An Electric Ferry Boat Rev 6 Mar MB
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Study of the sizing of the propulsion and storage system for an hybrid/electric ferry for the Ligurian Natural Parks Marco Bianucci 1, Luca Baruzzo 2, Marco Ferrando 2,3 Silvia Merlino 1 1 Istituto di Scienze Marine ISMAR-CNR, Forte Santa Teresa, Pozzuolo di Lerici, 19032 Lerici, La Spezia (IT) [email protected] 2 Polo Universitario G. Marconi di La Spezia (Università di Genova), Via dei Colli n.90, 19121 La Spezia 3Università di Genova – DITEN, via all’opera Pia 11, 16145 Genova, Genova (IT) Abstract The Gulf of La Spezia is one of the widest and deepest of the whole Tyrrhenian coast, enclosed between two headlands and bordered by an amphitheatre of hills and mountains. Just outside the bay to the west, the pristine Cinque Terre National Park is one of the most important and beautiful natural Mediterranean areas. Human activity and especially viticulture, have helped to create a unique landscape in which the total de- velopment of the typical “stone walls” reaches the length of the famous Great Wall of China. All this to- gether with the characteristics of a crystalline sea, a great network of paths, has made the Cinque Terre an increasingly popular destination for Italian and foreign tourists. The project faces the needs of tourist trans- port within the Park of 5 Terre, the islands of the Portovenere Park and town and the connection with La Spezia, and has the specific objective of defining the “optimal” Electric Ferry boat of 24-meter equipped with state of the art technology, but commercial, as a function of the size of the electric propulsion engine and of the energy storage, according to the different routes and possible stages in the transport service. Keywords: Ferry boat, hybrid Ferry, Ferry for natural parks We consider the state of the art, but commercial, 1 Introduction technologies as hybrid engine, energy storage and The Gulf of La Spezia is one of the widest and photovoltaic system, and we select those that are deepest of the whole Tyrrhenian coast, enclosed best suited to the type of service that the ferry has between two headlands and bordered by an am- to do in this particular case. phitheatre of hills and mountains. Just outside the bay to the west, the pristine Cin- 2 Objectives and motivations que Terre National Park is one of the most im- Ferry boats and waterbuses undertake important portant and beautiful natural Mediterranean ar- people transport and provide connections in many eas. Human activity and especially viticulture, seaside touristic areas often close or inside marine have helped to create a unique landscape in natural parks. Pollution and noise are particularly which the total development of the typical “stone undesirable in these contexts [1]. walls” reaches the length of the famous Great Eco - Ferry aims at promoting a substantial reduc- Wall of China. All this together with the charac- tion of chemical pollution and noise, the reduction teristics of a crystalline sea, a great network of of operating costs of public/private transport com- paths, has made the Cinque Terre an increasingly panies, and social acceptance transport on water- popular destination for Italian and foreign tour- ways. The hybrid/electric propulsion of boats ists. equipped with state of the art “marine” high effi- The project aims at defining the “optimal” elec- cient photovoltaic (PV) panels has a lot of advan- tric/hybrid 24-meter Ferry boat, suitable for tour- tages if compared with the conventional endother- ist transport within the Park of Cinque Terre, the mic propulsion: islands of the Portovenere Park and the tourist cities in the surrounding area as La Spezia and Lerici. 1 • the great energy efficiency of the electric (variable speed permanent magnet synchronous motor guarantees reduced emissions in air generator coupled to the electric motor, fixed and in water, speed genset etc..) the optimal size and angular • electric energy can be obtained directly from velocity of the propeller , the kind of the batteries renewable resources, as wind and sun, avoi d- etc . However in this paper we will not go inside ing the use of fossil fuels, this quite technical topics, but we will limit ou r- • an on board high efficient PV plant during selves in illustrating the electric/hybrid general the summer gives a great contribution to the configurations we considered, with the aim of energy balance for the boat, proving the actual feasibility and convenience of • the strong reduction of noise and vib rations using a Ferry with electric propulsion in a real allows a superior comfort, specific case. • the high torque of the electric motor allows a 3 The routes better control, a quick response of the pus h- ing force and rapid and secure manoeuvres, We took into account all the possible routes for • higher torque means increased transport Eco-Ferry in terms of travel distance in miles and capacity without increasing the engine power speed. These routes are: (l ess energy needs and wasting), 1. La Spezia – Portovenere, 4.5 nm; • in general the customer’s energy cost 2. Portovenere - Palmaria Terrizzo , 0.6 nm; (€/kWh) is lower when using an electric e n- 3. Palmaria Terrizzo - Palmaria Pozzale, 1.8 nm; gine than when using a standard endothermic 4. Portovenere - Cinque Terre, 11.5 nm; diesel engine, 5. Tour of the Islands (Palmaria, Tino, Tinetto) , • electric engines are easily controlled by 6.3 nm. automatic devices and this allows a safer navigation. However all these advantages should be co m- pared with the high cost, the problems of reliabi l- ity, and the reduced capacity in terms of energy density of the electric energy storage systems today available. Actually if we compare the gr a- vimetric e nergy density of the gasoline, about 12 kWh/kg (or 10 kWh/Litre ), with that of the sta n- dard commercial Li-ion batteries, about 0.1 -0.2 kWh/kg [2], we see that the transition toward the electric mobility is still actually a challenge. Also if we take into account that the efficiency of an Figure 1: A satellite map of the La Spezia Gulf with the endothermic engine is only about 30%, we get 4k routes we are interested on. Wh/kg that is still more than one order of magn i- tude of that of the best batteries today available 4 The Boat on the market. On the other hand for the boats We considered a 24 m displacement boat , a typical often the weight of the en ergy storage is not so shuttle with a gunwale high and closed with high important and there are cases where the benefits flexibility since the Portovenere Park requests to of the electric mobility are so great that you are transport also a van for some special occasions . willing to accept some compromises, such as the Here some general technical features: limited cruising range. The small boats used as - Length overall and at waterline about 24 m tenders of yachts are an example in w hich the - Beam about 6 m electric mobility is taking hold. Here we want to - Height over the water line about 3 m assess the feasibility and convenience of using electric boats in a specific case: the ferry service - Draft at full load 1.5 m for the tourist around the La Spezia gulf. In this - Full loa d displacement (estimated) 70 t project we have studied many different config u- - Fuel tank 10.0 m3 rations with different technical details concerning - Fresh water tank 2.5 m 3 the 24 meters ferry, as the kind of the electric - Waste water tank 1.5 m3 engine (permanent magnet motor, variabl e reluc- 3 - Holding tank 1.0 m tance motor, synchronous /asynchronous motor etc..) the different “in series” hybrid systems 2 Figure 2: Lines plan of the selected hull form Figure 3: Top view Figure 4: Main Deck Figure 5: Lower Deck Figure 2 illustrates the lines plan of the selected According to the fact that the foreseen speed hull form, while in figures from 3 to 5 the range of the boat will be in the pre-planing proposed general arrangement of the ferry can be regime, a hull from the SSPA Systematic Series found. [3] was selected. 3 The shuttle should fall under the certification plus space for two wheelchai rs, there is a bath- according to the RINA classification as a passen- room, and going up four steps we find the bar area ger vessel under 24 m for coastal navigation. and finally the wheelhouse. Figure 6 shows a sketch of the boat concept, The lower deck is almost entirely a technical area which is characterized by a huge flat deck that (motors, genset and batteries) but the forward part covers the superstructure. This solution allowed where there is a place for passengers with 12 the maximization of the useful surface for the seats. Thus the total number of seats is 58 + 2. solar panels, accommodating a photovoltaic sy s- The Engine room scheme is presented in Fig. 7. tem of 17 kWp. Here we can see the two diesel engines coupled to electric generators; electric motors drive the shaft lines through a gearbox. 4.1 Boat energy requirements In Fig. 8 the graph “Propulsion power vs. speed” is illustrated; it was obtained taking into account both the hydrodynamic resistance and the overall efficiency of the entire power train system, in- cluding the choice of the propeller (see details in Appendix A and B ). The shape of this curve is Figure 6. Sketch of the proposed concept . typical for this kind of hull and shows that over The open space in the stern can be used to carry a 10-11 knots the total hydrodynamic resistance van.