Photovoltaic toy cars racing circuits as hands-on learning solar energy: Results from a Problem Based Learning (PBL) experience for undergraduates - Fuentes M; Vivar M; López-Vargas A; Pichel N (2018 Ieee 7th World Conference On Photovoltaic Energy Conversion, Wcpec 2018 - A Joint Conference Of 45th Ieee Pvsc, 28th Pvsec And 34th Eu Pvsec, 2018)