This paper compares simulated versus recorded data for the RPM-SIM simulator, developed at the National Renewable Energy Laboratory's National Wind Technology Center.The simulator was used to study the system dynamics of a wind/diesel hybrid power system.We also provide information on newly developed simulator modules that will be released.The simulator performed extremely well, demonstrating flexibility in making modifications and including specialized modules required for problem solving.We also outline several possible applications for this tool.Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information.

Battery charging systems are very important in many developing countries where rural families cannot afford a solar-battery home system or other electricity options, but they can afford to own a battery (in some cases more than one battery) and can pay for it to be charged on a regular basis. Because the typical households that use batteries are located far from the grid, small wind battery charging stations can be a cost-competitive options for charging batteries. However, the technical aspects of charging numerous 12-volt batteries on one DC bus with a small permanent magnet alternator wind turbine suggest that a special battery charging station be developed. NREL conducted research on two different types of wind battery charging stations: a system that uses one charge controller for the entire DC bus and charges batteries in parallel strings of four batteries each, and one that uses individual charge controllers for each battery. The authors present test results for both system configurations. In addition, modeling results of steady-state time series simulations of both systems are compared. Although the system with the single charge controller for the entire bus is less expensive, it results in less efficient battery charging. The authors also include inmore » the paper a discussion of control strategies to improve system performance and an economic comparison of the two alternative system architectures.« less

Batteries in hybrid power applications that include intermittent generators, such as wind turbines, experience a very irregular pattern of charge and discharge cycles. Because battery life is dependent on both depth and rate of discharge (and other factors such as temperature, charging strategy, etc.), estimating battery life and optimally sizing batteries for hybrid systems is difficult. Typically, manufacturers give battery life data, if at all, as cycles to failure versus depth of discharge, where all discharge cycles are assumed to be under conditions of constant temperature, current, and depth of discharge. Use of such information directly can lead to gross errors in battery lifetime estimation under actual operating conditions, which may result in either a higher system cost than necessary or an undersized battery bank prone to early failure. Even so, most current battery life estimation algorithms consider only the effect of depth of discharge on cycle life. This paper will discuss a new battery life prediction method, developed to investigate the effects of two primary determinants of battery life in hybrid power applications, varying depths of discharge and varying rates of discharge. A significant feature of the model is that it bases its analysis on battery performance and cyclemore » life data provided by the manufacturer, supplemented by a limited amount of empirical test data, eliminating the need for an electrochemical model of the battery. It performs the analysis for a user-prescribed discharge profile consisting of a series of discharge events of specified average current and duration. Sample analyses are presented to show how the method can be used to select the most economical battery type and size for a given hybrid power system application.« less

One type of wind-powered battery charging will be explored in this paper. It consists of a wind turbine driving a permanent magnet alternator and operates at variable speed. The alternator is connected to a battery bank via rectifier. The characteristic of the system depends on the wind turbine, the alternator, and the system configuration. If the electrical load does not match the wind turbine, the performance of the system will be degraded. By matching the electrical load to the wind turbine, the system can be improved significantly. This paper analyzes the property of the system components. The effect of parameter variation and the system configuration on the system performance are investigated. Two basic methods of shaping the torque- speed characteristic of the generator are presented. The uncompensated as well as the compensated systems will be discussed. Control strategies to improve the system performance will be explored. Finally a summary of the paper will be presented in the last section.