## 1 Introduction  
For providers outside the U.S. and North American borders it is reasonably important to understand the market for original equipment manufacturers (OEMs), asset owners, and component and service providers. The Renewable Energy industry is a hot topic and will remain with steep level of growth of development despite the doubts fuelled by the change in U.S. political leadership [1, 2]. The wholesale price of electricity generated is by far the cheapest for onshore wind turbine. In the recent years, companies with upgraded solution or repair services showed a rapid growth in popularity. In the Wind Energy industry, there is still a poor level of knowledge sharing mostly due to the competition between OEMs and the protection of Intellectual Property. A published case study focusing on a technology challenge specific to an OEM can have a negative effect on the market for new wind turbine sales. On the other hand, it has to be recognized that these studies are helping to optimize costs, hence drive down the Levelized Cost of Energy (LCOE) for wind energy, which leads to larger investments [3]. The Onshore Wind Industry could be separated in four separate clusters regarding engineering challenges: (a) manufacturing, (b) wind site setup, (c) wind site operation, and (d) end of life. The activities are organized around these topics. In events organized by American Wind Energy Association (AWEA) the four stages are grouped into two main categories. One of them is focusing on manufacturing, selling and installing new turbines and everything that come in need for project management, sourcing, and logistics [4]. The other cluster focuses on operation, maintenance, and safety. In this section, turbines that are already online, as well as operations, are in focus. This part of the lifecycle also functions as a test for all the components whether they perform as it was supposed to. If not, there is an immediate engineering need to address the issues with the requirement to stay feasible in the wind turbine operational life cycle [5] and scheduling optimization [6]. Even though some of the turbines have reached the end of the life cycle, there is still no major focus from the industry to optimize this part of the business [7]. In the wind site operation cycle there are ongoing challenges which call for solution or process optimization in order to lower the costs and/or risks. There are many different wind site owners are using the same or similar turbines, hence once a good case practice is identified it can be deployed very easily. The motivation is common for all renewables, keep lowering the LCOE [8; 9; 10]. In the U.S. Wind Turbine market, as a rule of thumb, the owner signs for 5 years with the OEM to provide operation and maintenance services. After this period, the owner of the turbine can decide if they would like to extend the contract and continue to use the OEM's services or take the risk and operate and maintain the turbines on their own. Besides these two options, there are several hybrid setups, including independent service providers (ISPs) and authorized service providers (ASPs); it all comes down how much risks will be taken in house. In the cost optimization process, it is good practice to focus on the greater costs, then gradually move down on the list, and deal with the smaller items. As a comparison, a new gearbox for a 2 MW turbine is ca. $200,000 [11]. For this price, 23 turbines could get new pitch cylinders. The target group for this work includes the hydraulic pitch cylinder component manufacturer, the North American Wind Energy Advisory of the Danish Trade Council, and the Asset owner of the turbines, which were used as a case study. The main contributions of the proposed work are as follows. * A thorough investigation of the selected wind turbines and all error messages
* The severity of the economic loss due to the pitch mechanism failure was thoroughly studied, estimating downtime in wind farms.