Green Hydrogen Hub - Marghera

Hydrogen production, storage and utilization could represent a powerful solution to pursue the emission reduction targets of green house gases and pollutants towards the atmosphere. Hydrogen is the simplest and lightest chemical element present in nature, with a density of 0,0899 kg/m3. It is the fuel with the highest energy content per unit of mass, being characterized by a Higher Heating Value of 39,42 kWh/kg, which makes it about three times more energetic with respect to methane and gasoline. To date, up to 96% of hydrogen production comes from fossil fuels through processes as coal gasification or steam methane reforming. Only the remaining 4% is obtained mainly from water. Hydrogen could be used in a variety of sectors, from industry to the residential sector, passing through the transport one. The thesis focuses on the description of a plant related to the production, compression, storage and distribution of green hydrogen that will rise in an area currently disused inside Porto Marghera, near Venice. The energy demand equal to 5 MW, needed to produce the required hydrogen volumes, will be in part provided by a geothermal power plant and the remaining share of electricity will be supplied by the electric grid based on a Power Purchase Agreement. In particular, as a result of hydrogeological investigations carried out in the area, it has been stated the possibility to take advantage of a geothermal resource with a temperature lower than 150 °C. By means of a heat exchanger, the hot geothermal fluid will be used to power an Organic Rankine Cycle that allows a continuous generation of electrical energy equal to 2,3 MW. The electricity is needed to feed four Proton Exchange Membrane water electrolysers producing a total of 90 kg/h of high purity green hydrogen at around 30 bar. In order to comply with the "Do No Significant Harm" principle, the electrolysers will be characterized by an absorption of renewable electricity lower than 58 MWh per ton of hydrogen produced. Once generated, hydrogen will be temporarily stored in a tank called Buffer, at the output pressure of the electrolysers. Subsequently an underground pipeline, characterized by a length of about 700 m, will carry hydrogen towards the nearby Hydrogen Refueling Station. Hydrogen compression and storage will be performed at different pressure levels. Moreover, two stalls for tube-trailers will be constructed in order to insure the production flexibility of the plant. Tube-trailers will be used both in case of overproduction, so as to supply third parties of excess hydrogen and, in case of temporary plant failures or maintenance, to supplement production from external manufacturers. The refueling process, performed during night, of the local public transport company’s fleet will be carried out respecting SAE J2601 protocol. The local public transport company fleet will consists of 94 hydrogen buses. The 12 m length hydrogen buses are characterized by a tank capacity of around 37 kgH2 stored at 350 bar, for which the manufacturer declares a consumption of 1 kg of hydrogen every 14 km covered. The design phase has been performed considering the Italian Ministerial Decree on fire prevention either for production and distribution area, since hydrogen is highly flammable and the energy needed to ignite it is extremely low. Once realized, Green Hydrogen Hub - Marghera will be the first plant in Italy characterized by both production and distribution of green hydrogen.