Clipper Windpower, the California-based renewable energy company, has forecast a modest improvement in earnings for 2008 as larger shipments of wind turbines would be offset by low prices.

Clipper, one of the biggest renewable companies on Aim, was forced to put out profit warnings last year as problems with the quality of turbines made by its suppliers held back shipments.

It also reduced the number of turbines it intended to make from its initial target of 250. Yesterday it confirmed that it had made 137 in its first full year of production. However, it forecast the net loss for the second half of 2007 "is expected to be of similar magnitude" to the £78m it recorded in the first half after a series of one-off charges totalling $7m-$10m to address issues that included blade upgrades and penalties for delivery delays.

Clipper also cautioned that 2008 would be a "transitional" year as first-half results would be more heavily affected by lower average turbine prices from the backlog of orders, derived from contracts negotiated in 2006 when industry pricing was softer.

However, Clipper forecast margins would materialise in the second half of the year and expected 2009 turbine sale margins to "significantly improve" as average contracted turbine prices were 15 per cent - 20 per cent higher than Clipper's average 2008 contracted prices.

The group reconfirmed its target of making 311 turbines in 2008 and would continue to develop a 7.5MW turbine at Blythe in north-east England in what is set to be the largest wind turbine in the world.

Clipper, which is seeking funding to construct and manage its own wind farm projects, added that it had received a firm order for 155 turbines for delivery by 2011, taking total orders from third parties to 825.

The shares closed up 5p at 630p.