Reuters: Wealthier countries in the European Union will have to do more than poorer nations to meet a goal of boosting EU renewable energy usage under proposals being developed by the bloc’s executive branch. EU countries’ gross domestic product will partially determine how much they will have to contribute to an EU target to have 20 percent of the bloc’s energy use come from renewable sources such as wind or solar power by 2020, an official said. EU leaders agreed in March to make the …