True zero emissions? It's a very clear but easily misunderstood term. Forinstance, an all-electric car has no emissionsbut it isn't zero emissions if, for example, anyproportion of the power it uses to chargecomes from a coal-fired powerplant or froman internal combustion engine. For true zeroemissions, you need something far morespectacular. Technically, even fuel cells aren'tzero emissions - they do make water as aby-product but so far, no one thinks water isgoing to create problems like carbon dioxideand other tail pipe emissions.But before we get to the fuel cell itself, youshould know that electric and hybrid vehiclesare stop-gap solutions that postpone disasterbut don't prevent it. Fuel cell powered cars areseen as the ultimate solution.In sum, a fuel cell works by causinghydrogen and oxygen to combine - a violentreaction that produces lots of energy. The byproductis electricity and H2O, or water. Thereverse chemical reaction is also well-known- it's called electrolysis where the passage ofelectricity through water causes hydrogenand oxygen to split. A fuel cell generateselectricity that can be stored in a battery andbe used to power an electric vehicle.To understand this process further,let's look at a regular car battery. Insidethe battery box is a positive and negativeplate dipped in a special acid that servesas an electrically conducting solution(called electrolyte). The box keeps the acidcontained and ensures the plates are dippedin it. The plates exit the box on top in theform of the positive and negative terminalsto which the car or motorcycle connects.When we connect something thatconsumes electricity, like say a motor, to thisbattery, the completion of the circuit causesthe electrolyte to start to release positiveand negative ions that are attracted to andmove towards the opposite plates negativeand positive, respectively. The movementcontinues up the plates and towards themotor and generates electricity. Obviously,the ion supply is finite and when theelectrolyte is exhausted, we call the batterydischarged. Many batteries can be rechargedonce again but the process of adding ionsis very slow and that's why the rechargingprocess of a discharged battery takes so long.It's the reason why electric cars come withrange anxiety - because refilling the batteriesis a slow process.
It's the same chemical process, moreor less, that a fuel cell employs. It storeshydrogen in a tank, gets oxygen from theair and they combine inside the fuel cell tocreate electricity and water. It is the hydrogensupply that's a challenge. It is normally storedin a liquid state in a pressurised tank and thatliquid state means the tank can be refilledas easily and quickly as petrol or diesel, intheory. Both fuel cells and electricity are farmore efficient than internal combustion tooso these power units prove to be extremelyefficient too. And that is why there are a lotof fuel cell prototypes and early productionunits in the world.
But obviously, they're not the dominantform of the automobile for good reason.First, they are complex power units thatare currently very expensive to make. Forexample, fuel cells use platinum - very,very expensive - as a catalyst. There are alsopackaging challenges from the constructionof high strength hydrogen tanks to makingsure the passengers and cargo have enoughspace. There are safety challenges - the vehiclehas to be safe in an accident.Like with electric cars, there is also amassive distribution challenge that willhave to be overcome. There aren't too manyhydrogen filling stations in the world and thatnetwork will have to grow hand in hand withthe availability of the hydrogen-powered carsfor long term sustained success.You might wonder why hydrogen isexpected to be such an endless sourceof guilt-free power. For the simplest ofreasons - it is the most abundant element inour universe.