Greenbang’s a bit, well, naive, which probably explains why she has always thought that the stock market works on the same principle as an airplane. In the same way that planes are kept aloft by their passengers’ belief in the miracle of flight, the stock market is kept aloft by the faith of traders in the value of the commodities. Or to put it another way: if people stop believing, both will crash.

Okay, so Greenbang’s understanding of the workings of economics and aerodynamics is a little on the superstitious side, but belief does go a long way in finance: it looks like belief in the value of green tech is helping to drive its growth.

Proof, if proof were needed: US cleantech investment gurus Cleantech Group has announced that in the first quarter of this year, cleantech investments are up 42 percent on last year’s first quarter total to $1.25 billion.

Cleantech Group recorded 79 transactions in the first four months of 2008, with each averaging $15.8 million, up 53 percent from last year’s average of $10.3 million.

That said, it’s not all plain sailing. While the overall cleantech sector is growing, successive quarterly declines in the first gen biofuels and second gen solar tech industries show that their heyday is coming to an end. Cleantech’s data reveals that two particular investments waves have peaked:

ETHANOL AND WIND (2005-2006): Powered by investments in ethanol and European wind energy companies, the wave peaked in 3Q06 at $1.52 billion and has steadily declined since.

THIN FILM SOLAR (2007): Driven by investments in US and European thin-film solar companies, this wave peaked in 3Q07 at $1.83 billion in 1Q08. Thin-film technologies accounted for approximately two-thirds of investments in solar, while crystalline technologies accounted for one-third.

• ‘Solar as a service’ outfit lands $12m
• SunEdison lands $161 million from VCs, Duke deal
• Econcern to stump up €12 billion for green power
• Clean tech gets $2.2bn VC bonanza
• University team creates biofuel spit of petrol
• Foundation Capital opens $250m clean tech fund
• Clean energy revenues to hit $254.5 billion
• Clean tech investment comes in at $148.4 billion
• BP invests $1.5 billion in renewables
• UK government: A study in how NOT to show love for solar