Shares in solar power company First Solar fell over 20% in early trading Wednesday after the firm lowered its sales forecast for 2011. The Arizona based company, which is a leading maker of thin-film solar panels and also a developer of solar power projects, predicted net sales in 2011 of $2.8 to $2.9 billion. That’s down from earlier projections of $3.0 to $3.3 billion. The company said the lower sales were due to delays in its projects caused by weather and “other factors,” but predicted a healthy 2012. “Our diverse business model and robust project pipeline will help First Solar generate a significant amount of cash in 2012 while improving operational efficiencies,” Mike Ahearn, Chairman and Interim CEO of First Solar, said in a statement Wednesday.