Hydrogen bus lets NREL visitors glimpse future

Imagine making fuel for your vehicle by simply using water and the wind or sun, filling your tank and driving to your favorite weekend vacation spot before looking for a fueling station. It is not a chapter out of a "green" science fiction novel, but technology being demonstrated in a "big" way on the campus of the U.S. Department (DOE) of Energy's National Renewable Energy Laboratory in Colorado.

DOE recently funded the leases for 12 hydrogen-powered internal combustion engine (H2ICE) shuttle buses, which are being placed at federal facilities across the country to demonstrate market-ready advanced technology vehicles. NREL was the first facility to receive one of the leased buses, which it currently uses for tours of its Golden, Colo., campus.

"NREL's unique twist to this demonstration is that we are fueling our shuttle bus with hydrogen made from wind energy up at our National Wind Technology Center near Boulder," Hydrogen Technologies & Systems Director Robert Remick said. "So, the hydrogen in our shuttle was literally wind energy blowing off the Rocky Mountains last week."

Tweak to an old engine

The H2ICE shuttle bus in use at NREL was manufactured by Ford, one of the first automakers to develop commercially available H2ICEs. The shuttle uses the same basic technology as a conventional gasoline-powered engine but runs on the hydrogen fuel created at NREL's Wind to Hydrogen (Wind2H2) Project. The Wind2H2 project links wind turbines to electrolyzers, which pass the wind-generated electricity through water to split it into hydrogen and oxygen. The hydrogen can then be stored and used later to generate electricity from an internal combustion engine or a fuel cell.

The bus has a 6.8-liter supercharged Triton V-10 engine. Only modest design adjustments were needed to switch the basic gasoline-powered engine to a hydrogen-powered engine. Those modifications included using specially designed spark plugs and alternate materials for valve seats and other parts that may become brittle when exposed to hydrogen.

NREL's shuttle is up to 25 percent more efficient than similar gasoline-fueled passenger vans and can run 175-250 miles (depending on usage) before staff refuels. The lab outfitted its "green" hydrogen dispensing station with cascading storage tanks, which decreases the time required for refueling. This is particularly beneficial for vehicles with large onboard storage systems like the H2ICE bus, which can take up to 30 kilograms of hydrogen in a single fueling. Because NREL's fueling station has a 130 kg storage capacity at 413 bar (6,000 psi), filling the bus takes 20-30 minutes; however, refueling time is lower at other commercial hydrogen stations.

NREL is studying hydrogen use at the Wind2H2 site to gain practical experience operating and maintaining complete systems and to understand hydrogen's interaction with the shuttle and the storage system. "In addition to the fueling station, we are storing more than 200 kg of hydrogen at the Wind2H2 site," Keith Wipke, NREL Senior Engineer and Group Manager for Hydrogen Analysis said. "It allows us to capture intermittent renewable energy and both fuel the vehicle and put energy back on the grid at times when there is high demand for electricity."

Although making hydrogen from renewable resources and using it in an H2ICE shuttle bus is a step in the right direction, it is an incremental step for the use of hydrogen in vehicles.

"Fuel Cells are the most efficient way to use hydrogen in vehicles," Wipke said. "So, this type of passenger bus utilizing an internal combustion engine is less efficient than a fuel cell, but is a good stepping stone to get the technology into the market and provide an alternative to fleets while the infrastructure for hydrogen fueling stations develops."

Read more at www.nrel.gov.