In Venice 550 water taxis and buses transport 32 million visitors per year through the historic and picturesque lagoon town. Add to this thousands of private motor boats. The exhaust fumes and noise of the combustion engines cause alarming levels of pollution hazardous to both people and the environment. A quick, practical solution is needed.
Venice’s traffic problems on water are very similar to those of other cities on land. For this reason, hybrid drive systems – that is, a clever combination of combustion engines and emission-free electric motors – practically suggest themselves as a solution for Venice. At low speeds in the city, the diesel engine can be “clutched out” and deactivated. The purely electric drive then guarantees quiet, emission-free driving. During fast movement with the diesel engine, the electric motor may also assist to reduce exhaust emissions. During medium to high speed, such as when transiting the lagoon, the diesel engine automatically kicks in, driving not only the propeller but also the generator. The batteries are charged and the efficiency range of the engine is improved.
REAPsystems from Hampshire, England, specialises in developing environment-friendly drives. This English company is currently developing a prototype of a Venetian water taxi with a diesel-electric drive. The hybrid module consists of an efficient electric motor, lithium-ion batteries, an HSCU (Hybrid System Control Unit) and a belt drive with a clutch. HSCU is used for activating and deactivating the motors as required and dividing the drive capacity between the two units.
The hybrid module is flange-mounted to the crank shaft of the diesel engine. A CONTI® SYNCHROCHAIN CARBON high performance timing belt transfers the electric motor power to the propeller. Picture: TransDev
The electric motor is arranged parallel to the diesel engine and is connected to the drive train or propeller via the timing belt drive and the clutch. The clutch is engaged for the diesel drive and disengaged for the purely electric drive. REAPsystems has designed this hybrid module as a retrofittable solution. It has therefore been developed to be suitable for a large variety of boat drive configurations, e.g. stern drives and shaft systems. This is particularly important for retrofitting the large number of motor boats and water taxis in Venice. Apart from the environmental benefits, the company estimates an average fuel saving of at least 50% compared with modern diesel engine boats.
When it came to the drive belt and pulley solution REAPsystems turned to TransDev and ContiTech. The Mulco member TransDev, a specialist for drive technology based in Dorset, England, selected the high performance timing belt CONTI® SYNCHROCHAIN CARBON as power transmission belt. It is one of the strongest polyurethane timing belts in the market. It permits a construction width reduction of up to 80 % compared with other timing belts. Small space requirements were particularly crucial for the retrofitting solution.
This high-performance CONTI® SYNCHROCHAIN CARBON timing belt with its CTD profile makes even extreme applications such as the hybrid engine possible. Photo: ContiTech
A yellow mesh on the tooth surface makes the timing belt extremely wear resistant. The service life of the CARBON high performance timing belt is up to 100 % higher than the service life of timing belts using aramid tension members. As the carbon tension member is not subject to plastic elongation, there are practically no losses in pre-tension force. Retensioning the belt – and with it, maintenance work – becomes unnecessary. With its combination of cold, heat, oils, diesel and salt water, the engine compartment of any boat is a technological challenge. The CONTI® SYNCHROCHAIN CARBON timing belt is perfectly resistant to these factors. It is also resistant to oils, greases, UV and ozone, suitable for use in tropic climates and can be used in temperatures between -40 and 80°C.
TransDev has created special steel timing belt pulleys with through bores and flanges for the hybrid module. The Dorset-based drive specialists have become a main development partner and sponsor of the green project that hopes to transform marine traffic and transportation. The boat is set to transport passengers – noiselessly and without emissions – through romantic waterways shortly to prove the practical applicability of the hybrid drive.