SAN FRANCISCO, Calif. — Two hybrid ferries powered by the wind and sun will carry visitors to Alcatraz under a new ten-year contract between the National Park Service and Hornblower Cruises and Events.

To help win the multi-million dollar contract, the ferry operator committed to build two brand new hybrid-electric passenger vessels that maximize the use of solar and wind energy, with zero emissions at the wharf. The first will be built within two years, and the second by year five. The hybrid vessels in the winning proposal by Hornblower were designed by Solar Sailor and modeled on the Solar Sailor ferry in Sydney, Australia.

"Riding one of these ferries will be like switching from a gas-guzzling SUV to a hybrid car," said Teri Shore, director of Bluewater Network's Clean Vessels campaign. "The ferries will get far better mileage and pollute half as much because they will run on electricity or sail much of the time." Bluewater Network introduced the Solar Sailor concept to ferry planners on the Bay five years ago and have been lobbying for such a vessel ever since.

The new hybrid ferries will hold 600 passengers and operate at 12 to 15 knots. The vessels will be fitted with a large, rigid wing covered in solar panels that will capture sun and wind power. When conditions are right, the vessels will be able to sail back and forth. In extreme weather, the sail will automatically fold down flat above the deck like a roof.

Much like a hybrid car, large batteries on board the vessels will store electricity generated by the diesel generators and collected by solar panels. The electricity then powers the electric motors.

While loading and unloading passengers, the diesel engines will be turned off and run solely on electricity. The vessels can also be plugged into shorepower to regenerate the batteries.

As needed, the vessels will operate with diesel generators burning low-sulfur diesel fuel and equipped with air pollution controls that cut emissions by 70% to 90% (compared to conventional marine diesels). These generators make electricity that is transferred to the batteries to power the electric motors.

In the event of an earthquake or other disaster, the boats can operate at low speeds for emergency purposes on wind and electricity without any fuel, and could potentially help to shuttle commuters across the bay if necessary.