Modeling, testing and economic analysis of a wind-electric battery charging station

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 in the paper a discussion of control strategies to improve system performance and an economic comparison of the two alternative system architectures.