QBlade-Based Assessment of a Vertical-Axis Wind Turbine for On-board Electricity Production on Ships
Mahvash Jamalvand, Hochschule Emden/Leer
The reduction of fuel consumption and emissions in maritime transport has increased interest in auxiliary renewable energy systems on board ships. Wind energy is one possible option; however, for shipboard application, the benefit of a wind turbine cannot be assessed only by its generated power. The additional aerodynamic forces introduced by the turbine may increase vessel resistance and reduce the overall energy benefit. Therefore, a net-power assessment is required.
This study investigates the preliminary feasibility of using a straight-bladed Darrieus-type vertical-axis wind turbine for on-board electricity production. A vertical-axis concept was selected because it can accept wind from different directions without an active yaw system, which is relevant for ships where the apparent wind direction changes with ship speed, heading, and environmental conditions. The investigated rotor has a radius of 5 m and a height of 10 m, resulting in a swept area of 100 m².
The turbine performance was analysed using QBlade. First, the gross power output was estimated for different relative wind speeds based on the turbine power coefficient. The analysis was then extended by using QBlade rotor force outputs to estimate the drag-related power penalty and to assess the influence of aerodynamic loading on the vessel. In particular, the rotor lengthwise force F_x,rot was used to evaluate the longitudinal resistance effect, while the rotor crosswise force F_y,rot was considered for lateral loading.
At a relative wind speed of 10 m/s, the turbine produced a relevant level of gross power. However, after considering mechanical and electrical losses as well as the drag-related power penalty, the net-power balance became unfavourable for the baseline rotor in the headwind case. For an assumed ship speed of 10 knots, the QBlade-based rotor force resulted in a drag-related power penalty of approximately 36.5 kW, which was higher than the usable turbine power estimated under a conservative power-coefficient assumption.
Because the apparent wind direction on a ship is variable, a directional sensitivity assessment was also carried out. The QBlade force components were projected onto ship-fixed longitudinal and lateral directions for different apparent wind angles. The results show that the longitudinal drag penalty is highest in headwind conditions and decreases toward beam-wind conditions, while lateral loading becomes more important. This indicates that wind direction has a significant influence on the net-power balance, even if the turbine power itself is mainly governed by relative wind speed and rotor performance.
The study shows that a shipboard vertical-axis wind turbine is an interesting concept, but the present baseline design cannot yet be confirmed as energetically favourable. Further work should focus on improving the power-to-drag ratio, optimizing the rotor geometry, and assessing the complete shipboard installation with more detailed aerodynamic methods such as CFD.
