Van der Velden: FLEX Tunnel Provides Direct Results in Bunker Savings

The Rhenus Duisburg is said to have achieved an energy consumption reduction of about 27% by using the Flex Tunnel.

Van der Velden Marine Systems B.V. (Van Der Velden) says that measurements taken from the Rhenus Duisburg, a push-barge fitted with the company's first FLEX Tunnel technology, have shown that the tunnel system has successfully provided bunker savings.

"The initial findings, based on analysis of the measured data and comparison with vessels with conventional tunnels, suggest that the Rhenus Duisburg achieved around 27 percent lower energy consumption."

Van der Velden says the retractable tunnel was developed specially for inland vessels, which when embedded into the hull of the vessel lowers resistance and increases efficiency.

"Tunnels are commonly used on inland ships, ensuring optimal water flow to the propellers at shallow draughts," the company explains.

"The downside of conventional tunnels is an increase in hull resistance, lower efficiency and increased fuel consumption. Moreover, inland ships are loaded and therefore sail in deeper water conditions for about 85 percent of the time, during which a tunnel is superfluous.

"The Van der Velden FLEX tunnel is deployed when sailing in shallow waters to ensure sufficient water flow to the propellers and maintain their efficiency."

Measurements on the vessel, which is used to move coal between Rotterdam, Amsterdam, and Lünen, are said to have been taken during a trial voyage, as well as when the barge was completing regular service.

"While Van der Velden Marine Systems initially expressed a cautious estimate of energy savings between 10 and 20 percent, the provisional results actually proved surprisingly high."

During the tests, the vessel is reported to have sailed within a range of circumstances, including loaded and unloaded and at various speeds.

Van der Velden says that the results show that there are no restrictions on FLEX Tunnel use at any speed.

"As expected, the results confirm that extremely high vacuum levels are achieved with a deployed tunnel, which implies that the Van der Velden FLEX Tunnel is ideally suited for use with unloaden vessels," stated the company.

Van der Velden explains that to avoid loss of output that may be caused by the propellers breaching the surface of the water, airtight seals on the thrusters and hull are designed to ensure that there is enough water surrounding the propellers.

"The Van der Velden FLEX Tunnel therefore offers one the option of fitting large, 2,000 mm propellers, which improves propulsion and reduces fuel consumption as a direct result," the company said, adding that the FLEX Tunnel's "surprisingly high" energy savings results has "set the trend for the ship of the future."

In August, Rhenus PartnerShip (Rhenus) announced it had held a naming ceremony on August 14 for the Rhenus Duisburg, the first European inland waterway vessel to be equipped with newly developed flex tunnel technology and "father/son" engines, said to "significantly increase efficiency levels."