Associated Press: Dow Chemical Co. says it aims to start selling power-generating roof shingles by 2011. The Midland-based chemical giant has been at work for the past year on a $50 million project called Dow Solar Solutions. The company’s scientists and engineers are working to develop a product to sell thermoplastic solar roof shingles throughout North America. Dow Chemical is collaborating with three home builders – Lennar Corp. of Miami, Pulte Homes Inc. of Bloomfield Hills and Prost …