Pilot boats provide an important service at ports all over the world, ferrying the pilots who guide ships into and out of port facilities. The duty cycles for these boats vary depending on local conditions at each particular port: some are required to spend considerable time at sea, but others make only short trips, between which the boat is tied up at the dock. Commercial boat builder Robert Allan has developed a new all-electric pilot boat aimed at the latter type of service, in which the run to the ship is 5 nautical miles or less.

The RAlly 1600-E is an aluminum boat with an electric twin-screw drivetrain and a bank of batteries that are recharged from shore power. Twin small auxiliary generators provide “get home” and range extension capability, but are normally not used.

The boat is propelled by twin 500 kW 2,800 rpm permanent magnet 750 volt AC electric motors, which drive through standard ZF or Twin Disc 3:1 reverse/reduction gears to conventional shafting and 840 mm propellers. The battery system consists of 70 Spear SMAR-11N-224 modules, with a capacity of 815 kWh. Top speed is 20 knots.

Pilot boats typically run at or near top speed with the pilot on board, then loiter for some time, and may return at a more efficient medium speed. In this mixed-use scenario with a 5-nautical-mile run, the RAlly 1600-E can complete a full operation on batteries with 30% of nominal capacity to spare.

According to Robert Allan, some recent RFPs for pilot boats have specified noise levels of 65 dB or lower in the occupied spaces. This is almost impossible to achieve in a small, fast boat powered by ICE engines, but electric drive makes it feasible. The company also notes that the added capital cost of the electrical propulsion system is offset by the savings on fuel and maintenance costs.

Source: Robert Allan