Protecting renewable energy equipment from extreme weather

International standards help ensure wind turbines withstand external conditions

2018 was a year of extreme weather. Some of the lowest and highest temperatures were recorded in both hemispheres, while gale-force winds fuelled wildfires in a number of regions and hurricane-strength typhoons caused severe flooding in others.

Onshore wind turbines
Certification requirements for wind turbines cover aspects such as design and external environmental conditions

Different factors contribute towards global climate change, caused by the build-up of greenhouse gases. One way to address this issue is to use clean, renewable energies.

Growth of renewables continues

According to statistics from the International Renewable Energy Agency (IRENA), global renewable generation capacity increased by 167 GW and reached 2,179 GW around the world by the end of 2017, representing a yearly growth of around 8.3%.

Following solar photovoltaics (PV), wind grew by 10% with three-quarters of new capacity installed in five countries: China (15 GW), US (6 GW), Germany (6 GW), UK (4 GW), and India (4 GW).

How do wind turbines weather the storms?

As extreme weather events are likely to occur more frequently, manufacturers must ensure from the outset, that their equipment will endure all weather conditions throughout its lifecycle.

Sandy Butterfield, Chair of IECRE, the IEC System for Certification to Standards Relating to Equipment for Use in Renewable Energy Applications, for the wind, solar PV and marine energy sectors, explains how IEC standards reinforce wind turbines.

In practice, all commercial wind turbines are designed to meet international standards, specifically IEC 61400 series of standards, which have been developed by IEC Technical Committee (TC) 88. IECRE is the only transparent and international certification system for assessing whether a turbine design meets the requirements defined in the standards.

The turbine design conditions are defined in IEC 61400-1 and include external environmental conditions together with a wide variety of turbine operating conditions, which onshore wind turbines must satisfy in order to meet certification requirements. IEC 61400-3 covers external conditions for offshore turbine designs.

“Hurricane conditions are not specifically defined within the standard, instead they are treated as extreme conditions on a spectrum of combined weather and sea-state conditions that may be heavily affected by local geographic conditions.

Most offshore and many onshore wind turbines are designed to withstand 70 m/s (155 mph, nearly 250 km/h) winds (IEC Class I), which is greater than most hurricanes.

The latest revision of IEC 61400-1, which is in its final approval steps, contains a special design class for areas with very high extreme winds, which may result from tropical cyclones, also called hurricanes in the Atlantic ocean. The new design class raises the extreme wind speed that wind turbines are designed for to about 80 m/s (almost 180 mph, around 290 km/h) and allow design for more severe external conditions when needed.”

How to address unique hurricane characteristics in the design process

The standard contains informative annexes which includes the unique characteristics of hurricanes and guidance on how to address them in the design process. Magnitude of winds, waves and other important design conditions are determined by specific site data.

“Every offshore (and onshore) installation must specifically define all the external conditions that may occur at that site over the expected life of the project, which is usually 30 years but no less than 20 years. This requires the project developer to gather historical data for their site and use it to forecast a set of design conditions which projects the extreme winds, waves, currents, and any other events that the turbines could experience, including hurricanes.”

More design challenges may result from combinations of wind (less than the extreme wind) and waves together with certain wind turbine operating conditions. Designers simulate many thousands of these combinations with very sophisticated computer models to assure themselves, certification bodies, regulators, and customers that they have indeed addressed all the conditions that could damage the turbines.

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