Deal Week noted recently what could be termed as the 'Macquarie effect' on the global projects market – the popularity of privately-financed transport schemes and buy-out style acquisitions in the infrastructure sector, especially in the US.

But perhaps it was remiss not to mention the other unexpected figure that is transforming, for very different reasons, the once-staid projects world: one Al Gore. Of course, the former presidential candidate is one of many messengers, but it is fair to say that his Oscar-winning film, An Inconvenient Truth, symbolised the move into the mainstream of green issues – and the corresponding demand for clean energy. When you get down to business, for advisers this will not mean messing about with frivolities like being carbon-neutral – it will mean adapting to the new appetite for renewable energy projects.

Ironically, that global laggard, the US, is proving to be the most zealous of the converted, partly in the wake of California's lead on slashing carbon emissions last year. Driven at state level, one US projects partner estimates that more than 20 states now have renewable energy portfolios and targets.

He comments: "Renewables are unbelievably hot in the US right now. It is a confluence of events driving this, such as high oil prices, energy security concerns with the war in Iraq and global warming fears. Several years ago, if I was talking about this stuff to a utility executive he would look at me like I was nuts. Over the last 18 months there has been a dramatic shift in attitudes."

Over in the UK, such trends have seen a wave of refinancing work for the companies operating in the renewables sector, notably in the still-dominant wind sector, while firms are looking at tapping the public markets or obtaining venture capital.

Elsewhere, confidence – and investment – has poured into clean energy, buoyed by political commitments (particularly in Germany) and technological advances that have improved the viability of some energy forms (particularly solar power).

Firms to have handled substantial mandates in the sector include Clifford Chance and Freshfields Bruckhaus Deringer, which this month advised on a refinancing of Babcock & Brown's £700m wind farm portfolio. Linklaters has also made much of its renewables credentials in recent years, but so far a broad range of advisers has operated in the sector, among them McGrigor Donald, Norton Rose and Halliwells, in part a reflection of the importance of the Alternative Investment Market in securing funding for renewable energy companies. Watson Farley & Williams' merger bid with Chadbourne & Parke would also create a transatlantic firm with substantial exposure to the renewables sector.

A recent report from the UN Environment Programme (UNEP) also underlines the growth in the sector, concluding that capital investment last year grew by 25% to hit $100bn (£50.2bn), a figure predicted to rise to $120bn (£60.3bn) in 2007. Just as importantly, UNEP concluded that the sector was no longer reliant on high energy prices to survive.

What could possibly go wrong? In the long term, not much, as the fundamentals are clearly there to dramatically expand what is basically still a global cottage industry. But in the meantime, it is something of an open secret that the industry is currently operating on shaky foundations. For a start, the wind sector – still the largest section of the market – is facing the double whammy of falling electricity prices and spiralling manufacturing costs, not to mention a continually shifting tax and tariff environment in Europe. Biofuels producers are under pressure for different reasons, including rising material costs, low margins and oversupply issues. Clean energy is here to stay. But it is still well short of the clear-out that will divide the companies – and advisers – that are in it for the long haul and those just chasing the latest fad.