President Joe Biden's departing green energy loan czar this week finalized a controversial $1.6 billion federal loan to a green energy company with which he had prior financial ties—a farewell shot at federal investigators who have been probing conflicts of interest in his lending office. The Department of Energy's loan to Plug Power, a hydrogen fuel developer, comes months after Republican lawmakers raised concerns about the company's past business relationship with DOE Loan Programs Office director Jigar Shah. Shortly before joining the Biden administration, Shah invested $100 million in Plug Power through a green financial firm he founded called Generate...