It has also licensed its technology to US defence group L-3 Communications, and is part of project developing an emissions-free ferry in Hamburg. 

The company will be floating a week tomorrow having raised GBP4.7million through a placing at 80p a share, giving it a market value of GBP25million. 

German group Proton, led by chief executive Felix Heidelberg, reports it has already won 4.2million (GBP2.8million) in forward orders. 

Proton is looking to raise money to support a move into full commercialisation, with the money being invested in sales and marketing, beefing up its manufacturing to handle large orders and in research and development. 

The company has 42 patents and has applied for a further 32. 

Proton says its fuel cell technology which includes part direct hydrogen fuel-cell power offers several advantages over existing systems. 

Excess energy generated by the fuel cells when, for example, a bus is not using much energy, is stored in the battery for use when extra energy is required for example, this might be when the bus is accelerating away from a stop. As a result, the batteries do not require recharging, and nor do the fuel cells need to be refuelled during the course of a typical shift.

This facility explains why the company's initial markets are "back-to-base" applications, such as buses and fork-lift trucks. 

Another plus for its systems, says Proton, is that the technology is modular, so cells can be stacked up to provide the right level of power and can be adapted to various uses. 

The company adds the technology can also be incorporated easily into vehicles. 

Proton was founded when it was spun out of electric motor specialist Magnet Motor. 

Investors to date include Volvo's technology investment arm and venture capitalist Alchemy Capital, which is headed by Jon Moulton, who once tried to buy Rover. 

FACTFILE PROTON POWER SYSTEMS: Established 1998. FLOAT: October 31. ISSUE: Placing. CONTACT: Bell Lawrie.