The eco-ship uncovered

Are they or aren’t they worth the investment? The argument is one that rages constantly in the industry when reference is made to the much-maligned eco-ship. As the age of austerity has prompted economies to be made in all sectors of the industry, ship design companies have responded by formulating ship designs to reduce water resistance and increase fuel efficiency.

To some – namely the ship owners – this coincidence is striking and questionable. Fuel price hikes and increased regulation of emissions is forcing the owner to alter the way in which it operates its vessels. So when the market conditions finally exist in favour of paying more for a vessel with the latest state-of-the-art high-efficiency technology, have ship design companies joined the bandwagon to exploit the desperate owner with sham concepts?

Speaking recently at Sea Asia in Singapore, Khalid Hashim, managing director of dry cargo operator, Precious Shipping, suggested this was the case. “Basically the eco-ship concept is really just a marketing ploy by the almost dead shipyards to try and get a short lease on life. In the dry bulk and tanker space there is no such thing as an eco-ship,” Hashim said.

Hashim’s opinion, however, is just one of many on the subject. In October 2012, global commodity trading companies including Cargill and Huntsman Corporation announced that they would look to charter the more fuel-efficient vessels in the market. Speaking at the time about the company’s commitment to supporting fuel-efficient vessels, Jonathan Stoneley, Environment and Compliance Manager, Cargill Ocean Transportation, said: “We hope this action will demonstrate to ship owners that they can and should do more in terms of efficiency, and that the market will reward them.”

The Environship

Stealing the show at the recent Green Ship Technology Conference in Hamburg, Germany, was Rolls-Royce’s eco-ship concept titled the ‘Environship’. Building on its recognition at the 2011 Nor Shipping exhibition after winning the Next Generation Ship Award, a series of commercial orders and receipt of the Green Ship Technology Award in Hamburg has raised its status to beyond that of ‘concept’. Combining a range of the company’s design techniques and patented technologies, Rolls-Royce says that the vessel can reduce CO2 emissions by up to 40 per cent in comparison to similar diesel powered vessels.

Head of ship design, Per Vedlog, speaks in depth about the vessel’s design and components.

Background

“The Environship concept is founded on four main pillars of technology; the Promas integrated rudder propeller system, the hybrid shaft generator system, the gas engine and gas fuel system, and the Rolls-Royce wave-piercing technology for a new innovative hull design to get optimal performance in the sea way.

“The integration of all these technologies is very important. With our design we integrate these technologies in the optimal way, making sure that all the technologies have the necessary technical interface and logistics so that the owner isn’t faced with any technical problem when they operate the vessel.”

Initial design stage

“In-house, we have quite an extensive package of different software. We have advanced CFD (Computational Fluid Dynamics) iteration processes with an in-house CFD department. For hydrodynamics, we use the Marintek ShipX package with which we can do quite extensive simulation and analysis. We have actually participated in developing this ShipX package with Marintek.

“We spend 3-4 million NOK every year to do studies on hydrodynamics and vessel movements. We do quite extensive cost benefit analysis on all our projects and we always talk with our owner to define the operational profile as exactly as possible so we can develop, design and use optimal power at any time.”

Wave-piercing technology and hull design

“The merchant market has traditionally been dominated by a focus on the calm sea performance. But from our point of view, the sea is never calm. In the North Sea basin, you always have waves. Therefore, we have focussed on performance in real sea waves without compromising on the underwater hull form and performance in calm sea.

“The new wave-piercing technology has focussed on ensuring less resistance in real sea waves. In this regard, we have learnt a lot from our offshore business where the performance in the North Sea basin around offshore platforms is very important. And we have taken this into the merchant market, focussing a lot on its performance in sea ways.

“With the wave-piercing technology, we have taken the fore perpendicular and moved it to the forward fore part of the bulbous bow. We have increased and optimised the length beam ratio of the vessel and by that reduced the resistance. We have also reduced the water entrance angle on the foreship, which in turn reduces the pressure around the forward shoulder where you have the main resistance.

“In addition, we have taken the conventional out-falling flare or bow design away so that we have a more straight-line cross-section in the bow. This means the bow is not pushing the water forward and out as you see on a conventional bow but instead letting the water flow along the ship side. This reduces the resistance a lot when you enter into the waves.

“With this increased straight line cross-section, we also reduce the swell-up around the foreship, which is another one of the major resistance coefficients. With the Environship, there is an average of more than 10 per cent less resistance in different sea conditions than a conventional optimal outfalling flare vessel.”

Promas rudder/propeller system

“We like to have control right from the bunker flange to the propeller thrust. We have the Promas rudder/propeller system where we get 4 to 8 per cent greater propulsion efficiency than a conventional solution. We can do this with the Promas system where there is a hub cap on the propeller and a rudder bulb on the rudder, which is twisted.

“When we have a hub cap behind the propeller, we take away the hub vortexes from the propeller and this means that we can create an optimal load distribution over the propeller blades. We can do this by moving the load from the propeller tip closer to the hub. Due to that, we don’t have the hub vortexes to take into consideration, which means that we get much better propeller efficiency.

“In addition, we can significantly reduce pressure pulses on the hull and thereby reduce noise and vibration problems. Reduced pressure pulses also enable us to slightly increase the propeller diameter.

“In addition, we have a twisted rudder that recovers the rotational energy of the water behind the propeller and gives you a positive lift in forward direction. We see better improvement on high block efficient hull forms than on flatter hull forms.”

Hybrid shaft generator

“The hybrid shaft generator (HSG) allows you to take up optimal power when you are loitering and going to lower and lower speeds, for example when manoeuvring in and out of harbour and piloting. A traditional solution with a shaft generator requires a fixed rpm (revolutions per minute) on the engine and propeller so you use a lot of energy to rotate the propeller at fixed rpm.

“With the HSG, you can reduce the rpm on the engine and the propeller and still have the shaft generator connected to give stable frequency and voltage into the switchboard. You can reduce the rpm on the engine and propeller and adjust the propeller pitch.

“With the HSG, you can also run a PTI (power take-in) – that means that you can use the HSG as an electric motor and use the auxiliary engine (if diesel) to run the vessel in diesel-electric mode when you do maintenance on the main engine."

Gas engine

“Then we have the gas engine that has very flat fuel consumption all the way from 100 per cent and down to 20 per cent load; this makes it very suitable for operating together with the HSG. The thermal efficiency of our gas engine is very high compared to dual-fuel or diesel engine. We have more that 48 per cent thermal efficiency compared to 40 or 44 per cent on a diesel or dual-fuel engine.

“Compared to a dual-fuel engine, when on 100 per cent load the gas engine consumes seven percent less fuel and on 50 per cent load, we have more than 17 per cent reduction in fuel consumption.”

Technology add-ons

“Depending on the vessel, there are also additional technologies we can combine with the Environship technologies.

“On RORO general cargo vessels for instance, which have stricter requirements for ventilation, we have included a feature called ventilation-on-demand, applicable for instances in harbour where there can be as many as 20 to 30 changes in air characteristics. We don’t ventilate more than necessary at any time and we save a lot of energy resources by having that.”