Small Wind Energy Conversion Systems Research Articles

Operating experience from the ehecatl wind turbines

This paper presents a summary of the mechanical features and the medium term operating experience from three small horizontal axis wind energy conversion systems covering a range of 500 to 5000 Watt, intented for rural and isolated communities. These turbines have a new regulator which reduces gyroscopic loads, is easy to adjust and could be manufactured stronger and in smaller sizes than the conventional tail vanes. It is concluded that is feasible to build cheaps and reliable wind turbine generators with an acceptable efficiency employing common-use elements, but is needed a careful and optimized design.

Autonomous wind energy conversion system with a simple controller for maximum-power transfer

The paper describes a small autonomous wind energy conversion system that has been designed and implemented as a prototype unit for the demonstration of wind-electricity generation. A simple, closed-loop control system assures maximum-power transfer by the aid of a lookup table which relates the electrical power output of the system to the shaft speed. The lookup table is deduced from the turbine and generator data and corrected by field tests. A directly-coupled, wound-rotating field synchronous generator is used for energy conversion. The generator speed in this system is variable while the terminal voltage is substantially constant. The terminal voltage is kept under control by varying the field current to meet various load and battery conditions. In the paper a new criterion for determining optimum dimensions of a generator for wind energy conversion system applications is introduced. This criterion envisages a maximisation of the energy output for the chosen wind regime while keeping the generator cost at a minimum. To obtain the optimum solution of the cost minimisation problem, the constrained optimisation problem is first converted to the unconstrained form by using the external penalty approach and then solved using the Devidon-Fletcher-Powel method. Results of the optimisation are presented and evaluated in the paper.

Site assessment and feasibility analysis for a small wind energy conversion system

SYNOPSIS Wind data have been gathered over nine years in the city of Riyadh and an on-site wind data assessment program has been implemented. The results gave the daily, monthly and yearly variation of wind speed. The monthly and annual averages of Weibull factors were also determined. The wind distribution was found to be well represented by the Weibull distribution function. Four models for estimating the annual energy output (AEO) have been presented, straight line, cubic, Powell and piecewise linear approximation. The latter uses the actual power curve for a given wind energy system to determine the AEO and this is considered as a standard and reference method. An experimental double-bladed small wind energy system model MV05 of a rated power of 0.526 kW has been used and an actual power curve was obtained. The value of AEO has then been estimated by employing the different methods and comparing with the reference method. An economic analysis has been carried out to complete the feasibility study for ...

Feasibility of wind energy applications in Bahrain

An assessment of the potential and economical feasibility of wind application as a renewable source of energy in Bahrain is presented. The analysis is based on long term measurements of wind speeds at the Bahrain International Airport in Muharraq. The economical evaluation takes into consideration the interest recovery factor, the life time of the wind energy conversion system (WECS), the investment rate, the depreciation and the cost of maintenance. These factors are presented in the form of two convenient charts which provide fast evaluation of the economic feasibility of WECS. Using these charts indicates that the generation cost of electricity using a small WECS compares favorably with the current cost of electricity in Bahrain.

A guide to small wind energy conversion systems

A guide to small wind energy conversion systems

On the energy output estimation of wind turbines

During the operation of the German test field for small Wind Energy Conversion Systems (WECS) on the island of Pellworm five wind turbines were tested following recommendations of the International Energy Agency (IEA) expert group. Possible errors in the estimation of a tested wind turbine's total energy output at a potential installation site are investigated. Different wind speed frequency distributions (the measured one, the Rayleigh and the two-parameter Weibull distribution) are used to calculate the total energy output. The differences between the various distributions are mostly below 10 per cent. An improvement of the energy output estimate by a Weibull-instead of a Rayleigh distribution was not found. It is also shown that the use of the recommended 10 min averages or any other average overestimates the WECS' efficiency, up to 14 per cent on average depending on turbulence intensity. Wind power instead of wind speed is the appropriate parameter for power performance testing. Spectra of wind power and electrical power output show three areas of different correlation. A resistance length for wind turbines is shown to be dependent on the WECS operation status.

Wind characteristics and the available wind energy in egypt

Abstract Three sites in Egypt, differing in natural conditions but having almost the same wind characteristics are chosen for this study. Annual mean wind speed at a height of 20 m above ground level ranges between 4.6 and 5.5 m s−1. Daily wind-speed distribution for every month of the year is presented. Monthly average wind speeds throughout the year are also presented. The analysis shows that the yearly average of the available wind power ranges between 73 and 112 W m−2. In view of wind energy exploration for agricultural purposes, estimates are reported of the seasonal and annual duration of wind speed and of duration of the available wind power. The possibility of utilizing wind energy at the different sites using small scale wind energy conversion systems is discussed.

Feasibility study of wind energy utilization in Saudi Arabia

The wind map of Saudi Arabia indicates that the Kingdom is characterized by the existence of two vast windy regions along the Arabian Gulf and the Red Sea coastal areas. The mean annual wind speed in these two windy regions exceeds 9 knots (16.7 kmph) and ranges from about 14 to 22 kmph and 16 to 19 kmph over the Arabian Gulf and Red Sea coastal areas, respectively. The main characteristic features of the wind field of these regions are presented. Four sample sites are selected for possible installation of both small and large wind energy conversion systems. These sites are: Yenbo and Al-Wajh on the Red Sea coast, Dhahran on the Arabian Gulf coast and Quaisumah in the north east of the Kingdom. The manufacturers pre-mass production unit capital costs ($/kW) are used to estimate the cost of electricity produced, in cents/kW h. The estimated costs of electricity produced by WEC systems of various rated powers when installed at the four sites are presented. A further reduction in the manufacturers unit capital cost is still required to enable wind energy to compete with other conventional energy sources. For oil-producing countries, it may be a few decades before wind energy can become cost-competitive with other energy sources.

Small wind-energy conversion systems

Wind turbines of capacity less than 100 kW have been much neglected for power production and energy capture in the UK. Other countries have facilities for testing and development, and have encouraged successful manufacturing programmes. The 1983 UK Energy Act may, however, lead to significant changes

Effects of Dynamic Stall on SWECS

A study of dynamic stall is presented in order to define its influence on the airfoil force and moment coefficients so that these effects can be included in the calculation of small wind energy conversion system (SWECS) loads and responses. A review of past work indicates that semiempirical methods are best suited to SWECS requirements. A definition of a dynamic stall theory is made for use in SWECS design, and the theory is implemented in SWECS loads and dynamic response analyses. Sample calculations are made for a representative vertical-axis machine. It is shown that loads and moments on the blades may be underestimated if dynamic stall is not considered.

Economic analysis of small wind-energy conversion systems

The financial costs of obtaining electricity from small wind-energy conversion systems are calculated and compared with the cost of electricity from traditional utility companies. A 3 kW rated wind electric system for residential use is examined. The amount of energy from this system is estimated by using a computer-operated simulation model which incorporates wind speeds, residential electricity demands and parameters from the generator, inverter and storage components. Variations in electricity costs as a function of available wind energy, residential consumption patterns and system components and costs are examined. The cost of electricity from small wind-energy conversion systems has considerable variations under differing assumptions or parameters but may, in some cases, be competitive with utility company costs.

Economics of Wind Energy for Heating Rural Structures

ABSTRACT SMALL wind-energy conversion systems (SWECS) are very close to economic feasibility for heating many rural buildings when they are located in wind regimes of at leasts to 6 m/s (11.2 to 13.4 mph) and when presently available tax incentives are used. The building heating possibilities and the procedures for determining SWECS output and economics are given.

Net energy analysis of small wind energy conversion systems

The net energy of a small wind electric conversion system is calculated and compared with the net energy of other electricity sources. Net energy is the amount of energy remaining for consumer use after deducting the energy required to find and upgrade the energy source and construct and maintain the electricity generating system. A 3 kW rated wind electric system for residential use is examined. The amount of energy obtained from this system is estimated by using a computer-operated simulation model which incorporates wind speeds, residential electricity demands and parameters from the generator, inverter and storage components. The net energy gain for this wind system is better than that of other systems with which it is compared.

Current developments in small wind energy conversion systems

A survey and review of the current state-of-the-art research and development is presented for Small Wind Energy Conversion Systems (SWECS). Current technical and economic status of SWECS is given including some advantages and disadvantages of various technical approaches to wind energy conversion. Programs are described which are managed by Rockwell International, for the U.S. Department of Energy, to advance the commercialization of SWECS. References provided should allow the reader to pursue details of many aspects of design, testing and utilization of SWECS.