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While energy demand in this fast developing world is increasing, its future is being compromised by the CO 2 emissions produced through the burning of fossil fuels. Clean energy technologies are available, but there are still barriers hindering their full integration into the society, the majority of which are economic and social. For these reasons, the development of new technologies and configurations to make renewable energies systems more cost-effective is urgently needed. The plant design proposed in this paper consists of basic Dish-Stirling collectors supported by a reversible solid oxide fuel cell acting as a power generator and storage unit, and therefore offering dispatchable power on demand. Further, the system reuses the waste heat for seawater desalination, which is very convenient for arid areas with high solar radiation and shortage of freshwater. The present work is an analytical study in which thermodynamic investigation of the performance evaluation of a self-sustainable polygeneration system with integrated hydrogen production, power generation, and freshwater production is conducted. An evaluation in a real context (South Africa) showed the potential of this system to supply 500 kW, 24 h a day, while producing a considerable amount of freshwater. Although the distillation system presented is able to produce 8464 L per day, there is potential for it to increase its output by nine times or more. • Design and introduction of an alternative energy system based on solar energy solid oxide cell. • Reversible solid oxide cells integrated with dish- Stirling and seawater desalination plant. • A new polygeneration plant able to produce power and freshwater simultaneously at all time. [ABSTRACT FROM AUTHOR]

Demand for the clean and sustainable energy encourages the research and development in the efficient production and utilisation of syngas for low-carbon power and heating/cooling applications. However, diversity in the chemical composition of syngas, resulting due to its flexible production process and feedstock, often poses a significant challenge for the design and operation of an effective combustion system. To address this, the research presented in this paper is particularly focused on an in-depth understanding of the heat generation and emission formation of syngas/producer gas flames with an effect of the fuel compositions. The heat generated by flame not only depends on the flame temperature but also on the chemistry heat release of fuel and flame dimension. The study reports that the syngas/producer gas with a low H 2: CO maximises the heat generation, nevertheless the higher emission rate of CO 2 is inevitable. The generated heat flux at H 2: CO = 3:1, 1:1, and 1:3 is found to be 222, 432 and 538 W m-2 respectively. At the same amount of heat generated, H 2 concentration in fuel dominates the emission of NO x. The addition of CH 4 into the syngas/producer gas with H 2: CO = 1:1 also increases the heat generation significantly (e.g. 614 W m-2 at 20%) while decreases the emission formation. In contrast, adding 20% CO 2 and N 2 to the syngas/producer gas composition reduces the heat generation from 432 W m-2 to 364 and 290 W m-2, respectively. The role of CO 2 on this aspect, which is weaker than N 2 , thus suggests CO 2 is preferable than N 2. Along with the study, the significant role of CO 2 on the radiation of heat and the reduction of emission are examined. • Heat generation and emission of co-flow laminar flames of syngas/producer gas studied. • Impacts of variability in chemical fuel compositions of syngas/producer gas reported. • Low H 2 :CO ratio increases the heat generation. • CH 4 in syngas/producer gas also provides overall benefits. • CO 2 /N 2 reduces the heat transfer capability of flame. [ABSTRACT FROM AUTHOR]

The demand of green energy will be the major issue in this 21 century. The researchers are trying to develop green energy using a variety of ways. Among various forms of green, safe and sustainable energy, hydrogen is considered as the best one due to its inexpensiveness and no pollution to the environment. Moreover, the abundance of sunlight and water resources are great assets for us to generate hydrogen fuel. The research has incased on water splitting after the development of nanotechnology but the various chemical routs of nanoparticles synthesis are toxic to the human and the environment. In recent years, many nanoparticles are synthesized by green methods utilizing plants and other microbes. Some papers are available on the applications of water splitting using these green nanoparticles. The future of this research is very bright and to increase the further research in this area, a review is written. The present article describes the state-of-the-art of water splitting using green nanoparticles. The attempts are made to describe the various methods of nanoparticles syntheses, their optimizations and applications in hydrogen generation. Besides, the efforts are also made to discuss the working mechanism and future challenges and perspectives. • Importance of green energy hydrogen and green nanoparticles. • Water photo splitting by green nanoparticles. • Strategies to tune green nanoparticles for efficient water splitting. • Future challenges and perspectives. [ABSTRACT FROM AUTHOR]

Abstract While the integration of the fuel cell (FC) and the semiconductor thermoelectric device (TED) to form a clean energy hybrid FC-TED system has been previously studied using 0-D mathematical equations, a 3-D finite element model that couples together the physics between the two devices is yet to be comprehensively studied. This paper introduces a 3-D finite element model developed in COMSOL Multiphysics that simulates both the FC and the TED subsystems where the FC electrochemical dynamics and the TED's thermoelectric effect and heat transfer physics take place between them. The studied FC stack is in direct contact with one side of the TED via the top of the gas channel structure and the other side is then convectively cooled by active air cooling. Results demonstrate that the proposed model can easily simulate the TED as both a thermoelectric generator (TEG) or as a Peltier device for cooling and heating. In the TEG mode, energy harvesting efficiency is observed at only 0.1% but expected to improve with better TED to FC relative sizing. The Peltier heating mode is also found to be advantageous in terms of quickly regulating the FC stack temperature, a valuable feature for startup processes. Highlights • A multifield coupled analysis of an integrated FC-TED numerical model is performed. • This model marks a significant progress over conventional simplified equations. • The model involves both FC electrochemical and TEG electro-thermal physics. • The analysis involves parametric sweeps of the FC stack and TED operating voltages. • The TEG mode and TEC heating mode are found to be better modes for operation. [ABSTRACT FROM AUTHOR]

Nowadays, the use of renewable energy sources is one of the keys to achieve the sustainable development of societies. The intensive use of fossil fuels has caused effects in the environment and the human health. Greenhouse gas emissions and the carcinogenic effect of diesel are widely demonstrated. The production of clean energy based on renewable sources and the use of hydrogen as an energy vector in general and as an alternative fuel in particular represent a technically feasible reality. However, it is necessary to study the economic variables of centralized or distributed production of hydrogen as an alternative fuel. The aim of this paper is to analyze the technical and economic viability of a centralized generation hydrogen plant for mobility use. It was performed a sensitivity analysis of main parameters such as size of hydrogen production plant, operating hours of the plant, investment costs of the main equipment and electricity price. A NPV of 1,272,692 and a 9-year pay-back were obtained for a centralized hydrogen production plant of 2 MW, considering commercial values of the main evaluation parameters. The sensitivity analysis determines that the main variables affecting the NPV are the price of electricity and the operating hours of the plant. With 95% of confidence, the NPV will be positive with an 80.19% of certainty. Therefore, centralized hydrogen production represents a technically viable, environmentally friendly and economically attractive process that can rapidly position hydrogen as an alternative fuel for mobility. [ABSTRACT FROM AUTHOR]

The aim of this paper is the implementation of a PV panel system operating at its optimal state. The investigation is divided into two parts. The first part focuses on the estimation of the position of the sun at each moment of the year. Thus an optimum fixed tilt of the panel is defined in order to get the best capture of the sun power for a year in a studied area. The second part of this investigation aims at maximizing the yield of the whole PV system. A maximum power point of the PV panel is reached thanks to a chopper for which a predictive duty cycle is considered and successfully tested. This proposed control involves less oscillations and fast response resulting in better accuracy compared to the Perturb and Observe technique. [ABSTRACT FROM AUTHOR]

The demand for clean energies grows rapidly, therefore, research into new materials to be used as hydrogen reservoirs are necessary. With this work we try to provide some understanding on complex hydrides. The compounds studied are of the type Li–X–H, where X are lighter elements in the periodic table. With the participation of these elements we can obtain a high gravimetric hydrogen density. We performed a systematic study on these materials. In this work we used different ab-initio codes. The predictive power of first principle calculations have shown their importance in determining properties of new materials not yet synthesized. The ab-initio calculations help to shorten development times of new materials such as those proposed in this paper. Additionally, new data on materials studied in the past and others designed in this work are shown here. [ABSTRACT FROM AUTHOR]

This paper provides a design of a drop-in hydrogen fueling station. Drop-in stations are expected to be an important factor in the introduction of hydrogen fueling infrastructure. The stations not only allows a streamlined introduction of hydrogen in the vehicle fueling infrastructure, but also, acts as mini pilot plants that can allow for detailed control studies. The effect of the location and availability of utilities, the closeness to residential area, unintended safety concerns, people outlook towards hydrogen, etc. are some of the factors that can be readily studied with such drop-in stations. The proposed design of a drop-in station mainly considers off-the-shelf items and is conceptualized to be implemented at the Missouri University of Science and Technology. The modular design approach, with the off-the-shelf items allows for a design with the capability of mass production, and ease in transport and integration. [ABSTRACT FROM AUTHOR]

When looking at future energy systems, hydrogen offers a range of benefits as a clean energy carrier, which are receiving great attention as policy priorities. This is first and foremost as an alternative fuel in the transport sector. Car makers have recently started the market introduction of fuel cell electric vehicles and are currently entering a pre-commercial phase, as they are progressing from prototype vehicles for demonstration to producing small volumes. At the same time, market development initiatives aiming at implementing hydrogen refuelling station networks are spreading in Europe, Asia, and the USA. But also in recent years, hydrogen electrolysis has gained considerable attention as a potential flexibility option to help facilitate the large-scale integration of intermittent renewable energies. Given the sustained interest in and controversial discussions on the prospects of hydrogen, this paper aims to provide a comprehensive coverage of the most relevant aspects related to the wider use of hydrogen in the energy system, including the most recent developments and insights. [ABSTRACT FROM AUTHOR]

Abstract: Water management in cathode gas diffusion layers and catalyst layers of PEFCs (Polymer Electrolyte Fuel Cells) plays an important role toward the obtainment of optimal performance. Flooding may indeed occur under different operating conditions, in these components, requiring special attention both in the development and in the design processes. Simulation is a reliable tool to support the design of PEFCs, and thus provide designers with a better interpretation of experimental data. Flooding within porous media is still a critical issue for multiphase flow fuel cell modeling, representing a challenge in terms of model reliability. This paper aims at extending the validity of a literature available 1D GDL multiphase model presented in Ref. . Special attention has been devoted to the analysis of the difference between multiphase and non-multiphase (multispecies) approaches, and to the 3D aspects of cell design related to flooding issues. Results indicate that flooding must be treated as a 3D phenomenon, as it has a different impact on the different active area regions. In fact, although the land is the most affected zone, current is mainly limited in the channel zone close to the gas inlet section. [Copyright &y& Elsevier]

Biohydrogen production through photofermentation has gained significant attention as it provides a sustainable solution for clean energy supply and addresses wastewater concerns by utilizing volatile fatty acids (VFA) which are produced in dark fermentation. In this study, response surface methodology via a Face-centered Central Composite Design (FCCD) was employed to optimize buffer solution pH, ferric citrate concentration, sodium glutamate concentration to maximize biohydrogen production by Rhodobacter sp. MAY2 with mixed VFA (acetate, propionate, butyrate) as substrates. Results showed that the concentrations of ferric citrate, sodium glutamate, and buffer solution pH positively impact the biohydrogen production of Rhodobacter sp. MAY2. The optimal conditions were shown to be 0.36 mM ferric citrate, 11 mM sodium glutamate, and buffer solution of pH 7. The predicted hydrogen production potential (HPP) at these conditions (661.1 mL/L) was within 2 % of the actual HPP (647.7 mL/L). Kinetic parameters using the modified Gompertz equation showed that the predicted values for maximum potential cumulative H 2 production (P), maximum hydrogen production rate (R m), and lag time (λ) are comparable to those reported in literature. Overall, the study highlighted the potential of a local isolate, Rhodobacter sp. MAY2, for biohydrogen production and the suitable fermentation conditions for its growth. • Optimized pH, ferric citrate, and sodium glutamate enhanced Rhodobacter sp. MAY2 biohydrogen production. • Buffer pH, ferric citrate, and sodium glutamate significantly influenced biohydrogen yield. • Rhodobacter sp. MAY2 exhibited high substrate consumption efficiency for volatile fatty acids. [ABSTRACT FROM AUTHOR]