Business Green: Despite the rough ride that may clean tech companies have faced over recent months, market analysts are predicting healthy growth over the next decade. In its Clean Energy Trends 2009 report, released this week, research company Clean Edge claims that by 2018 wind power, solar photovoltaics (PV) and biofuels will have revenues of $325.1bn (£237bn). The researchers admit that 2009 will be a “challenging year” for the clean-energy industry, due to credit constraints affecting …