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2006/4/12

Vehicle powered by hydrogen fuel cell

Lucas Pérez Lafarga, a Technical Electronics Engineering student at the Polytechnic University School at the University of the Basque Country (EHU-UPV) and past student, César Gutiérrez Couceiro, who is currently a researcher at the Cidetec-IK4 Electrochemical Technological Centre, have designed a scooter powered by a hydrogen fuel cell, the result of a previous project undertaken in collaboration with the Department of Sustainable Development of the Regional Government of Gipuzkoa (Diputación) and which consists of designing an electric bicycle driven in the same way by a fuel cell.

As a result of the experience acquired from the project on this pedal-aided bicycle, Cidetec-IK4 decided to develop this type of technology and incorporate it into other vehicles. With a 500-watt fuel cell weighing 2.5 kilograms, this scooter was able to achieve a speed of about 20 Km/h. The main advantage of scooters powered by electric batteries is the savings in time, given that traditional batteries need hours in recharging time, while in this model all that is needed is to substitute the used bottle of hydrogen by a new one. Another advantage of using a fuel cell is that the motor can operate at full power whenever there is a supply of hydrogen. With traditional batteries, on the other hand, as they run down, they reach a point where they cannot supply all the power demanded by the motor.

It also has to be emphasised that, within the differences between the various existing fuel cell technologies, the PEMFC (proton exchange membrane fuel cell) type has been opted for, mainly because they work at relatively low temperatures – in the order of 70 ºC, with a high density of power.

As regards the operation of fuel cells, it has to be pointed out that they are electrochemical devices that, based on hydrogen and air, generate electricity and heat. Its functional unit is made up of what is known as a MEA (membrane / electrode assembly), incorporating a central polymeric membrane that enables ionic exchange but, at the same time, is an electrical insulator. An electrode is located at either side: the anode where the hydrogen molecules dissociate on the protons that pass through the membrane and on the electrons which are diverted by the electric circuit; and the cathode where the hydrogen protons, taking advantage of the energy electrons freed at the anode, recombine with oxygen groups from the supplied air, thus generating water and heat.

Hydrogen in the future

Until the relevant authorities and the industries involved do not make the step from oil and other fossil fuels, society is not going to change its `chip´. The reserves of petroleum oil are running out, its price rocketing and society is becoming impatient. The use of new fuels (hydrogen, ethanol, methanol) is being studied but the obtention of this type of fuel is, today, “very difficult and very costly”. A comparison carried out by researchers at Cidetec-IK4 shows clearly the situation we find ourselves in: “50 litres of high-purity hydrogen stored at 200 bars pressure costs approximately 180 €. With a cell of 500 Watts (nominal), 6 litres a minute are consumed, i.e. the cell will function for 24 hours at full power”.

Obtaining hydrogen through the electrolysis of water, for example, would be a simpler and cleaner way of obtaining hydrogen but, today, this is costly. How to reduce costs with this technology is currently being studied using solar panels to obtain the hydrogen, but these panels are still too costly and provide little energy efficiency. Moreover, storing hydrogen in volumes similar to the storage of petroleum oil is “almost impossible”. In order to achieve energy efficiency similar to a car’s 55-litre petrol tank, the hydrogen would have to be stored at 700 bars in the same volume and, today, this is only possible at 350 bars. New materials capable of storing greater densities of hydrogen are being studied, such as metal hydrides, but we are now referring to technologies still under development.