PNNL

Abstract

The White House is pushing to operationalize 1000-times today’s U.S. offshore wind power capacity by 2035. Lightning damage has been noted as the leading cause of unplanned downtime of wind farms, and in Q2 of 2020 turbine manufacturer Vestas had €175M in warranty claims attributed to ‘high intensity lightning’. Here we try to understand if lightning poses a risk to future U.S. offshore wind power development, using observations of lightning stroke and energy densities during 2020-2022. The focus here is on U.S. East Coast Wind Lease and Wind Planning areas, with a related analysis for context over operational wind farms in Europe’s North Sea. On average, U.S. wind areas received about 14-times the lightning strokes and transferred about 18-times the energy compared to offshore North Sea wind farms. In the U.S. there is a clear north-south gradient: lightning activity off the coast of Maine is quite low, higher off Chesapeake Bay, and high south of Virginia. Very high lightning activity also occurs about 250km from the U.S. coastline, which is 50-100km outside currently designated Wind Area but may be a consideration for the expansion of floating wind farms further from shore. Engineering standards, such as IEC 614200-24, can estimate ‘dangerous’ lightning events from stroke density and turbine top-height — that application is explored herein. The usefulness of IEC 614200-24 for offshore wind is also uncertain, as there is currently a void in detailed spatiotemporal public data on turbine damage from lightning strikes, particularly offshore where these turbines will be the tallest object by hundreds of meters for tens to hundreds of kilometers. Our analysis suggests that wind turbines off the U.S. East Coast will likely encounter the same lightning activity every year as a North Sea wind turbine experiences once a decade. Understanding where and how lightning may damage U.S. offshore wind turbines is a pro-active step to securing offshore wind’s contribution to a low-carbon energy future.