It is popular opinion that wind energy is a realistic alternative to fossil fuels and undoubtedly will be a major player in helping us reach climate targets. According to Ørsted, Offshore wind has the potential to generate more than 420,000 twh per year worldwide. That is more than 18 times the global energy demand of today. As of today Offshore wind is about one-twentieth of installed capacity (743GW) as that of onshore wind with a cumulative installed capacity of just 34GW at the end of 2020. Despite being less prominent than its onshore counterpart, Offshore wind capacity has grown by more than 30% every year for the past 10 years and is expected to reach 200-230 GW already by 2030.
Onshore Wind Vs Offshore Wind
As shown by the statistics above, onshore wind is dominant in total wind energy production. This is because onshore wind is one of the most cost-effective and mature of all the renewable technologies while due to construction difficulties, immature technologies, high maintenance costs, development constraints and costly connection to the national grid, offshore wind is one of the most expensive energy technologies. It is for example nearly double as expensive than fossil fuel generators and indeed, double as expensive as Onshore wind turbines.
Due to, quick installation and cost benefits, it begs the question why more onshore wind farms are not built rather than offshore to meet renewable energy demand. The main reason focus is moving to offshore is because onshore wind farms are typically located in areas where there is low conservation or habitable value with good wind speeds. Finding enough of these spots can be difficult with land in many countries is at a premium and available spaces limited. Similarly, Onshore farms often do not produce energy all year round due to poor wind speeds or physical environmental blockages. In addition, one of the biggest issues with onshore wind farms is that they often face local resistance due to the noise pollution and visual impact. These negating factors plus the global need to quickly move to renewable energy sources has led to an explosion in the growth of offshore wind farms in recent years despite the higher cost.
Offshore wind farms have their benefits despite being more costly to build and maintain. More energy can be produced per structure because they can be built larger and taller than their onshore counterparts. As they are built out at sea, they also do not have the same visual and noise impact on people. Importantly, there is also typically a much higher wind speed out at sea with no physical restrictions blocking wind flow which again leads to more energy being created. Today there are 5566 offshore wind turbines in Europe. It is expected by 2050 there will 150,000 plus (Energy Central 2021). This creates technical challenges as placing foundations on deeper water sites due to space issues is more complicated. The development of floating wind turbines and better cables will be an important factor in facilitating this.
Below we will look at some operational challenges within the wind energy industry focusing on offshore wind. Wind farms face a variety of risks including maintenance costs, weather conditions, innovation challenges, environmental factors, political considerations, and local opposition.
Carbon Foot Print
Despite being one of the cleanest forms of electricity generation there is still a significant carbon cost to manufacture, install, operate and maintain windfarms onshore and offshore. This includes mining for the raw materials, producing materials such as concrete and steel, transportation, and maintenance.
With Offshore wind projects moving further away from land, as sites closer to shore are filled there is a heightened cost and risk with moving crew to and from offshore wind installations for installation or maintenance work. Challenging weather conditions and the unknowns of new technologies also add to the risk. Safety incidents related to crew transfer made up two thirds of total incidents in 2016 according to the Global Offshore Wind Health & safety organization.
Planning & Maintenance
Planning, installing, operating, and maintaining wind farms are complicated with many variables to include. Up to 30% of overall costs of offshore wind are attributed to operations and maintenance activities (SINTEF 2022).
Illustration of common offshore wind operations and maintenance activities.
Offshore wind turbines have higher maintenance costs than on-land wind turbines due to less accessibility, corrosion from seawater and harsher weather conditions. Below are four key challenges that affect foundations, cables and turbine blades.
1. Turbine Blade
The impact of fatigue on turbine blades is an ongoing challenge, with each blade being subjected to more than 100 million loading cycles over the course of its lifetime. The cyclic loading of the blades is also worsened by leading edge erosion and ice build-up. Even a small amount of leading edge erosion can result in a 5% drop in annual energy production. The increased height of turbines and the span of blades both raise the risk of lightning strikes and the cost of repair. Lightning strikes can result in the loss of turbine blades and damage to electrical systems (Heering Et al. 2019).
2. Export cable and grid connection
Inspecting and repairing the connection of the offshore power plant to the onshore power transmission system, including onshore and offshore electrical substations and export cable are also common challenges. Cable Failure results in interruptions in power generation. This can be exacerbated by cost-cutting efforts made during installation or poor designs not able to endure the harsher marine conditions. Cable failure obviously require quick response times to ensure continued power flow.
3. Array cable
Inspecting and repairing the subsea cables to connect the turbines to create a unified power plant. As with export cables failure results in interruptions in power generation. Harsh marine conditions means that more frequent maintenance is required compared to their onshore equivalent.
4. Foundation maintenance
Inspecting and repairing the turbine foundations and subsea structures. As offshore wind farms move to increasing water depths and aim to operate with larger turbines, foundation designs have needed to adapt accordingly. The challenging marine environment means that the monopile foundations are subject to both internal and external corrosion causing maintenance issues. There are also tough challenges relating to fatigue, including the effect of loading during the initial piling operations and the cyclic loading of the structure from wind and waves. These fatigue difficulties can be intensified by the composition of the seabed and any developing biofouling, which increases hydrodynamic load as well as creating challenges in routine inspection and maintenance
As detailed above, planning and maintenance teams needs to take multiple variables into account, including weather conditions, tide, and the availability of spare parts and technicians when planning and executing the work. Established industries such as Oil and Gas tend to do most of their maintenance work in a planned proactive manner to ensure an efficient use of resources and limit the amount of stops required. As a relatively new industry with new technology, Off-shore wind operators tend to be more reactive when it comes to maintenance activities and waste time and resources reacting to unplanned events and/or production stops.
Digitalization and new opportunities
Digitalization is a key enabler for operational efficiency. By connecting all operational elements and systems that cater for them like helicopters, vessels, equipment and crew, operations become more visible to all relevant stakeholders. With full information available, detailed plans can be made and adjusted when needed, leading to more proactive and efficient maintenance and in addition reduce the amount of stops. Real time insights allow operators to be better informed about weather-sensitive operations and facilitate live re-scheduling to avoid potentially dangerous situations. Similarly, transport logistics can be optimized so no trips are wasted, and task emissions reduced. HSSE can also be improved due to increased situational awareness.
In summary, wind energy represents an incredible opportunity to meet growing energy needs via a renewable energy source.
When considering the complexities of the wind energy industry, the number of companies involved, required resources, and the sensitivity to disruption by changing weather conditions and harshness of the marine environment, it becomes clear that there are many factors that can influence operating efficiency.
Implementing a software solution that gives full visibility over all planning and maintenance data to analyze, optimise and automate many of these processes will drastically increase efficiency, lower the carbon footprint, and reduce costs for operators.
Visavi is a system that collates all your operational data systems in one user-friendly interface and facilitates re-scheduling. Based on our data, increasing plan attainment, increasing tool-time, reducing emissions and operational cost savings are possible right now by implementing Visavi.