Other vessels such as traditional liquid bulk tankers, auto/RoRo carriers, break and dry bulk carriers, fishing trawlers, ocean tugs, and harbor vessels are all technically feasible applications due to their sub-megawatt power requirements.

The consideration of commercial feasibility revealed that some target vessel types are not as favorable as others. These include all the bulk liquid tankers, reefer vessels, both dry and break bulk carriers. The reason is that to utilize shore power, any vessel needs to have specialized on-board equipment installed, and to achieve a reasonable return on investment for this additional cost, shore power would need to be frequently utilized. These types of vessels are typically not frequent visitors to a single port, meaning that investment in the infrastructure required is not likely to make economic sense for the vessel owner/operator. Although there are exceptions, auto/RoRo carriers typically are also not frequent visitors so it is likely they would not make commercially-successful applications either.

Finally it must be noted that of the remaining types (harbor vessels, ocean tugs, fishing trawlers, and container ships) the first three usually have shore power infrastructure installed at their home berths already. That means that a shore power barge would be most applicable to container ships at berth, assuming that their power needs can be adequately defined or restricted.

On the positive side, the current regulatory situation has resulted in a high likelihood of enthusiastic participation by the container fleets, especially those that have vessel traffic to/from California ports. Ironically, however, the applicability for these vessels would be when they are visiting ports outside of California (such as Portland (OR), and Tacoma and Seattle (WA)) since the major California ports are currently installing grid-supplied shore power capability at all container terminals. Thus, with proper design and coordination, a shore power barge with a hydrogen-fueled PEM fuel cell system for powering container ships at berth could become a commercially viable product.

—Pratt and Harris (2013)

Auxiliary power to docked ships, usually provided by on-board diesel engines, is a significant source of greenhouse gas emissions and air pollution, accounting for one-third to one-half of the in-port emissions attributed to ocean-going vessels. According to a 2004 study by the Natural Resources Defense Council, average daily emissions for a busy port could exceed the total emissions from nearly 500,000 vehicles.

The study evaluated a simple fuel cell strategy that consists of mounting a hydrogen-fueled proton exchange membrane (PEM) fuel cell on a floating barge. Supplying a container ship with average power and run times (1.4 MW over 48 hours) requires four 40-ft containers, two for the fuel cell and two for hydrogen fuel storage, which could readily fit on a typical flat-top barge. For ships requiring less power, such as tugboats, a single container housing both the fuel cell and hydrogen will suffice, according to the Sandia study.

To evaluate the feasibility of the fuel cell barge strategy and analyze potential deployment options, Sandia’s Joe Pratt visited ports up and down the West Coast and in Hawaii. He gathered data from two US Department of Transportation Maritime Administration facilities and the ports of Long Beach, Calif.; Los Angeles, Calif.; Oakland, Calif.; Portland, Ore.; Tacoma, Wash.; Honolulu, Hawaii; and Seattle, Wash.

The US Navy has been employing grid-based cold-ironing for many years to save fuel. Ports in California are now turning to the practice due to a California Air Resources Board regulation that requires shore power in many instances beginning in 2014. While only a few berths have grid-based cold-ironing, ports throughout California are installing infrastructure to meet the state Air Resources Board’s regulations that take effect in 2014.

However, grid-based cold-ironing is complex and costly, and most ports lack the infrastructure needed to meet the power needs of multiple ships at berth. Those costs can run up to $5-10 million or more per berth, the study found. The Port of Oakland is installing 11 berths on six terminals at an estimated cost of about $70 million.

In addition, switching to grid-based power doesn’t eliminate emissions. Instead, that approach shifts the emissions to the source of electricity. Depending on the electricity source, the overall reduction in emissions can be relatively small.

The hydrogen fuel cell barge bypasses the need for electrical infrastructure. The barge also has the capability of being moved from berth to berth as needed and to anchorage points to power vessels that are waiting for berths.

In California, ports are already installing the necessary infrastructure for cold-ironing because of the regulations introduced a few years ago. So hydrogen fuel cell auxiliary power has the opportunity for greater impact elsewhere. While this was an unexpected finding, we discovered other locations and applications for hydrogen fuel cell power.

—Joe Pratt

At ports in Oregon and Washington, grid-based cold ironing infrastructure is limited or nonexistent. Using a hydrogen fuel cell to power container ships at berth has attracted interest for its potential economic and environmental benefits, Pratt said, and he continues to work with those ports on quantifying the benefits and deployment options.

Hawaii’s Honolulu Harbor in Oahu had a different need. Much of the cargo is unloaded and then reloaded onto barges for distribution to the other islands. As the barges have no power, they carry diesel generators to provide power to shipping containers that require refrigeration, known as “reefers.”

You can replace the diesel generator with a hydrogen fuel cell without changing the operations. It’s just a power source in a box, a shipping container in this case.

—Joe Pratt

Hawaii ports aren’t facing the same emissions regulations as California ports, but the potential savings in fuel cost is attractive for the company operating the inter-island transportation service, along with anyone else suffering from high fuel expenses.

The study’s basic fuel cost analysis showed that at today’s prices hydrogen, at about $4 per kilogram, with a fuel cell is cost-competitive with maritime fuels using a combustion engine. Subsequent analysis has shown that when generators are frequently producing less than maximum power, such as in the Hawaii application, the efficiency advantage of fuel cells compared to the combustion engine is widened. Even hydrogen at $5 per kilogram can potentially save tens of thousands of dollars per year for each generator.

Pratt is now developing a detailed plan for the Hawaiian inter-island transport barge application.

Resources

• Joseph W. Pratt and Aaron P. Harris (2013) Vessel Cold-Ironing Using a Barge Mounted PEM Fuel Cell: Project Scoping and Feasibility. SAND2013-0501