Rapid economic growth has contributed to the increasing energy demand observed nowdays with a consequent increase in the use of fossil fuels. Their combustion and following carbon dioxide (CO2) emissions recently arose as a cause of concern due to the adverse effect on the environment, since CO2 has been widely recognized as a major greenhouse gas and as the main cause of global warming. Energy demand is still expected to grow in the decades to come, thus, new pathways for its production should be pursued. Renewable enery sources (RES) have been identified as the long term solution to reduce CO2 emissions, but their intermittency can hinder the effectiveness of such technologies.