Energy Secretary Steven Chu is ending his tenure after four years and three months.
Deputy Energy Secretary Daniel Poneman will serve as acting secretary beginning Tuesday and serve until a successor is sworn in.
President Barack Obama has nominated physics professor Ernest Moniz to succeed Chu. A Senate vote on Moniz’s nomination could come as soon as this week.
Chu, who won a Nobel Prize in physics, announced his resignation in February.
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As energy secretary, he was credited with boosting renewable energy such as wind and solar power, but was criticized for his handling of a half-billion-dollar federal loan to solar panel maker Solyndra, which later went bankrupt, laying off 1,100 workers.
Poneman has been deputy secretary since 2009. He also serves as the department’s chief operating officer.