(Reuters) - Veteran investor and Silicon Valley executive Sam Altman led a $500 million funding round in clean energy firm Helion, a company that he also serves as an executive chairman. The funding round, announced on Friday, also drew investment from existing investor Dustin Moskovitz, currently the chief executive at workplace software maker Asana who also co-founded Facebook. Venture capital firm Mithril Capital, co-founded by Ajay Royan and Peter Thiel, and Capricorn Investment Group also participated in the latest round. Helion did not disclose the valuation at which the new funds were raised. Everett, Washington-based Helion was founded in 2013 by David Kirtley, Chris Pihl and George Votroubek. It is focused on generating zero-carbon electricity from nuclear fusion. Kirtley, who heads the company now, has also worked at NASA and the U.S. Air Force Research Laboratory in the past. Altman was previously the president of Silicon Valley startup accelerator Y Combinator, which over the years has influenced the creation of dozens of leading companies, including Airbnb Inc and Dropbox Inc. Currently, he heads artificial-intelligence research firm OpenAI, which is also backed by Tesla Inc chief Elon Musk. Reporting by Niket Nishant in Bengaluru; Editing by Shailesh Kuber