Energy is a fundamental and cross-cutting concept, therefore a major learning objective of school science. However, teaching and learning about energy is very challenging because it is an abstract, purely mathematical concept, and definitions vary across science disciplines. Taking into account research on science education in non-formal environments, we investigated primary school students’ ideas about energy in a university laboratory using a model simulating a hydroelectric power station intended for training Civil Engineering students. Unlike models normally used in K-12 science education, it was an original 3-D model, qualitatively and quantitatively analogous to a real-life system. Participants were given a worksheet and worked in groups, trying to figure out what the model does and how it works. Their discussions were recorded and later debriefed and coded. Our findings reassert literature on common misconceptions about energy. Further study of the prospects such trans-departmental collaborations offer in terms of fostering K-12 science education and prospective school teachers’ training is deemed appealing and potentially promising.