Residents at close to two dozen affordable housing buildings will soon be getting electricity from the sun via solar panels on their rooftops. Hippolito “Paul” Roldan, president and CEO of Hispanic Housing Development Corp., is kicking off a $7 million renewable energy initiative this month at 13 housing projects in Chicago neighborhoods including Humboldt Park, Logan Square, West Town and Rogers Park. More than 3,900 photovoltaic panels and other retrofits will be installed on 21 buildings with 1,300 apartments. Co-generation systems that direct energy from hot water tanks back into the building power supply will be added as another renewable feature. Mr. Roldan created Affordable Community Energy Inc., a new for-profit subsidiary within HHDC, to carry out these efforts. He estimates the program will result in a 17 percent annual energy savings and an 850-ton reduction in carbon dioxide emissions.