Hydrogen in focus
Your ‘letter of the week’ in the 25 October issue put forward hydrogen internal combustion engines as a possible way forward in future. Such engines are entirely feasible and, indeed, were road tested by BMW some years ago. However, they have a couple of disadvantages.
Most important, they have low efficiency. In optimum conditions, a small turbocharged piston version operating at constant full load against a generator recharging the main propulsion battery might get slightly better than 40%, but this is poor compared with a fuel cell capability of 80%. The ICE engine thus needs twice the fuel capacity of the FC and finding room to accommodate the necessary hydrogen tanks is one of the main challenges for the hydrogen car.
Second, burning hydrogen in air produces very high temperatures so NOX will be produced and must be absorbed. This could be achieved using catalysts similar to those already developed for petrol ICES, but they are not perfect and the vehicles would not be emission-free. Small gas turbines are notoriously inefficient and would be challenged by tank capacity, the cost of hydrogen as fuel and finding means of eliminating NOX from their considerable volumes of exhaust gas.
So I agree hydrogen will be the way forward because of the immense problems to the national and local electrical infrastructures that would be caused if all vehicles were battery-only, and I guess the hydrogenpowered vehicles will use fuel cells. Anthony Lunt Saint-pons-de-mauchiens, France