Excerpt from an Astro City Police Department file:
Real Name: Rachelle H. Brown
A Bakerville prostitute, "Energy" Brown fell under the thumb of Morris "The Ace" Reynolds late in his domination of the ghetto mobs. He manipulated her as a tool, another of his super-powered recruits used to compete against the growing number of superhuman heroes in the inner city.
She's able to project some sort of energy.
Despite her mob associations, Energy Brown has also acted to prevent violence in Astro City during times of chaos, most notably in trying to stop Black Velvet's energy from taking a hold of the city's populace in the aftermath of the 1977 Gang War.
Since "Ace" Reynolds was a known client of Dr. Lewis Oscar Croft (crossref EAGLE file 1WMG1223CSG), it is possible that Energy Brown was a product of his experiments, which induced paranormal powers in captured subjects.