I. Introduction
The reduction of CO2,eq emissions is an international priority to limit the global warming. According to the Paris Agreement, the signatory states (174 countries and the European Union) are obliged to introduce specific energy policies to achieve this goal. Since the anthropic production of CO2,eq is deeply related to the meeting of the energy demand, this sector needs significant changes in order to improve its sustainability. The two main ways to contain the CO2,eq emission are [1]: