Reuters: The world faces a doubling of energy demand by 2050 but renewable sources are still too expensive and will take decades to make a big impact, Royal Dutch Shell CEO Jeroen van der Veer said on Thursday. In a speech on "Shell scenarios for the 21st century," van der Veer said one of the three hard truths facing the world was a big rise in demand as the global population rose from around six billion to nine billion by mid-century. He told the EastWest Institute …