Vessel propulsion unit is a maritime equivalent of the jet engine
06 May 2013
GE's Power Conversion business has increased its offshore systems portfolio with Inovelis, a podded thruster offering high fuel efficiency and performance.
The Inovelis maritime propulsion unit
Inovelis incorporates an electrically powered propeller with its motor housed within a steerable pod mounted beneath the hull of the vessel. It incorporates all the assets of a podded thruster, including manoeuvrability, responsiveness and excellent fuel economy.
Based on pump jet principles, it features fixed stator vanes and a nozzle that act together to guide the water flow across the impeller blades, substantially enhancing propulsion efficiency. Its compactness enables an even greater degree of integration between the hull and the propulsion unit, further influencing the ships’ fuel economy and emissions.
Pump jet technology was originally used in submarines, and is already used for high-speed surface vessels. Now GE is applying it to offshore platform support vessels (PSVs).
Inovelis has higher thrust capability than a more conventional propulsion system, as well as improved hydrodynamics, providing higher efficiency over a wider range of operations, in dynamic positioning (DP) and in transit.
A traditional propulsion set-up for a PSV has a large propeller with a nozzle, which has reduced performance when the speed of the ship increases.
Whereas a vessel with a traditional propulsion system has a propeller pushing on the water, a pump jet draws in water and then forcibly ejects it out through a nozzle.
It is the marine equivalent of a jet engine, except that while jet engines are fixed, Inovelis can be pointed in any direction on a horizontal plane.
“Inovelis is a new concept that brings better performance – both improved thrust capability as well as improved hydrodynamics – combined maximize performance of pod technology and will bring fuel efficiency,” says Paul English, Marine Leader of GE Power Conversion.
He cites a PSV driven by two 2.5MW Inovelis pods, operating 30 percent of the time in transit at full speed. “The benefit in terms of fuel savings could be, based on our estimates, up to $250,000 in one year”, English says.
“There is a clear trend towards larger, more capable offshore support vessels and a second trend towards the search for oil and gas taking these vessels ever further from home ports,” says English. “Ship operators are looking for systems that support cost-effective, fuel efficient, rapid transit without sacrificing the capability to operate effectively and efficiently once on site in DP mode. This raises a dilemma as many current designs are a compromise between these two differing requirements.”
Inovelis is different. It’s a system designed to best suit the performance and fuel efficiency needs of both modes of operation, transit and dynamic positioning.
English says that the Inovelis advantage is so significant that it has the potential to permit ship designers to incorporate reduced capacity power plant – fewer cylinders or smaller engines - when designing offshore vessels.
Inovelis uses GE’s induction motor technology, which brings further reliability and helps reduce maintenance requirements. In fact, the pod has a 'no man access' design, which helps reduce overall size and provides an additional differentiation from other designs.
GE has already received a number of orders all destined for large PSVs. The first is scheduled for delivery soon, with ship commissioning around the end of the year.