How much Hydrogen is required to produce 1Kw in a fuel cell?

Answer 1

A kiloWatt is a unit of power (energy per unit time).
1 kW = 1000 Watts = 1000 Joules per second.

The question is not how much Hydrogen is required, but rather the rate at which Hydrogen will react within the fuel cell to produce such a power.


For every 2 moles of Hydrogen gas which combine with 1 mole of Oxygen gas, a net change of -237.13 kJ of Gibbs free energy occurs (specifically, the number corresponds to the reaction occurring at 298 K).
This means that for every 2 mole of Hydrogen reacting, 237.13 kJ of energy can be extracted. If one wants to extract 1000 Joules (= 1 kJ), then one would need to react 4.2 E-3 moles of Hydrogen. If one wants to extract 1 kJ every second, one would need to react this amount of Hydrogen every second.
So in order to receive a power output of 1 kW, 4.2 E-3 moles of Hydrogen gas would need to be reacting every second.

At STP (273.15 K, 1 atm), 1 mole of an ideal gas (which we will assume Hydrogen gas is) has a volume of 22.4 Liters.
4.2 E-3 moles of Hydrogen gas would have a volume at STP of about 94 mL.

This assumes 100% efficiency which in reality is not possible to achieve. A more realistic estimate of the efficiency of the fuel cell would be somewhere around 50% depending on the type of fuel cell and the conditions it was operating under.

http://230nsc1.phy-astr.gsu.edu/hbase/thermo/electrol.html

Answer 2

really more than its worth