Aditya - India’s First Solar Ferry

Navalt built Aditya, India’s pioneering solar ferry, for the Kerala State Water Transport Department. This ferry represents the world's and India's inaugural commercially viable mode of transport, driven solely by solar energy.

Recipient of the 2020 Gustave Trouve Award for the World’s Best Electric Ferry, Aditya redefined India’s inland water transportation.

Celebrating five years of unparalleled success, Aditya continues to stand out for its enduring fame and accomplishments. Remarkably, this vessel achieved breakeven in 2019 and is currently accruing profits.

ADITYA, 7 Years Of Success

Aditya: India's first solar-electric ferry



The Kerala State Water Transport Department (SWTD) operated approximately 100 ferry boats of varying sizes, accommodating 75 to 100 passengers across the state. These boats, constructed from wood or steel, were all single-hulled and propelled by diesel engines. By 2013, a significant challenge loomed.

While air and water pollution posed substantial environmental concerns, they weren't the primary issue. Rather, the diesel engines' noise, vibration, and subsequent fatigue on passengers and crew, as well as the smell of fuel, although notable, weren't the foremost problem. The crux of the issue was the exorbitant operating costs that rendered the boats financially unsustainable.

A typical ferry on the Vaikom-Thayvanakkadavu route, covering 2.8 km with a modest fare of 4 per journey, yielded daily revenue of approximately 5,000. Astonishingly, the energy cost for 100 liters of diesel surpassed this revenue, totaling around $6,041. Considering direct energy expenses and maintenance at $6,645 daily, along with crew costs and overheads of roughly $3,000, the total operational expenditure (OPEX) amounted to $9,645 each day.

Consequently, the department incurred a substantial loss of about $4,645 daily, considering solely the OPEX. Seeking a solution to this predicament, SWTD explored harnessing solar energy.

Aditya, India's largest solar boat and the pioneering solar ferry, was inaugurated on January 12th, 2017. The inauguration took place in the presence of Shri Pinarayi Vijayan, Chief Minister of Kerala, Shri Piyush Goyal, Minister of New and Renewable Energy, Kerala State Transport Minister Shri A.K. Saseendran, along with members of parliament and the state assembly.

Notably, Aditya became the world's first solar ferry to fulfill over 80% of its energy needs through solar power. With a seating capacity for 75 passengers, it can cruise for over 6 hours on a sunny day without requiring an external charge. Commissioned for the Kerala State Water Transportation Department, the ferry adheres to the highest safety standards under the Indian Register of Shipping (IRS) classification, ensuring reliability.

The Navalt team initiated the design and construction of a solar ferry in 2014, employing advanced materials and enhanced design methodologies. Utilizing lighter materials like GRP and aluminium drastically reduced its weight. Innovative design techniques such as computational fluid dynamics slashed the vessel's drag to a mere 1/3 of the typical ferry size. Furthermore, the inclusion of a robust propulsion motor and marine-grade lithium-based battery storage, meeting stringent international safety standards, bolstered efficiency and longevity.


Optional plug & charge
75 passengers
80 kWh
20m long x 7m wide
Max speed of 7 knots
Range 120 km
20 kWp
2 x 20 kW

ADITYA is a catamaran ferry boat with a GRP (Glass Reinforced Plastic, also known as FRP, or Fiber Reinforced Plastic) hull and an aluminium superstructure built under IR Class (Indian Register of Shipping, a member of the International Association of Classification Societies).


For a public transport service like SWTD, where profitability is not important, the operating costs should be covered by revenue from passenger tickets. In this case, we’re looking at a cost comparison of multiple options, as well as the total cost of ownership for both options.


This is the initial cost of owning the boat. The cost of ADITYA was 1.95 crore (at the 2013 tender price). Years later, such a boat would be worth 3.5 CR. A diesel ferry with a similar capacity (75 passengers) built under the IR class (or any other IACS (International Association of Classification Societies) member class) would cost around 1.5 million dollars.


In the total cost of operating the boat, there are three broad cost groups:

  • Energy
  • Maintenance
  • Crew and overheads

On average, a vessel operates for 350 days a year.

  • Energy cost

A typical ferry boat crossing the backwater in the Vaikom-Thavanakkadavu sector, a distance of 2.8 kilometers, charges only 4 rupees for the journey on one side.Each trip takes about 13–15 minutes (at a speed of 10–12 km/hr). If it operates from 7 a.m. to 7 p.m., taking 22 trips and having sufficient time for passenger embarkation and crew breaks, it would need about 100 litres of diesel (at 10 litres per hour). It is the cost of fuel for running the boat and its systems, i.e., running both main and auxiliary engines.

For a solar ferry without any fuel onboard, the energy cost is the cost of the grid used to charge the batteries. The total energy consumption is 7,969 units, and the energy cost is $62,235. This energy cost is expected to increase by 5% every year with the increase in grid costs. The primary cost of a diesel ferry is energy.The daily fuel consumption is 100 liters, and for a diesel price of 60.41, the daily energy cost is 6,041 (at 60.41 per liter, the average price in Kerala for 2017). This was 21,02,429 for the first year.The diesel price is also expected to increase by 5% every year.

  • Maintenance cost

These are the total costs to keep the boat running.There are three kinds of maintenance activities. The first type is exclusively for diesel engines. This includes the replacement of consumables.

like lube oil and filters, as well as engine overhaul charges, both of which are regularly done every 45 days for diesel ferries. For solar ferries without any engines, this is not there. Net of fuel costs, the average maintenance cost is about 3% for lube oil and 7% for filters and engine overhauls.The total is about $604 per day. In the first year, this was 2,10,243. The second type is the cost of replacing the battery cells. The propulsion battery has a warranty of five years. However, based on the battery discharge level, the replacement cycle for the battery would be seven years. It is important to note that the battery’s storage capacity is expected to be 80% of the new one at this time, not that it becomes unusable.At the current price, the replacement cost of the cells is expected to be 25 lakhs.This would be lower considering the annual reduction in the price of lithium cells due to the increased adoption of electric vehicles. The third type is the cost of replacing or repairing damaged parts or equipment and the cost of maintaining the boat in good condition. It is assumed that this is similar in both boats and is therefore not considered.

  • Crew and overheads

These are the costs of maintaining the crew as well as the overheads of the head office for boat operation. For these kinds of boats, three crew members are needed to operate them. Since these are similar in both kinds of boats, this is not considered for comparison.


Most passenger ferries are designed to last twenty years. It is not prudent to design ferry systems for a longer period since, by then, a far better technology would have come to enable replacement. At the end of its life, there is a recycling cost, but the residual value of materials and equipment in the boat may be higher than this, and hence there might be a net positive value of the boat. The batteries are recycled by the manufacturer as per EU guidelines. At the end of its life, the recycling cost of the boat is insignificant.


To factor in the time value of money, the difference in the initial cost between the boats is financed, and the EMI for the same is taken as the finance cost for the solar ferry. The interest rate is assumed to be at 12%, although the Kerala government has lower costs. The cost difference of 45 lakh (Sec 5.2) needs to be financed. After iteration, we can see that in 36 months (3 years), with an EMI of 1.49 lakhs and an annual cost of 17.94 lakhs, this difference in cost can be repaid. The total cost of financing for the 45 lakhs is 53.81 lakhs. After this period, there are huge savings every year.


TCO Summarizing the calculation, we can see that in its life cycle of twenty years, the TCO comparison is:

Solar Ferry – 274.4 lakhs
Diesel Ferry – 914.7 lakhs

The cost of diesel ferry is three times more than the solar ferry. Read the complete paper published at IEEE here.