Analysis and simulation of a wind-electric battery charging system

Abstract

SUMMARYA small commercial wind-electric battery-charging system based on a three-bladed rotor has been analysed in a detailed fashion. The system consists of a synchronous generator with permanent magnets, a six-pulse rectifier and a battery bank with charge controller. A steady-state power curve is predicted based on the electric characteristics found experimentally and the aerodynamic performance of the rotor simulated with a version of blade element momentum (BEM) theory developed in our group. The BEM code has been designed to account for variable Reynolds numbers at different blade sections and stall conditions. The findings are compared with the manufacturer's specifications, and a detailed discussion is provided. A very good agreement with the steady-state power curve given by the manufacturer has been obtained after accounting for different sources of power losses, such as voltage drops in the rectifier, Joule heating in the power cables and losses in the generator's core. The system is found to operate near the aerodynamic optimum for all wind speeds studied, whereas electrical losses are significant near rated power. Some recommendations for improving the system performance are provided.

Development of the all-vanadium redox flow battery for energy storage: a review of technological, financial and policy aspects

“…A similar model was recently developed by Shah and co-workers for the all-vanadium system [111]. Although not able to capture the same level of detail at the unit cell scale as the models in [103][104][105][106][107][108], the equivalentcircuit approach is the ideal basis for control applications and stack/system-level modelling [112,113].…”

“…The projected overall costs of renewables and batteries can be revised downwards by considering the potential growth in renewable power and by considering improved energy efficiency measures, together with an associated reduction in environmental insults [32]. The application of market-based (policy) instruments (MBIs) [113] could incorporate lead-in energy storage based government subsidies and investment tax credits (or tax reform) to more accurately price the externalities. The inclusion of energy storage technologies into national emissions trading schemes, such as the phase-three trading period of the EU ETS post 2012, would provide substantial economic benefit to battery developers.…”

Design, application, and power performance analyses of a micro wind turbine

“…The mechanical angular speed depends on frequency f (Hz, 1/s), and it is defined by f = ω t /2 π . The mechanical angular speed can be expressed by ω t = 2 π n/60 as a function of the rotational speed of the MWT [31], where n is the rotational speed of the MWT (rev/min) and it is n = 60f (rev/s). Depending on the number of poles of the PMSG, the rotation is given by n = 60f/2P, where 2P is the number of pole pairs of the PMSG.…”

Small Wind Turbine Technology

“…Most small wind turbines are variable-frequency devices, allowing for an optimal operation at all wind speeds below the threshold for the onset of the overspeed and power control mechanism. While in the case of battery-charging applications the use of a passive rectifier together with the selection of an appropriate voltage level may be sufficient to maintain the operating point close to the system optimum, especially when the aerodynamic efficiency curve (section 6) is broad (Elizondo et al, 2009, some commercial systems rely on the use of an active load control in order to maintain the system at the optimal operating point for each wind speed (Martínez et al, 2006). In the case of a coupling to the electric grid, a full wild AC/fixed frequency AC conversion is generally feasible through the use of a back-to-back AC/DC/AC converter, as opposed to large wind turbines where a direct full conversion is still rather the exception than the rule and most commercial large wind turbines rely on doubly fed induction generators (DFIG) where only a fraction of the total power is passed through a converter.…”