GM and its Opel subsidiary had aimed at a compact fuel cell powered vehicles.By 2010, up to 10% of total sales are expected to be taken by this category.The efficiency of cells tested by the company is over 60% and CO2 emissions, produced during the reformation of methanol to obtain hydrogen, are about half that of an equivalent powered IC engine. Fuel cells have already been successfully exploited in power generation, at Westervoort in the Netherlands, and experimental versions have been shown to successfully power laptop computers. According to GM, in principle four basic fuels are suitable: sulphur-free modified gasoline, a synthetic fuel, methanol or pure hydrogen. Modified gasoline is preferred because of the existing distribution infrastructure but CO2 emission in reforming is higher than with methanol. Synthetic fuel and methanol can be obtained from some primary energy sources including natural gas. Transportation and storage of hydrogen is still at the development stage for commercial viability, Liquefying by low temperature and/or pressure being seen as the only means of on-vehicle storage .
GM engineers have been working on a fuel-cell drive version of the Zafira van (a) in which electric motor, battery and controller are accommodated in the former engine compartment (b). The ‘cold combustion’ of the fuel-cell reaction, hydrogen combining with oxygen to form water, takes place at 80–90 C and a single cell develops 0.6–0.8 V. Sufficient cells are combined to power a 50kW asynchronous motor driving the front wheels through a fixed gear reduction. The cell comprises fuel anode, electrolyte and oxygen cathode. Protons migrate through the electrolyte towards the cathode, to form water, and in doing so produce electric current. Prospects for operating efficiencies above 60% are in view, pending successful waste heat utilization and optimization of gas paths within the system. The reforming process involved in producing hydrogen from the fuel involves no special safety measures for handling methanol and the long-term goal is to produce no more than 90 g/km of CO2. In the final version it is hoped to miniaturize the reformer, which now takes up most of the load space, (c), and part of the passenger area, so that it also fits within the former engine compartment. Rate of production of hydrogen in the reformer, and rate of current production in the fuel cell, both have to be accelerated to obtain acceptable throttle response times–the flow diagram is seen at (d). The20 second start-up time also has to be reduced to 2 seconds, while tolerating outside temperatures of 30 C in fuel cell powered vehicles .