Complex sentence: J.A. Rodiek (2005) Solar powered Stirling engines are increasingly popular as they offer an environmentally sound option for producing power while some designs are economically attractive in development projects.
Split into simpler sentences: J.A. Rodiek (2005) Solar powered Stirling engines are becoming increasingly popular, as they are a very environmentally sound option for producing power. Also, some designs are economically attractive in development projects.