It is India's first solar-powered ferry[4] and was the largest solar-powered boat in India until Indra_(boat) was launched in 2023[5] .[6] The vessel was designed and built by Navalt Solar and Electric Boats[7] in Kochi, India. Navalt is a technology joint venture firm between Navgathi Marine Design and Constructions,[8] Alternative Energies[9] (France) and EVE Systems[10] (France).
In August 2020, MarineLink reported that by the end of the year the Kerala state would replace the three diesel ferries operating the same route with solar ones, mentioning that Aditya costs about US$79 per month compared to US$2867 for diesel-powered ones.[11] In three years the Aditya has saved more than 100,000 liters of diesel.[11] The State Water Transport Department of the Government of Kerala also decided to replace all of its 48 diesel ferries with solar ones.[11]
The 20-metre-long and 7-metre-wide boat is covered by 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[12] and AltEn[13] 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.[14]
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 maneuvering, when leaving the jetty or approaching it, about 22 kW of power is needed. Hence, on 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).[15]
Although the maximum power needed is a total of 22 kW during maneuvering 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 others. 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.[16] The boat is registered in Kodungallur Port under Kerala Ports.
The boat is remotely monitored and troubleshooting can also be done remotely. All the operating parameters of the boat are recorded and transmitted to the NavAlt Solar and Electric Boats's 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 into the boat. This makes the boat even safer.
The project cost was US$370,000.[17] [18]
The boat is operating since launch on 12 January 2017 between Vaikkom and Thavanakkadavu.[24] The numbers for this total period is as follows:
| No.of passengers (million) | 2.23 | 2 | 1.68 | 1.35 | 1.06 | 0.6 | 0.3 | |
| Distance travelled | 142,000 | 125,000 | 102,500 | 80,000 | 63,000 | 38,000 | 19,000 | |
| Diesel saved (litres) | 210,000 | 190,000 | 160,000 | 130,000 | 105,000 | 58,000 | 29,000 | |
| Savings (USD) | 243,000 | 187,500 | 147,500 | 110,000 | 93,750[25] | 65,000 | 36,000 | |
| Savings (lakh INR) | 200 | 150 | 118 | 88 | 75 | 45 | 25 | |
| CO2 avoided (tonnes) | 563 | 509 | 420 | 330 | 283 | 156 | 81 | |
| NOx avoided (tonnes) | 8.3 | 7.5 | 6 | 4.6 | 3.9 | 2.2 | 1.1 | |
| SOx avoided (tonnes) | 1.7 | 1.5 | 1.25 | 1 | 0.8 | 0.4 | .2 | |
| Particulates avoided (kg) | 211 | 191 | 158 | 124 | 106 | 59 | 30 |
The first year of operation shows the following summary.[27]
The Government of India under the leadership of Prime Minister, Sri. Narendra Modi and the Ministry of New and Renewable Energy 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 the conventional boat and they would start saving money from day one. However the ministry is yet to give the subsidy amount to Kerala State Water Transport Department. Another unfulfilled demand is the equal treatment of electric boats to electric buses under FAME scheme that would have enabled 20% cost reduction in the project. NITI-Aayog is yet to remove this discrimination.
The first 150 days operation data shows that even rainy days during monsoon did not affect the schedule of the boat.[28]
The first 60 days operation data of ADITYA yielded the following results[29]
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.
During conceptualising the project, it was envisaged that the total energy needed to operate the ferry for 5.5 hours is 110 kWh (20 kW is average power). As 1 kW solar panels produce approximately 4 kWh of energy per day, factoring the system efficiency and standard sun of the location of 5.72 (averaged 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 was estimated to need the energy of 5 kWh. Hence a total of 22 trips would 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 prediction for 22 trips in each column, and for each trip the start time and end time. It also lists 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 the 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 the trip and end of the 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 from 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 during 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 the battery by 21 kWh. With two upcoming landmark projects, NavAlt boats will be foraying into the fishing sector and defence industry for the first time.[31]
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Vaikom | 7:00 | 7:45 | 8:00 | 8:40 | 8:50 | 9:30 | 9:40 | 10:25 | 10:40 | 11:25 | 13:35 | 14:20 | 14:35 | 15:20 | 15:35 | 16:20 | 16:30 | 17:10 | 17:20 | 18:00 | 18:15 | 19:00 | |
| Thavanakadavu | 7:15 | 7:30 | 8:15 | 8:25 | 9:05 | 9:15 | 9:55 | 10:10 | 10:55 | 11:10 | 13:50 | 14:05 | 14:50 | 15:05 | 15:50 | 16:05 | 16:45 | 16:55 | 17:35 | 17:45 | 18:30 | 18:45 | |
| Break | 0:15 | 0:15 | 0:10 | 0:10 | 0:10 | 0:10 | 0:15 | 0:15 | 0:15 | 2:10 | 0:15 | 0:15 | 0:15 | 0:15 | 0:15 | 0:10 | 0:10 | 0:10 | 0:10 | 0:15 | 0:15 | ||
| Total Time | 0:30 | 0:30 | 0:25 | 0:25 | 0:25 | 0:25 | 0:30 | 0:30 | 0:30 | 2:25 | 0:30 | 0:30 | 0:30 | 0:30 | 0:30 | 0:25 | 0:25 | 0:25 | 0:25 | 0:30 | 0:30 | 0:15 | |
| 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 |