Wind energy technology has undergone a sea change over the years. The turbine capacities have shifted from kW to MW with improved efficiency parameters. The technology is constantly evolving towards improved reliability, increased capacity factors, and reduced associated fixed and variable costs. Modern wind turbines incorporate longer and lighter rotor blades, taller turbine towers, more reliable drivetrains and performance optimising control systems. The amount of wind power generated is largely influenced by factors such as wind speed and technology of the generating systems.
Wind power is a mature industry across the globe and significant growth is expected in this space owing to the high available potential, intent of both the governments and industry as well as technology advancements. Wind turbine generators have advanced over the years with locally produced state-of-the-art technologies now available in the every country.
With the passage of time and technological advancements, wind turbine hub heights have grown from just 50 metres initially to more than 120 metres, with plans to increase them up to 150 metres. With the increase in height, the power generation capacity by wind turbines has increased from 250 kW to around 2.5 MW currently. Most turbines have three blades that vary in size and material composition. As reported in a research paper titled “Materials for wind turbine blades: An overview”, different types of materials such as glass and carbon fibres, aramid and basalt fibres, hybrid composites and natural fibres are used to manufacture the wind turbine blades. The blades and hub together form the turbine’s rotor. When wind blows across the blade, the air pressure on one side falls. Lift and drag are created by the difference in air pressure between the two sides of the blade. When the lift force is greater than the drag force, it causes the rotor to spin. A wind turbine converts wind energy into electricity by using the aerodynamic force of the rotor blades. The rotor is either directly connected to the generator or through a shaft and a series of gears which speed up the rotation and it allows for a physically smaller generator. The aerodynamic force which leads to generator rotation results in the generation of electricity.
Wind turbine generators must be robust, cost effective, fault tolerant and must require minimal maintenance. These characteristics are required for wind applications because the deployed structures and machines are frequently placed in hostile environments at remote locations far from immediate technical assistance. Thus, technology advancements are a must to constantly improve the quality of components and their reliability.
Innovations in rotors and blades
The increase in the size of wind turbines is a major trend in the segment. The weight of the rotor blades increases with size, so, gravitational loads become design drivers. UK-based company ACT Blade is working on making technological changes to address this issue of blade weight. It is developing blades with lower weight which allows for building longer blades with lower mass. These blades can produce more energy with minimal change in turbine loads. As reported by the company, a 10 per cent longer blade can produce 9.3 per cent more energy and reduce the cost of energy by 6.7 per cent. Unlike conventional fibreglass blades, the ones designed by ACT Blade are partly recyclable. This would help in reducing landfill waste and contribute towards responsible energy production.
Sustainability and recycling are important factors especially considering the massive volume of wind turbines already installed and also being deployed around the globe Significant amount of waste is expected from these installations at the end of project lives. As per a recent report by researchers at the Institute for Manufacturing, University of Cambridge, wind turbine blade waste could amount to 43.4 million metric tonnes by 2050. With such forecasts, more wind turbine manufacturers are looking at ways to recycle their products when they are no longer operational.
In April 2022, researchers from the DLR Institutes of Aeroelasticity, and Composite Structures and Adaptive Systems assisted in the manufacturing of six rotor blades for two wind turbines at a research farm. This was done in collaboration with ForWind: Centre for Wind Energy Research at Leibniz University Hannover. The team equipped the rotor blades with approximately 1,500 sensors in the Portuguese factory of industrial partner Enercon, enabling state-of-the-art measurement technology from the blade tip to the blade root. This is the first time that a wind turbine’s vibration and load behaviour as well as its aerodynamics and statics have been thoroughly investigated on a full-scale device and during actual operation. Rotor blades twist as well as bend under load. This is also recorded by sensors inside the blades. This data can help in the creation of novel strategies for controlling wind turbines in order to operate them more efficiently and for a longer period of time.
Blade maintenance and logistics
Large blades, which are designed to spin at high speeds and produce more power, are essential to every wind turbine. However, these blades are prone to failure that can be due to weather conditions, insufficient blade material strength, fatigue loads or any other manufacturing process defect. According to a research paper titled, “Failure mechanisms of wind turbine blades in India: climatic, regional, and seasonal variability”, there are a bunch of reasons that lead to failure of wind turbine blades. These factors are damage mechanisms commonly observed in blades such as skin or adhesive debonding, adhesive joint failure, sandwich debonding, delamination, splitting along fibres, gelcoat cracks, etc. Advanced blades should be made of materials such as carbon fibre and smart materials that are cost effective, lighter and stiffer.
In comparison to their onshore equivalents, offshore wind energy components are larger and have longer support structures and blades. In many countries, moving these parts over land is a significant challenge. By situating the necessary manufacturing facilities, supply networks and infrastructure close to ports, this can be avoided. Additionally, the ports must be big enough and have the right kind of vessels available. Furthermore, with the increasing number of outdated wind turbines, it is expected that demand for new rotors and blades will increase over the years.
Since materials can account for a major share in the price of a turbine blade, develping novel cost-effective materials can result in significant cost savings. The operations and maintenance (O&M) of wind turbines is an important factor influencing the wind energy price. Thus, considerations while manufacturing components should ensure lower O&M related costs.
Many wind turbines are very old and have capacities of less than 1 MW. Older turbines can be replaced with larger wind turbines with bigger rotors and longer blades to capture more wind energy. Thus, there is a huge scope for repowering wind power plants across the globe to ensure more energy generation and optimum utilisation of the available wind power potential.