Gloria Williams intentionally sits in darkness at her Belle Haven home, wary of the high electric bill that comes with switching on a light. The 76-year-old has seen energy-saving solar panels pop up on homes near Chilco Street, but it’s a luxury that the retiree hasn’t been able to afford until Facebook and local nonprofits stepped in to help. On Tuesday, Williams placed a hard hat on her head as workers from GRID Alternatives lifted glimmering black solar panels onto the roof of her two-story home.