Analysis of Tower Shadow Effects on Battery Lifetime in Standalone Hybrid Wind- Diesel-Battery Systems

In a standalone hybrid wind-diesel-battery system, the battery lifetime is often optimistically overpredicted by hybrid system designers and battery manufacturers. As a result, battery replacement takes place more often than required. One of the reasons is due to the underestimation of battery wear from the short charge-discharge cycles, otherwise known as microcycles. A microcycle takes place when the power generation closely matches the load demand. The detrimental effect of microcycles on a battery-based standalone hybrid renewable energy system was previously investigated, however only from the perspective of short-term renewable energy fluctuations. This research paper provides new insight on battery lifetime reduction, resulting from microcycles which are generated through the tower shadow phenomena. Downwind wind turbines are considered here as their tower shadow effects are more significant compared to the upwind counterpart. This paper briefly presents the modeling of tower shadow profiles for both tubular and four-leg tower configurations. Experimental results have shown that the microcycles due to this non-ideal effect are significant in a battery-based standalone hybrid system. The quantification of the battery lifetime reduction due to this effect is demonstrated. Finally, the paper concludes with a sensitivity analysis of the battery lifetime reduction for different tower configurations, operating at different load conditions.