A numerical study on the active reaction thickness of nickel catalyst layers used in a low-pressure steam methane reforming process

With the advancement of fuel cell technologies and growing interest in the hydrogen economy, the small-scale, distributed production of hydrogen has recently been receiving considerable research attention. The steam methane reforming (SMR) process, an established industrial process for large-scale hydrogen production, can also be successfully deployed for small-scale, low-pressure hydrogen production systems, including compact reformers, microchannel reformers, plate reformers, and monolithic reformers. In this study, the active reaction thickness of nickel catalyst layers was numerically determined by solving one-dimensional reaction/diffusion problems with finite volume method. The small-scale SMR conditions were considered, such as the reforming pressure of 1–3 bar, reforming temperature of 600–800 °C, and steam-to-carbon ratio of 2–4. The results showed the active thickness for the steam reforming and reverse methanation reactions hardly exceeded 0.15 mm for 600 °C, 0.07 mm for 700 °C, and 0.05 mm for 800 °C, at the reforming pressure of 1 bar. Besides, the effects of the volume-specific nickel surface area and diffusion properties were also investigated.     

Scaling up of the hybrid direct carbon fuel cell technology

A hybrid direct carbon fuel cell (HDCFC), combining molten carbonate fuel cell (MCFC) and solid oxide fuel cell (SOFC) technologies, is capable of converting solid carbon directly into electrical energy without intermediate reforming. The performance level achieved on small-scale cells (area <4 cm²) suggests that engineering developments should now be undertaken to scale up and demonstrate the feasibility of practical systems. The scaling up of the HDCFC through the design and test of single stack repeat unit with realistic cell sizes was investigated in this study. A single cell of ∼12.56 cm² active area produced a maximum power of ∼1.2 W at 800 °C and a current density of ∼200 mA cm² at 0.6 V, using wood-based pyrolyzed medium density fiberboard (p-MDF) as fuel. In comparison, the HDCFC with activated carbon as fuel produced a maximum power density of 36 and 53 mW cm⁻² at 700 and 800 °C, respectively, and an electric efficiency of ∼40% evaluated under 0.7 V for 17 h at 700 °C. These results demonstrated the applicability of HDCFC to practical systems while stack units were operated in batch mode and an appropriate fuel feeding mechanism has to be designed. Moreover, more engineering advances should be done to enhance power output since a HDCFC stack unit involves multiple challenges that have not been addressed yet, including system configuration and corrosion protection, and durability.     

Energy storage in remote area power supply (RAPS) systems

Preliminary cost analyses indicate that hybrid RAPS systems are more economically attractive as a means to provide electricity to remote villages than are alternatives such as 24 h diesel generation. A hybrid remote area power supply (RAPS) system is being deployed to provide 24 h electricity to villages in the Amazon region of Peru. The RAPS system consists of modules designed to provide 150 kWh per day of utility grade ac electricity over a 24 h period. Each module contains a diesel generator, battery bank using heavy-duty 2 V VRLA gelled electrolyte batteries, a battery charger, a photovoltaic array and an inverter. Despite early difficulties, the system in the first village has now commenced operation and the promise of RAPS schemes as a means for providing sustainable remote electrification appears to be bright.     

Fuel cell and ultra-capacitor hybridization: A prototype test bench based analysis of different energy management strategies for vehicular applications

An energy storage system with sufficient power capacity should be incorporated with fuel cells (FCs) to compensate the slow dynamics of FCs. Ultra-capacitors (UCs) are potential candidates for a solution in this aspect. A test bench of such an FC/UC hybrid configuration that can emulate the dynamics of vehicular systems is presented in this paper. Namely, the test bench performance verification of wavelet transform and fuzzy logic based energy management strategy that was discussed in earlier simulation-based studies of the authors is investigated. Of equal importance is the comparison of the cascade wavelet-fuzzy logic based strategy with the case of using only fuzzy logic in the energy management is presented. Experimental results with small-scale devices, a PEMFC (5 kW, 48 V) manufactured by Plug Power^® Company, and a UC bank composed of 430 F, 16 V and 165 F, 48 V UC modules manufactured by Maxwell Technologies^® Company, illustrate the successful performance analysis of employed energy management schemes during similar motor cycles.     

Increased power output from micro porous layer (MPL) cathode microbial fuel cells (MFC)

Microbial fuel cells are bio-electrochemical transducers that utilise microorganisms to generate electricity, through the oxidation of organic matter. They consist of a negative anode and a positive cathode, separated by an ion selective membrane. The key to improve power, in open-to-air cathode MFCs, is the efficient utilisation of oxygen, by using high surface area materials and effective gas diffusion. This study investigated the effect of single micro porous layers, used as the coating on various electrode substrata, on the performance of small-scale MFCs. Furthermore, 2 of the modified small-scale (6.25 mL) MFCs were implemented as the power source for the TI Chronos digital wristwatch, thus successfully substituting the 3 V button cell, at least for the duration of the experiment.     

Analysis and design of PEM fuel cell/photovoltaic system to supply a traffic/light signals in Ouargla city based on field experience

The idea of powering street traffic lights using stand-alone renewable systems has attracted much attention, in recent years. Classical configuration of photovoltaic (PV) cells connected to a battery bank is the most commonly employed approach in this regard. However, the low sunlight intensity in a lot of places around the globe, as well as the short-stage batteries autonomy, make this kind of systems technically less adequate. In this paper, and in order to improve the efficacy of the PV-based classical traffic lights, a hybrid system composed of a PV panel, battery, and a small PEM fuel cell is proposed. The goal is to develop a more reliable, efficient, and clean power supply that able to meet the load demands of the traffic lights during all the year. Ouargla region in Algeria (Latitude of 31°95′ N, Longitude of 5°24′E, and Altitude of 0.141 km above Mean Sea Level) is taken as a case study to be investigated. The influence of stack temperature on PEMFC I–V characteristics are also given and analyzed, furthermore, the proposed Whale Optimization Algorithm WOA is used to solve the parameters identification problems of the PEMFC electrochemical model. Comprehensive experiment results and analyses indicate that the proposed algorithm has good performance considering a two temperature samples (26 °C and 39 °C), in such a way, the lowest Mean Absolute Error reaches 0.0589 V and 0.1044 V respectively. Finally, an optimal computer program to design the system components is established and the results show that the optimum PV area, hydrogen generator number, and battery capacity for powering regular light signals are obtained to be 0.72 m², one electrolyser of 60 l/h, and one battery of 80 Ah, respectively.     

High performance solid oxide fuel cell operating on dry gasified coal

A fluidized coal bed-solid oxide fuel cell (FB-SOFC) arrangement is employed for efficient conversion of dry gasified coal into electricity at 850 °C. It consists of an anode-supported tubular solid oxide fuel cell of 24 cm² active area coupled to a Boudouard gasifier. A minimally fluidized bed of low sulfur (0.15 wt%) Alaska coal is gasified at 930 °C by flowing CO₂ to generate CO. The resulting CO fuel is oxidized at the Ni/YSZ cermet anode. The highest cell power density achieved is 0.45 W cm⁻² at 0.64 V with 35.7% electrical conversion efficiency based on CO utilization. This power density is the highest reported in the literature for such systems and corresponds to a total power generation of 10.8 W by this cell. Similarly, 48.4% is the highest conversion efficiency measured at a power density of 0.30 W cm⁻² and 0.7 V. The open circuit voltages are in good agreement with values expected based on thermodynamic data.     

Biomass fired small-scale CHP in Sweden and the Baltic States: a case study on the potential of clustered dwellings

Sweden as well as the three Baltic states has an abundant supply of biomass, mostly wood waste. Much of it goes into district heating (DH), which has expanded continuously since the first system started 50 years ago. DH now accounts for 43% of the heating consumption and a further expansion is possible in many directions. Firstly existing DH systems can be enlarged, secondly DH can be upgraded to combined heat and power (CHP) to a much larger extent, thirdly new DH (and CHP) systems can be implemented in many smaller places down to 1000 inhabitants or less. The last alternative, biomass and especially pellets fired small-scale cogeneration in combination with local heating networks, is the topic for this paper. It presents a method to estimate the potential for small-scale DH and CHP and results from a “test” area in southeast Sweden. The method estimates local heat demand using databases with individual and statistical property data. It identifies areas with clusters of buildings where the heat demand is enough to implement decentralized small DH networks if possible in combination with small-scale CHP. In the event for Swedish circumstances very sparsely populated test area of 36×48 km² with around 8000 inhabitants, the total heat consumption in residential buildings is estimated to 84 GW h. When we have identified the areas with clusters of buildings, we have set the minimum heat consumption in such an area to 500 MW h. The area size is varied in 250 m steps from 250×250 m² to 1000×1000 m². For the four area sizes, the method then identifies and locates 30, 38, 38,30, respectively, clustered areas with a potential for small-scale DH and CHP worth investing closer.     

Green hydrogen as feedstock: Financial analysis of a photovoltaic-powered electrolysis plant

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.     

Capacitive load based on IGBTs for on-site characterization of PV arrays

This paper describes the practical design of a portable capacitive load based on insulated gate bipolar transistors (IGBTs), which is used to measure the I–V characteristics of PV arrays with short-circuit currents up to 80 A and open circuit voltages up to 800 V. Such measurement allows on-site characterization of PV arrays under real operating conditions and also provides information for the detection of potential array anomalies, such as broken cells or defective connections. The presented I–V load is easy to reproduce and low-cost, characteristics that are within the reach of small-scale organizations involved in PV electrification projects.     

Miniature microbial fuel cells and stacks for urine utilisation

MFCs are becoming a stronger contender in the area of alternative energy sources and show great promise in utilising a wide variety of organic sources. This paper describes the utilisation of neat undiluted urine as the main feedstock for different types of individual MFCs and stacks of small-scale MFCs, for direct electricity production, with conversion efficiencies of >50%. The smallest MFC (1.4 mL total volume) produced equal amounts of power to that produced by larger MFCs (6.25 mL), resulting in increased power densities. Power densities of 4.93 mW/m² (absolute power of 1.5 mW) were recorded when 48 small-scale MFCs were connected as a stack and fed with urine. This study demonstrates the feasibility of using urine as an untreated fuel and that improved power outputs can be achieved through MFC miniaturisation and multiplication into stacks.     

Development of optimisation model for direct methanol fuel cells via cell integrated network

A cell network consists of a combination of fuel cells to achieve the targeted power consumption for a specific application. The main objective of this study is to design and optimise direct methanol fuel cell (DMFC) via cell integrated network model targeted for small portable application, such as cell phones and tablets. The target current and voltage was 1400 mA and 3.7 V, respectively, for a 5.18 W of cell network power. The optimisation was performed using 16 cells that were arranged in series with a voltage output of 3.781 V and a current of 1400 mA. The overall active area for the cell network was 128 cm², and the cost of 1 set of cell networks is USD 1400.     

Integration of a light mobility urban scale hydrogen refuelling station for cycling purposes in the transportation market

Road transportation consists of a significant contributor to total greenhouse gas emissions in developed countries. New alternative technologies in transportation such as electric vehicles aim to reduce substantially vehicle emissions, particularly in urban areas. Incentives of using two-wheel electric vehicles such as bicycles in big cities centres are promoted by local governments, and in fact, some countries are already trying to adopt this transition. An interesting case consists of the use of hydrogen fuel cells in such vehicles to increase their driving range under short refuelling times. To this end, this paper investigated the social and financial prospects of hydrogen infrastructure for city-oriented fuel cell electric vehicles such as bicycles. The results of the research indicated that a light mobility urban hydrogen refuelling station able to provide refuelling processes at pressures of 30 bar with a hydrogen fuel cost of 34.7 €/kgH₂ is more favourable compared to larger stations.     

The use and optimization of stainless steel mesh cathodes in microbial electrolysis cells

Microbial electrolysis cells (MECs) provide a high-yield method for producing hydrogen from renewable biomass. One challenge for commercialization of the technology is a low-cost and highly efficient cathode. Stainless steel (SS) is very inexpensive, and cathodes made of this material with high specific surface areas can achieve performance similar to carbon cathodes containing a platinum catalyst in MECs. SS mesh cathodes were examined here as a method to provide a higher surface area material than flat plate electrodes. Cyclic voltammetry tests showed that the electrochemically active surface area of certain sized mesh could be three times larger than a flat sheet. The relative performance of SS mesh in linear sweep voltammetry at low bubble coverages (low current densities) was also consistent with performance on this basis in MEC tests. The best SS mesh size (#60) in MEC tests had a relatively thick wire size (0.02 cm), a medium pore size (0.02 cm), and a specific surface area of 66 m²/m³. An applied voltage of 0.9 V produced a high hydrogen recovery (98 ± 4%) and overall energy efficiency (74 ± 4%), with a hydrogen production rate of 2.1 ± 0.3 m³H₂/m³d (current density of 8.08 A/m², volumetric current density of 188 ± 19 A/m³). These studies show that SS in mesh format shows great promise for the development of lower cost MEC systems for hydrogen production.     

Dynamic simulation of hydrogen-based off-grid zero energy buildings with hydrogen storage considering Fanger model thermal comfort

In this study, some locations with different climates, off-grid zero energy buildings with hydrogen energy storage systems are designed, and transient analysis is conducted. These considered buildings supply their electricity consumption without using the electrical grid and PV panels or wind turbines. Also, they supply thermal comfort to occupants by using a vapor compression chiller and humidifier. Domestic hot water of occupants is supplied using solar collectors. For analyzing building's performance and objectives achievement, TRNSYS software is used. Also, for evaluating occupant thermal comfort, the Fanger model is used. The considered building is a one-story building with a 150 m² area. Four occupants are considered. Both of them are seated at rest, and another is seated with light working such as typing. Using the Fanger model equation and MATLAB software, the thermal comfort of occupants is determined. For domestic hot water consumption, verified profiles that vary during 24 h of the day are considered. Achieved results show that for humid and cold cities, PV panels with an area of 73 and 76 m² can be supplied the required electricity of considered building with four occupants and battery state of charge is higher than 50% and 10%, respectively. Moreover, with a suitable air conditioner system, the predicted percentage of dissatisfied (PPD) can be lower than 12% and 8% for humid and cold cities. Therefore, the building can be converted to a zero-energy building using its rooftop area.     

Assessment of the potential for hydrogen production from renewable resources in Argentina

The potential for hydrogen production from three major renewable resources (wind energy, solar energy and biomass) in Argentina is analyzed. This potential for the annual production of wind, solar and biomass hydrogen is represented with maps showing it per unit area in each department. Thus, by using renewable resource databases available in the country, a new Geographic Information System (GIS) of renewable hydrogen is created. In this system, several geographic variables are displayed, in addition to other parameters such as the potential for renewable hydrogen production per department relative to transport fuel consumption of each province or the environmental savings that would imply the production of hydrogen required to add 20% V/V to CNG, with the aim of developing the cleaner alternative CNG + H₂ fuel. In order to take into account areas where energy development would be restricted, land use and environmental exclusions were considered.     

Identification of potential areas for biomass production in China: Discussion of a recent approach and future challenges

A standard methodology is needed to recognize potentially suitable areas for sustainable bioenergy crop production. This facilitates better identification of promising crops and cropping systems, logistical and economic studies, and work needed to meet regulatory criteria. A possible approach is built upon three layers of internationally available spatial data: (1) degrading and abandoned areas, (2) potentially suitable land cover classes, (3) exclusion zones such as nature reserves and areas of high biodiversity. For China, areas identified as potentially suitable range from 1.2 to 6.0% of the national territory, depending on different levels of statistical confidence in degrading area status and allowable limits of terrestrial carbon. Verification on the ground showed that about 60% of points tested conformed to the remote suitability assessment in the scenario, which represents the results for the combination of all degrading areas and a terrestrial carbon stock limit of 200 t ha⁻¹. A top-down approach is useful in framing potentially suitable locations, but a complementary bottom-up analysis is still required to ultimately identify areas for sustainable bio-fuel production.     

Physicochemical and structural characterization of biochar derived from the pyrolysis of biosolids,cattle manure and spent coffee grounds

In the framework of circular economy, the need of new feedstock materials for the production of alternative new products is of high priority. Biowastes such as manure, sewage sludge (biosolids, BS) and food-waste are used as raw materials for the production of biochar. The present study aims at characterizing biochars produced from three distinct biowastes (i) manure from cattle waste (manure-derived biochar; MDB), (ii) biosolids (BS) from a conventional Urban Wastewater Treatment Plant (UWTP) (biosolids-derived biochar; BDB), and (iii) spent coffee grounds (SCG)-derived biochar (SCGDB). Samples were slowly pyrolyzed in a small-scale kiln with a capacity of 20–24 kg. The samples were heated under nitrogen atmosphere at approximately 6–7 °C min⁻¹ up to the desired temperature (550 °C) and held for 1.5h. The physicochemical characterization of biochars showed the production of alkaline materials with similarities and variations in their characteristics, which depend to the type of feedstock used. The surface area of the raw materials was considerably low (<0.1 m²/g) and increased after pyrolysis to 14.03 m²/g, 3.98 m²/g and 1.53 m²/g for MDB, BDB and SCGDB, respectively. The high %C content, the low H/C ratio and the FTIR adsorption peaks revealed high aromaticity, polymerization and carbonization of the biochars and the presence of several functional groups. These, are some of the biochar properties which could lead to different sorption mechanisms of organic and inorganic contaminants. Also, they presented good stability in soil, which enables to be used as soil amendment and C sequestration mechanism. Finally, the produced biochars showed promising properties for environmental applications.     

Thermodynamic analysis of gasification-driven direct carbon fuel cells

The gasification-driven direct carbon fuel cell (GD-DCFC) system is compared with systems using separate gasification steps prior to work extraction, under autothermal or indirect constraints. Using simple system exergy analysis, the maximum work output of the indirect gasification scheme is 4–7% lower than the unconstrained direct approach, while the work output of the autothermal gasification approach is 12–13% lower than the unconstrained case. A more detailed calculation for the DCFC and indirect gasification plants, using common solid fuel compositions, gives conversion efficiencies in the range of 51–58% at an operating voltage of 0.7 V selected for both systems in this study. In contrast, the conversion efficiency of the autothermal gasification approach is estimated to be 33–35% at 0.7 V. DCFC efficiencies can be increased to over 60% by an increase in operating voltage and/or inclusion of a bottoming cycle. The thermodynamic model also indicates that steam gasification yields similar work output and thermal efficiency as for CO₂ gasification. Open circuit potential measurements agree with equilibrium calculations both for the C–O and C–H–O gasification systems, confirming the governing mechanism and feasibility of the GD-DCFC. Current–voltage measurements on an un-optimized system demonstrate power densities of 220 mW cm⁻² at 0.68 V during operation at 1178 K.