Analysis: dirt on a blade's surface can decrease a wind turbine's efficiency by up to 40% after just two weeks of operation
Ireland's energy production is undergoing a transformation. Far from wanting to be left out of the growing trend of Europe's development of green energy infrastructure and spurred on by such accords as the Paris climate agreement, Ireland has committed that 80% of its energy will be renewable by the year 2030, with a projected 50% of that energy being generated by wind.
Ireland sits in a sweet spot of European wind energy production, with average wind speeds greater than most EU countries. The nation's high potential for wind energy production is fortunate, as familiar weather patterns of cloudiness and rain limit solar output.
With the evident importance of wind turbine farms in the future of Irish energy production, a closer look at the effectiveness and longevity of the turbines is needed. Turbine blades have a lifespan of up to 30 years, but have proven difficult to recycle at the end of use. In addition, each blade is exceptionally costly to manufacture. Once decommissioned, turbine blades are often left unused, save for a few creative engineering projects, such as footbridges made of recycled blades, as seen In Midleton and Youghal in Cork.
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From RTÉ Brainstorm, what can you do with used wind turbine blades?
Over its lifetime, a blade experiences damage to its edge, making it rough and less aerodynamic, resulting in reduced electricity production. Dirt on the blade's surface significantly degrades wind turbine efficiency. This contamination can come from many sources, such as insects, soil, sand and salt, to name a few.
Studies show that gradual contamination build-up can decrease a wind turbine's efficiency by up to 40% after just two weeks of operation. In other words, the impact is that the dirt creates drag and as a result blade turns more slowly, producing less renewable electricity over time. As a by-product of contamination build-up, more wind farms must be constructed to compensate for the reduced electricity output if energy targets are to be met.
To fix the contamination problem, turbine cleaning must be considered. However, it is costly due to the laborious nature of the task, with modern blades being up to 80m long and up to a few metres wide. When cleaning the blade, the turbine must be stopped from spinning resulting in energy production downtime, which incurs high costs (a turbine that is not spinning loses revenue). In addition, working at a high elevation is dangerous, and safety considerations for those involved are significant. The urgent need for a cost-effective, efficient, green and non-hazardous cleaning process provides the impetus for pursuing alternative solutions to manual cleaning.
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From RTÉ News, public support for wind farms reaches record high
To help Ireland to meet its 2030 wind energy targets, the Sustainable Energy Authority of Ireland (SEAI) is funding a number of wind energy research projects. One of these is to investigate a possible solution to blade contamination by focusing on using laser light to analyse the material on the blade surface while simultaneously cleaning the blade via laser cleaning.
It might sound futuristic, but laser cleaning has been applied extensively to archaeological artefacts and paintings, among other applications. For example, it was applied in the ancient Egyptian tomb chapel of Neferhotep, which is over 3,000 years old, showing that the technology displays great promise for cleaning surfaces with virtually none, or at worst absolutely minimal, damage.
In its design, the Laser Clean project will selectively remove the contaminants from wind turbine blades. Light is created from the laser vaporisation process and is subsequently analysed. Specifically, spectral analysis is used, where the light emitted by the vaporised contamination is broken up into its constituent colours.
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From RTÉ Radio 1's Drivetime in 2019, a discussion about wind farm guidelines
Each element making up the contamination (eg carbon, nitrogen, oxygen, etc) has a specific colour pattern or 'spectral fingerprint' allowing it to be identified and quantified (what is it and how much is there?). This fingerprint is inputted into machine learning algorithms, which have been demonstrated to classify the difference between a clean blade and a contaminated blade with near-perfect accuracy in a fraction of a second. This identification allows for rapid scanning of the surface with minimal damage.
The American military has already effectively investigated and utilised these light analysis techniques to test for explosive materials from considerable distances, allowing safe and stand-off explosive detection. Moreover, laser light and machine learning have already been effectively combined to sort, in real-time, aluminium scrap metal types in their recycling process. This application significantly improved the speed and success, correctly sorting the metals into groups and reducing manual labour and error.
Incorporating this technology into the blade contamination project, the prototype under construction is a "stand-off system" which will operate from the ground, collecting light via a mounted telescope. This system will allow for a mobile hands-free cleaning solution operated by on-site engineers. The laser will auto-scan the blade's surface, focusing on areas of contamination while ignoring clean areas, classifying through machine learning. In addition, alternatives, such as mounted robotics or drone delivery of the laser system, are also being investigated.
As Ireland transitions from legacy greenhouse gas emitting systems to green and sustainable technologies, every step must be made to maximise its effectiveness and lifespan. Merging high-end science with real-world problems is how the renewable industry must grow if climate goals are to be met. If the research underway is successful, wind turbine efficiency and lifespan can be increased, leading to improved energy production, which is economically advantageous and environmentally friendly.
More information on the Laser Clean project can be found here
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
