An energy self-sufficient public building using integrated renewable sources and hydrogen storage

The control of the use of fossil fuels, major cause of greenhouse gas emissions and climate changes, in present days represents one of Governments' main challenges; particularly, a significant energy consumption is observed in buildings and might be significantly reduced through sustainable design, increased energy efficiency and use of renewable sources. At the moment, the widespread use of renewable energy in buildings is limited by its intrinsic discontinuity: consequently integration of plants with energy storage systems could represent an efficient solution to the problem. Within this frame, hydrogen has shown to be particularly fit in order to be used as an energetic carrier. In this aim, in the paper an energetic, economic and environmental analysis of two different configurations of a self-sufficient system for energy production from renewable sources in buildings is presented. In particular, in the first configuration energy production is carried out by means of photovoltaic systems, whereas in the second one a combination of photovoltaic panels and wind generators is used. In both configurations, hydrogen is used as an energy carrier, in order to store energy, and fuel cells guarantee its energetic reconversion. The analysis carried out shows that, although dimensioned as a stand-alone configuration, the system can today be realized only taking advantage from the incentivizing fares applied to grid-connected systems, that are likely to be suspended in the next future. In such case, it represents an interesting investment, with capital returns in about 15 years. As concerns economic sustainability, in fact, the analysis shows that the cost of the energy unit stored in hydrogen volumes, due to the not very high efficiency of the process, presently results greater than that of directly used one. Moreover, also the starting fund of the system proves to be very high, showing an additional cost with respect to systems lacking of energy storage equal to about 50%. From the above, it can be deduced that, in the aim to obtain a quick, effective penetration of hydrogen into the market, it is at the moment indispensable to enact incentivizing policies, attributing to hydrogen production fares able to cover the additional costs due to its production, storage and reconversion.