Revolve Technologies, formerly Roush Technologies of the U.K., has developed a hydrogen bi-fuel conversion system for gasoline engines. The company recently displayed its demonstration vehicle based on a Ford Transit cargo van powered by the 2.3-L four-cylinder gasoline engine available as an option with Transit models sold in Europe. Roush selected this engine because it was designed to run on “dry fuels”—the engine could be fueled by either liquefied petroleum gas (LPG) or compressed natural gas (CNG) through existing Ford programs.
Revolve has added a belt-driven Rotrex supercharger and charge intercooler to the engine for hydrogen-fueled operation. The supercharger provides a boost pressure of 0.85 bar (12.3 psi) and features a bypass system to prevent operation when the engine is used while gasoline-fueled. As Revolve’s Technical Director of Product Development Paul Turner told Automotive Engineering International, “The supercharger is there to give us the additional airflow we need to maintain a suitable level of performance, whilst running very lean.”
The vehicle retains the gasoline tank, fuel system, and ignition circuit. A second set of injectors is also added between the inlet manifold and cylinder head, as an extension to the inlet manifold, to permit operation on either fuel.
The spark plugs for hydrogen operation are also different. “We can’t run the platinum spark plug, otherwise that acts as a catalyst and ignites the charge,” explained Turner. The hydrogen plugs run at a cooler temperature and require a narrower gap. The engine can be started on hydrogen. As Turner pointed out, “It probably starts better on hydrogen than it does on gasoline; being a gaseous fuel, you don’t have to worry about fuel ‘puddling.’”
Power output on gasoline is around 140 hp (104 kW), but under hydrogen operation is reduced to around 90 hp (67 kW). “That’s perfectly adequate for the size of the van,” said Turner. “It is designed as a city delivery vehicle. We’re not developing it as a motorway cruiser, primarily because the amount of hydrogen you can carry on board would suit urban rather than highway operation. The aim is to give you adequate performance for the task you need to do, and we size and shape everything to give you that adequate performance.”
Hydrogen is stored in three tanks beneath the load floor of the vehicle, without intruding into the load area. The three tanks are designed to provide storage for 4.5 kg (9.9 lb) of hydrogen at 350 bar (5076 psi), which should provide a range of between 95 and 135 mi (153 and 217 km). The range could be extended by adding further tanks.
The tank construction consists of an aluminum core with a carbon-fiber shell. The tanks are protected by inner and outer side-impact protection plates on the carrier subframe and removable under-tray skid plates.
Revolve has entered into a joint-venture arrangement with ITM Power to develop hydrogen fueling equipment. The electrolyzer operates from an available source of electricity and de-ionized water to produce the hydrogen and can be used for hydrogen production at home.
“One kilogram of hydrogen is roughly equivalent to 1 gal of gasoline, in terms of the energy content,” explained Marcus Scott, Chief Financial Officer of ITM Power. “The electrolyzer can produce around 3 kg of hydrogen in a 24-h period running continuously. With the high-pressure refueling unit, the commercial version that we’re putting together, we have three times the capacity of the electrolyzer, so it can produce a potential total of 9 kg per day.”
The commercial variant is designed as a depot refueling system. The high-pressure unit should provide a refueling time of around 10 to 15 min. The first system is scheduled for delivery by the end of 2008.
The smaller electrolyzer could produce hydrogen overnight using electricity from off-peak or renewable sources.