Techno-economic analysis of two hydrogen-based power generation systems: NG-H blending ICE and FC

The climate crisis has sped up the energy transition, which is nowadays a global problem. Achieving a more sustainable energy mix is a challenge from both technical and economic point of view. Hydrogen may represent a viable solution for the decarbonisation, but the real challenge is its integration into the energy systems. In this work, a real industrial case study is analysed: a semiconductor production plant that uses hydrogen as a gas carrier. The factory energy demand is covered by the on-site cogeneration plant that is fuelled with NG from the grid and generates heat and electricity. The system is made of three ICEs, two with a nominal power of 3.180 kW and one of 2.682 kW that burn 11,4 ktons of NG per year releasing 30,3 ktons of CO2. Currently, the hydrogen exiting from the production process is released into the atmosphere. In this study, two different solutions for the waste hydrogen reuse are presented. For both cases a techno-economic analysis is carried out and two KPIs (NPV and PBT) are evaluated. In the first solution a NG-H2 blending ICE is analysed. A 10% blending limit of H2 into NG is considered, as higher blending limits may damage the engine. The evaluation is done by considering two scenarios: keeping the NG input flow constant, thus increasing the power output, or by reducing the NG input and keeping the power constant. Both scenarios are evaluated, but only the second one was chosen by the company to be estimated in the economic analysis. The costs are determined by the piping system only, while the revenues are the savings coming from the reduction of NG consumption. The base case considers the NG prices of 2021. The results show a decrease in the CO2 emissions by almost 1 kton and a significant reduction in the costs for energy generation. A sensitivity analysis is carried out to consider the variation of the NG prices and piping system cost, resulting in an NPV after 20 years over a million of euros and a PBT up to 5 years. The second solution analyses the introduction of a fuel cell. PEMFC and SOFC technologies are considered; as for the first one it can only be fuelled with hydrogen, while the second one is fuel flexible, hence a NG-H2 blending solution is also considered. Since the H2 input flow is highly fluctuating, the fuel cells operation may be affected; this could be solved by adding a storage tank before the fuel cell. Both constant and variable input flow scenarios are evaluated. In this solution the CAPEX and OPEX are significantly higher than those of ICE blending, as more equipment is needed. Most of the results are positive, with very different values of NPV and PBT depending on the technology chosen; current SOFC prices are still quite high, making them non economically feasible for these applications. Better results are achieved with expected future prices. Hydrogen fed fuel cell installation allows to avoid CO2 emissions, while in case of blending a significant reduction can be achieved. These scenarios show two ways of implementing hydrogen in a power generation system: one that converts an existing technology and makes it more sustainable, and the other that exploits an innovative one. The results are encouraging, and the techno-economic feasibility and the environmental benefits prove that hydrogen is a promising solution towards sustainable energy.