The head of the Energy Department's embattled clean energy loan program is leaving in what officials called a planned departure.

Jonathan Silver, who has headed the loan program since November 2009, is leaving to join a nonpartisan think tank.

Energy Secretary Steven Chu said in a statement that Silver informed him in July he was leaving. A key section of the loan program expired on Friday. The program has come under fire from Republicans after a California solar energy company collapsed despite receiving a $528 million federal loan.

President Barack Obama defended the loan program Thursday, saying officials knew some companies that received government aid were likely to fail.

He said the process of awarding the loan to solar panel maker Solyndra was straightforward and based on merits.