Search

The weather-dependent electricity generation from Renewable Energy Sources (RES), such as solar and wind power, entails that systems for energy storage are becoming progressively more important. Among the different solutions that are being explored, hydrogen is currently considered as a key technology allowing future long-term and large-scale storage of renewable power. Today, hydrogen is mainly produced from fossil fuels, and steam methane reforming (SMR) is the most common route for producing it from natural gas. None of the conventional methods used is GHG-free. The Power-to-Gas concept, based on water electrolysis using electricity coming from renewable sources is the most environmentally clean approach. Given its multiple uses, hydrogen is sold both as a fuel, which can produce electricity through fuel cells, and as a feedstock in several industrial processes. Just the feedstock could be, in the short term, the main market of RES-based hydrogen. In this paper, we present the results obtained from a techno-economic-financial evaluation of a system to produce green hydrogen to be sold as a feedstock for industries and research centres. A system which includes a 200 kW photovoltaic plant and a 180 kW electrolyser, to be located in Messina (Italy), is proposed as a case study. According to the analyses carried out, and taking into account the current development of technologies, it has been found that investment to realise a small-scale PV-based hydrogen production plant can be remunerative.

Photoelectrochemical water splitting is a green, sustainable technology for harnessing solar energy to generate H-2; however, the energy demand needed to drive this non-spontaneous reaction limits the technology's competitiveness. In addition, the poor efficiency of photoanodes in photoelectrochemical cells (PECs) has been one of the factors governing the overall solar conversion efficiency of PECs. Here, a novel stacking approach of n-type titanium dioxide nanotubes (TiO2 NTs) photoanodes was proposed to improve their light-harvesting and charge transfer properties. Interestingly, the stacked photoanodes exhibited a much higher photocurrent of -0.79 mA/cm2 at 1 V (vs. SHE) than single sheet TiO2 NTs photoanode (i.e., -0.07 mA/cm(2)) at the same po-tential, implying that TiO2 NTs stacking approach resulted in effective light absorbance and management and much lower charge transfer resistance across the interface of photoanode and electrolyte. In addition, a self-biased, integrated solar-microbial system was developed, in which a microbial fuel cell (MFC) fed with real animal manure wastewater was used as a power source to drive sustainable H-2 production in a photo-electrochemical cell having stacked TiO2 NTs photoanodes. Without any external bias, the integrated system, which comprises an MFC and a three-sheet TiO2 NTs photoanode-based PEC, generated a photocurrent of 0.44 mA/cm(2) with an H-2 production rate of 0.45 +/- 0.03-m(3) H-2/m(3) day under 1 sun illumination (100 mW/cm(2)), which is -1.5-1.9-fold higher than other tested systems. This study demonstrates the synergetic effect between MFCs and PECs, in which electrons recovered from wastewater biodegradation in MFCs significantly increase H-2 generation in PECs without the need for an external power source.

This paper presents the optimization of the driving strategy of a high efficiency fuel cell based power train. This power train is developed to equip a light duty urban-concept vehicle that runs energetic races. The objective is to go the furthest with the lowest quantity of fuel. A comprehensive dynamical model is presented, including the mechanical requirement, the thermal behavior of the fuel cell stack and the various losses and consumptions of the power train devices. This model is next integrated into a global optimization algorithm, to determine the best race strategy to be adopted. These results are validated on experimental measurements, obtained during a real race at the Shell Eco-Marathon, in 2015.

The goal that the international community has set itself is to reduce greenhouse gas (GHG) emissions in the short/medium-term, especially in Europe that committed itself to reducing GHG emissions to 80–95% below 1990 levels by 2050. Renewable energies play a fundamental role in achieving this objective. In this context, the policies of the main industrialized countries of the world are being oriented towards increasing the shares of electricity produced from renewable energy sources (RES). In recent years, the production of renewable energy has increased considerably, but given the availability of these sources, there is a mismatch between production and demand. This raises some issues as balancing the electricity grid and, in particular, the use of surplus energy, as well as the need to strengthen the electricity network. Among the various new solutions that are being evaluated, there are: the accumulation in batteries, the use of compressed air energy storage (CAES) and the production of hydrogen that appears to be the most suitable to associate with the water storage (pumped hydro). Concerning hydrogen, a recent study highlights that the efficiencies of hydrogen storage technologies are lower compared to advanced lead acid batteries on a DC-to-DC basis, but “in contrast […] the cost of hydrogen storage is competitive with batteries and could be competitive with CAES and pumped hydro in locations that are not favourable for these technologies” (Moliner et al., 2016) [1]. This shows that, once the optimal efficiency rate is reached, the technologies concerning the production of hydrogen from renewable sources will be a viable and competitive solution. But, what will be the impact on the energy and fuel markets? The production of hydrogen through electrolysis will certainly have an important economic impact, especially in the transport sector, leading to the creation of a new market and a new supply chain that will change the physiognomy of the entire energy market.

In this article, the liquid water eruptive transport occurring during the water breakthrough from the Gas Diffusion Layer (GDL) of a PEMFC into the gas channel is investigated. A dedicated experimental set-up is used enabling the simultaneous measurement of pressure inside the water system and visualization of droplet formation. A single-drop capillary model is proposed to explain the eruptive nature of droplet formation. The model is built on four physical equations involving Laplace's law, a water system compressibility law, the pressure losses occurring during droplet formation, and a spherical droplet geometrical function. Two numerical resolution methods are implemented and compared. For this model, three parameters have to be identified from the experimental data. The identification procedure is explained in the paper and the comparison with experimental results shows the ability of the present model to reproduce the eruptive nature of liquid water breakthrough from the GDL.

This work presents the PEMFC stack design methodology developed at CNR-ITAE, in theframe of a collaboration with an industrial partner, Electro Power Systems (EPS), operatingin the Uninterruptable Power Supply (UPS) market. A detailed description of the designprocedure of a 7 kW PEMFC stack is reported, starting from technical requirements of theUPS system to experimental tests. Bipolar plate layout, active area surface and shape,maximum (OCV) and minimum voltage, maximum cooling circuit pressure drop,maximum cathodic flow-field pressure drop, were the main constraint that influenced theconstructive solutions. The electrochemical performances of Gore Primea 5621 MEA withSGL Sigracet GDL were chosen as reference to select the appropriate operating point interms of current density and single cell voltage. A current density of 800 mA/cm 2 wasimposed as operating point of the stack, subsequently main stack parameters werecalculated. Three different cathodic flow fields, that were designed to fulfill UPS systemrequirements, were tested in a single cell arrangement, to find the best gas flow path interms of compromise between cell performance and pressure drop. Also a specific studywas dedicated to the selection of gasket material to find the best compromise between cellperformance and limited mechanical stress. The assembled 70 cells unit was tested ina test bench simulating the power system. Preliminary tests of the full unit yielded toa power of 6.2kW at 36 V.a 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

The research activity in polymer electrolyte fuel cell (PEFC) is oriented to the evolution of components and devices for the temperature range from 20 to 130 °C, and covers all the aspects of this matter: membranes and electrodes, fuel cell stack engineering (design and manufacturing) and characterization, computational modelling and small demonstration systems prototyping. Particular attention is devoted to portable and automotive application. Membranes research is focused on thermostable polymers (polyetheretherketone, polysulphone, etc.) and composite membranes able to operate at higher temperature ( > 100 ∘ C ) and lower humidification than the commercial Nafion ® , while Pt load reduction and gas diffusion layer improvement are the main goals for the electrode development. PEFC stack engineering and characterization activity involve different aspects such as the investigation of new materials for stack components, fuel cell modelling and performance optimization by computational techniques, single cell and stack electrochemical characterization, development of investigation tools for stack monitoring and data acquisition. A lot of work has been focused to the fuel cell stack architecture, assembling, gas leakage and cross-over reduction (gasketing), flow field and manifold design. Computational fluid dynamics studies have been performed to investigate and improve reactants distribution inside the cell. A flow field design methodology, developed in this framework and related to serpentine like flow field, is actually under investigation. All of these aspects of PEFC stack research are realized in the framework of National and European research projects, or in collaboration with industries and other research centres. In the present work our stack research activity is reported and the most important results are also considered.

The operative conditions influence the performance of a polymer electrolyte fuel cell (PEFC). In particular, when a multi-cell (stack) instead of a single cell is investigated, a proper water management and flow stoichiometric ratio are essential for obtaining high electrical conversion efficiency. In this paper, a five cell air cooled PEM fuel cell stack was designed and realized, and systematic studies on the influence of the reactants humidification have been carried out to optimize the operative conditions. Polarization curves and time test at a fixed current have been conducted for various cathode (RHC) and anode (RHA) inlet humidity conditions. In particular, a small decay and low performance were obtained for RHA and RHC 70 % and a considerable decay and low performance for RHA and RHC > 70 % . A good compromise for water management, in terms of decay and performance, is obtained when a symmetrical RH of 70% was used, because in this case an optimal water balance was probably reached considering that high flow of gases was used. In fact, insufficient water content implies a lower ion conductivity of the membrane whereas excess of water yields to flooding of the electrodes and parasitic losses due to the presence of water in the gas channels. Consequently, these effects lead to a lowering of voltages during lifetime tests. In any case, the cathode RH has a stronger influence on the stack decay compared to the anode one. In the optimal selected conditions of RH a constant and stable power of about 55 W (at 20 A) was obtained during the 15 h of operation.

This study aims at investigating the effects of platinum (Pt) loadings on the cathodic reactions in Single Chamber Microbial Fuel Cells (SCMFCs) and developing cost-effective MFC operational protocols. The power generation of SCMFCs was examined with different Pt loadings (0.005–1 mgPt/cm 2 ) on cathodes. The results showed that the power generation of the SCMFCs with 0.5–1 mgPt/cm 2 were the highest in the tests, decreased 10–15% at 0.01–0.25 mgPt/cm 2 , and decreased further 10–15% at 0.005 mgPt/cm 2 . The SCMFCs with Pt-free cathode (graphite) had the lowest power generation. In addition, the power generation of SCMFCs with different Pt loadings were compared in raw wastewater (Chemical oxygen demand (COD): 0.36 g/L) and wastewater enriched with sodium acetate (COD: 2.95 g/L). The solution conductivity in SCMFCs decreased with the degradation of organic substrates. Daily polarization curves ( V – I ) showed a decrease in current generation and an increase in ohmic losses over the operational period (8 days). The SCMFCs (with 0.5–1 mgPt/cm 2 at cathode) fed with wastewater and sodium acetate (NaOAc) reached the highest power generation (786 mW/m 2 ), while the SCMFCs (with 0.5–1 mgPt/cm 2 at cathode) fed only with wastewater obtained the lower power generation (81 mW/m 2 ). The study demonstrated that lowering the Pt loadings in two magnitude orders (1 to 0.01, 0.5 to 0.005 mgPt/cm 2 ) only reduced the power generation of 15–30%, and this reduction of the power generation become less substantial with the decrease in the solution conductivity of SCMFCs.