Empty fruit bunch, a significant by-product of the palm oil industry, represents a tremendous and hitherto neglected renewable energy resource for many countries in South East Asia and Sub-Saharan Africa. The design and simulation of a plant producing pure hydrogen through autothermal reforming (ATR) of palm empty fruit bunch (PEFB) was carried out based on successful laboratory experiments of the core process. The bio-oil feed to the ATR stage was represented in the experiments and in the simulation by a surrogate bio-oil mixture of 11 organic compounds shown to be main constituents of PEFB oil from previous work, and whose combined elemental composition and volatility was determined to be as close as possible to that of the real PEFB bio-oil. The experiments confirmed that H2 yields close to equilibrium predictions were achievable using an in-house synthetised Rh-Al2O3 catalyst in a packed bed reactor. Initial sensitivity analysis on the plant revealed that feed molar steam to carbon... [more]

The study investigated co-digestion batch experiments using kitchen waste (KW) and garden waste (GW) collected from individual households. Grass and leaves were first subjected to a 3-day hyperthermophilic pretreatment at 70 °C and 80 °C and then co-digested with kitchen waste at 35 °C and 55 °C. The hyperthermophilic pretreatment resulted in the solubilization of organic material with the release of fatty acids, whereas the biogas yield was negligible. In the second stage, the greatest methane yield of 387 NmL/gVS was achieved for the mono-digestion of leaves, whereas the co-digestion of grass with 50% KW gave the highest hydrogen production of 88 NmL/gVS. Considering the overall process performance, the best operating conditions were established using a 3-day hyperthermophilic pretreatment at 70 °C, followed by co-digestion at 55 °C in the second stage for the mixture of 25% garden waste with 75% KW.

The main part of mankind’s ecological footprint is the carbon footprint, a measure of the environmental impact of humanity’s energy release from fossil fuels. The use of fossil fuels will have to change in the forthcoming decades to a largely climate-neutral use of solar energy enabled by dramatic cost reductions for PV and wind energy systems. The impact of this trend on world society has been discussed in a previous paper. In connection with these important technical developments, the role of electricity, its transport and storage will alter in the coming decades, allowing the design and use of larger and larger electricity grids and a parallel use of hydrogen for both storage and energy transport. This will further change the energy landscape of the world. All these developments and their relationship to global sustainable development are elaborated in this cross-disciplinary paper by specifically analyzing whether the Sustainable Development Goals by the United Nations are an effec... [more]

Several carbon sequestration technologies have been proposed to utilize carbon dioxide (CO2) to produce energy and chemical compounds. However, feasible technologies have not been adopted due to the low efficiency conversion rate and high-energy requirements. Process intensification increases the process productivity and efficiency by combining chemical reactions and separation operations. In this work, we present a model of a chemical-electrochemical cyclical process that can capture carbon dioxide as a bicarbonate salt. The proposed process also produces hydrogen and electrical energy. Carbon capture is enhanced by the reaction at the cathode that displaces the equilibrium into bicarbonate production. Literature data show that the cyclic process can produce stable operation for long times by preserving ionic balance using a suitable ionic membrane that regulates ionic flows between the two half-cells. Numerical simulations have validated the proof of concept. The proposed process cou... [more]

This paper covers the hydrogen technologies regarding the role of hydrogen as an energy carrier and the possibilities of its production and use. It is initially presented the modalities and the efficiency of the current technologies of obtaining hydrogen, detailing its obtaining by the electrolysis of the water, the electrochemical efficiency and the specific consumption of electricity as well as the thermodynamics of the electrochemical processes. The following paragraph addresses hydrogen conversion possibilities. This paragraph details the thermodynamic analysis of the fuel cell, the external characteristic of the fuel cell and the types of fuel cell. The last paragraph addresses the possibilities of using the fuel cells for electrical vehicles and cogeneration systems for buildings.In this context, the traditional transport and distribution grid will have to adapt to the new realities as they will need to actively participate in the internal energy market by the transformation of t... [more]

In both the private and public sectors, green hydrogen is treated as a promising alternative to fossil energy commodities. However, building up production capacities involves significant carbon production, especially when considering secondary infrastructure, e.g., renewable power sources. The amount of required capacity as well as the carbon production involved is calculated in this article. Using Germany as an example we show that the switch to purely green hydrogen involves significant bow waves in terms of carbon production as well as financial and resource demand. An economic model for an optimal decision is derived and—based on empirical estimates—calibrated. It shows that, even if green hydrogen is a competitive technology in the future, using alternatives like turquoise hydrogen or carbon capture and storage is necessary to significantly reduce or even avoid the mentioned bow waves.

In December 2019, the European Commission unveiled an ambitious project, the European Green Deal, which aims to lead the European Union to climate neutrality by 2050. This is a significant challenge for all EU countries, and especially for Poland. The role of hydrogen in the processes of decarbonization of the economy and transport is being discussed in many countries around the world to find rational solutions to this difficult and complex problem. There is an ongoing discussion about the hydrogen economy, which covers the production of hydrogen, its storage, transport, and conversion to the desired forms of energy, primarily electricity, mechanical energy, and new fuels. The development of the hydrogen economy can significantly support the achievement of climate neutrality. The belief that hydrogen plays an important role in the transformation of the energy sector is widespread. There are many technical and economic challenges, as well as legal and logistical barriers to deal with in... [more]

With the global warming of the planet, new forms of energy are being sought as an alternative to fossil fuels. Currently, hydrogen (H2) is seen as a strong alternative for fueling vehicles. However, the major challenge in the use of H2 arises from its physical properties. An earlier study was conducted on the storage of H2, used as fuel in road vehicles powered by spark ignition engines or stacks of fuel cells stored under high pressure inside small spheres randomly packed in an envelope tank. Additionally, the study evaluated the performance of this new storage system and compared it with other storage systems already applied by automakers in their vehicles. The current study aims to evaluate the H2 leaks from the same storage system, when inserted in any road vehicle parked in conventional garages, and to show the compliance of these leaks with European Standards, provided that an appropriate choice of materials is made. The system’s compliance with safety standards was proved. Regar... [more]

Lignocellulose and starch-based raw materials are often applied in the investigations regarding biohydrogen generation using dark fermentation. Management of the arising post-fermentation broth becomes a problem. The Authors proposed sequential processes, to improve the efficiency of both hydrogen generation and by-products management carried under model conditions. During the proposed procedure, the simple sugars remaining in broth are converted into organic acids, and when these products are used as substrates for the photo fermentation process. To enhance the broth management also conditions promoting Deep Eutectic Solvents (DES) precursors synthesis are simultaneously applied. Application of Box-Behnken design allows defining of the optimal conditions for conversion to DESs precursors. During the procedure hydrogen was obtained, the concentration of hydrogen in the photo fermentation reached up to 819 mL H2/L medium/7 d, depending on the broth type, i.e., when the broth was optimiz... [more]

This paper aims at addressing the exploitation of solid-state carriers for hydrogen storage, with attention paid both to the technical aspects, through a wide review of the available integrated systems, and to the social aspects, through a preliminary overview of the connected impacts from a gender perspective. As for the technical perspective, carriers to be used for solid-state hydrogen storage for various applications can be classified into two classes: metal and complex hydrides. Related crystal structures and corresponding hydrogen sorption properties are reviewed and discussed. Fundamentals of thermodynamics of hydrogen sorption evidence the key role of the enthalpy of reaction, which determines the operating conditions (i.e., temperatures and pressures). In addition, it rules the heat to be removed from the tank during hydrogen absorption and to be delivered to the tank during hydrogen desorption. Suitable values for the enthalpy of hydrogen sorption reaction for operating condi... [more]

Hydrogen used as an energy carrier can provide an important route to the decarbonization of energy supplies, but realizing this opportunity will require both significantly increased production and transportation capacity. One route to increased transportation capacity is the shipping of liquid hydrogen, but this requires an energy-intensive liquefaction step. Recent study work has shown that the energy required in this process can be reduced through the implementation of new and improved process designs, but since all low-temperature processes are affected by the available heat-sink temperature, local ambient conditions will also have an impact. The objective of this work is to identify how the energy consumption associated with hydrogen liquefaction varies with heat-sink temperature through the optimization of design parameters for a next-generation mixed refrigerant based hydrogen liquefaction process. The results show that energy consumption increases by around 20% across the coolin... [more]

The world of energy is on the cusp of profound transformation. Hydrogen or hydrogen-containing fuel mixtures in the form of synthesis gas, as carriers of clean energy, will be in the short term among the most efficient solutions to pressing environmental problems, reducing the amount of greenhouse gases as well as pollution of cities and dependence on oil-based fuels. Carbon dioxide conversion of methane is the most promising method for the production of synthesis gas due to the simultaneous consumption of two greenhouse gases and, accordingly, a successful solution to environmental problems. Ni/Mn-based catalysts have been prepared by self-propagating high-temperature synthesis (SHS) for this process. The samples were characterized by X-ray diffraction, scanning electron microscopy, and nitrogen porosimetry. The effects of the catalysts’ composition on activity, selectivity, and product yield were investigated. The influence of the content of Ni, Mn on the behavior of catalysts has be... [more]

Hydrogen is an environmentally friendly biofuel which, if widely used, could reduce atmospheric carbon dioxide emissions. The main barrier to the widespread use of hydrogen for power generation is the lack of technologically feasible and—more importantly—cost-effective methods of production and storage. So far, hydrogen has been produced using thermochemical methods (such as gasification, pyrolysis or water electrolysis) and biological methods (most of which involve anaerobic digestion and photofermentation), with conventional fuels, waste or dedicated crop biomass used as a feedstock. Microalgae possess very high photosynthetic efficiency, can rapidly build biomass, and possess other beneficial properties, which is why they are considered to be one of the strongest contenders among biohydrogen production technologies. This review gives an account of present knowledge on microalgal hydrogen production and compares it with the other available biofuel production technologies.

Energy storage, both short- and long-term, will play a vital role in the energy system of the future. One storage technology that provides high power and capacity and that can be operated without carbon emissions is compressed air energy storage (CAES). However, it is widely assumed that CAES plants are not economically feasible. In this context, a mixed-integer linear programming (MILP) model of the Huntorf CAES plant was developed for revenue maximization when participating in the day-ahead market and the minute-reserve market in Germany. The plant model included various plant variations (increased power and storage capacity, recuperation) and a water electrolyzer to produce hydrogen to be used in the combustion chamber of the CAES plant. The MILP model was applied to four use cases that represent a market-orientated operation of the plant. The objective was the maximization of revenue with regard to price spreads and operating costs. To simulate forecast uncertainties of the market... [more]

The Energy System lab at the University of Trieste has carried out a study to investigate the reduction in performance of high temperature polymer electrolyte membrane (HTPEM) fuel cell membrane electrode assemblies (MEAs) when subjected to different ageing tests. In this study, start and stop cycles, load cycles, open circuit voltage (OCV) permanence and constant load profile were considered. Polarization curves (PC) together with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) data were recorded during the ageing tests to assess the fuel cell performance. In this paper, experimental data are presented to confirm the test methodology previously proposed by the authors and to quantitatively correlate the performance degradation to the operational profiles. It was demonstrated that OCV condition, start and stop and load cycling increase degradation of the MEAs with respect to constant load operation. As expected, the OCV is the operational condition that influen... [more]

The achievement of a carbon-free emissions economy is one of the main goals to reduce climate change and its negative effects. Scientists and technological improvements have followed this trend, improving efficiency, and reducing carbon and other compounds that foment climate change. Since the main contributor of these emissions is transportation, detaching this sector from fossil fuels is a necessary step towards an environmentally friendly future. Therefore, an evaluation of alternative fuels will be needed to find a suitable replacement for traditional fossil-based fuels. In this scenario, hydrogen appears as a possible solution. However, the existence of the drawbacks associated with the application of H2-ICE redirects the solution to dual-fuel strategies, which consist of mixing different fuels, to reduce negative aspects of their separate use while enhancing the benefits. In this work, a new combustion modelling approach based on machine learning (ML) modeling is proposed for pre... [more]

In recent years, several researchers have studied the potential use of ammonia (NH3) as an energy vector, focused on the techno-economic advantages and challenges for full global deployment. The use of ammonia as fuel is seen as a strategy to support decarbonization; however, to confirm the sustainability of the shift to ammonia as fuel in thermal engines, a study of the environmental profile is needed. This paper aims to assess the environmental life cycle impacts of ammonia-based electricity generated in a combined heat and power cycle for different ammonia production pathways. A cradle-to-gate assessment was developed for both ammonia production and ammonia-based electricity generation. The results show that electrolysis-based ammonia from renewable and nuclear energy have a better profile in terms of global warming potential (0.09−0.70 t CO2-eq/t NH3), fossil depletion potential (3.62−213.56 kg oil-eq/t NH3), and ozone depletion potential (0.001−0.082 g CFC-11-eq/t NH3). In additio... [more]

The effects of climate change and global warming are arising a new awareness on the impact of our daily life. Power generation for transportation and mobility as well as in industry is the main responsible for the greenhouse gas emissions. Indeed, currently, 80% of the energy is still produced by combustion of fossil fuels; thus, great efforts need to be spent to make combustion greener and safer than in the past. For this reason, a review of the most recent gas turbines combustion strategy with a focus on fuels, combustion techniques, and burners is presented here. A new generation of fuels for gas turbines are currently under investigation by the academic community, with a specific concern about production and storage. Among them, biofuels represent a trustworthy and valuable solution in the next decades during the transition to zero carbon fuels (e.g., hydrogen and ammonia). Promising combustion techniques explored in the past, and then abandoned due to their technological complexit... [more]

Recent studies have demonstrated that ammonia is an emerging energy vector for the distribution of hydrogen from stranded sources. However, there are still many unknown parameters that need to be understood before ammonia can be a substantial substitute in fuelling current power generation systems. Therefore, current attempts have mainly utilised ammonia as a substitute for natural gas (mainly composed of methane) to mitigate the carbon footprint of the latter. Co-firing of ammonia/methane is likely to occur in the transition of replacing carbonaceous fuels with zero-carbo options. Hence, a better understanding of the combustion performance, flame features, and radical formation of ammonia/methane blends is required to address the challenges that these fuel combinations will bring. This study involves an experimental approach in combination with numerical modelling to elucidate the changes in radical formation across ammonia/methane flames at various concentrations. Radicals such as OH... [more]

Biological methanation as a method of sector coupling between electric and gas grids is expected to be an integral part of the green energy change. Wastewater treatment plants (WWTPs) involving anaerobic digestion (AD) allow existing infrastructure to operate as energy conversion plants, to close carbon cycles and to generate long-term storable energy in the form of biomethane. Therefore, municipal raw sludge and additional organic residuals (co-substrates) are converted into biogas. Hydrogen is added to convert the carbon dioxide in the biogas into methane via biological methanation (BM). In this study, the energy amount that is convertible via BM in municipal digesters in Austria was calculated. The amount of energy, which can be transformed from electric surplus energy into biomethane, was assessed. Operational data from lab-scale digesters were combined with data from 28 Austrian full-scale wastewater treatment plants with AD. They represent 9.2 Mio population equivalents (PE), or... [more]

Germany’s energy transition, known as ‘Energiewende’, was always very progressive. However, it came technically to a halt at the question of large-scale, seasonal energy storage for wind and solar, which was not available. At the end of the 2000s, we combined our knowledge of both electrical and process engineering, imitated nature by copying photosynthesis and developed Power-to-Gas by combining water electrolysis with CO2-methanation to convert water and CO2 together with wind and solar power to synthetic natural gas. Storing green energy by coupling the electricity with the gas sector using its vast TWh-scale storage facility was the solution for the biggest energy problem of our time. This was the first concept that created the term ‘sector coupling’ or ‘sectoral integration’. We first implemented demo sites, presented our work in research, industry and ministries, and applied it in many macroeconomic studies. It was an initial idea that inspired others to rethink electricity as we... [more]

This paper provides a comprehensive review and critical analysis of the latest research results in addition to an overview of the future challenges and opportunities regarding the use of hydrogen to power internal combustion engines (ICEs). The experiences and opinions of various international research centers on the technical possibilities of using hydrogen as a fuel in ICE are summarized. The advantages and disadvantages of the use of hydrogen as a solution are described. Attention is drawn to the specific physical, chemical, and operational properties of hydrogen for ICEs. A critical review of hydrogen combustion concepts is provided, drawing on previous research results and experiences described in a number of research papers. Much space is devoted to discussing the challenges and opportunities associated with port and direct hydrogen injection technology. A comparison of different fuel injection and ignition strategies and the benefits of using the synergies of selected solutions... [more]

The energy security landscape that we envisage in 2050 will be different from that of today. Meeting the future energy needs of the armed forces will be a key challenge, not least for military security. The World Energy Council’s World Energy Scenarios forecast that the world’s population will rise to 10 billion by 2050, which will also necessitate an increase in the size of the armed forces. In this context, energy extraction, distribution, and storage become essential to stabilizing the imbalance between production and demand. Among the available solutions, Power to Hydrogen (P2H) is one of the most appealing options. However, despite the potential, many obstacles currently hinder the development of the P2H market. This article aims to identify and analyse existing barriers to the introduction of P2H technologies that use hydrogen. The holistic approach used, which was based on a literature survey, identified obstacles and possible strategies for overcoming them. The research conduct... [more]

The effects of doping manganese ions into a cerium oxide lattice for a thermochemical two-step water-splitting cycle to produce oxygen and hydrogen and new synthesis methods were experimentally investigated. In order to comparison of oxygen/hydrogen producing performance, pristine CeO2, a coprecipitation method for Mn-CeO2, and a direct depositing method for Mn-CeO2 with different particle sizes (50~75, 100−212, over 212 μm) and doping extents (0, 5, 15 mol%) were tested in the context of synthesis and fabrication processes of reactive metal oxide coated ceramic foam devices. Sample powders were coated onto zirconia (magnesium partially stabilized zirconia oxide, MPSZ) porous foam at 30 weight percent using spin coating or a direct depositing method, tested using a solar reactor at 1400 °C as a thermal reduction step and at 1200 °C as a water decomposition step for five repeated cycles. The sample foam devices were irradiated using a 3-kWth sun-simulator, and all reactive foam devices... [more]

Hydrogen derived from biomass feedstock (biohydrogen) can play a significant role in Germany’s hydrogen economy. However, the bioenergy potential and environmental benefits of biohydrogen production are still largely unknown. Additionally, there are no uniform evaluation methods present for these emerging technologies. Therefore, this paper presents a methodological approach for the evaluation of bioenergy potentials and the attainable environmental impacts of these processes in terms of their carbon footprints. A procedure for determining bioenergy potentials is presented, which provides information on the amount of usable energy after conversion when applied. Therefore, it elaborates a four-step methodical conduct, dealing with available waste materials, uncertainties of early-stage processes, and calculation aspects. The bioenergy to be generated can result in carbon emission savings by substituting fossil energy carriers as well as in negative emissions by applying biohydrogen prod... [more]