Business Green: Stocks in the clean tech sector have become undervalued and are on the verge of a major bull run that could deliver sizeable returns for investors, according to a fund manager at one of Europe’s leading clean tech investment funds. Speaking to BusinessGreen.com, Nicola Donnelly, fund manager at WHEB Asset Management, said that the inherent volatility of clean tech stocks meant that they had suffered disproportionately during the global economic downturn and were now well positioned for a rapid…