Upscaling wind turbines: theoretical and practical aspects and their impact on the cost of energy

Abstract

Wind turbines with a rated power of 5 to 6 MW are now being designed and installed, mostly for offshore operation. Within the EU supported UpWind research project, the barriers for a further increase of size, up to 20 MW, are considered. These wind turbines are expected to have a rotor diameter up to 250 m and a hub height of more than 150 m. Initially, the theoretical implications of upscaling to such sizes on the weight and loads of the wind turbines are examined, where it is shown that unfavourable increases in weight and load will have to be addressed. Following that, empirical models of the increase in weight cost and loads as a function of scale are derived, based on historical trends. These include the effects of both scale and technology advancements, resulting in more favourable scaling laws, indicating that technology breakthroughs are prerequisites for further upscaling in a cost-efficient way. Finally, a theoretical framework for optimal design of large wind turbines is developed. This is based on a life cycle cost approach, with the introduction of generic models for the costs, as functions of the design parameters and using basic upscaling laws adjusted for technology improvement effects. The optimal concept or concepts is obtained as the one that minimizes the total expected costs per megawatt hour (levelized production costs).

Expert elicitation survey on future wind energy costs

“…Engineering assessments provide a bottom-up, technology-rich complement to learning analyses [15]. They involve detailed modelling of specific technology advancements [22][23][24][25][26] and often consider both cost and performance, providing better insights into trends in levelized cost of energy (LCOE). But they also generally require sophisticated design and cost models, often emphasize more-incremental advances, and rarely provide insight into the probability of different outcomes.…”

System dynamic modelling of three different wind turbine gearbox designs under transient loading conditions

“…For Drivetrains A and B, the field measurements of torque spectrums under different operational conditions are not available. For each of these two drivetrains, the rotor torque input data is determined by applying a scaling factor to the field measured torque data of the 2-MW wind turbine, based on scaling relations given in [23][24][25] . It is assumed that the tip speed ratio of 3MW WTs is the same as that of the 2MW WT 25 .…”

Determining Division Location for Sectional Wind Turbine Blades

“…For T-bolted joints, , would be larger than that of the embedded sleeve connection. According to the scheme proposed in Section 2.3, we assumed that the stiffness of the SB-38 sectional blade increases with α of 4,6,8,9.62, and 12 as much as the original blade at the division location. At α = 9.62 is a specific characteristic for the CTC-38 blade, and the other values of 4, 6, 8, and 12 were also considered to study the impacts on natural frequencies.…”

“…Conversely, the first edge natural frequencies decrease faster and faster when division locations are from 14 m to the blade tip. Figure 10b indicates that the second natural edge frequencies increase when the division location is within 6 m and between 24 and 30 m, and the increments of natural frequencies keep pace According to the scheme proposed in Section 2.3, we assumed that the stiffness of the SB-38 sectional blade increases with α of 4,6,8,9.62, and 12 as much as the original blade at the division location. At α = 9.62 is a specific characteristic for the CTC-38 blade, and the other values of 4, 6, 8, and 12 were also considered to study the impacts on natural frequencies.…”

“…Meanwhile, manufacturing long blades would be beset with difficulties without special tooling and molding equipment. In fact, the cost of wind energy is not necessarily reduced by upscaling WTs based on current technology [7][8][9], due to size effects such as expensive transportation and logistics, overloads, and mass increase [8,9]. Sectional blades, as an innovative technique, are the key solution to transportation issues and to help reduce the cost of wind energy [5].…”