Smart energy research - at the crossroads of engineering, economics, and computer science 3rd and 4th IFIP TC 12 International Conferences, SmartER Europe 2016 and 2017, Essen, Germany, February 16-18, 2016, and February 9, 2017 : revised selected papers - Derksen, Christian; Weber, Christoph 1964- (IFIP Advances in Information and Communication Technology, 2017)