Wind turbines and other tall structures in cold locations are prone to ice accumulation. As with any structure, under the right atmospheric conditions, ice can build-up over a period. Whilst the accumulation of ice is highly dependent on weather conditions and the turbines operational state, this build-up can lead to potential risks as the ice melts, causing hazards for people, animals, infrastructure and assets adjacent to the installations. Therefore, an effective risk management system for monitoring and controlling these risks must be applied to ensure adequate safety around installations.
What is risk?
The general definition of risk is; Risk= Probability x Consequence. Probability, being how often can it happen or what is the frequency, e.g. how many times does it occur per year. Consequence is ‘what is the effect of an event, e.g. ice accumulation can lead to ice throw which can cause someone to be injured.
The risk associated with wind turbines
Risks is not only an issue to people directly involved in your business activity, such as employees, supplier, goods delivery personnel, but can also directly affect people that are not at all related to your business, but could still be at risk from business activities, such as those who live, work or access the surrounding area. This can be relevant to wind turbines and other tall structures, as they are often located in remote locations away from your primary business premises. There can often be discrepancy between these groups, and the risk perception between these groups, as those directly related to your business, must have a good understanding of the risk associated and how to mitigate against them, however those not directly related to your business do not have an obligation to understand the risks associated with your activities. Therefore, the key principles for businesses operating these types of assets is that the facility should not increase the risk to the public significantly compared to the daily risk in society.
Managing ice risk from turbines
Due to all the unique nature of managing risk in these types of environments, such as unpredictable weather, multiple risks groups affected with differing levels of understanding of the risks. Therefore, a risk management method must combine risk analysis and risk controlling barriers, such as these three steps:
1. Risk assessment
Risk assessment is a term used to describe the overall process or method where you: identify hazards and risk factors that have the potential to cause harm (hazard identification), and analyze and evaluate the risk associated with that hazard (risk analysis, and risk evaluation).
Risk assessments are included as one of the elements of systematic risk management in any business or business activity, and provides support for safety and security-related decisions. A risk analysis should surely be completed prior to construction, alternatively during operation. The risk analysis can be conducted with the help of simulations and barrier analysis frameworks. The barrier analysis supplements the simulations to visualise how preventive systems and technical barriers prevents and mitigates incidents. These risk assessments should also be based on best practise for the industry as guidance, such as The Norwegian Water Resources and Energy Directorate, which give recommendations on how to manage the risk of ice throws from wind turbines and avoiding third party injuries resulting from ice, or the IEA Wind TCP Task 19: Wind energy in cold climates, which is the international recommendations for ice fall and ice throw risk assessments, which provides best available recommendations for assessing risk of ice fall/throw as well as reducing the uncertainties in such assessments.
2. Identify maturity, vulnerability and effectiveness of barriers
It is imperative to identify the maturity, vulnerability and effectiveness of the implemented barriers to ensure that the barrier functionality performs as intended. Further, identify the current preventative and mitigating barriers to visualise the risk picture and the measures which mitigates the the risk. The focus should be on preventative measures to reduce the likelihood of the risk occurring, and if needed, identify additional barriers in addition to identifying the effectiveness of these barriers. This is an iterative process until you meet acceptable level of risk or as low as reasonably practical (ALARP). Support systems must further be identified to ensure that the barrier management system is robust and resilient. This is the day-to-day activity that ensures that the functionality is there when demanded and performance is within its operating criteria. A lean response plan must also be developed for the most critical incidents, with clearly defined responsibilities and tasks, and to ensure that you are not dependent on one person to be able to have an effective barrier.
3. Ensure effective communication
You need to ensure effective communication of the barriers to all related parties, employees, subcontractors, and the general public when relevant. This can be in the forms of signs, lights etc. The human factor is all about the interaction between the human and the system, such as barriers you put in place to avoid harm, this can especially be important when manging risk to the general public. Facilitating effective communication and reducing discrepancy in risk perception is key in ensuring risk mitigation against the risk of ice from high structures.
Learning from other industries
Overall methodology for safety studies stays the same regardless of industry, following the key principles of risk management strategies, including carry out risk assessments, identifying maturity of barriers and ensuring effective communication of barriers. These are learnings that can be implemented in to the wind industry. An example of this is the learnings taken from Tryvannsmasta, a 209-meter-tall broadcasting tower near Oslo. In Tryvannsmasta we investigated whether the risk was at an acceptable level or not. We combine simulated data with technical barriers in an integrated approach to validate the safety, design and the effectiveness of the barriers to ensure safe operations for Tryvannsmasta. This method was also aligned with the recently released guide from The Norwegian Water Resources and Energy Directorate, Icefall from wind turbines.
Wind turbines and other tall structures in cold location are prone to ice accumulation, and whilst some of these conditions can’t be predicted or managed due to the dependent of weather conditions, you can mitigate against the highest risks and implement successful risk mitigation strategies to ensure risk is managed to the most effective level, reducing the risk to both your own company and employees, as well as the wider public around your assets.