Four tools for the future of energy

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

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