The Obama administration on Tuesday announced an initiative to help low- and middle-income Americans gain access to solar energy, part of a series of steps President Obama is taking to tackle climate change, according to administration officials. The administration announced that it intends to triple the capacity of solar and other renewable energy systems it installs in federally subsidized housing by 2020, make it easier for homeowners to borrow money for solar improvements and start a nationwide program to help renters gain access to solar energy, the officials said. The actions were announced in Baltimore by Brian Deese, Mr. Obama’s senior adviser for climate issues, and Representative Elijah E. Cummings, the Democrat who represents the city.