INTRODUCTION
The Shipping industry is challenged with increasing demands to reduce the environmental impact of shipping operations. Wind-assisted propulsion provides significant potential for the reduction of fuel consumption, exhaust gas emissions and operational costs of ships.
Norsepower was established in 2012 with the ambitious target of developing a modernised version of the Flettner rotor, an invention dating back to the 1920s. The challenge was to design a Rotor Sail solution which is economically justifiable as an investment. Currently, the financial incentive to install auxiliary wind propulsion is fuel cost savings, however, the reduction of CO2
and other
emissions will also play a significant role as shipping strives to play its part towards achieving a lower carbon economy.
When considering the most important requirements for a successful product, Norsepower focused on ease of use and low life cycle costs. Moreover, extensive tests and practical experience onboard the pilot project M/S Estraden have confirmed that Norsepower has succeeded in developing a technically and economically sound Rotor Sail solution. Thrust producing performance and reliability of the Rotor Sails are according to expectations. Most importantly, the shipowner and crew are very satisfied with the technology onboard. The experience has encouraged Norsepower to develop larger Rotor Sail designs to provide auxiliary wind propulsion for a range of different sized vessels.
HOW DOES A ROTOR SAIL PRODUCE
THRUST The Norsepower Rotor Sail Solution is a modernised version of the Flettner rotor – a spinning cylinder that uses the Magnus effect to harness wind power to propel a ship. The Magnus effect is described using Figure 1, while Figure 2 visualises the wind direction and thrust produced at an angle of 90 degrees to the
wind direction. An example of how the thrust (expressed as main- engine equivalent propulsion power) produced by the Rotor Sail changes with the true wind speed and direction can be seen in Figure 3 (the polar diagram). As can be seen on the polar diagram, the Rotor Sails are able to start saving fuel at a 20 degrees true wind angle, when the true wind speed is at least 7 m/s. The savings are maximised when the true wind angle is circa 120 degrees, and when the true wind speed is at least 20 m/s or more.
AUTHOR BIOGRAPHY:
M.Sc. (Naval Architecture and Marine Engineering) and eMBA, Jukka Kuuskoski has worked with ABB’s marine business unit for 15 years in management positions of electric propulsion project delivery, sales and marketing and service operations. Before joining Norsepower Jukka worked 7 years in the wind power industry.
Figure 1. The Magnus effect is caused by a thin layer of air which rotates along the rotor surface and meets the wind on opposite sides of the rotor. On the high (accelerated) wind speed side the air pressure is reduced and on the low (decelerated) wind speed side the air pressure is increased. The pressure difference creates the lift (thrust).
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