Despite its tempting low price compared with petrol, many motorists shun liquefied petroleum gas. Bulky LPG cylinders that rob storage space are one reason why. LPG is too bulky to store as a gas but it turns to liquid when compressed to 120psi, or 8.5 times atmospheric pressure. To store it in liquid form requires a strong pressurized container. Previously these could only be cylinders, or a smaller and more expensive circular tank called a donut, which fitted in the spare wheel well.

A new type of conformable LPG tank can be made to fit more easily into most cars without evicting the spare wheel or taking up luggage space. The prototype is half the width and one third taller than a cylinder holding the same amount of LPG. The tank holds the gas in the same way an air bed holds air – in a row of cells.

Previous attempts to weld such shapes were expensive but a new conformable tank developed by the New Zealand firm Propane Performance Industries uses interlocking aluminium extrusions to hold the cells together under pressure. The maker says this design is safer than traditional cylinders and can withstand impacts up to 160km/hour.