Even as land-based solar power plants have been mooted for the upcoming Water Metro project in the Greater Kochi area, a section of naval architects say that sourcing solar power from panels installed atop the 23 ferries that will be introduced in the project’s first phase will be technically and financially more viable.
The solar panels should ideally be installed atop boats, in order to reduce the battery size and subsequently the size of the vessel. This is important since boats are not connected to the grid when moving, unlike electric trains which source power from the grid even as they are on the move, says Sandith Thandasherry, founder of the firm that designed Aditya, India’s first solar ferry that the State Water Transport Department (SWTD) operates in the Vaikom-Thavanakadavu route.
It is seen that capital expenditure (capex) is the lowest when solar panels are atop a boat, since increase in solar panel cost is more than compensated by decrease in battery cost. In the case of operational expenditure (opex), involving both energy cost as well as maintenance cost, maximum number of solar panels on a boat will usher in the lowest energy cost. The cost of power from solar panels is cheaper, be it to operate the vessel’s propulsion or air conditioning system, than the expense of grid energy stored in batteries, or the power from genset on board. Even while presuming that energy is sourced from land-based solar plants, it is effective to have a single large solar plant rather than multiple small plants (in ferry terminals), says Mr. Thandasherry.
The private firm is now constructing what would be the largest solar boat in India - a 25-m-long catamaran with 100-passenger capacity. “We have installed a 24 kW solar plant on the vessel to maximise the use of energy from the sun, thus keeping the battery size small, although it would be fully air-conditioned and capable of attaining maximum speed of 7.5 knots (approximately 13 kmph),” he says.
Dileep Krishnan, former head of the department of ship technology at the Cochin University of Science and Technology, says ferries will invariably have to source a portion of their energy needs from the grid, since solar power is not available after dusk and will be scarce in cloudy weather. “The economic and environmental cost will still be negligible as compared to relying on fossil fuels like diesel. Whether to source energy from solar panels atop ferries or from land-based plants would depend on the specifications and requirements of each project,” he says.