Publications

Based on the concept of sustainable development to promote the development and application of renewable energy and enhance the capacity of renewable energy consumption this paper studies the design and optimization of renewable energy hydrogen production systems. For this paper six different scenarios for grid-connected and off-grid renewable energy hydrogen production systems were designed and analyzed economically and technically and the optimal grid-connected and off-grid systems were selected. Subsequently the optimal system solution was optimized by analyzing the impact of the load data and component capacity on the grid dependency of the grid-connected hydrogen production system and the excess power rate of the off-grid hydrogen production system. Based on the simulation results the most matched load data and component capacity of different systems after optimization were determined. The grid-supplied power of the optimized grid-connected hydrogen production system decreased by 3347 kWh and the excess power rate of the off-grid hydrogen production system decreased from 38.6% to 10.3% resulting in a significant improvement in the technical and economic performance of the system.

The transition from fossil fuels to carbon-neutral energy sources is necessary to reduce greenhouse gas (GHG) emissions and combat climate change. Hydrogen (H2) provides a promising path to harness fossil fuels to reduce emissions in sectors such as transportation. However regional economic analyses of various H2 production techniques are still lacking. We selected a well-known fossil fuel-exporting region the USA’s Intermountain-West (I-WEST) to analyze the carbon intensity of H2 production and demonstrate regional tradeoffs. Currently 78 % of global H2 production comes from natural gas and coal. Therefore we considered steam methane reforming (SMR) surface coal gasification (SCG) and underground coal gasification (UCG) as H2 production methods in this work. We developed the cost estimation frameworks of SMR SCG and UCG with and without carbon capture utilization and sequestration (CCUS). In addition we identified optimal sites for H2 hubs by considering the proximity to energy sources energy markets storage sites and CO2 sequestration sites. We included new production tax credits (PTCs) in the cost estimation to quantify the economic benefit of CCUS. Our results suggest that the UCG has the lowest levelized cost of H2 production due to the elimination of coal production cost. H2 production using the SMR process with 99 % carbon capture is profitable when the PTCs are considered. We also analyzed carbon utilization opportunities where CO2 conversion to formic acid is a promising profitable option. This work quantifies the potential of H2 production from fossil fuels in the I-WEST region a key parameter for designing energy transition pathways.

Sustainable aviation is a key part of achieving Net Zero by 2050 and is arguably one of the most challenging sectors to decarbonise. Hydrogen has gained unprecedented attention as a future fuel for aviation for use within fuel cell or hydrogen gas turbine propulsion systems. This paper presents a survey of the literature and industrial projects on hydrogen aircraft and associated enabling technologies. The current and predicted technology capabilities are analysed to identify important trends and to assess the feasibility of hydrogen propulsion. Several key enabling technologies are discussed in detail and gaps in knowledge are identified. It is evident that hydrogen propelled aircraft are technologically viable by 2050. However convergence of a number of critical factors is required namely: the extent of industrial collaboration the understanding of environmental science and contrails green hydrogen production and its availability at the point of use and the safety and certification of the aircraft and supporting infrastructure.

During a severe accident in a nuclear power plant one of the potential threats to the containment is the occurrence of energetic combustion events. In modern plants Severe Accident Management Guidelines (SAMG) as well as dedicated mitigation hardware are in place to minimize/mitigate this combustion risk and thus avoid the release of radioactive material into the environment. Advancements in SAMGs are in the focus of AMHYCO an EU-funded Horizon 2020 project officially launched on October 1st 2020. The project consortium consists of 12 organizations (from six European countries and one from Canada) and is coordinated by the Universidad Politécnica de Madrid (UPM). The progress made in the first two years of the AMHYCO project is here presented. A comprehensive bibliographic review has been conducted providing a common foundation to build the knowledge gained during the project. After an extensive set of accident transients simulated both for phases occurring inside and outside the reactor pressure vessel a set of challenging sequences from the combustion risk perspective for different power plant types were identified. At the same time three generic containment models for the three considered reactor designs have been created to provide the full containment analysis simulations with lumped parameter models 3-dimensional containment codes and CFD codes. In order to further consolidate the model base combustion experiments and performance tests on passive auto-catalytic recombiners under explosion prone H2/CO atmospheres were performed at CNRS (France) and FZJ (Germany). Finally it is worth saying that the experimental data and engineering models generated from the AMHYCO project are useful for other industries outside the nuclear one.

Motivated by the growing importance of fuel cell systems as the basis for distributed energy generation systems this work considers a micro-combined heat and power (mCHP) generation system based on a fuel cell integrated to satisfy the (power and thermal) energy demands of a residential application. The main objective of this work is to compare the performance of several CHP configurations with a conventional alternative in terms of primary energy consumption greenhouse gas (GHG) emissions and economic viability. For that a simulation tool has been developed to easily estimate the electrical and thermal energy generated by a hydrogen fuel cell and all associated results related to the hydrogen production alternatives: excess or shortfall of electrical and thermal energy CO2 emission factor overall performance operating costs payback period etc. A feasibility study of different configuration possibilities of the micro-CHP generation system has been carried out considering different heat-to-power ratios (HPRs) in the possible demands and analyzing primary energy savings CO2 emissions savings and operating costs. An extensive parametric study has been performed to analyze the effect of the fuel cell’s electric power and number of annual operation hours as parameters. Finally a study of the influence of the configuration parameters on the final results has been carried out. Results show that in general configurations using hydrogen produced from natural gas save more primary energy than configurations with hydrogen production from electricity. Furthermore it is concluded that the best operating points are those in which the generation system and the demand have similar HPR. It has also been estimated that a reduction in renewable hydrogen price is necessary to make these systems profitable. Finally it has been determined that the most influential parameters on the results are the fuel cell electrical efficiencies hydrogen production efficiency and hydrogen cost.

In the context of the European decarbonization strategy hydrogen is a key energy carrier in the medium to long term. The main advantages deriving from a greater penetration of hydrogen into the energy mix consist in its intrinsic characteristics of flexibility and integrability with alternative technologies for the production and consumption of energy. In particular hydrogen allows to: i) decarbonise end uses since it is a zero-emission energy carrier and can be produced with processes characterized by the absence of greenhouse gases emissions (e.g. water electrolysis); ii) help to balancing electricity grid supporting the integration of non-programmable renewable energy sources; iii) exploit the natural gas transmission and distribution networks as storage systems in overproduction periods. However the hydrogen injection into the natural gas infrastructures directly influences thermophysical properties of the gas mixture itself such as density calorific value Wobbe index speed of sound etc [1]. The change of the thermophysical properties of gaseous mixture in turn directly affects the end use service in terms of efficiency and safety as well as the metrological performance and reliability of the volume and gas quality measurement systems. In this paper the authors present the results of a study about the impact of hydrogen injection on the properties of the natural gas mixture. In detail the changes of the thermodynamic properties of the gaseous mixtures with different hydrogen content have been analysed. Moreover the theoretical effects of the aforementioned variations on the accuracy of the compressibility factor measurement have been also assessed.

Herein a novel methodology to perform optimal sizing of AC-linked solar PV-PEM systems is proposed. The novelty of this work is the proposition of the solar plant to electrolyzer capacity ratio (AC/AC ratio) as optimization variable. The impact of this AC/AC ratio on the Levelized Cost of Hydrogen (LCOH) and the deviation of the solar DC/AC ratio when optimized specifically for hydrogen production are quantified. Case studies covering a Global Horizontal Irradiation (GHI) range of 1400e2600 kWh/m2 -year are assessed. The obtained LCOHs range between 5.9 and 11.3 USD/kgH2 depending on sizing and location. The AC/AC ratio is found to strongly affect cost production and LCOH optimality while the optimal solar DC/AC ratio varies up to 54% when optimized to minimize the cost of hydrogen instead of the cost of energy only. Larger oversizing is required for low GHI locations; however H2 production is more sensitive to sizing ratios for high GHI locations.

Green hydrogen generation driven by solar-wind hybrid power is a key strategy for obtaining the low-carbon energy while by considering the fluctuation natures of solar-wind energy resource the system capacity configuration of power generation hydrogen production and essential storage devices need to be comprehensively optimized. In this work a solar-wind hybrid green hydrogen production system is developed by combining the hydrogen storage equipment with the power grid the coordinated operation strategy of solar-wind hybrid hydrogen production is proposed furthermore the NSGA-III algorithm is used to optimize the system capacity configuration with the comprehensive performance criteria of economy environment and energy efficiency. Through the implemented case study with the hydrogen production capacity of 20000 tons/year the abandoned energy power rate will be reduced to 3.32% with the electrolytic cell average load factor of 64.77% and the system achieves the remarkable carbon emission reduction. In addition with the advantage of connect to the power grid the generated surplus solar/wind power can be readily transmitted with addition income when the sale price of produced hydrogen is suggested to 27.80 CNY/kgH2 the internal rate of return of the system reaches to 8% which present the reasonable economic potential. The research provides technical and methodological suggestions and guidance for the development of solar-wind hybrid hydrogen production schemes with favorable comprehensive performance.

The role of negative emissions technologies (NETs) in climate change mitigation remains contentious. Although numerous studies indicate significant carbon dioxide removal (CDR) requirements for Paris Agreement mitigation goals to be achieved others point out challenges and risks associated with high CDR strategies. Using a multiscale modeling approach we explore NETs’ potential for a single country the United Kingdom (UK). Here we report that the UK has cost-effective potential to remove 79 MtCO2 per year by 2050 rising to 126–134 MtCO2 per year with well-integrated NETs in industrial clusters. Results highlight that biomass gasification for hydrogen generation with CCS is emerging as a key NET despite biomass availability being a limiting factor. Moreover solid DACCS systems utilizing industrial waste heat integration offer a solution to offsetting increases in demand from transportation and industrial sectors. These results emphasize the importance of a multiscale whole-systems assessment for integrating NETs into industrial strategies.

The current need to reduce carbon emissions makes hydrogen use essential for selfconsumption in microgrids. To make a profitability analysis of a microgrid the influence of equipment costs and the electricity price must be known. This paper studies the cost-effective electricity price (EUR/kWh) for a microgrid located at ‘’La Rábida Campus” (University of Huelva south of Spain) for two different energy-management systems (EMSs): hydrogen-priority strategy and batterypriority strategy. The profitability analysis is based on one hand on the hydrogen-systems’ cost reduction (%) and on the other hand considering renewable energy sources (RESs) and energy storage systems (ESSs) on cost reduction (%). Due to technological advances microgrid-element costs are expected to decrease over time; therefore future profitable electricity prices will be even lower. Results show a cost-effective electricity price ranging from 0.61 EUR/kWh to 0.16 EUR/kWh for hydrogen-priority EMSs and from 0.4 EUR/kWh to 0.17 EUR/kWh for battery-priority EMSs (0 and 100% hydrogen-system cost reduction respectively). These figures still decrease sharply if RES and ESS cost reductions are considered. In the current scenario of uncertainty in electricity prices the microgrid studied may become economically competitive in the near future