Italy

Vented deflagration tests were conducted by UNIPI at B. Guerrini Laboratory during the experimental campaign for HySEA project. Experiments included homogeneous hydrogen-air mixture in a 10-18% vol. range of concentrations contained in an about 1 m3 enclosure called SSE (Small Scale Enclosure). Displacement measurements of a test plate were taken in order to acquire useful data for the validation of FE model developed by IMPETUS Afea. In this paper experimental facility displacement measurement system and FE model are briefly described then comparison between experimental data and simulation results is discussed.

Efficient energy production and consumption are fundamental points for reducing carbon emissions that influence climate change. Alternative resources such as renewable energy sources (RESs) used in electricity grids could reduce the environmental impact. Since RESs are inherently unreliable during the last decades the scientific community addressed research efforts to their integration with the main grid by means of properly designed energy storage systems (ESSs). In order to highlight the best performance from these hybrid systems proper design and operations are essential. The purpose of this paper is to present a so-called model predictive controller (MPC) for the optimal operations of grid-connected wind farms with hydrogen-based ESSs and local loads. Such MPC has been designed to take into account the operating and economical costs of the ESS the local load demand and the participation to the electricity market and further it enforces the fulfillment of the physical and the system's dynamics constraints. The dynamics of the hydrogen-based ESS have been modeled by means of the mixed-logic dynamic (MLD) framework in order to capture different behaviors according to the possible operating modes. The purpose is to provide a controller able to cope both with all the main physical and operating constraints of a hydrogen-based storage system including the switching among different modes such as ON OFF STAND-BY and at the same time reduce the management costs and increase the equipment lifesaving. The case study for this paper is a plant under development in the north Norway. Numerical analysis on the related plant data shows the effectiveness of the proposed strategy which manages the plant and commits the equipment so as to preserve the given constraints and save them from unnecessary commutation cycles.

Membrane reactors for hydrogen production can increase both the hydrogen production efficiency at small scale and the electric efficiency in micro-cogeneration systems when coupled with Polymeric Electrolyte Membrane fuel cells. This paper discusses the achievements of three European projects (FERRET FluidCELL BIONICO) which investigate the application of the membrane reactor concept to hydrogen production and micro-cogeneration systems using both natural gas and biofuels (biogas and bio-ethanol) as feedstock. The membranes used to selectively separate hydrogen from the other reaction products (CH4 CO2 H2O etc.) are of asymmetric type with a thin layer of Pd alloy (<5 μm) and supported on a ceramic porous material to increase their mechanical stability. In FERRET the flexibility of the membrane reactor under diverse natural gas quality is validated. The reactor is integrated in a micro-CHP system and achieves a net electric efficiency of about 42% (8% points higher than the reference case). In FluidCELL the use of bio-ethanol as feedstock for micro-cogeneration Polymeric Electrolyte Membrane based system is investigated in off-grid applications and a net electric efficiency around 40% is obtained (6% higher than the reference case). Finally BIONICO investigates the hydrogen production from biogas. While BIONICO has just started FERRET and FluidCELL are in their third year and the two prototypes are close to be tested confirming the potentiality of membrane reactor technology at small scale.

The synthesis of a Substitute Natural Gas (SNG) that is compatible with the gas grid composition requirements by using surplus electricity from renewable energy sources looks a favourable solution to store large quantities of electricity and to decarbonise the gas grid network while maintaining the same infrastructure. The most promising layouts for SNG production and the conditions under which SNG synthesis reduces the environmental impacts if compared to its fossil alternative is still largely untapped. In this work six different layouts for the production of SNG and electricity from biomass and fluctuating electricity are compared from the environmental point of view by means of Life Cycle Assessment (LCA) methodology. Global Warming Potential (GWP) Cumulative Energy Demand (CED) and Acidification Potential (AP) are selected as impact indicators for this analysis. The influence of key LCA methodological aspects on the conclusions is also explored. In particular two different functional units are chosen: 1 kg of SNG produced and 1 MJ of output energy (SNG and electricity). Furthermore different approaches dealing with co-production of electricity are also applied. The results show that the layout based on hydrogasification has the lowest impacts on all the considered cases apart from the GWP and the CED with SNG mass as the functional unit and the avoided burden approach. Finally the selection of the multifunctionality approach is found to have a significant influence on technology ranking.

The study of hydrogen as an alternative fuel clean and “environment friendly” has been in the last years and continues to be object of many studies international projects and standard development. Hydrogen is a fundamental energy carrier to be developed together with other renewable resources for the transition to a sustainable energy system.<br/>But experience has shown how often the introduction and establishment of a new technology does not necessarily pass through radical changes but can be stimulated by slight modifications to the “present situation”.<br/>So the worldwide experience with natural gas as industrial automotive and domestic fuel has been the incentive to the present interest towards hydrogen–methane mixtures. The possible use of existing pipeline networks for mixtures of natural gas and hydrogen offers a unique and cost-effective opportunity to initiate the progressive introduction of hydrogen as part of the development of a full hydrogen system.<br/>The aim of the work presented in this paper is the investigation of the dispersion and stratification properties of hydrogen and methane mixtures. Experimental activities have been carried out in a large scale closed apparatus characterized by a volume of about 25 m3 both with and without natural ventilation. Mixtures of 10%vol. hydrogen – 90%vol. methane and 30%vol. hydrogen – 70%vol. methane have been studied with the help of oxygen sensors and gas chromatography.

Biomass gasification is a promising technology to produce secondary fuels or heat and power offering considerable advantages over fossil fuels. An important aspect in the usage of producer gas is the removal of harmful contaminants from the raw syngas. Thus the object of this study is the development of a simulation model for a gasifier including gas clean-up for which a fluidized-bed gasifier for biomass-derived syngas production was considered based on a quasi-equilibrium approach through Gibbs free energy minimisation and including an innovative hot gas cleaning constituted by a combination of catalyst sorbents inside the gasification reactor catalysts in the freeboard and subsequent sorbent reactors by using Aspen Plus software. The gas cleaning chain simulates the raw syngas clean-up for several organic and inorganic contaminants i.e. toluene benzene naphthalene hydrogen sulphide hydrogen chloride and ammonia. The tar and inorganic contaminants final values achieved are under 1 g/Nm3 and 1 ppm respectively.

In a scenario characterized by an increasing penetration of non-dispatchable renewable energy sources and the need of fast-ramping grid-balancing power plants the EU project GRASSHOPPER aims to setup and demonstrate a highly flexible PEMFC Power Plant hydrogen fueled and scalable to MW-size designed to provide grid support.<br/>In this work different layouts proposed for the innovative MW-scale plant are simulated to optimize design and off-design operation. The simulation model details the main BoP components performances and includes a customized PEMFC model validated through dedicated experiments.<br/>The system may operate at atmospheric or mild pressurized conditions: pressurization to 0.7 barg allows significantly higher net system efficiency despite the increasing BoP consumptions. The additional energy recovery from the cathode exhaust with an expander gives higher net power and net efficiency adding up to 2%pt and reaching values between 47%LHV and 55%LHV for currents between 100% and 20% of the nominal value.

Explosion venting is a frequently used measure to mitigate the consequence of gas deflagrations in closed environments. Despite the effort to predict the vent area needed to achieved the protection through engineering formulas and CFD tools work has still to be done to reliably predict the outcome of a vented gas explosion. Blind-prediction exercises recently published show a large spread in the prediction of both engineering formula than CFD tools. University of Pisa performed experimental tests in a 25 m3 facility in inhomogeneous conditions and with the presence of simple obstacles constituted by plates bolted to HEB beams. The present paper is aimed to share the results of hydrogen dispersion and deflagration tests and discuss the comparison of maximum peak overpressure generated with different blockage ratio and repeated obstacles sets. Description of the experimental set-up includes all the details deemed necessary to reproduce the phenomenon with a CFD tool.

Magnesium hydride owns the largest share of publications on solid materials for hydrogen storage. The “Magnesium group” of international experts contributing to IEA Task 32 “Hydrogen Based Energy Storage” recently published two review papers presenting the activities of the group focused on magnesium hydride based materials and on Mg based compounds for hydrogen and energy storage. This review article not only overviews the latest activities on both fundamental aspects of Mg-based hydrides and their applications but also presents a historic overview on the topic and outlines projected future developments. Particular attention is paid to the theoretical and experimental studies of Mg-H system at extreme pressures kinetics and thermodynamics of the systems based on MgH₂ nanostructuring new Mg-based compounds and novel composites and catalysis in the Mg based H storage systems. Finally thermal energy storage and upscaled H storage systems accommodating MgH₂ are presented.

A method for determination of hazardous zones for hydrogen installations has been studied. This work has been carried out within the NoE HySafe. The method is based on the Italian Method outlined in Guide 31-30(2004) Guide 31–35(2001) Guide 31-35/A(2001) and Guide 31-35/A; V1(2003). Hazardous zones for a “generic hydrogen refuelling station”(HRS) are assessed based on this method. The method is consistent with the EU directive 1999/92/EC “Safety and Health Protection of Workers potentially at risk from explosive atmospheres” which is the basis for determination of hazardous zones in Europe. This regulation is focused on protection of workers and is relevant for hydrogen installations such as hydrogen refuelling stations repair shops and other stationary installations where some type of work operations will be involved. The method is also based on the IEC standard and European norm IEC/EN60079-10 “Electrical apparatus for explosive gas atmospheres. Part 10 Classification of hazardous areas”. This is a widely acknowledged international standard/norm and it is accepted/approved by Fire and Safety Authorities in Europe and also internationally. Results from the HySafe work and other studies relevant for hydrogen and hydrogen installations have been included in the case study. Sensitivity studies have been carried out to examine the effect of varying equipment failure frequencies and leak sizes as well as environmental condition (ventilation obstacles etc.). The discharge and gas dispersion calculations in the Italian Method are based on simple mathematical formulas. However in this work also CFD (Computational Fluid Dynamics) and other simpler numerical tools have been used to quantitatively estimate the effect of ventilation and of different release locations on the size of the flammable gas cloud. Concentration limits for hydrogen to be used as basis for the extent of the hazardous zones in different situations are discussed.