Business Green: Despite reports this week of funding difficulties for a number of high-profile clean tech projects – such as delays to T Boone Pickens’ plans for the largest wind farm in the US and concerns over cash flow at electric car manufacturer Tesla – clean tech investment levels are continuing to climb. That is the conclusion of the latest report from Ernst & Young, which found that venture capital investment in US clean tech firms reached a record $1.6bn (£0.9bn) during the third …