Winter's bitter cold can stall wind turbine blades, congeal biodiesel and render solar panels useless, UPI quoted U.S. power developers as saying today. As renewable energy assumes a larger role in the U.S. power grid, green energy advocates find they must plan carefully for obstacles presented by ice and snow, The New York Times reported today. Ralph Brokaw, a Wyoming cattle rancher who has 69 wind turbines on his land, says his machine can hurl chunks of ice as they rotate. Solar panels covered with snow are rendered useless, though panels kept clean get extra power from sunlight reflected off snow, the Times reported. As for biodiesel, without internal heaters to warm the fuel, even a small amount of biodiesel, typically made from vegetables oil, will congeal and clog a fuel line, as John Jones well knows. "We can't have people sitting on buses freezing to death while we get out there trying to get them restarted," Jones, a transit director for a Colorado bus line that hauls skiers to resorts, told the Times.