As a proton-exchange membrane fuel cell (PEMFC) can be started instantly at ambient temperatures and can work with air as oxidant without carbon dioxide problems, it is so far the most viable fuel cell (FC) system that has the potential to replace internal combustion engines (ICEs) and batteries for transportation applications to power cars, buses, and personal electric vehicles (PEVs). This article focuses on the application of this technology for light traction vehicles, such as scooters, bicycles, forklifts, wheelchairs, and tour carts. . | Light Traction Fuel Cells Z Qi Plug Power Inc. Latham NY USA 2009 Elsevier . All rights reserved. Introduction As a proton-exchange membrane fuel cell PEMFC can be started instantly at ambient temperatures and can work with air as oxidant without carbon dioxide problems it is so far the most viable fuel cell FC system that has the potential to replace internal combustion engines ICEs and batteries for transportation applications to power cars buses and personal electric vehicles PEVs . This article focuses on the application of this technology for light traction vehicles such as scooters bicycles forklifts wheelchairs and tour carts. Fuel Cell Systems There is no doubt that a vehicle should be able to start instantly regardless of the powering technology used. Because onboard hydrocarbon reforming takes too much time to generate hydrogen an FC that powers a vehicle has to use either hydrogen or liquid fuels directly. For light traction applications it is also desirable that the FC system is simple compact and cost-effective. Hydrogen-Air Systems Figure 1 depicts a hydrogen-air FC system. Basically an FC stack receives hydrogen from a storage tank and oxygen from air through a fan a blower or a pump. The direct current DC electrical power generated by the FC is used to power an electrical motor that drives a vehicle. Figure 1 Function block diagram of a hydrogen-air fuel cell FC system. DC direct current. The motor is preferred to be one that can operate with a wide voltage range so that a DC-DC converter does not need to be used thereby reducing cost and increasing system efficiency. In addition in-wheel or wheel-hub motor configurations where an electrical motor is located in the wheel should be considered in order to save space and to eliminate freewheeling. A microprocessor can be used to control the system operation. In order to reduce the size and weight of the FC stack and to meet acceleration and hill climbing demands it is helpful to include either a .