A complete thermo-economic analysis on a cutting-edge Power-to-Gas system that comprises innovative technologies (a Solid Oxide Electrolyte Cell co-electrolyzer and an experimental methanator) and coupled with a renewable generator is provided in this study. The conducted economic analysis (which has never been applied to this typology of system) is aimed at the estimation of the synthetic natural gas cost of a product through a cash flow analysis. Various plant configurations—with different operating temperatures and pressure levels of the key components (electrolyzer: 600–850 °C; 1–8 bar)—are compared to identify possible thermal synergies. Parametric investigations are performed, to assess both the effect of the thermodynamic arrangements and of the economic boundary conditions. Results show that the combination of a system at ambient pressure and with a thermal synergy between the co-electrolyzer and the high-temperature methanator presents the best economic performance (up to 8% lower synthetic natural gas value). The production cost of the synthetic natural gas obtained by the Power-to-Gas solutions in study (up to 80% lower than the natural gas price) could become competitive in the natural gas market, if some techno-economic driving factors (proper size ratio of the storage system and the renewable generation, electrolytic cell cost developments and introduction of a carbon tax) are considered.

The liquefied natural gas (LNG) is considered a viable solution to replace oil-based engines (common in heavy-duty truck and naval industry) reducing the environmental impact in the transport sector. Since liquefaction plants represent energy intensive processes, the best configurations/operation assessment is of primary importance. In this paper, a novel general procedure for the thermodynamic design and optimization, engineering design and off-design evaluation for small-scale LNG production systems is presented. The procedure can be used for the complete design and performance evaluation of plug & play facilities at filling stations for vehicles/boats, with the contemporary benefits of reducing pollutant emission in the city/port area and operating as electrical storage, coupled with renewable generators. Furthermore, the procedure has been applied to a case study (ferry boat operating at the main canal in the port of Ravenna, Italy), evaluating the optimal size for the integrated wind plant by minimizing the electricity introduction into the grid. The obtained results show 78 kW as optimal wind size, allowing the LNG plant to operate 187 h/year in design and 4720 h/year in off-design conditions, with electricity surplus around 33 MWh/year. A prototype will be installed to reduce pollutant emissions and test this technology as a storage option for renewable sources.

In the last years, the increased demand of the energy market has led to the increasing penetration of renewable energies, in order to achieve the primary energy supply. Simultaneously, natural gas is predicted to play a vital and strategic role in the energy market, on account of its lower environmental impact than other fossil fuels, both as gaseous fuel for stationary energy generation and as liquefied fuel. In particular, the Liquefied Natural Gas (LNG) is becoming interesting in transports as an alternative to diesel fuel, allowing a decrease in pollutant emissions and a reduction in fuel’s costs for the users. As a consequence, in this context, the LNG production process can be seen as an electrical storage system by the integration with renewables, becoming an interesting solution to avoid the issues related to intermittency and unpredictability of renewables. The aim of the paper is the development of a calculation code and the evaluation of the off-design operation of a LNG production plant coupled with wind renewable energy sources. With this purpose, on the basis of mathematical models from literature, a dedicated calculation code has been developed, able to thermodynamically analyze both design and off-design operation of the integrated process. In addition, in this study the proposed model is employed to investigate the correct integration between renewables and LNG generation, in order to define the optimal choice of the wind size for a given LNG production plant. With this purpose, the LNG plant size of a real prototype has been considered and an economic analysis has been carried out, accounting for the revenue of the LNG sale, the costs for NG purchase, for operation and maintenance and for the initial investment costs, but also with the aim to minimize the electricity introduction into the grid, considered in this study as a penalty.

In order to pursue the goals of de-carbonization and renewable sources exploitation, an efficient, cost-effective and environmental friendly employment of energy systems is mandatory. In this context, the ERA-Net funded Project ZEHTC (Zero Emission Hydrogen Turbine Center) has been developed, aimed at the realization of a pilot plant consisting in the world first gas turbine test facility making use of the power produced during turbine tests – along with renewables (solar in particular) – for hydrogen production and batteries storage. The produced hydrogen will be locally used to run the gas turbine, thus reducing its environmental impact. The aim of this paper is to present the results of the first steps of the project, consisting in the definition of an optimized grid and in the development of a calculation model for the optimal energy systems design. To this respect, the typology of energy systems to be included into the grid (in addition to the current set-up of the existing turbine test center) will be presented. In addition, the mathematical models specifically developed for each component, as well as the developed operational logic of the entire grid, will be presented and discussed in order to set the optimal size of each systems.