India's First Solar Ferry

History
India
Name:	ADITYA
Owner:	Kerala State Water Transport Department
Operator:	Kerala State Water Transport Department
Port of registry:	Kerala Ports
Route:	Vaikom - Thavanakkadavu
Builder:	Navgathi Marine Design and Constructions, Kochi, India
Cost:	370,000 US$
Yard number:	Y-09
Launched:	9 November 2016
Completed:	November, 2016
In service:	December, 2016
Status:	Crew Training underway
General characteristics [1]
Class and type:	Indian Register of Shipping IRS +IW ZONE 3 FERRY
Displacement:	23 tonnes
Length:	20 m
Beam:	7 m
Height:	3.7 m
Draught:	0.85 m
Depth:	1.75 m
Decks:	Single
Installed power:	40 kW
Propulsion:	2 Permanent Magnet Asynchronous Electrical Motors - 20 kW each (max) @ 900 rpm
Speed:	7.5 knots (13.9 km/h; 8.6 mph) (max) 5.5 knots (10.2 km/h; 6.3 mph) (cruising)
Capacity:	75 Passengers
Crew:	3

India's First Solar Ferry^[2][3][4][5] is also the largest solar-powered boat in India.^[6] The vessel was designed by NavAlt Solar and Electric Boats, built by Navgathi Marine Design and Constructions in Kochi, India and was tested on November 16, 2016. It is expected to get inaugurated in December, 2016.^[2] NavAlt Solar and Electric Boats is a joint venture firm between Navgathi Marine Design and Constructions, Alternative Energies (France) and EVE Systems (France). The core technology and expertise for design and construction of the boat was provided by the French firms.

Kerala State Water Transport Department has shown immense vision and leadership in deciding to build this solar-powered passenger ferry that do not have any fuel on board.^[7] The Government of Kerala under the leadership of Sri. Pinarayi Vijayan and transport minister Sri. A. K. Saseendran has put its weight behind solar ferry boats and has proposed to Government of India led by Sri. Narendra Modi and Ministry of New and Renewable Energy led by Piyush Goyal for 50 such boats in Kerala waters.^[8]

Ferry and Cruise Boat

A ferry differs from cruise boat in the redundancy, reliability and ruggedness of power train and propulsion systems. The power train consists of battery, battery management system (BMS), motor controller and motors. The propulsion system consists of coupling, thrust bearing, shaft, stern tube and propeller. In a ferry the systems are designed for 12 hours operation in a day and 365 days in a year. This implies higher grade power train and propulsion systems compared to a cruise boat which operate 3–4 hours in a day and 150–250 days in a year.

Test and Trials

After launching the boat on November 9, 2016, multiple sets of tests and trials were conducted on the boat to verify the operational characteristics and high safety standards of the boat.

• Optimisation Trials - to refine the settings in the internal software to ensure higher efficiency in the solar energy conversion and propulsion system, the tests was done on 2016 November 13 and 14 with the experts from France.
• Builders Trials - done on November 15, 2016, to ensure the systems was functioning as per specifications.
• IRS and Technical Committee Trials - done on November 16, 2016^[9] to verify the operation, speed, safety of the boat. The maximum speed was noted as 7.4 knots @ 90% propulsive power. The power needed to move the boat at cruise speed of 5.5 knots was 15 kW. The boat was also tested for redundancy trials by shutting down one system and checked whether using one system the boat can still move at cruise speed of 5.5 knots. Other manoeuvring tests were also done.
• Client Trial - done on November 25, 2016,^[8][10] along with Transport Minister Sri. A. K. Saseendran, Aroor MLA Sri. A. M. Ariff, Vaikom MLA C. K. Asha. The performance was satisfactory for the dignitaries as well as the operators of the Kerala State Water Transport Department. The Transport Minister proclaimed that 14 more such ferries are planned this year.

Technical features

The 20-metre long and 7-metre wide boat is covered by 140 m² of solar panels rated at 20 kW, which in turn connect to two electric motors of 20 kW, one in each hull. There are 700 kg of lithium-ion batteries in the ship's two hulls with a total capacity of 50 kWh. The Catamaran hull and it's shape allows it to reach speeds of up to 7.5 knots. This was verified by Indian Register of Shipping surveyor, Kerala Port surveyor and Technical committee. The hull was designed based on extensive experience of Navgathi and AltEn and extensive Computational Fluid Dynamics (CFD) was done to determine its hydrodynamics. The boat is designed to be used as a passenger ferry top operate between Vaikom and Thavanakadavu.^[11]

The normal operating speed is 5.5 knots (10 km/h) to achieve a 15 minutes travel time between Vaikom and Thavanakkadavu, a distance of 2.5 km on water. For achieving this speed, the power needed is about 16 kW. During manoeuvring, when leaving the jetty or approaching it, about 22 kW power is needed. Hence, on an average about 20 kW power is needed. The total running hours, without counting the time in jetty for embarkation and disembarkation of passengers, 5.5 hours on a sunny day (as per client needs).^[4][12]

Although the maximum power needed is a total of 22 kW during manoeuvring and 16 kW under cruise, more than double power, a total of 40 kW is provided as two motors of 20 kW each. The two system on either side of the boat (in each demi-Hulls) are electrically independent to ensure redundancy in case of system failure in one. Even if one system fails the power is available to safely cruise to shore with other. Also, unlike diesel engines, the since efficiency do not drop with load, the electric motors can normally be operating at 50% load and in emergencies at 100%.^[4][12]

Although not mandatory to be built under class, for higher safety standards and reliability, the vessel is built under Indian Register of Shippingrules for inland vessels and operating conditions of Vaikom - Thavanakkadavu route. The boat construction is complete and was tested by Technical committee, Indian Register of Shipping surveyor and Kerala Port surveyor on November 16, 2016 near in backwaters at Aroor.^[4][13] The boat is registered in Kodungallur Port under Kerala Ports.

The boat is remotely monitored and trouble shooting can also be done remotely. All the operating parameters of the boat are recorded and transmitted to NavAlt Solar and Electric Boats server from where the technical experts can monitor the boat. The upgrades and settings in the software can also be done remotely as if a computer is plugged on the boat. This makes the boat even more safer.

The project cost was 370,000 US$.^[3][4][5]

Safety features

• System Redundancy - The two system on either side of the boat (in each demi-Hulls) are electrically independent to ensure redundancy in case of system failure in one. Even if one system fails the power is available to safely cruise to shore with other.
• Power Redundancy - The available power on the boat is twice that is necessary for normal cruising. The boat needs about 18 kW to cruise at 5.5 knots. Each side of the boat is provided with 20 kW power to ensure that in the scenario one system fails the other can deliver the necessary 18 kW and cruise at 5.5 knots to the other side. This was tested by Indian Register of Shipping surveyor during the sea trials on November 16, 2016.^[9]
• Alarm monitoring (3 Levels) - There three levels of alarms. The first is N1 (level 1) where the display indicates that one of the parameter is approaching the limit and pilot is aware of it. In next level N2 (level 2) the indication denotes some action that needs to be done to avoid the problem to escalate. In final level N3 (level 3), the system take necessary shut down action to protect the device in consideration. For example, motor temperature once it reach 120 deg, it is a level 1. When it goes to 130 deg is it a level 2 action and the pilot can take action to reduce the rpm. When the temperature cross 140 deg, the motor shuts down for protecting the device.

Energy Balance

The total energy needed to operate the ferry for 5.5 hours is 110 kWh (20 kW is average power). 1 kW solar panels produce 4 kWh of energy per day, factoring the system efficiency and standard sun of the location of 5.72 (average through out the year). Hence the energy from solar panels is 80 kWh. The gap in energy is provided by lithium battery that can provide up to 40 kWh (80% discharge) from a total capacity of 50 kWh. The lithium batteries are fully charged in the morning because of overnight grid charging.^[4][12]

A trip between the two boat points takes 15 mts and it needs energy of 5 kWh. Hence a total of 22 trips can be made daily transporting 1,650 people daily, or 580,000 people every year without burning fuel.

Trips on average sunny day: 7:00 AM to 7:00 PM (running hours 5.5 hours)

The below table describes the 22 trips in each column, and for each trip the start time and end time. It also list the break time at the end of each trip. In non-peak hours this is about 15 mts, in peak time it is 10 mts and around noon it is two hours. The energy from sun is cumulative at the end of the period and for an average sunny day it is about 72 kWh from 18 kW panels (the rest is for auxiliary systems and charges a different battery bank). The battery state of charge (SOC) is shown at the beginning of trip and end of trip. At the end of the day, the battery has about 20% charge left. The energy use can be further optimised by adding one more trip (5 kWh usage) so that end of day battery SOC can be 10%.

On a bright sunny day, the no. of trips can be increased by taking trips during 11:55 to 14:05 break. About four more trips can be made in this period.

On a cloudy day, the no. of trips is reduced and the break time is increased. If it is very cloudy in the break time, then shore charging can be done. This is a 32A charger and charges at 7 kW. Hence in the three hour break, it can charge battery by 21 kWh.

Pay-back period

Compared to a conventional boat powered by diesel with same functional features and safety standards which costs 231,000 US$, the solar ferry costs 370,000 US$. An efficient conventional boat consumes 120 litres per day (12 litres per hour), or 3,500 litres per month and 42,000 litres per year of diesel. This amounts to 39,000 US$ for diesel (@ 0.93 US$/litre) and total operating costs including lube oil and other maintenance costs amounts to 44,600 US$ per year.

The operating cost of solar ferry is 40 units of electricity or 6.2 US$ per day which amounts to 185 US$ per month and 2,150 US$ per year.

The pay-back period is under three years.^[4][12]

The Government of India under the leadership of Prime Minister, Sri. Narendra Modi is very supportive of the project and the Ministry of New and Renewable Energy has also agreed to sponsor the project considering that this is a first of its kind in India. The benefit of sponsorship would mean that Kerala State Water Transport Department would get the boat at almost free of cost. In this scenario the boat is cheaper than conventional boat and they would start saving money from day one.^[4][5]

Benefits of solar boats

Solar boats are better than conventional boats because they:

• do not pollute water^[5]
• do not release harmful emissions in air are very silent and comfortable for passengers^[5]
• have low vibrations^[5]
• no smell of diesel or petrol^[5]
• have lower cost of ownership (high initial cost but low operating cost)^[5][12]

Solar boat design philosophy^[4]

The critical step is to drastically reduce the propulsion power compared to a conventional boat. This is achieved by five different process, all of which are necessary.

1. Almost always an adopted practice for solar passenger boat is to make the boat as a multi-hull, usually catamaran, which ensures a lower resistance for the same displacement and speed. This also has higher stability compared to a single hull vessel. Designing a solar boat as a catamaran has an added benefit of having larger deck area for providing sufficient number of solar panels.
2. The propulsion power can be reduced by lowering the drag of the hull. This can be achieved by optimising the hull form using the latest techniques like computational fluid dynamics (CFD). The hull shape has to be optimised for the operational condition (displacement, draft, trim, speed) so that the resistance of the boat is minimum. Fore-body and aft-body shape is optimised to get best results.
3. The propulsion power is also reduced by reducing the weight of the boat. The greatest contributor to a boat weight is the hull. Solar boats are almost always built of composite (FRP, Carbon fibre) or aluminium. The superstructure of the boat is also of such light material. Every single item that goes to the boat is checked to meet two conditions:
   • Is it necessary. Can it be avoided?
   • Can it be lighter?
4. The propeller design is critical to ensure high efficiency so that maximum power delivered to propeller is converted to useful thrust. It usually leads to larger propeller diameter and optimum rotating speed (RPM), pitch and area ratio to give the highest efficient propeller, usually in the range of 55%.
5. Apart from the major factors outlined, other minor aspects that affect propulsion power demand need to be taken care - flow to propeller, clearances, shaft bearing, rudder design, etc.

Economic Analysis^[4][12]

For a conventional 75 passenger ferry the diesel propulsion related operating costs are as follows:

• With a two 50 HP main engine and consumption of 12 litres diesel per hour on average, and total of 120 litres per day (engines are running all the time). At current price of diesel (0.93 US$) that amounts to 111 US$ per day and 39,000 US$ per year (350 days running). The diesel price is assumed to increase by 5% every year.
• Lubricating oil can be taken as 10% of fuel cost, which is 3,900 US$ per year.
• Maintenance cost for engines is another 5%, i.e. 1,900 US$ per year.
• Thus the total operating cost per year is 44,600 US$ (excluding labour and other expenses that are same in both). These are expected to grow each year at 5%.

For India's first solar ferry the electric propulsion related operating costs are as follows:

• A daily grid charging of 40 units (kWh) that cost of 6.2 US$ (@ 0.15 US$/unit for commercial power) and total of 2,150 US$ per year expected to grow at 5% per year.
• An operating cost that comes every seven years is replacement of battery bank of 50 kWh. At today's price this can be taken as 46,000 US$. This is expected to come down as technology evolve. In its life time of 20 years there would be two times when the battery will need to be replaced.
• Thus the total operating cost per year is 2,150 US$. (excluding labour and other expenses that are same in both). Only electricity cost is expected to grow at 5%..

The above table shows that although solar boats have higher upfront costs, the total cost of ownerships is lower. This boat has a break-even period of just three years. Also the boats are designed for twenty years, hence the savings will accummulate. The total saving in using a solar boat in its 20 years life time is 1.2 million US$ - with which another four solar boats can be built.

If one were to factor the cost of pollution and uncomfortable journey by conventional ferry then break-even would be even lower. Also one must remember that battery technology improvement is expected to drastically reduce cost of replacement.

Emission Reduction

Compared to an efficient conventional boat (described above), this solar ferry saves 42,000 litres of diesel every year. This translates to savings of 112 tonnes of CO2 emission reduction (1 litre of diesel = 2.67 kg of CO2) in a year.^[14] However in comparison to existing diesel ferry made of steel or wood, this solar ferry saves 52,500 litres of diesel every year and 140 tonnes of CO2 emission reduction in a year.

Construction Images

Some of the images of the boat in the final stages of construction.

Images in Instagram account of NavAlt

See also

• Electric boat
• Solar Impulse, a solar powered airplane
• List of solar-powered boats

References

External links

• SWTD