As a hobby, Denis is a researcher in renewable energies. He has written several books : “Vent artificiel” (Artificial Wind), 2003, “A fond contre le CO2” (Full Speed against CO2), 2006, “20 énergies renouvelables insolites” (20 Unusual Renewable Energies), co-authored with Renaud de Richter, « Fautes : climatoscepticisme, incompétence et irresponsabilité » (Errors: Climate Scepticism, Incompetence and Irresponsibility), 2011, « La poule aux œufs d’or : électricité solaire massive, court-termisme et autarcie » (The Goose that Laid the Golden Eggs : Massive Solar Electricity, Short-Term View and Autarcy), « Welcome to Paris Solar Energy : a French Proposal for the 2015 Climate Conference of Parties », 2014. Denis also works on the different technologies to manage intermittence in energy supply. As a professional, he is a government-appointed auditor to local governments. Previously, he was a teacher in physics for 19-21 year old graduates from technical schools. He is a former student of the Ecole Normale Superieure (1977-1980) and of the Ecole Nationale d’Administration – ENA – (1993-1995), and passed a doctorate (PhD) in physics/economics in 2004.