Transformative technology advancements are under way in the wind power space, across its various sub-segments. The size and shape of wind turbines are undergoing a change with the use of different types of foundations, increase in the heights of towers and hubs, emergence of longer blades, application of lighter drivetrains, and a shift towards gearless technologies. All of these changes are being made in a bid to increase power generation by tapping stronger winds at higher altitudes, and to increase operational efficiencies. To manufacture such components, innovative technologies are being deployed at manufacturing facilities in order to automate various processes. The wind operations and maintenance space is also deploying artificial intelligence to facilitate predictive maintenance, and drones to reduce the need for manual labour.
Renewable Watch covers the various technological developments under way in the wind power segment…
Taller towers and hubs
The use of tubular steel towers that are conical in structure is common in wind power plants. They are manufactured in two halves and bolted together at the site. The halves are constructed from rolled steel plates and welded together. Other kinds of towers in use include:
- Lattice towers, which use steel rods that are put together to form a lattice. These steel rods are inexpensive and easy to transport and assemble, but lack aesthetic value.
- Concrete towers, which are deployed in countries where steel is expensive, although such towers are quite heavy.
- Guyed pole towers, which are cheaper than other towers, but require more space for the use of guy wires. They are typically used in smaller wind turbines.
- Hybrid concrete and lattice towers, which have greater strength but can be expensive to install.
Hub heights have also increased over the years. Original equipment manufacturers are now moving towards modular steel and steel and concrete hybrid towers to support the increasing hub heights and rotor diameters. The option of on-site tower manufacturing is also being explored.
A key method to increase wind power generation at a particular site is to have bigger blades, which can cover a wider area. The benefits of using longer blades are twofold. One, they can tap wind speeds at higher altitudes. Two, large rotor diameters can help in harnessing more wind energy.
The industry is investing in new technologies at all stages from manufacturing to project commissioning. At the manufacturing stage, the increase in the size of blades has brought with it a need for stronger composite materials. Therefore, new composite materials are currently being deployed that will increase the lifespan of a turbine blade, improve the manufacturing process, and contribute to the overall efficiency of turbine systems. Moreover, new heating techniques are being developed that will work well with this new material. In addition, focused research and development is being undertaken to reduce the time taken to manufacture a single turbine blade by almost 40 per cent. Further, advanced carts and material handling systems are being designed that can rotate a blade 270 degrees, thus reducing the number of times blades must be moved throughout the manufacturing process. Meanwhile, new equipment handling systems are being designed to aid the installation of larger blades. Going forward, 3D-projected blueprints will be used in the assembly of large blades, enabling better time management.
Lighter and more efficient drivetrains
Currently, the technological advancements in the drivetrain space revolve around reducing the mass of drivetrain components through innovative designs, and producing more efficient components with fewer moving parts. It is expected that advanced manufacturing techniques will produce more efficient, reliable and affordable drivetrains. These technological advancements include new single-stage gearboxes, permanent magnet generators, high efficiency power electronics, direct drive systems and hybrid systems.
Conventional gearbox systems in wind turbines have three or more stages; each stage increases the speed of the high speed shaft attached to the generator. The newer single-stage gearbox designs have only one gearbox stage and use a fewer number of moving parts, thus significantly reducing the chances of gearbox failure. In fact, a significant amount of research has been done on direct drive generators, which do not require a gear box and can generate power at much lower rotation speeds, further reducing the number of moving parts and improving operational efficiency.
In general, the commissioning of a wind turbine using either direct drive or gearbox technology is a cumbersome task. This is because both technologies are large and heavy, and have to be placed on top of the wind turbine tower. Consequently, the weight and cost of the tower and the foundation of the turbine also have to be increased. Moreover, transportation of these components is an arduous task. Additionally, large and expensive cranes are needed to install these parts atop wind turbines. Installation has become even more difficult now with the height of wind turbine towers increasing. As wind turbine capacities keep increasing, larger and heavier direct drives and gearboxes will be required, further complicating the commissioning process. All of these complications get further compounded when it comes to offshore wind turbines. With floating offshore wind technology expected to grow further, discussions are taking place on the need to make floating foundations larger to support heavier direct drives and gearboxes.
The use of circular foundations is common as such foundations are able to evenly dissipate the strain to the ground. With time, the design of foundations has slowly evolved, especially for offshore wind plants. Overall, this segment has not seen much innovation. However, there are several structural design variations that have been deployed, which have helped improve the performance of wind turbines.
While a typical foundation involves setting concrete on top of steel bars, there is another type that requires the embedding of a steel cylinder into the foundation. This is done by placing a cylinder on top of a foundation hole, around which steel bars are placed and concrete is poured. An alternative to the traditional steel and concrete foundation is the modular precast foundation. In this design, the structure is partially precast using braces, combined with sturdy conventional foundations. According to research, such a structure increases the hub height by 5-6 metres, thereby increasing electricity generation by 1-3 per cent. Meanwhile, foundation costs are reduced by around 25 per cent for such structures, with approximately 40 per cent reduction in steel and concrete requirement, leading to a reduction of Rs 500,000 per MW in capital expenditure.
In the wind power sector, there is immense scope for automation and the use of technology at all stages of project execution, from wind turbine manufacturing to project development. On the manufacturing front, automation has become necessary to develop larger wind turbines. Robots are replacing the human workforce in the manufacturing of wind turbines and the painting of wind turbine blades. Going forward, the use of 3D printing and augmented reality will help developers test and modify blade designs in real time, thereby reducing manufacturing time and costs.
Automation is serving two purposes. First, with limited manual labour, production time has been reduced significantly, leading to increased productivity. Second, with the greater precision afforded by automation, more homogeneous products are being manufactured, leading to minimal manufacturing errors.
The industry has already started to automate operations. The use of drones, for example, enables project developers to survey sites and perform soil and topographical analyses more efficiently and comprehensively.
The way forward
Significant wind power capacity was installed in India a long time ago, albeit with lower capacity wind turbines. These projects need to be repowered using more efficient and advanced wind turbine technologies. To this end, the technology upgrades vis-á-vis towers, foundations, blades and drivetrains are all helpful.
Going forward, key technological developments are expected to take place in the Indian offshore wind power segment, which is currently a non-existent market. Also, a huge opportunity lies in domestic manufacturing of small and micro wind turbines, which can be set up at remote places across India with high wind speeds at ground level. Ladakh is considered the most promising destination for such technology. A more futuristic vision that is being discussed in the wind energy space is the deployment of bladeless wind turbines, which are a lighter, noiseless alternative to traditional wind turbines with comparatively lower manufacturing costs.
Overall, the wind power segment will see interesting technological advancements going forward, in a bid to decrease manufacturing and deployment costs and increase power generation and operational efficiencies.
By Sarthak Takyar