1,721,048 research outputs found
Dynamic Quality Tracking of Natural Gas and Hydrogen Mixture in a Portion of Natural Gas Grid
Full text linkAbstractDirect injection of alternative fuels (biomethane, hydrogen) in the natural gas grid appears to be a promising solution to reach environmental objectives of CO2 emission reduction in the current energy scenario. This approach is justified by the large amount of biogas producible, which can be upgraded to biomethane; while another proposed solution to increase renewable energy sources exploitation lies in producing hydrogen from excess wind energy, followed by injection in the natural gas grid. Nevertheless, compliance with composition limitsand quality constraints in the resulting natural gas mixture has to be analysed in both stationary and dynamic operations, tracking the gas quality downstream the injection point of the alternative fuels. A model was developed to simulate unsteady operation of a portion of gas grid dealing with realistic industrial and residential consumptions concentrated in offtake points. Two case studies were investigated focusing on the comparison between different amounts of hydrogen injectionin the pure natural gasflow, yieldingcomposition, flow rate and pressure profiles. The analysis shows how imposed quality thresholds can berespected, although the hydrogen fraction within the natural gas mixture is highly sensitive to the profile and size of the loads connected to the gas pipeline
Optimal design of hydrogen delivery infrastructure for multi-sector end uses at regional scale
Full text linkHydrogen is a promising solution for the decarbonisation of several hard-to-abate end uses, which are mainly in the industrial and transport sectors. The development of an extensive hydrogen delivery infrastructure is essential to effectively activate and deploy a hydrogen economy, connecting production, storage, and demand. This work adopts a mixed-integer linear programming model to study the cost-optimal design of a future hydrogen infrastructure in presence of cross-sectoral hydrogen uses, taking into account spatial and temporal variations, multiple production technologies, and optimised multi-mode transport and storage. The model is applied to a case study in the region of Sicily in Italy, aiming to assess the infrastructural needs to supply the regional demand from transport and industrial sectors and to transfer hydrogen imported from North Africa towards Europe, thus accounting for the region's role as transit point. The analysis integrates multiple production technologies (electrolysis supplied by wind and solar energy, steam reforming with carbon capture) and transport options (compressed hydrogen trucks, liquid hydrogen trucks, pipelines). Results show that the average cost of hydrogen delivered to demand points decreases from 3.75 €/kgH2 to 3.49 €/kgH2 when shifting from mobility-only to cross-sectoral end uses, indicating that the integrated supply chain exploits more efficiently the infrastructural investments. Although pipeline transport emerges as the dominant modality, delivery via compressed hydrogen trucks and liquid hydrogen trucks remains relevant even in scenarios characterised by large hydrogen flows as resulting from cross-sectoral demand, demonstrating that the system competitiveness is maximised through multi-mode integration
Dynamic modeling of natural gas quality within transport pipelines in presence of hydrogen injections
No full textIn the near future, the natural gas grid could face an increasing share of alternative fuels (biomethane, hydrogen) injected in addition to the traditional mixture. Indeed, this pathway is particularly promising in order to reach environmental objectives of CO2 emissions reduction, in both thermal and electrical final uses. Biogas is already abundantly produced and could be easily upgraded to biomethane; hydrogen technologies are still under development, but they can help the exploitation of the increasing availability of renewable energy sources. A promising solution to problems due to unpredictable fluctuations of renewable energy production (in particular related to wind parks) or excess energy with respect to the load lies in hydrogen production by electrolysis and further injection in the natural gas grid. In this scenario, the effects on design and management of the transport infrastructure should be investigated, and the compliance with composition limits and quality constraints has to be analyzed in both stationary and dynamic operation, tracking the gas quality downstream the injection point of the alternative fuels. A model was developed to simulate the unsteady operation of a portion of the gas grid; with respect to traditional volume-based approaches, a novel energy-based approach is developed, including variable composition along the pipes and allowing to consider a given energy delivery to customers as a constraint. After the validation against available operational data, a case study considering concentrated realistic domestic and industrial offtakes is simulated. The effects of hydrogen injection, usually not considered in NG grid design and operation analyses, are investigated in terms of composition, flow rate and pressure profiles with comparison to the reference natural gas case. The analysis shows how imposed quality thresholds can be respected, although the effects on calorific value, Wobbe index and density are not negligible; results indicate that the allowed hydrogen fractions are limited and highly sensitive to the profile and size of the offtakes connected to the pipeline. The discussion also evidences the potential impact of hydrogen injection on gas metering and measurements errors
Development of a multi-modality hydrogen delivery infrastructure: An optimization model for design and operation
Full text linkHydrogen deployment as an energy vector will play a crucial role in the decarbonization of the energy and industrial sectors. Its integration with the energy system requires the development of an adequate delivery infrastructure. The identification of an optimal design and operation strategy is complex due the variety of technological options in each stage of the hydrogen supply chain. This work develops a mixed-integer linear programming model to optimize the design and operation of a hydrogen infrastructure, comprising the entire supply chain from production to demand. A crucial novelty element is the combination of technical alternatives and modelling features. The proposed multi-modality formulation optimizes the transport technology at each stage, selecting between pipelines, compressed hydrogen trucks, and liquid hydrogen trucks. The pipeline and road networks are built through the model integration with a Geographic Information System, and the operation is tracked with a daily resolution, following the typical day approach. The model application looks at hydrogen employment for clean mobility in a long-term scenario in the Italian region of Sicily, assuming a demand of 1.1 million equivalent passenger cars (30% of today’s stock). The resulting cost-optimal infrastructure features an average cost of delivered hydrogen of 3.81 €/kg, in line with mobility targets. The supply chain relies on the concurrent use of all transport modalities, thus showing that the multiplicity of options is a key asset in the development of a hydrogen economy
Development of diagnostic instrumentations for fuel cells based on consumer electronics
Full text linkThe 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
Long-term P2G and hydrogen potential in an integrated energy system: coupling of power grid and mobility in Italy
No full textThis work analyses future high-RES energy scenarios at country scale, focusing on the interaction between the power grid and the mobility sector, where Power-to-Gas (P2G) is a key technology. A multi-node model is developed to represent the energy system, including additional load form plug-in electric vehicles and clean hydrogen generation from excess electricity (P2G) for fuel cell vehicles. Energy from RES is prioritised, either covering the load or feeding the storage. Italy is investigated as case study, considering the possible evolution up to 2030 and 2050. The simulations of the Italian energy system behaviour in 2050 yield a maximum of 57% RES share in the electricity mix, while biomass could account for a further 5%. The introduction of P2G technology results in a good exploitation of excess energy, thus increasing the overall RES share. High coverage of hydrogen mobility demand (about 81%) is achieved in presence of large installation of RES plants; however, the e-RES share stays far from the high targets proposed
Impact of hydrogen energy storage on California electric power system: Towards 100% renewable electricity
Full text linkDecarbonization of the power sector is a key step towards greenhouse gas emissions reduction. Due to the intermittent nature of major renewable sources like wind and solar, storage technologies will be critical in the future power grid to accommodate fluctuating generation. The storage systems will need to decouple supply and demand by shifting electrical energy on many different time scales (hourly, daily, and seasonally). Power-to-Gas can contribute on all of these time scales by producing hydrogen via electrolysis during times of excess electrical generation, and generating power with high-efficiency systems like fuel cells when wind and solar are not sufficiently available. Despite lower immediate round-trip efficiency compared to most battery storage systems, the combination of devices used in Power-to-Gas allows independent scaling of power and energy capacities to enable massive and long duration storage. This study develops and applies a model to simulate the power system balance at very high penetration of renewables. Novelty of the study is the assessment of hydrogen as the primary storage means for balancing energy supply and demand on a large scale: the California power system is analyzed to estimate the needs for electrolyzer and fuel cell systems in 100% renewable scenarios driven by large additions of wind and solar capacities. Results show that the transition requires a massive increase in both generation and storage installations, e.g., a combination of 94 GW of solar PV, 40 GW of wind, and 77 GW of electrolysis systems. A mix of generation technologies appears to reduce the total required capacities with respect to wind-dominated or solar-dominated cases. Hydrogen storage capacity needs are also evaluated and possible alternatives are discussed, including a comparison with battery storage systems
Enhancement of energy generation efficiency in industrial facilities by SOFC – SOEC systems with additional hydrogen production
No full textIndustry is one of the highest energy consumption sector: some facilities like steelworks, foundries, or paper mills are highly energy-intensive activities. Many countries have already implemented subsidies on energy efficiency in generation and utilisation, with the aim of decreasing overall consumption and energy intensity of gross domestic product. Meanwhile, researchers have increased interest into alternative energy systems to decrease pollution and use of fossil fuels. Hydrogen, in particular, is proposed as a clean alternative energy vector, as it can be used as energy storage mean or to replace fossil fuels, e.g. for transport
Utilization or Sequestration for Captured CO2 from Cement Plants?
No full textThe scope of this work is to assess the economic competitivity of optimized CO2 capture and utilization process (CCU) for e-methanol production with respect to CO2 capture and sequestration (CCS) in three locations (southern Italy, northern Germany, northeastern Egypt) and two economic scenarios (short- and long-term) for the cost of renewable energy technologies. The final aim is to determine the optimal sizing and operation of the process units of the system by minimizing the total costs to be sustained by a cement producer. At a methanol selling price of 550 /t, which is consistent with the current market price, CCS is economically more competitive than CCU in the short-term scenario in all locations. In the long-term scenario, due to the reduced costs of renewable energy technologies, CCU becomes the preferable option in a large majority of the assessed cases. In the long-term scenario, the breakeven methanol selling price in Italy with respect to CCS was found to increase from 384 /t to 570 /t if low-cost hydrogen storage is not available and H2 is stored in pressurized vessels (as alternative to caverns). In Germany, from 542 /t to 778 /t. In Egypt, from 402 to 501 /t. Overall, this study shows that e-methanol production from captured CO2 in European countries may be competitive with e-methanol produced in more favorable locations, such as Egypt, only in the long-term, at the condition of a substantial cost reduction of renewable energy technologies, and of the persistency of a differential cost of capital with respect to renewables-rich emerging countries
Simulation of the HiPowAR power generation system for steam-nitrogen expansion after ammonia oxidation in a high-pressure oxygen membrane reactor
Full text linkThe EU project HiPowAR studies a novel power generation system based on ammonia flameless oxidation with pure oxygen in a high-pressure membrane reactor and expansion of the resulting high-temperature H2O-N2 stream. The system combines the advantages of high temperature at expander inlet, typical of gas turbines, and small compression demand, typical of steam cycles. Water is injected into the reactor to control the very high adiabatic temperature, at the limited energy expenditure of liquid pumping. This work assesses the performance potential of the HiPowAR system under different design conditions, through simulations with a model developed in Aspen Plus®. The system shows a high efficiency (up to 55%) when operating at high temperature (e.g., 1350°C at expander inlet); hence, O2 membranes capable of working at very high temperature are required. The cycle features an optimal sub-atmospheric expansion pressure (in the range 0.1-0.2 bar), which requires the re-pressurization of the off-gas (steam-saturated nitrogen). The system also produces liquid water as a net output. A reduction of the expander inlet temperature to values acceptable by typical steam cycles (600°C) significantly limits the efficiency, despite allowing to demonstrate the process using conventional steam expanders
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