Complex sentence: George Philippidis is an international expert in renewable energy technologies and business and a strong advocate of the US need for diversification of power and fuel resources to enhance energy security, combat climate change, and secure sustainable economic growth.
Split into simpler sentences: George Philippidis is a business leader and technology expert in renewable energy and a strong advocate of the global need for energy diversification. He promotes the development and commercialization of renewable low-carbon power and fuels to enhance energy security, combat climate change, and secure sustainable economic growth.