The judge ruled that Energy Secretary Chris Wright violated the law when he handpicked researchers to work in secret to produce a government report on global warming.
Many of the cancellations had been known for months, but the announcement underscored the drastic change in the energy landscape under President Trump.
The Energy Department canceled a partial loan guarantee to Sunnova Energy, a residential solar panel installer that was experimenting with a novel way to link home solar and battery systems.
Companies like Kairos Power are building new types of reactors with the encouragement of the Trump administration, but their success is far from assured.
Trump Media plans to merge with a company developing nuclear fusion technology, putting the presidentβs financial interests in competition with other energy companies over which his administration holds sway.