How does the ASV concept function?

The patented air supported vessel concept uses pressurized air, capture in a hull integrated cavity underneath the hull, to support up to 80 +% of the vessels weight and to create a "cushion of air" between the hull and water. Almost like a hovercraft but without any rubber skirts/bags.

Why is reducing "wetted surface areas so important"?
Wetted surface underneath the hull is a main resistance component. Less hull contact with water equals less resistance.

Tell us a little about the lift fan system?
An ASV uses a special centrifugal fan system; located in the bow of the vessel. The BB GREEN fan will be powered by an electric motor. Hydraulic power from a separate engine or via main engine PTO may also be used (diesel powered vessels).

Controlling the ASV functions?
A proprietary control system – ASV Automation system - manages the lift fan and other ASV specific components (including the air cushion flap in the aft section of the air cushion chamber). All automatic is the norm, but the master may override certain functions. The simpler the better!

How will BB GREEN be propelled?
The ASV concept may use a wide range of propulsion systems. In BB GREEN a twin installation of high efficiency contra rotating duo-prop pod propulsors will be used. Electric permanent magnet motors will power to the pods. Pod propulsion has been tested with excellent results in another ASV – for more info please consult: www.effectships.com 

Why is reduction of weight so important for the vessel's efficiency?
For any fast vessel concept; ASV or other; keeping lightship weight down is very important for the operational efficiency. Weight increases hull resistance /generation of waves, and more power is needed for achieving a given high speed. A main challenge for BB GREEN is the weight of the battery. Reducing hull weight with use of carbon sandwich construction keeps overall weight at an acceptable level.

Carbon sandwich construction – must be very expensive?
Although the initial construction / material cost for carbon sandwich is higher than conventional GRP or aluminum, the life time cost will still be favorable for a carbon craft. The weight savings could be substantial, and when a commercial vessel is operated 2.000 – 3.000 hours pr. year the fuel savings from less weight will quickly pay back the initial extra cost. 

Will 30 + knots for a commuter ferry be possible?
All assessments made to this date give reason to believe 30 knots can be achieved with the "BB GREEN component package". Tank testing results and additional evaluations support speed expectations of 30 knots with less than 2 x 300 kW for propulsion power.

Market opportunities?
If the project can prove a zero emission, fast commuter vessel can function in a commercial setting; a large global market will opens up. 

What kind of battery will be used?
Based on comparison studies and extensive cell testing, the project agreed to use Lithium Ion Titianate cell chemistry. As a matter of fact this battery type was considered the only viable alternative factoring in the tough use (charge and recharge) and use profile. 

What is the size of the battery?
For the planned BB GREEN application the volume of the battery is no problem. Unlike in a car, the BB GREEN battery compartment below main deck offers plenty of space. It is more a weight than a volume issue. A full commercial size battery; envisioned for BB GREEN ferries will have a weight of approx. 6 tons. Such a battery will have a capacity of 400 kWh. For the prototype/test-vessel a half size battery will be used. 

Recharging time?
Recharging time will depend on power availability and on route- and schedule/operational profile. For a commercial BB GREEN vessel; provided an average speed of approx. 25 knots could be maintained, and the distance travelled between recharging is 12 – 14 NM; recharging the battery in less than 30 minutes and operating an hourly schedule may be possible. 

Battery-life expectancy?
According to accelerated cell testing and other studies, 12.000 – 20.000 recharging cycles (given approx. 70 % use of max battery capacity) should be within reach. Given 10 recharges pr. day and operation 350 days a year up to 5 years battery life could be expected.

Realistic range @ 25 – 30 knots on battery power?
Speed will depend on local conditions; local speed limits and traffic density. Assuming an operational speed of 25 – 30 knots could be maintained, a 25 tons (laden) BB GREEN ferry will have a range of up to 14 NM in calm water conditions. 

Most efficient speed for a 20 m BB GREEN ferry?                                              
The power vs. speed curve for an ASV is quite flat (see curve “tank testing results”), with almost no “hump”. The selected propulsion system has high efficiency in the 20 – 40 knots speed range. In conclusion BB GREEN can be operated very efficiently at any speeds between 20 – 35 knots.

Typical routes and operations?
The BB GREEN consortium foresees single routes and route networks for sheltered waterways and coastal operations where the weather- and sea conditions are not too demanding. Effect Ships may also offer other ASV Mono hulls and modified superstructures designed for tougher conditions, but with the same basic configuration. Recharging stations will have to be set up and matched with the route length and traffic schedule. 

Wake wash conditions?
On several routes wake wash should be kept below certain levels (wash height and/or energy levels). Tank tests results show favorable levels for the BB GREEN mono-hull. An ASV will have a very rapid acceleration from standstill to 25 knots + with modest wake wash problems at transit speeds. 

Any noise from the fans?
The fan system (fan, inlet and outlet) has been designed and will be insulated for securing a low noise level. The fan is sitting in the bow; far away from the passenger compartment.

Will BB GREEN type of diesel and/or hybrid powered ferries be available?
On request BB GREEN type of fast commuter ferries may be configured for either lean burning diesel engines only or hybrid set ups. Even the pure diesel variants will have considerable less power consumption and emissions than conventional mono hulled ferries. 

How to increase the range?
In the same fashion as being used on cars, BB GREEN vessels can be fitted out with a range extender; in the form of a diesel motor connected to a charger / generator; for increased slow speed range.