Although wind currently provides 5 percent of the world’s electricity, the growing push for renewables has led many scientists and engineers to predict that wind turbines may generate at least half of all power by 2050. That is not a given, however, as significant advances must first be made in understanding the atmosphere at higher altitudes, predicting weather patterns and re-engineering turbines to perform at higher levels of efficiency.
The overriding objective throughout all the redesigns and enhancements is to build larger and more powerful wind turbines to produce more energy for the cost, thus lowering the per-unit cost of electricity. According to Global Wind Energy Council (GWEC), in 2019, the average turbine size surpassed 2,750 KW. This was a 72% increase in average size over the past decade.
Wind turbine improvements
Previously, wind turbine design has focused largely on optimized blade shapes; lighter-weight, flexible, yet durable, materials; and the addition of intelligent control and monitoring systems. Some in the industry believe, however, that we have reached a point in technological advancements where advancements are incremental at best.
Simply increasing the size of the towers, blades and other components is not the answer, as this would lead to turbines that are excessively costly and heavy. That has prompted an ongoing search for advanced, lighter-weight materials that withstand increased forces without failing prematurely, as well as simplified designs that remove costs and weight.
Creating more power more efficiently
Meeting global targets for wind energy generation means finding ways to generate a lot more energy from existing wind farms. Historically, engineers have focused on the performance of individual turbines, but newer approaches are based on the performance of the wind farm as a whole.
Consider the fact that wind turbines produce the most power when pointed directly into the wind. However, when multiple turbines are near each other, they create wakes from upstream generators that can interfere with the performance of turbines located downstream. Researchers found that turbine wakes can reduce the efficiency of downwind generators by more than 40 percent.
This revelation has led to the practice of pointing turbines slightly away from the oncoming wind—a practice known as wake-steering— to reduce interference and improve the quantity and quality of power from the wind farm. This can also help to lower operating costs.
Adjusting for wind variability
Of the various renewable options, wind energy is probably the most variable. Wind velocity can change without warning, as can the direction of the wind. That means blades and rotor RPM must be able to adjust accordingly to adapt to wind speed. Otherwise, operational and cost inefficiencies could result.
Conventional wind turbines were not designed to change directions or speeds quickly, and they are even more challenged to do so as rotor blades have increased in size. Larger rotor blades have made it necessary to consider blade/rotor concepts that can adjust themselves to non-homogenous wind flow, such as gusts, turbulence spots, shear, etc. The longer the blade, the greater the difficulty to define the optimal operating point since the inflow situations may vary quite a bit along the blade. Determining the optimal operating point is critical for reducing loads and increasing or smoothing out power output.
The challenge to maintaining the optimal operational point, despite wind inconsistency, has opened the door to what is known as smart rotor technology. Design options include:
- Wind turbines with tip-rotors.
- Replacing a large single rotor with a multiple rotor system consisting of a large number of standardized rotors.
Extending service life with predictive maintenance
Advances in sensors and analytics allow for predictive and preventative maintenance strategies to reduce unplanned outages. In the past, condition monitoring systems for wind turbines focused on the detection of failures in the main bearing, generator, and gearbox because these are the most expensive components of a wind turbine. Today there are several ways to help maintenance teams stay ahead of failures, including fluid sensors, particle counters and vibration sensors. Contaminated fluids and worn bearings due to vibration are two leading causes of gearbox failures.
Making wind energy more cost-competitive
With other forms of renewable energy also showing promise, pressure is on OEMs in the wind industry to lower costs.
“We’ve seen a trend of getting better performance using less. Because of this streamlining, the cost of wind turbines has come down 40-60% in just the last five years as everyone is working harder to design them bigger, better, and cheaper while making them last longer.”
Tom Ulery, business development manager, renewable energy, Parker Hannifin
While there is still a need to identify alternative materials that will result in cost savings, the big focus is on streamlining the overall design and reducing component complexity. There’s an increased need to standardize sizes to realize economies of scale and facilitate installations in multiple countries. Additional cost savings can be realized by maximizing the efficiency of wind turbines and minimizing maintenance costs.
Overcoming energy storage issues
Energy storage remains a key challenge, as the greatest potential for wind energy occurs at night when demand for electricity is typically lower. Battery technologies have evolved a lot but do not fully solve the problem of long-term storage. In addition to being expensive,
- Lithium-ion batteries are limited as to how much energy they can store.
- Flow batteries offer a lot of promise but are not currently able to operate at a utility scale.
Currently, all eyes in the industry are on converting excess energy into hydrogen as a preferred storage option. Hydrogen is ideal for storing energy for long periods of time because of its high energy density. Being lightweight makes it easier to handle. Hydrogen, however, is not without its challenges.
Minimizing environmental impact
Although wind energy is seen as environmentally friendly, it has been criticized for its detrimental effect on wildlife. It’s been estimated that between 140,000 and 500,000 bird deaths occur at wind farms each year. Wind turbines have also been found to be one of the leading causes of mass bat mortality, with some estimates as high as 888,000 bat fatalities a year.
Another environmental concern relative to wind turbines is noise pollution. As turbines grow, so does the noise they make, with most of the noise occurring at the outer edge of the blades. Yet, size is not the only factor affecting noise pollution. It is also about the location of the wind turbines relative to each other.
What steps can help improve the efficiency of your wind operations?
While new innovations are coming onto the market to improve the cost and efficiency of wind energy overall, there are some simple, yet highly impactful, things that can be done operationally to optimize the performance of existing wind turbine designs and materials.
SOURCE: Parker
