|Owner:||Kerala State Water Transport Department|
|Operator:||Kerala State Water Transport Department|
|Port of registry:||Kerala Ports|
|Route:||Vaikom - Thavanakkadavu|
|Builder:||NavAlt Solar and Electric Boats, Kochi, India|
|Launched:||9 November 2016|
|In service:||12 January 2017|
|General characteristics |
|Class and type:||Indian Register of Shipping IRS +IW ZONE 3 FERRY|
2 × 9 kW (cruise)2 × 20 kW (max)
|Propulsion:||2 Permanent magnet asynchronous electrical motors - 20 kW each (max) @ 700 rpm|
Aditya, India's first solar ferry, is a solar-powered ferry operating between Vaikkom and Thavanakkadavu in the Indian state of Kerala. The boat was inaugurated by Kerala Chief Minister Sri. Pinarayi Vijayan and Central Cabinet Minister for Power, Renewable Energy, Sri. Piyush Goyal on 12 January 2017. It is India's first solar-powered ferry and the largest solar-powered boat in India. The vessel was designed and built by NavAlt Solar and Electric Boats in Kochi, India. NavAlt is a joint venture firm between Navgathi Marine Design and Constructions, Alternative Energies (France) and EVE Systems (France).
- Propulsion energy per day for 22 trips – 73.7 kWh
- Propulsion energy per trip – 3.5 kWh
- Battery state of charge (SOC) at end of day – 60%
- Grid charging cost per day – 2.5 US$ (₹ 163)
The first 60 days operation data of ADITYA yielded the following results
- Propulsion energy per day for 22 trips – 73.3 kWh
- Propulsion energy per trip – 3.33 kWh
- Battery state of charge (SOC) at end of day – 65%
- Grid charging cost per day – 1.9 US$ (₹ 124)
Test and trials
The boat was launched on 9 November 2016. After that multiple sets of tests and trials were conducted to verify the operational characteristics and 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 13 and 14 November 2016 with the experts from France.
- Builders Trials - done on 15 November 2016, to ensure the systems was functioning as per specifications.
- IRS and Technical Committee Trials - done on 16 November 2016 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 Trials - done on 25 November 2016, 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.
- Site Trials - done at Vaikom to Thavanakkadavu route in presence of Technical committee, IRS and Kerala Port surveyor from morning to evening. As per the specifications, 22 trips was done with full load and it was satisfactory.
The 20-metre-long and 7-metre-wide boat is covered by 140 square metres (1,500 sq ft) 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 its shape allow 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 to operate between Vaikom and Thavanakadavu.
The normal operating speed is 5.5 knots (10 km/h) to achieve a 15-minute 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 of power are needed. Hence, on an average about 20 kW power is needed. The total running time, neglecting the time in jetty for embarkation and disembarkation of passengers, is 5.5 hours on a sunny day (depending on client needs).
Although the maximum power needed is a total of 22 kW during manoeuvring and 16 kW under cruise, more than double the power, a total of 40 kW, is provided in two motors of 20 kW each. The two systems on either side of the boat (in each demi-Hull) 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, since efficiency does not drop with load, the electric motors can normally operate at 50% load and in emergencies at 100%.
For higher safety standards and reliability, the vessel is built under Indian Register of Shipping rules for inland vessels and operating conditions of the Vaikom – Thavanakkadavu route. The boat construction is complete and was tested by Technical committee, Indian Register of Shipping surveyor and Kerala Port surveyor on 16 November 2016, near in backwaters at Aroor. 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 the 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 performed remotely as if a computer is plugged on the boat. This makes the boat even more safe.
Energy balance as per the Specifications
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 throughout 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.
A trip between the two boat points takes 15 minutes 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 minutes, in peak time it is 10 minutes 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%.
|Battery SOC (kWh) at start||50||45||40||35.5||31.7||28.8||26.5||25.5||25.2||25.5||26.1||49.3||49.3||48.7||47.3||45||41.4||35.1||27.1||22.1||22.1||17.1|
|Sun Production (kWh)||0||0||0.5||1.7||3.8||6.5||10.5||15.2||20.5||26.1||54.3||59.3||63.7||67.3||70||71.4||72.1||72.1||72.1||72.1||72.1||72.1|
|Motor consumption (kWh)||5||10||15||20||25||30||35||40||45||50||55||60||65||70||75||80||85||90||95||100||105||110|
|Battery SOC (kWh) at end||45||40||35.2||31.1||27.9||25.3||23.4||22.8||22.8||23.3||24.1||46.8||46.6||45.6||43.8||40.9||36.9||32.1||27.1||22.1||17.1||12.1|
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.
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.
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.
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