CMR joins a handful of fuel cell companies that have listed on the Alternative Investment Market in the past 18 months, including Acta, Ceres Power, ITM Power and Voller Energy Group. Nasdaq listed Enova Systems raised £11.5m in July through a share placement in its secondary listing on Aim.

The increasing interest marks a turnround in behaviour by investors in the past four years, as memories fade of the performances of fuel cell glamour stock following the crash of the technology boom in April 2000.

"Three or four years ago there was still a lot of scepticism about green technology, but now there appears to be a coming of age as more products are closer to commercialisation," said Jag Mundi, head of corporate finance at Numis, broker for the Acta float. Numis also worked on the Ceres float in 2004.

Scepticism about green technology has waned in recent years as concerns about energy prices remaining higher for longer and the impact of carbon emissions on climate change have become more widespread.

These factors have prompted companies and investors to search for cleaner fuel alternatives to fossil fuel, putting fuel cell technology under the spotlight. However, with few commercial products, the industry is in more of a research and development stage than a manufacturing and marketing stage.

Toddington Harper, managing director of Fuel Cell Markets, a consultancy said, given that many fuel cell companies are still in the development stage with prototype products rather than a commercial product, Aim was a more suitable place to list than the main market.

So far, investors are buying Aim-listed fuel cell companies on optimism about the future. Ceres Power shares are up20 per cent since their float, ITM Power stock is 140 per cent above its 50p issue price in June 2004. Acta shares have held steady since its listing on October 3. However, Voller Energy, has seen its shares slide around 50 per cent since listing in February.

Many more start-up fuel cell companies want to list on Aim.

"After we floated Ceres, we had hundreds of companies knocking on our door?.?.?.?and of the 30 to 40 companies we have seen on fuel cell technology, Acta is one of the best," said Mr Mundi from Numis.

Fuel cell development is far from the sole domain of small companies, with most of the $4bn spent on fuel cell research each year coming from large companies including the major car makers and industrial groups United Technology and General Electric.

In the UK, Johnson Matthey, the autocatalysts, chemicals and precious metals group, and Rolls Royce, the engine maker, are investing significant sums in fuel cells.

Fuel cells are not new. The first application of the technology was in the 1960s as a source of electricity for the US space missions.

"I think the dynamics of the industry will change as we see more commercial products come to the market in the next year or two," said Martin Green, strategic director of fuel cells at Johnson Matthey.

Mr Green said the first sectors to see commercial fuel cells are in portable devices, which rely on lead alkaline batteries or rechargeable batteries, as used in mobile phones.

Promises about fuel cell potential have been made before. Shares in Ballard Power Systems, a Canadian-listed fuel cell company, peaked at C$210.80 in March 2000, just before the tech crash, and have never recovered. Ballard shares were trading at C$5.20 yesterday.

Plug Power, another former fuel cell stock of the tech-boom era, also saw its share price plunge. The Nasdaq-listed company's shares peaked at $156.50 in January 2000. They have struggled to remain above $6 in the past two months.

"They made bold claims about commercialisation of their technology, but that was five, six years ago. The industry has moved on a lot since then," said Mr Harper from Fuel Cell Markets.