In the wake of increasingly devastating storms, what do utilities and engineers need to consider about the resiliency of offshore wind systems?
Over the last year, three states have had rolling blackouts due to weather extremes: California, Washington, and Texas. With these recent events and others, climate and grid reliability considerations have been brought to the fore. In March 2021, FERC opened a docket on climate change and grid reliability. This article discusses aspects of climate and resiliency considerations as it pertains to offshore wind.
In particular, we highlight our recent work with the New York State Energy Research and Development Authority (NYSERDA), which set out to aggregate, refine, and distill climate adaptation and resiliency considerations for offshore wind in New York and the broader northeastern Atlantic region of the U.S.
The resulting paper, NYSERDA: Offshore Wind Climate Adaptation and Resilience Study, offers utilities and engineers alike some things to consider—and shines a spotlight on offshore wind system resilience. We provide a few key highlights below.
Factors impacting offshore wind systems
Climate variables such as harsh environments and storm severity can disrupt and impact the reliability of offshore wind systems. Climate change can affect offshore wind systems in two ways. The first is by affecting the performance of systems such as reducing the ability to deliver the expected energy output over the life of the offshore wind system. The second is to affect offshore wind reliability or the ability of a system to deliver energy, without disruption, as a result of climatic conditions outside the normal operating range, such as storms.
For wind turbines, the most significant variables for performance are wind speed and direction. Assessments of offshore wind turbine sites generally consider the annualized mean wind speeds and directions, wind speed frequency distributions, and seasonal variations in wind patterns. Remember that wind energy density is directly proportional to the cube of wind speed, which means high wind speeds will equal high wind energy and potential power production.
The frequency and amplitude of wind speed distribution is important for utilities and engineers planning offshore wind farms because short-term wind speeds impact power output. For example, high wind speeds over operating limits can cause damage or failures if they happen in sudden gusts or require turbine operators to suspend production until conditions improve. Increased turbulence, or high frequency changes in wind speed, can hinder turbine performance and power production. Smooth air is key to the efficient extraction and production of power from the wind.
Another factor to keep in mind is the distribution of the wind’s direction. Consistent wind direction is critical for optimal turbine power production and longevity because it reduces overall wear and tear on wind turbines. It also allows for a more efficient layout for placing turbines and creating optimized wind farms. (Also, large-scale geographical changes in wind distribution can have a negative impact on the overall energy production from existing wind farms.)
Other climate-related factors that can shape the performance of offshore wind turbines include:
- Air temperature, which affects air density, with higher air temperatures reducing wind turbine power output.
- Air moisture, which can lead to blade-leading edge erosion and lost power production.
- Ocean wave amplitude and frequency, which can affect turbine foundations, inter-array and export cabling, and cable landings on the seafloor.
- Sea level rise, which may threaten the infrastructure for fixed and floating foundation wind turbines.
- Ice and freezing rain, which can build up on the leading edge of wind turbine blades and damage tower bottoms and cabling.
How to boost wind turbine resilience
Turbines are designed to optimize power production efficiency and to minimize structural damage in their operating region. But if the average wind velocities shift higher, or high-wind events become more frequent, turbines in that location may experience more frequent shutdowns, decreasing overall power output. Modern industrial-scale wind turbines typically are designed to the limits of the intended operational loads envelope. Climate change can push a wind turbine into an operational condition that was not envisioned as part of the original design.
Given this, what can be done to boost offshore wind system resilience to climate change?
The task will require ingenuity and collaboration between stakeholders at all levels of the wind turbine design and implementation process.
In regards to wind speed, potential design options could include passive and active aerodynamic “lift modification” devices. These devices can improve wind turbine performance in conditions with low wind speeds or reduce loads in conditions with extremely high wind speeds.
A key design aspect of offshore wind turbines that engineers will need to reassess is the blades themselves. One possible solution involves optimizing wind turbine blade design to handle a larger range of incoming wind angles. Light detection and ranging (LiDAR) can allow wind turbines to “look” upwind and “see” what wind loading is coming toward the turbine rotor, allowing them to dynamically adjust to optimize performance.
Other design possibilities to meet inconsistent winds include improved and strengthening pitch and yaw systems to take on higher wind loads, as well as simple methods such as improved wind turbine maintenance efforts.
We expect developers will continue to incorporate higher elevations into their future fixed-foundation wind turbine designs to account for the anticipated rise in sea level. Additionally, as floating foundation designs become technically and economically viable options, we expect floating designs to be more adaptable to sea level rising, and thus offer an alternative solution.
And when it comes to increased precipitation, the use of hydrophobic coatings on wind turbine blades could minimize the buildup of ice that would threaten operations.
The impact of climate change on offshore wind systems should be included in future planning of new developments. A number of options are available to turbine OEMs, developers, and operators. The cost of each option must be factored with the relative improvement in performance and reduction of risk.
Read the NYSERDA full report
While existing offshore wind energy systems are designed to withstand climate hazards such as extreme winds and storm surges, climate change has the potential to test the design and operational limits of these clean energy systems.
NYSERDA: Offshore Wind Climate Adaptation and Resilience Study offers even more insights into options for maintaining offshore wind systems’ resilience in the face of climate change. By taking steps to mitigate and possibly avoid future climate change damage to offshore wind systems, the industry will be in a stronger position when the next storm rolls around.