Reheating as an option to increase the efficiency of a novel power generation system based on ammonia oxy-combustion

Ammonia is a promising hydrogen-based energy vector. In the HiPowAR project, an innovative system is developed, based on oxy-combustion of ammonia in a membrane reactor and expansion of the obtained nitrogen-steam mixture. The system combines high temperature and pressure (typical of gas turbines) and large expansion ratio (typical of steam cycles). This work studies the impact of reheating, which proves advantageous, with stronger benefits at lower temperature

Development of diagnostic instrumentations for fuel cells based on consumer electronics

The decarbonization process is pushing the energy sector into a transition towards clean energy vectors. In the hard-to-abate sectors, such as heavy-duty transport and industry, hydrogen can act as an energy carrier and a sector coupler. Key devices for hydrogen exploitation are fuel cells. Diagnostic is a crucial element for safety and efficiency during operation. This work regards the development process – from the conception to the validation and use – of an acquisition system made of consumer electronic components. By measuring differential voltage at high frequency, it enables to perform Electrochemical Impedance Spectroscopy (EIS). The system consists of an Arduino board running a self-developed circuit composed of an operational amplifier, an analog-to-digital converter, and a buffer memory. The system is designed to be expanded with multiple synchronized modules to monitor several cells at once. The module can be applied to a single cell or a group of cells (e.g., a stack) by tuning the operational amplifier. A dedicated software has also been developed, involving assembly language to achieve the required speed performance. The circuit has been validated using a function generator to apply sinusoids with frequencies between 100 Hz and 10 kHz and amplitudes of 10-500 mV (reflecting the EIS requirements on a single cell). An oscilloscope is used to double-check the generated signal. The results proved that the system features errors below 3% on amplitude and below 0.3% on frequency. Finally, the developed system has been tested against a commercial device performing EIS measurements. The obtained impedance values generally differ by less than 3% in the range of interest, while a few specific frequencies are affected by external disturbances

A Mathematical Tool for Optimising Carbon Capture, Utilisation and Sequestration Plants for e-MeOH Production

Carbon capture, utilisation, and sequestration is key for the decarbonisation of hard-to-abate industries, as it allows avoiding the direct release of CO2 to the atmosphere and generating carbon-based products. However, for these products to be truly carbon-neutral, intermittent renewable electricity must be deployed at scale, leading to the necessity of optimising flexible plants with potential for local buffer storages, geological sequestration, and conversion units. The scope of this work is to provide a mathematical framework for the economic optimisation of a carbon capture, utilisation, and sequestration system, to decarbonise a cement plant located in the Puglia region (Italy), via CO2 geological confinement and/or power and CO2-to-methanol conversion. The final aim is to determine the optimal sizing and cost of the process units of the plant, depending on economic conditions such as the methanol sale price and different perspective costs scenarios. The main outcome is an economic convenience of geological sequestration, as opposed to utilisation, while a long-term scenario would allow for a cost-effective production of methanol when the sale price is above 550 EUR/t

Impact of Detailed Hydropower Representation in National Energy System Modelling

Renewables are becoming more and more important due to the ambitious decarbonization targets. In this scenario, the improved integration of hydropower can play a crucial role thanks to its programmable operation, which is a valuable feature. In some countries it is a primary alternative to fossil resources, for example Italy, where hydro currently covers roughly half of the renewable power generation. Hydropower flexibility poses considerable modelling challenges due to the scarce availability of data. This work aims at addressing this research gap, by analysing the impact of hydropower details on energy system models. Using open-source information, a detailed dataset of Italian hydroelectric programmable plants (pumped hydro and reservoirs) is created. For each plant, storage capacity, geographical location, and nominal power are available. The multiannual historical operational data are exploited to derive a precipitation inflow timeseries for each electricity market bidding zone, which is then distributed on power plants aggregated by administrative region. This new set of data is applied to a multi-node, multi-sector, and multi-vector energy system model, which optimises the design and operation of a carbon-neutral Italian energy system, looking at a 2050 framework with assigned energy vectors demand. Results are compared to those of a fixed-hydropower operation case, thus being able to assess how the modelled flexibility impacts the optimal solution. The analysis favours an improved understanding of future energy systems, helping to shape properly integrated systems with a great amount of non-programmable sources

A Mathematical Tool for Optimising Carbon Capture, Utilisation and Sequestration Plants for e-MeOH Production

Carbon capture, utilisation, and sequestration is key for the decarbonisation of hard-to-abate industries, as it allows avoiding the direct release of CO2 to the atmosphere and generating carbon-based products. However, for these products to be truly carbon-neutral, intermittent renewable electricity must be deployed at scale, leading to the necessity of optimising flexible plants with potential for local buffer storages, geological sequestration, and conversion units. The scope of this work is to provide a mathematical framework for the economic optimisation of a carbon capture, utilisation, and sequestration system, to decarbonise a cement plant located in the Puglia region (Italy), via CO2 geological confinement and/or power and CO2-to-methanol conversion. The final aim is to determine the optimal sizing and cost of the process units of the plant, depending on economic conditions such as the methanol sale price and different perspective costs scenarios. The main outcome is an economic convenience of geological sequestration, as opposed to utilisation, while a long-term scenario would allow for a cost-effective production of methanol when the sale price is above 550 €/t

Techno-economic study of chimneyless electric arc furnace plants for the coproduction of steel and of electricity, hydrogen, or methanol

Electric arc furnace (EAF) is the most common technology for steel production from steel scrap. Although the input energy is mostly constituted by electricity, significant amounts of carbon dioxide are emitted with the exhaust gases, most of which are classifiable as process-related. The main goal of this study is to perform a techno-economic analysis of chimneyless electric arc furnace plants, fed by either scrap or direct reduced iron (DRI), and able to coproduce steel as well as electricity, hydrogen, or methanol. Several plant configurations are investigated, featuring different combinations of oxy-postcombustion, carbon capture, carbon monoxide-rich gas recovery, hydrogen or syngas production by high-temperature electrolysis or coelectrolysis, and methanol synthesis. These configurations are also characterized by decreased false air leakage and by heat recovery for steam production. Results show that all cases allow achieving a substantial reduction of direct carbon dioxide emissions, close to 99% compared to the unabated conditions. From an economic perspective, in a long-term scenario, the internal rate of return is always above 8%, and up to 73% for the DRI-fed case. However, in a short-term scenario, only cases with sole power production are economically viable. Hydrogen and methanol are competitive with market prices only for low electricity costs. In a higher electricity cost scenario, the case of carbon capture and storage is more competitive than the case of carbon capture and utilization. With an electricity cost of 100 €/MWh, a steel premium of 10-40 €/t allows to reach economic feasibility if methanol or hydrogen selling prices are in line with current market conditions. In general, the configurations with DRI-fed furnaces obtain more favorable economic performance than scrap-fed ones. The competitiveness of sole electricity, hydrogen or methanol production configurations depends on the case study and on the future market prices

Zero-dimensional dynamic modeling of PEM electrolyzers

The transition to a low-carbon system foresees the introduction of hydrogen as a clean energy vector. Electrolyzers play a key role in its production from renewable energy, and PEM technology seems the most promising alternative thanks to efficiency, flexibility and compactness. Modeling the device dynamic behavior allows investigating its combination with renewable electricity sources. A dynamic 0D model is developed using Aspen Custom Modeler, including a detailed description of the various phenomena involved in the electrochemical process. General formulations are implemented and multiple options for correlations are present, when available. The model is validated against available literature data, showing an appropriate reconstruction of the cell behavior. Unsteady behavior is studied and the role of thermal capacity is shown, under a test-case with a simple operating input profile

Hydrogen Production Using Solid Oxide Electrolysis as a Flexibility Option for Nuclear Power Plants

In the context of decarbonization, it is crucial to integrate low-carbon sources effectively. Among these, nuclear power can offer a significant and stable contribution to the electricity balance, but its integration is hindered by the limited flexibility. A promising option is coupling with high-temperature electrolysis, which utilizes both thermal and electric power from the nuclear plant to obtain hydrogen, which is a high-value and storable product. In this work, a hybrid system combining a solid oxide electrolyser (SOE) with a small modular reactor nuclear power plant (SMR-NPP) is investigated, to assess potential and performance. In the SMR-NPP, thermal energy is transferred to water/steam that then drives a steam turbine. In the hybrid configuration, a fraction of the high-pressure steam is diverted towards the SOE section, where it provides heat for the evaporation of the water stream that is fed to the stack. Due to the higher operating temperature of SOE (700 °C) than that of the steam cycle (317 °C), exothermic operation of the electrolysis stack is considered, enabling regenerative heat exchange. The model allows to observe the SOE section operation in different configurations to assess the effects on components sizing and operating parameters. Results show promising performances in the analysed scenarios, with an important role played by the SOE modularity

Modelling the integrated power and transport energy system: The role of power-to-gas and hydrogen in long-term scenarios for Italy

This work analyses future energy scenarios at country scale, focusing on the interaction between power and transport sectors, where Power-to-Gas is expected to play a key role. A multi-node model is developed to represent the integrated energy system, including additional electrical load from plug-in electric vehicles, energy storage, and hydrogen production from excess electricity for fuel cell vehicles. Electricity supply-demand balance is solved hourly, while liquid and gaseous fuels for mobility are accounted for cumulatively over the year. The Italian system is investigated, considering different evolution scenarios up to 2030 and 2050. The simulations yield a maximum 57% share of renewable sources in the electricity mix in 2050, while biomass could account for a further 5%. Results show that the use of Power-to-Gas increases the overall share of renewable sources across the sectors. High coverage of hydrogen mobility demand by clean production (about 81%) is achieved in presence of a large installation of renewables and a substantial introduction of fuel cell vehicles. However, greenhouse gas emissions reduction does not attain the ambitious long-term targets. In the best scenario, transport approaches the 60% cut, while power sector achieves only half of the desired 95% variation, thus calling for additional measures

Benefits of the multi-modality formulation in hydrogen supply chain modelling

Hydrogen is recognized as a key element of future low-carbon energy systems. For proper integration, an adequate delivery infrastructure will be required, to be deployed in parallel to the electric grid and the gas network. This work adopts an optimization model to support the design of a future hydrogen delivery infrastructure, considering production, storage, and transport up to demand points. The model includes two production technologies, i.e., steam reforming with carbon capture and PV-fed electrolysis systems, and three transport modalities, i.e., pipelines, compressed hydrogen trucks, and liquid hydrogen trucks. This study compares a multi-modality formulation, in which the different transport technologies are simultaneously employed and their selection is optimized, with a mono-modality formulation, in which a single transport technology is considered. The assessment looks at the regional case study of Lombardy in Italy, considering a long-term scenario in which an extensive hydrogen supply chain is developed to supply hydrogen for clean mobility. Results show that the multi-modality infrastructure provides significant cost benefits, yielding an average cost of hydrogen that is up to 11% lower than a mono-modality configuration