Modern Windships; Phase 2

Abstract

This report presents the findings of the modern WindShip project, phase 2. The project is funded through the Danish Environmental Protection Agency, acting on behalf of the former Danish Council for Recycling and Lesser Polluting Technology.

In the previous phase 1 of the project a broad background on historical WindShips was summarised and a proposal for a new type of Wind Ship was drafted. Building on the experiences from phase 1, the second phase of the project focuses on:

Detailed design of the rig. A new rig concept is developed, using high lift profiles with movable flaps. On a central rotating high tensile steel mast sandwich profiles acting as slats and flaps are hinged on horizontal axes. The mechanical construction is covered in some detail, indicating how the mast profiles are turned, locked etc.

Realistic simulations based on measured and simulated performance. Measurements include wind tunnel as well as towing tank tests. Simulations are performed using a velocity prediction programme (VPP) developed specifically for the modern WindShip. Weather routing based on real weather statistics is performed as well as finite element modelling (FEM). A computer simulation of the modern WindShip sailing is also included, but not covered in the report.

Economical feasibility study. A commercial comparison between existing product carriers and the economical performance of the modern WindShip is performed. The comparison uses existing trade routes and patterns, drawing from the weather routing performed above, to calculate with high precision the fuel consumption of a modern WindShip.

A product carrier is chosen as design study object in the economical analysis. The product carrier is selected since such a vessel of the same size as the modern WindShip, approximately 50.000 dwt, are common. Two trade patterns are chosen as representative for product carrier traffic, one mainly in the Atlantic region, the other in the Indian-Pacific region. The economical study also investigates the effects of varying the bunker oil price, and the average speed of the ship.

Results from strength calculations (FEM) show that the overall scantlings of the mast are in accordance with leading classification societies, such as DNV. Polar diagrams are plotted using the velocity prediction programme, showing that the modern WindShip reaches 13 knots sailing speed already at about 9 m/s of true wind at 100°. Weather routing shows large variations in fuel consumption, depending on route, direction and time of year.

The economical analysis shows that on average the modern WindShip is approximately 10% less economical than a "normal" product carrier. There is a large fuel consumption penalty in sailing at 13 knots with the modern WindShip, as the engine arrangement is not chosen for these speeds, and normally winds are not strong enough on some of the selected routes to drive the ship at that average required speed. Lowering the average speed has positive effects on both the fuel consumption and the required freight rate per day.

Proposals for further optimisation are put forward.