India is the fourth largest producer of wind energy in the world. Despite slow growth in recent years, the country will be looking at big expansion, going forward. With technological upgrades, turbines are getting bigger in size and are being developed in difficult-to-access areas even offshore. At the same time, older turbines are more likely to fail and hence, need increased efforts for operations and maintenance (O&M). The cost of O&M for a wind turbine represents about 20-25 per cent of the total levellised cost per kWh that it produces over its lifetime. For newer turbines, this figure is 10-15 per cent.
With the nature and scale of wind operations today, it is becoming increasingly clear that manual methods of O&M will have to be replaced with robots and drones. To this end, there have been big developments in the automation of the O&M process across the globe. Robots and artificial intelligence have come to play a significant role in prominent industries such as transport, manufacturing and even healthcare. The renewable energy sector has started adopting these technologies and given the safety risks in the wind energy segment, it only seems necessary.
Drones for inspection
To reduce the human risk in the O&M process, drones can be used for inspection, while robotic technology can be utilised for cleaning and maintenance. As per the analytics company Nanonets, semi-automatic drones could inspect about 12-15 wind turbines in a day, while only about two to three turbines can be inspected with conventional methods. If the process is fully automated, drones can potentially inspect up to 20 turbines every day. In terms of cost, drones reportedly cost about $300-$500 per wind turbine or 20-25 per cent of the manual inspection methods. However, this does not include the costs of the pilot (for a semi-automated drone), and the data analysis technician, which could take the cost to more than $800 per wind turbine.
In most situations, drones can give better quality data than manual inspections. These devices can fly 3-10 metres above the blade and can circle it to cover the turbine’s entire surface area. These drones are often equipped with a digital camera, a thermographic camera, or a combination of both. With thermographic inspection, one can get more accurate data regarding the temperature in large areas, hidden defects, corrosion and other abnormalities. This data can be meta-tagged and used to construct a three-dimensional model of the blade with accuracy that is hard to achieve with manual methods.
For offshore wind plants, underwater drones can be used to survey and inspect array cables and export cables for the project. These systems offer regular inspection underwater so that potential issues can be addressed. They have a less-than-average capital expenditure and negligible operational expenditure and make the inspection process less cumbersome for offshore wind operators.
Robots for maintenance and repair
The ice gathered on the surface of wind turbine blades can reduce their efficiency by up to 20 per cent. In colder parts of the world, drones can be equipped with nozzles that spray liquid to de-ice turbine blades. Such drones are connected to the ground via cables that supply the liquid. Colder climate locations house about 25 per cent of the world’s wind turbines and this further justifies the need for such drone systems to clean them.
Once issues are detected in the wind power plant, robotic technologies can be useful in carrying out cleaning and repairs. However, the use of robots for the repair work is still in the development stage. Crawling robots have slowly been gaining popularity to carry out dangerous and risky work on wind turbines. These devices carry out both inspection and minor repairs such as cleaning and polishing of turbines and use vacuum pumps for vertically climbing wind turbine blades. These robots are also fitted with microwave scanners to verify the structural integrity of blades.
Globally, laws are changing to allow the increasing penetration of drones and robotic technology and the wind energy segment is adopting it very fast. With drones being increasingly adopted, strong efforts are also being made for robots to do much more in wind turbine maintenance. The need for robotic technologies has been amplified by the growing offshore wind sector.
In 2020, a Swiss robotics firm, Anybotics, introduced Anymal, a four-legged robot that is designed to detect thermal hotspots and oil and water leakages in offshore wind turbines, using visual and thermal cameras, microphones and gas-detection sensors. In 2021, a robotic start-up, Bladebug went a step further by developing a six-legged crawling robot that can even carry out repairs on the surface of the turbine blade. The device uses a hyperspectral camera to analyse the chemical composition of the surface of the blade and assess the potential damage. The robot is also equipped with a robotic arm that will carry out repairs if needed. It is designed to withstand strong winds and does not require a traditional rope access team. The device has just completed field trials and is expected to be launched soon.
More recently, the British consortium, Forth Engineering announced the development of the RADBLAD technology, which is designed to complete a full X-ray survey of a large wind turbine (onshore or offshore) and all its blades in just a few hours. The device is set to be revolutionary, as it weighs just less than 25 kg and uses a magnetic arm that deploys the X-ray system on the blade. As it uses a radiographic system for inspection, it is expected to be ideal for the early detection of internal damage of wind turbine blades.
Challenges in adoption
The biggest advantage of the drone technology in turbine inspection also ends up being a cause for its downfall. Drones capture large volumes of data and to draw relevant conclusions from it, they need appropriate applications or software. When there are many drones, the process of analysing data becomes more complicated; at the same time, there is a need for a dedicated team of experts to analyse this data. The analysis is especially important because even if the smallest faults are overlooked, it may result in fatal consequences for the wind power plant.
Another reason that drone technology is still in its infancy in the wind power segment is that components and subsystems of a drone can fail, which can have disastrous consequences such as loss of wind turbine, loss of electricity production, and in some cases, the drone can crash to cause serious injuries or even loss of life. Adding to this is the extreme weather conditions in wind farms; temperature, dust, and strong winds can pose a huge challenge for drones. Linked to this, regulations can also present a barrier for drones with many countries mandating flying data due to safety concerns. This does seem to be improving, however, as many countries are easing these restrictions. For example, the US eased its restrictions for drones in 2016, by increasing the maximum altitude at which drones can fly. The country also removed the requirement for a pilot’s licence to operate a drone.
Although operational costs may not seem to be much of a barrier for drones, the upfront costs are high. Wind turbine inspection robots and drones are estimated to cost about $20,000, while cleaning robots could be priced as high as $150,000. Unless the wind farm is very large, developers are not quite convinced about the initial investment and the long payback period. The batteries used in drones and robots need to have features such as good energy density and quick charging capabilities to have a adequate payload carrying capacity and flight time.
Despite witnessing delays in the adoption of the technology, the renewable drones market is growing at a rapid pace. It is estimated by Fatpos Global that the global market for these devices is currently valued at about $42 million and is expected to grow at a compound annual growth rate of 26.5 per cent, to reach $152 million in 2030. Despite this promise, the reliability of drones still needs to be improved. As per a 2021 analysis on the failure rate of drones in wind parks, there are only a limited number of studies that test the actual performance of these devices. Hence, there is a need to develop methodologies to assess the reliability, availability and maintainability of drones to avoid system and component failures. This could go a long way in addressing the apprehensiveness of developers in taking up these automated methods. Robotic cleaning and repair systems are still in the development phase, but with some big innovations in recent months, there could be an overhaul in the methods used to service wind turbines across the globe.
In India, wind development has been extremely slow in the past five years, but going forward, turbines are only going to get bigger as the country aims to integrate 60 GW wind energy into the grid by 2022. Even existing wind capacities are scattered among various captive players and a big policy push might be required to incentivise the widespread adoption of drones and robots in the country. As all other industries and sectors are embracing robotics, it is high time that the wind energy segment also powers its O&M with automation technologies.
By Rithvik Kumar