Four tools for the fu­ture of energy

These energy tech­nolo­gies are paving the way for a more sus­tain­able fu­ture, writes BELINDA SMITH.

Cosmos - - Cosmos Science Club -

FU­TURE FUEL CELLS

Imag­ine driv­ing a car, but in­stead of ex­haust fumes and car­bon diox­ide, it emits only pure wa­ter. Cars pow­ered by hy­dro­gen fuel cells do just that, con­vert­ing energy stored in molec­u­lar bonds into elec­tri­cal energy. The Toy­ota Mi­rai (Ja­panese for ‘fu­ture’) is one of the first com­mer­cially sold ve­hi­cles pow­ered by fuel cells and rated the most fuel-ef­fi­cient hy­dro­gen fuel cell ve­hi­cle by the US En­vi­ron­men­tal Pro­tec­tion Agency. It made its de­but at the Novem­ber 2014 Los An­ge­les Auto Show and, last year, landed in Australia for a three­year trial.

So what’s un­der the hood? In­stead of an in­ter­nal com­bus­tion en­gine, where hot gases push a pis­ton to turn a crank­shaft, it has a stack of hy­dro­gen fuel cells.

There are a few dif­fer­ent types of hy­dro­gen fuel cells but their ba­sic prin­ci­ples are the same. Cars like the Mi­rai use what are known as pro­ton ex­change mem­brane fuel cells. They com­prise two elec­trodes – an an­ode and a cath­ode – sep­a­rated by an elec­trolyte mem­brane that lets spe­cific types of charged par­ti­cles pass through.

Pres­surised hy­dro­gen gas (H ) is pumped from a stor­age tank to the an­ode, where it’s forced through a cat­a­lyst – a thin layer of plat­inum. The cat­a­lyst tears the H mol­e­cule apart into two pos­i­tively charged (or ionised) hy­dro­gen atoms and two elec­trons.

The ionised hy­dro­gen atoms cruise through the elec­trolyte to the cath­ode – but the elec­trons are blocked. So they travel around the cir­cuit to the cath­ode, cre­at­ing the cur­rent.

At the cath­ode, air is pumped in. Oxy­gen gas mol­e­cules (O ) in air are also bro­ken apart to cre­ate two neg­a­tively charged oxy­gen atoms. These re­act with the hy­dro­gen ions that passed through the mem­brane and elec­trons that tra­versed the cir­cuit to form wa­ter mol­e­cules (H O).

Ger­man-swiss chemist Chris­tian Friedrich Schoen­bein first pub­lished fuel cells’ un­der­ly­ing prin­ci­ples in a magazine in 1838. He knew that

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