What does it look like A single cell may be smaller than a matchbox Modern single cells consist of three fl at discs two of a thin metal and one of a coated polymer fi lm As the voltage of a single cell is only between 0 5 and 1 volt several identical cells are combined into a stack A 100 kW fuel cell system with pumps lines heating system and control electronics for a vehicle powertrain fi lls the engine compartment of a mid sized car Why is a battery still needed as well Because fuel cells are unable to recover energy for instance from braking force but assistance for powerful acceleration makes sense and because energy must also be available for starting the fuel cell Such batteries however can be much smaller than the traction batteries of battery electric vehicles about 10 percent of their size How effi cient is a fuel cell A fuel cell generates electricity and heat Both electric and thermal effi ciency may amount to as much as 65 depending on the design without considering losses during production transportation and storage of the fuel While the electric power is used for propulsion the heat can be used for heating the car Why has it been a niche product so far As a combined heat and power producer in buildings it s still too costly In vehicle applications the fact that no country has an extensive network of fi lling stations is another inhibiting factor It s the old chicken and egg problem for energy corporations an expansion of the network is not profi table because there are not enough fuel cell vehicles while the automotive industry argues that there s a lack of fi lling stations Who invented it In 1838 the Swiss German chemist and physicist Christian Friedrich Schönbein immersed two platinum wires in hydrochloric acid together with hydrogen and oxygen and detected electrical voltage between the two wires the world s fi rst fuel cell The British physical scientist Sir William Robert Grove adopted the idea in 1839 and combined several of these cells into a gas battery the world s fi rst usable fuel cell stack Why is it becoming attractive now In the past there was no need to use them After all we had wood coal and petroleum These fuels were lying around and just had to be ignited explains Michael Fröba a professor of chemistry at University of Hamburg However in view of the pursuit of carbon neutral clean mobility to combat climate change hydrogen operated fuel cells are an intelligent key technology Membrane polymer fi lm Bipolar plate metal 64

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