Microcosmic Mechanism Investigation on Lightning Arc Damage of Wind Turbine Blades Based on Molecular Reaction Dynamics and Impact Current Experiment

Li Zhang,Liang Zou,Liyang Jiang,Tong Zhao

doi:10.3390/en10122010

Abstract

PVC and balsa wood are usually used in the interlayer structures of wind turbine blades. In this paper, a comparative study on the lightning damage characteristics of the two materials was carried out by molecular dynamic simulations and impact current experiments. The simulations show that the glycosidic bonds in cellulose break first, which leads to a strong decrease in the degree of polymerization (DP) of cellulose (while the DP of PVC changes irregularly), then C−O bonds in the pyranoid ring break and the main chain of cellulose is destroyed, producing small molecule fractions and a lot of gas molecules. There are two steps in the pyrolysis of PVC. H and Cl atoms fall off the main chain and combined for form HCl, which needs less energy and occurs earlier than cellulose pyrolysis at 2000 K, but cellulose generates more gas products than PVC at the same temperature. Thus the damages to balsa wood and PVC mainly appear as fiber fractures and pore extension, respectively, which are consistent with the morphological features of the damage to the two materials in the impact current experiments. The experimental results also show that the pyrolysis temperature of PVC was lower than that of balsa wood, and the residual strength decreases faster in PVC than in balsa wood with the increase of peak current. This study should play an important guiding role for lightning protection and material selection of wind turbine blades.

Highlights

Wind energy is one of the most promising renewable energies, and wind power generation has developed rapidly in recent years
With the increase of the wind turbine unit capacity and the wind farm scale, the hub height and blade length of wind turbines has increased, and most wind farms are located on open ground and mountains, so they are struck by lightning [1,2,3]
There are some flow control devices such as improved microtab system [4,5] to decrease damage and loads on wind turbine blades, these methods cannot protect the blades against lightning

Summary

Introduction

Wind energy is one of the most promising renewable energies, and wind power generation has developed rapidly in recent years. According to the US wind energy insurance claims report in 2012, the proportion of the damage caused by lightning was 23.4% of the turbine failures. Damage caused by lightning can occur in the blades, generators, controllers, control cables and other parts. Epoxy resin reinforced by glass fiber is mainly used in the spar cap of wind turbine blades, and the interlayer structure is usually made by PVC and balsa wood in order to reduce weight. These two materials are seldom compared in terms of their lightning damage characteristics

Methods

Results

Conclusion