. The main purpose of the EnergyPLAN model is to design suitable national energy planning strategies by analysing the consequences of different national energy investments. The model emphasises the analysis of different regulation strategies and different market economic optimisation strategies.At present wind power supply 15% of the Danish electricity demand and ca 50% is produced in CHP (combined heat and power production). The model has been used in the work of an expert group conducted by the Danish Energy Agency for the Danish Parliament. Results are included in the paper in terms of strategies, in order to manage the integration of CHP and wind power in the future Danish energy supply in which more than 40% of the supply is expected to come from wind power.     

Fostering a renewable energy technology industry: An international comparison of wind industry policy support mechanisms

This article examines the importance of national and sub-national policies in supporting the development of successful global wind turbine manufacturing companies. We explore the motivations behind establishing a local wind power industry, and the paths that different countries have taken to develop indigenous large wind turbine manufacturing industries within their borders. This is done through a cross-country comparison of the policy support mechanisms that have been employed to directly and indirectly promote wind technology manufacturing in 12 countries. We find that in many instances there is a clear relationship between a manufacturer's success in its home country market and its eventual success in the global wind power market. Whether new wind turbine manufacturing entrants are able to succeed will likely depend in part on the utilization of their turbines in their own domestic market, which in turn will be influenced by the annual size and stability of that market. Consequently, policies that support a sizable, stable market for wind power, in conjunction with policies that specifically provide incentives for wind power technology to be manufactured locally, are most likely to result in the establishment of an internationally competitive wind industry.     

Investigation on wind power potential on Hong Kong islands—an analysis of wind power and wind turbine characteristics

This paper discusses the potential for electricity generation on Hong Kong islands through an analysis of the local weather data and typical wind turbine characteristics. An optimum wind speed, u_op, is proposed to choose an optimal type of wind turbine for different weather conditions. A simulation model has been established to describe the characteristics of a particular wind turbine. A case study investigation allows wind speed and wind power density to be obtained using different hub heights, and the annual power generated by the wind turbine to be simulated. The wind turbine's capacity factor, being the ratio of actual annual power generation to the rated annual power generation, is shown to be 0.353, with the capacity factor in October as high as 0.50. The simulation shows the potential for wind power generation on the islands surrounding Hong Kong.     

Profitability of wind energy: Short-term risk factors and possible improvements

The wind energy industry has grown considerably in recent years. If the current rate of growth of installed capacity of 1500 MW per year continues, by 2006 Spain will achieve the objective established for 2010 in the “Plan de Fomento” [Plan to Promote Renewable Energies] or for 2008 in the more ambitious “Plan de Infraestructuras Eléctricas y Gasísticas” [Plan for Electrical and Gas Installations]. Achieving these important goals, which require significant investment, depends upon the continued stability of salaries and the willingness of banks to provide financing. Therefore, we studied those factors that had the greatest short-term impact on the economic viability of wind energy projects in Spain and we found that the inherent risk within the sector can become a real obstacle in terms of development and short-term financing. Given the possibility of carrying out financial analysis that is more exhaustive than traditionally employed methods, the various models for evaluating investment in risk conditions were studied with the aim of choosing the ideal tool that takes account of the highly fortuitous nature of wind velocity.     

Large-scale integration of wind power into the existing Chinese energy system

This paper presents the ability of the existing Chinese energy system to integrate wind power and explores how the Chinese energy system needs to prepare itself in order to integrate more fluctuating renewable energy in the future. With this purpose in mind, a model of the Chinese energy system has been constructed by using EnergyPLAN based on the year 2007, which has then been used for investigating three issues. Firstly, the accuracy of the model itself has been examined and then the maximum feasible wind power penetration in the existing energy system has been identified. Finally, barriers have been discussed and suggestions proposed for the Chinese energy system to integrate large-scale renewable energy in the future. It is concluded that the model constructed by the use of EnergyPLAN can accurately simulate the Chinese energy system. Based on current regulations to secure grid stability, the maximum feasible wind power penetration in the existing Chinese energy system is approximately 26% from both technical and economic points of view. A fuel efficiency decrease occurred when increasing wind power penetration in the system, due to its rigid power supply structure and the task of securing grid stability, was left primarily to large coal-fired power plants. There are at least three possible solutions for the Chinese energy system to integrate large-scale fluctuating renewable energy in the long term: Redesigning the regulations to secure grid stability by means of diversifying the participants, such as including hydropower and CHP plants; integrating large-scale heat pumps combined with heat storage devices to satisfy district heat demands and developing electric vehicles to promote off peak electricity utilisation.     

Maximization of generated power from wind energy conversion system using a new evolutionary algorithm

In this paper, a grid-connected Doubly Fed Induction Generator controlled by a Sliding Mode Controller (SMC) is used to maximize the Wind Energy Conversion System (WECS) output power. A SMC is implemented using a PID controller that is tuned using a new algorithm based on hybrid Differential Evolution with a Linearized Biogeography-Based Optimization (LBBO-DE). Biogeography-Based Optimization (BBO) is an evolutionary optimization algorithm based on a mathematical model of organism distribution. BBO permits a recombination of the solutions features by migration. A new migration model based on the sigmoid function is proposed. An analysis of the LBBO-DE is conducted using six different models, including the sigmoid model. Their performance were tested with 23 benchmark functions. The comparison reveals that the sigmoid model has the best performance. Therefore, the LBBO-DE with a sigmoid model is used to optimize the controller parameters to maximize the WECS output power. The LBBO-DE with the sigmoid model is compared with the Tyreus-Luyben tuning method, Genetic Algorithm (GA) and Linearized BBO (LBBO). The results showed that the LBBO-DE has the best performance. The proposed algorithm is verified using an experimental setup for the maximization of the generated power from the WECS and reducing power loss.     

Combining hydro and variable wind power generation by means of pumped-storage under economically viable terms

Pumped hydro storage (PHS) systems which are located at isolated regions and are able to exploit the rejected wind energy amounts produced by local wind farms, seem to gain interest worldwide and to become essential in regard to higher shares of renewable-generated electricity. Despite the high wind potential encountered in many Greek island regions, the wind energy contribution to the electrification of these areas is significantly restricted due to imposed electrical grid limitations. In this context, the current work examines the economic viability of a wind-based PHS system (wind-hydro solution) which provides the local electrical grid of an Aegean Sea island, Lesbos, with guaranteed energy amounts during the peak load demand periods. Based on the maximization of the project’s net present value, the optimum system configuration is proposed while many other feasible solutions are revealed. According to the results obtained the implementation of this project demonstrates excellent technical and economic performance, while at the same time renewable energy sources (RES) contribution is doubled reaching almost 20% of the Lesbos island electrical energy consumption.     

An application of a combined wind and solar energy system in Izmir

In this work, a combined system which is produced electrical energy from both solar radiation via solar cells and wind energy by using wind turbine was studied. For wind energy, measurements of wind velocities at 12 m height were taken. Then, these values were calculated for 42 m by using Hellmann equation. After that, wind energy converted to the electrical energy. However, value of solar radiation from solar cells was taken at the optimum slope angle of collector which provided higher energy production for each 1 h during this application. Thus, obtained data from each system were used together for finding total energy. For this study, measurements, which would be used in calculation of wind energy and solar energy were taken for four years between 1995 and 1998 in Izmir. As a result, energy of the combined system could support each other when one of them produces energy insufficiently.     

Transient stability of a fixed speed wind farm

A typical fixed speed wind farm connected to a simple grid is modelled. Using this model, a three-phase fault is applied close to the wind farm, and cleared by disconnecting the affected line. The effect of several electric, mechanical and operational parameters on the critical fault-clearing time of this base case is evaluated and discussed. The studied parameters are the short-circuit power at the connection bus, the reactive power compensation, the distance to the fault, the rotor inertia, the hub-generator resonant frequency, the wind speed and the power output. For each parameter, the relationship between its value and the critical fault-clearing time is shown graphically. The results help to understand the transient stability phenomena in fixed speed wind farms, and could help to design fixed speed wind farms attending to transient stability requirements.     

Peak current mode control of three-phase boost rectifiers in discontinuous conduction mode for small wind power generators

This paper presents a peak current mode control scheme of a boost rectifier with low distortion of the input current for wind power systems based on permanent magnet synchronous generators with variable speed operation. The three-phase boost rectifier is operated in discontinuous conduction mode (DCM), and power factor correction techniques are applied. It is shown that the DCM operation significantly reduces the total harmonic distortion of the currents in the permanent magnet synchronous generator, increasing the power factor of the system, so that the vibrations and mechanical stress of the generator are minimized. The characteristics of the DCM boost rectifier are studied considering: (1) the series resistance of the inductors; (2) the modeling and adjustment of peak current mode control yielding a stable loop; (3) the design of an input filter that reduces the switching noise in the currents of the generator.     

Optimal sizing study of hybrid wind/PV/diesel power generation unit

In this paper, a methodology of sizing optimization of a stand-alone hybrid wind/PV/diesel energy system is presented. This approach makes use of a deterministic algorithm to suggest, among a list of commercially available system devices, the optimal number and type of units ensuring that the total cost of the system is minimized while guaranteeing the availability of the energy. The collection of 6 months of data of wind speed, solar radiation and ambient temperature recorded for every hour of the day were used. The mathematical modeling of the main elements of the hybrid wind/PV/diesel system is exposed showing the more relevant sizing variables. A deterministic algorithm is used to minimize the total cost of the system while guaranteeing the satisfaction of the load demand. A comparison between the total cost of the hybrid wind/PV/diesel energy system with batteries and the hybrid wind/PV/diesel energy system without batteries is presented.The reached results demonstrate the practical utility of the used sizing methodology and show the influence of the battery storage on the total cost of the hybrid system.     

KiteGen: A revolution in wind energy generation

Control of tethered airfoils is investigated, in order to devise a new class of wind generators to overcome the main limitations of the present wind technology, based on wind mills. A model from the literature is used to simulate the dynamic of a kite whose lines are suitably pulled by a control unit. Energy is generated by a cycle composed of two phases, indicated as the traction and the drag one. The kite control unit is placed on the arm of a vertical axis rotor, connected to an electric drive able to act as a generator when the kite pulls the rotor and as a motor in dragging the kite against the wind. Control is obtained by “fast” implementation of Nonlinear Model Predictive Control (NMPC). In the traction phase the control is designed such that the kite pulls the rotor arm, maximizing the amount of generated energy. When energy cannot be generated anymore, the control enters the drag phase and the kite is driven to a region where the energy spent to drag the rotor is a small fraction of the energy generated in the traction phase, until a new traction phase is undertaken. Simulation results are presented, showing encouraging performances.     

Model-based analysis of effects from large-scale wind power production

For an economically and ecologically optimised integration of fluctuating renewable power generation (especially wind power) into electricity generation, a detailed consideration of fluctuation-induced effects on the existing power system is essential. A model-based approach is introduced in this paper, which comprehensively analyses the impact of such effects on power plant scheduling and facilitates their integration into the development of strategies for an optimised evolution of the future power system structure. The newly developed Aeolius tool for the simulation of power plant scheduling is described. In a combined analysis of long- and short-term effects it is used together with the multi-periodic cost-optimising energy system model PERSEUS-CERT. Based on the Matlab/Simulink^® package, Aeolius considers the challenges for plant scheduling down to a time scale of 10 min. Special attention is paid to the provision of stand-by capacities and control power, as well as intermediate storage. Thus, a sophisticated quantification of the actual (net) benefits of wind power feed-in is achieved. Model results for Germany show that wind mainly substitutes power from intermediate-load and base-load plants (coal-, lignite-, and nuclear-fired). However, the required provision of stand-by capacities and control power does not only limit the substitution of conventional capacities, but also the achievable net savings of fuel and emissions in conventional power generation.     

Braking wind in Australia: A critical evaluation of the renewable energy target

This paper provides a critical evaluation of Australia’s new Renewable Energy Target (RET) program with respect to its capacity to support wind power development. Four structural flaws associated with the RET which undermine its effectiveness as a catalyst for technological change in the electricity sector are discussed: (i) the inclusion of waste coal mine gas (WCMG) as an eligible fuel source which acts as an indirect coal industry subsidy, (ii) program duration which is too short and ill-structured, (iii) a multiplier that is well-intended to support small-scale renewable technologies but which creates “phantom capacity”, and (iv) the capped target of 45,000 GWh which will stymie long-term wind power market investment. The paper concludes with recommendations which stress the importance of passing effective Carbon Pollution Renewable Scheme (CPRS) legislation to offset the weaknesses associated with the RET. If an effective CPRS cannot be implemented, the paper recommends that amendments be made to the RET to (i) remove WCMG from the list of approved alternative energy sources, and (ii) extend the RET targets to reach 120,000 GWh by 2030.     

Viability of wind energy as a power generation source in Maiduguri, Borno state, Nigeria

In this work, a statistical analysis of wind energy potential in Maiduguri is carried out, using Weibull distribution and 10 years (1995–2004) of wind data. The results show the Weibull distribution parameter C and K, the probability function T (V), the velocity frequency distribution f (V), the energy and power densities. The cost benefit analysis shows the economic feasibility of using wind energy conversion systems for electric power generation and supply in Maiduguri.