Ashburton coachbuilding company Designline is building a prototype commuter bus powered by a chemical fuel cell using reusable, renewable materials.

The space-technology prototype is expected to be running early next year, according to the company's managing director, John Turton.

An American company, Alchemy Enterprises Ltd, is producing the magnesium-based fuel cell which will power the electric bus.

Alchemy has developed its fuel cell with the Nasa space agency and its Jet Propulsion Labs and Cal Tech in Pasadena, California, and Cal Tech is expected to take an 8 per cent stake in the company in return.

Alchemy will have exclusive worldwide rights to the patent rights related to the metal-air fuel cell developed by Nasa/JPL under the agreement.

Designline is well known internationally as a producer of hybrid buses and vehicles, and three of its hybrid electric buses powered by water-cooled batteries provide a shuttle service in Christchurch.

Alchemy's technology uses magnesium -- one of the most common minerals on earth -- as its catalyst material for a chemical reaction that generates electricity. Metal-air fuel cells (MAFC) use metal and oxygen to generate electricity, rather than combining hydrogen and oxygen as in a polymer electrolyte membrane (PEM) fuel cell.

The Alchemy fuel cell pumps an electrolytic liquid consisting of magnesium and salt water into the power cell, and when exposed to air, it generates electricity. When the electrolytic liquid is exhausted, it is pumped out of the power cell into a storage tank, and "recharged" to be pumped back into another fuel cell.

Alchemy chief executive Jonathan Read said in a statement that the company's fuel cell would provide a significant alternative to some other hydrogen-based systems.

"Our system provides power on demand -- hydrogen on demand -- and is a model for sustainable affordable long-term power systems," he said.

"Our first prototype is being developed for the public transportation sector as it is the easiest to control and monitor ... we hope to then expand to fleet applications, and will be entertaining automobile joint ventures".

Mr Read said Designline was a recognised leader in the manufacture of advanced electric drive systems for buses and installing the fuel cell in buses with the Designline drive system, would demonstrate to the world the efficiency of the technology.

The fuel cells were first developed for long-range solar-powered unmanned aircraft flying for long times at extremely high altitudes, and have been further refined for use in heavy vehicles.

The company said it expected to be able to unveil a working prototype of the fuel cell by December this year and have it powering a bus by March 2007.