A modular design approach for PEM electrolyser systems with homogeneous operation conditions and highly efficient heat management

Because of its advantages, which are fast response times, high power densities and, therefore, compact system design, using polymer electrolyte membrane electrolyser (PEMEL) technology is a promising way to store the excess energy generated by renewable energy sources. With the approach of hydraulic cell compression homogeneous pressure and current distribution is guaranteed, and waste heat management as well as high-pressure operation are improved compared to conventional mechanically compressed PEMEL stacks. The new design approach presented in this work brings the concept of hydraulic cell compression close to an industrial design while preserving the mentioned advantages and providing a high level of modularity. The concept was experimentally validated for hydrogen production using a laboratory scale stack consisting of five single cells having an active cell area of 25 cm² each. A study on process water independent stack temperature control was performed using water as a hydraulic medium. Furthermore, the capability of high-pressure operation was investigated up to a process media pressure of 30 bar.     

Reduced graphene oxide-supported ruthenium nanocatalysts for highly efficient electrocatalytic hydrogen evolution reaction

Hydrogen energy has received great attention because of its advantages such as large energy density and not producing carbon dioxide, and it is currently considered to be one of the most valuable green energy sources. Therefore, the development of efficiently hydrogen production is of great importance. Hydrogen production from water electrolysis has large application prospects due to its cleanliness and no pollution. However, how to prepare an efficient, stable and low-cost electrocatalyst for this process is still challenging. Here, we develop a reduced graphene oxide-supported ruthenium (Ru) nanoparticle electrocatalyst synthesized by a simple method. The ruthenium precursors are encapsulated and isolated with N,N-dimethylformamide (DMF) (Ru³⁺-DMF), which effectively inhibits the further agglomeration growth of ruthenium. After Ru³⁺-DMF being loaded on graphene oxide, Ru is supported on reduced graphene oxide (Ru/rGO) by the liquid phase chemical reduction method and the remaining organic solvent could be removed by calcination to form a well-dispersed Ru-based electrocatalyst. Ru/rGO shows excellent electrocatalytic activity and long-term stability for hydrogen evolution reaction (HER). In a solution of 1.0 M KOH, the overpotential of 3.0 wt%Ru/rGO for the HER at 100 mA cm^?2 is only 111.7 mV, and the Tafel slope is 31.5 mV dec^?1. It exhibits better HER performance compared to commercial Pt/C and other Ru/rGO catalysts with different Ru loadings. The work could give a new strategy for the synthesis of efficient electrocatalysts.     

Long-term evaluation of biomass production and quality of two cardoon (Cynara cardunculus L.) cultivars for energy use

Cardoon (Cynara cardunculus L.) is an herbaceous species indicated as one of the most suitable energy crop for southern European countries. The aim of this work was to outline the productivity of two cardoon cultivars, Bianco Avorio (BA) and Gigante di Romagna (GR), over 11 years of cultivation in rain fed field conditions in the temperate climate of Central Italy. The quantitative and qualitative aspects of its biomass (calorific value, ultimate and proximate analyses, ash composition) as well as its energy balance (energy efficiency, net energy yield) have been determined. Crop dry yield was not different between the two cultivars and it was rather stable with a mean value (averaged from year 3 to 11) of 14 and 13 t ha^?1 for GR and BA respectively. Furthermore the biomass dry matter content was higher in BA than GR (51% vs 42%). The chemical analysis of cardoon biomass showed a similar composition in both cultivars with good calorific value (15 MJ kg^?1) but with an ash content (13.9% d.w.) higher than other herbaceous energy crops. The total energy input was higher in the establishing than in the following years, however from the planting year onward, both cardoon crops were characterised by a positive energy balance. Even if its mean net energy is lower than other perennial energy crops (182 GJ ha^?1 year^?1), cardoon can be easily propagated by seed with important advantages for crop management and production costs.The results confirmed cardoon's good biomass yield and favourable energy balance even in cultivation systems characterised by limited water input. Moreover future works are necessary in order to improve cardoon biomass quality and to evaluate the possibility of using it in blends with other biomass sources.     

Characteristics and anode reaction of organic wastewater-assisted coal electrolysis for hydrogen production

Electrolytic hydrogen production has the advantages of distributed on-demand hydrogen production, high purity and facile coupling with renewable energy sources, but this process is very energy intensive. In this study, the organic wastewater-assisted coal electrolysis process for hydrogen production was studied in an H-type electrolytic cells. Part of the energy can come from the carbon sources in coal and wastewater to reduce power consumption. Linear sweep voltammetry and potentiostatic techniques were used to study the electrolysis characteristics and anode reaction of the wastewater coal slurry. The results showed that the difference in the composition of the wastewater made the electrolysis characteristics quite different. The gas washing water, sulfur water and slag water produced by coal conversion could significantly increase the current density of coal slurry electrolysis. As for the gas washing water, it has no obvious effect on the catalytic effect of Fe³⁺, and the increase in current density was mainly due to the effects of organic matter and chloride. With increasing voltage, the main anode reaction of the wastewater coal slurry was divided into three stages, namely oxidation of coal particles (0.7–1.0 V), oxidation of organic matter in wastewater (1.0–1.5 V) and oxidation of chloride ions (1.5–2.0 V). Below the chlorine oxidation potential, chloride ions could also promote the oxidation of coal particles. The oxidation mechanism of coal slurry in the presence of wastewater was proposed.     

Electrolysis of waste water containing aniline to produce polyaniline and hydrogen with low energy consumption

Hydrogen generation from water electrolysis is attempted to be one of the replacement of sources as a clean fuel with high energy density. However, its application is limited by the high overpotential of oxygen evolution reaction (OER). Herein, hydrogen fuel is obtained from waste water by replacing OER with aniline electrochemical polymerization. Compared to the OER, the potential of aniline electro-polymerization greatly decreases 1240 mV at the current density of 30 mA cm⁻² even using carbon paper electrode. Moreover, the Faradaic efficiency of hydrogen production is close to 100%. The as-prepared polyaniline demonstrates good performance as electrochemical capitative materials. This work provides efficient and lower energy consumed access to co-generate hydrogen and polyaniline in a convenient step by starting from the toxic and environmental-unfriendly wastewater.     

Design and analysis of an integrated concentrated solar and wind energy system with storage

This study analyzes a renewable energy‐driven innovative multigeneration system, in which wind and solar energy sources are utilized in an efficient way to generate several useful commodities such as hydrogen, oxygen, desalted water, space cooling, and space heating along with electricity. A 1‐km² heliostat field is considered to concentrate the solar light onto a spectrum splitter, where the light spectrum is separated into two portions as reflected and transmitted to be used as the energy source in the concentrated solar power (CSP) and concentrated photovoltaics (CPV) receivers, respectively. As such, CSP and CPV systems are integrated. Wind energy is proposed for generating electricity (146 MW) or thermal energy (138 MW) to compensate the energy need of the multigeneration system when there is insufficient solar energy. In addition, multiple commodities, 46 MW of electricity, 12 m³/h of desalted water, and 69 MW of cooling, are generated using the Rankine cycle and the rejected heat from its condenser. Further, the heat generated on CPV cells is recovered for efficient photovoltaic conversion and utilized in the space heating (34 MW) and proton exchange membrane (PEM) electrolyzer (239 kg/h) for hydrogen production. The energy and exergy efficiencies of the overall system are calculated as 61.3% and 47.8%, respectively. The exergy destruction rates of the main components are presented to identify the potential improvements of the system. Finally, parametric studies are performed to analyze the effect of changing parameters on the exergy destruction rates, production rates, and efficiencies.     

Physical insights into alkaline overall water splitting with NiO microflowers electrodes with ultra-low amount of Pt catalyst

Electrochemical water splitting represents a promising alternative to conventional carbon-based energy sources. The hydrogen evolution reaction (HER) is a key process, still if conducted in alkaline media, its kinetics is slow thus requiring high amount of Pt based catalysts. Extensive research has been focused on reducing Pt utilization by pursuing careful electrode investigation. Here, a low-cost chemical methodology is reported to obtain large amount of microflowers made of interconnected NiO nanowalls (20 nm thick) wisely decorated with ultralow amounts of Pt nanoparticles. These decorated microflowers, dispersed onto graphene paper by drop casting, build a high performance HER electrode exhibiting an overpotential of only 66 mV at current density of 10 mA cm^?2 under alkaline conditions. Intrinsic activity of catalyst was evaluated by measuring the Tafel plot (as low as 82 mV/dec) and turnover frequencies (2.07 s^?1 for a Pt loading of 11.2 μg cm^?2). The effect of Pt decoration has been modelled through energy band bending supported by electrochemical analyses. A full cell for alkaline electrochemical water splitting has been built, composed of Pt decorated NiO microflowers as cathode and bare NiO microflowers as anode, showing a low potential of 1.57 V to afford a current density of 10 mA cm^?2 and a good long-term stability. The reported results pave the way towards an extensive utilization of Ni based nanostructures with ultralow Pt content for efficient electrochemical water splitting.     

Climbing the energy ladder or diversifying energy sources? The continuing importance of household use of biomass energy in urbanizing communities in Northeast Thailand

Following the energy ladder model, the role of biomass energy will diminish and even disappear as rural communities become more urbanized. However, the alternative fuel stacking model suggests that, as households become more urbanized, they diversify their energy sources while continue using firewood and charcoal. This study aimed to assess the extent to which biomass energy still plays an important role as a source of energy for household consumption across the urbanization spectrum of communities. Three villages in Khon Kaen province in Northeast Thailand representing the rural, suburban and urban communities were selected for study. Data were collected on energy uses at household level using a formal questionnaire survey along with field observation and field measurement. The results showed that total household energy consumption increased with urbanization. The absolute quantity of biomass energy used slightly increased when going from rural (5.52 GJ caput⁻¹ y⁻¹) to suburban (6.06 GJ caput⁻¹ y⁻¹) but greatly decreased for urban community (1.98 GJ caput⁻¹ y⁻¹), while the relative share declined with greater urbanization, being 46.2, 37.4 and 10.2% for the rural, suburban and urban communities, respectively. Both firewood and charcoal were used primarily for cooking, with a small amount used for home industry. It was concluded that, although the share of biomass energy in household energy portfolios does decline relative to modern energy sources in the course of urbanization, as predicted by the energy ladder model, there is no sharp discontinuity in utilization of energy sources between communities at different stages of urbanization and biomass continue to be an important component of household energy portfolios in all communities, supporting the fuel stacking model. It appears likely that biomass will remain an important source of household energy in Thailand for an extended period.     

An analysis of used lubricant recycling, energy utilization and its environmental benefit in Taiwan

Utilizing used lubricants as energy sources has been currently demonstrated to be one of the best available waste management methods. In this regard, used lubricants for use as energy sources in Taiwan thus became popular in recent years. The objective of this study was to present a comprehensive analysis of used lubricant-to-energy in Taiwan, which includes status of lubricant consumption, and used lubricant generation and its recycling (i.e., collection & treatment) management system. It was found that a major market for utilizing used lubricants in Taiwan (over 90%) was reused as fuel oils or auxiliary fuels in the cogeneration system. Under the regulatory authorization of the Waste Management Act and the Petroleum Administration Act, the central competent authorities encouraged the energy-intensive industries in the waste-to-energy through the excess electricity purchase and subsidiary incentives. Based on the certified volume of collected used lubricant and its energy use proportion in 2009, the total energy potential and the environmental benefit of mitigating CO₂ emissions in place of fuel oils were preliminarily calculated to be around 9.4 × 10² TJ and 7.3 × 10⁷ kg, respectively.     

From wave to jet and from jet to hydrogen: A promising hybrid system

One of the main challenges that our society must overcome in this century is that of finding alternative energy sources to fossil fuels. These, ideally, must be inexpensive, less polluting than current fuels and available for a substantial time. One promising alternative is hydrogen, which has the great advantage that it can be produced by coupling renewable energy devices with water electrolysis. Several projects devoted to connecting photovoltaic and wind systems with electrolysis devices have been successful; however, little research has been done into the coupling of ocean wave energy converters with water electrolysis. The work here proposes a basic system that stores the energy from waves in the form of hydrogen. The WEC considered is a novel design known as a Blow-Jet, which captures waves and converts them into a water jet. The performance of the Blow-Jet is found to depend more on wavelength than on wave height. The electrolyser results show, at 0.200 A and 1.88 V, that the electrolysis of water produces 0.082 Nl h⁻¹ of hydrogen and a current efficiency (η_I) of 90.58%.     

Optimal angles for harvesting solar electricity in some African cities

In recent years, the quest for renewable and sustainable energy has been extensive while solar energy has been on the vanguard of sustainable alternative and renewable energy sources due to its clean nature and cost effectiveness for most human activities such as water pumping and electric power generation, amongst others. The off beam installation of Photovoltaic (PV) modules has posed a severe challenge to the optimal functioning of these PV cells despite the abundance of solar irradiation receivable in most African cities. This paper presents the Optimal Inclination Angles (OIA) for mounting PV modules in the absences of a mechanized or automated solar tracking device, for optimum yield in solar electricity generation for some selected African cities using the Photovoltaic Geographic Information Systems (PVGIS) dataset. The OIA of the selected African cities has been identified for optimal solar irradiation exploitation and if the modules are mounted on a horizontal plane, it is expected that considerable amount of solar irradiation would not be harnessed as it has been estimated using the difference from the Irradiation on OIA (Hopt) and the Irradiation on horizontal plane (Hh), whose difference shows that the northern African cities, Algiers, Rabat and Tripoli, are seen to have high levels in unutilized solar irradiation of 780 Wh/m², 760 Wh/m² and 680 Wh/m² respectively while Harare, Lusaka, Maiduguri, Khartoum, Maputo and Luanda would have considerably high levels in untapped solar irradiation of 360Wh/m², 330 Wh/m², 180 Wh/m², 260 Wh/m², 570 Wh/m² and 80 Wh/m² respectively if PV modules are mounted on horizontal plane. However cities such as Bangui, Abidjan and Mogadishu have quite low levels in unexploited solar irradiation of 40 Wh/m², 70 Wh/m² and 10 Wh/m² respectively when PV modules are mounted on horizontal plane. These differences show the amount of solar irradiation which if adequately harnessed, adds to the solar energy potentials of the region.     

Composition-controlled chemical bath deposition of Fe-doped NiO microflowers for boosting oxygen evolution reaction

Water electrolysis for green hydrogen production is gaining tremendous attention in the quest towards sustainable energy sources. At the heart of water splitting technology are the electrocatalysts, which facilitate the two half-cell reactions, i.e., the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with the latter being the most thermodynamically uphill. Herein, we managed to fabricate Ni_1-xFe_xO microflowers (μFs) with varying % of Fe doping (0 < x < 0.36) via an easy chemical bath deposition (CBD) method. The as-synthesized μFs drop-casted on graphene paper (GP) are then applied as electrocatalysts for OER. Compared to contrast catalysts, the electrocatalyst with x_Fe = 0.1 exhibits a lower overpotential of 297 mV at a current density of 10 mA cm⁻², Tafel slope of 44 mV dec⁻¹ and unprecedented turnover frequency of 4.6 s⁻¹ at 300 mV. It is believed that this remarkable electrochemical performance mainly stems from the synergistic effects of Ni and Fe species, working in harmony to enhance charge transfer kinetics and intrinsic activity of the catalyst. This work provides a promising avenue for developing cost-effective and highly active electrocatalysts as advanced electrodes for energy related applications.     

The integration of parabolic trough solar collectors and evacuated tube collectors to geothermal resource for electricity and hydrogen production

In this study, electricity and hydrogen production of an integrated system with energy and exergy analyses are investigated. The system also produces clean water for the water electrolysis system. The proposed system comprises evacuated tube solar collectors (ETSCs), parabolic trough solar collectors (PTSCs), flash turbine, organic Rankine cycles (ORC), a reverse osmosis unit (RO), a water electrolysis unit (PEM), a greenhouse and a medium temperature level geothermal resource. The surface area of each collector is 500 m². The thermodynamics analysis of the integrated system is carried out under daily solar radiation for a day in August. The fluid temperature of the medium temperature level geothermal resource is upgraded by ETSCs and PTSCs to operate the flash turbine and the ORCs. The temperature of the geothermal fluid is upgraded from 130 °C to 323.6 °C by the ETSCs and PTSCs. As a result, it is found that the integrated system generates 162 kg clean water, 1215.63 g hydrogen, and total electrical energy of 2111.04 MJ. The maximum energy and exergy efficiencies of the overall system are found as 10.43% and 9.35%, respectively.     

Energy production from landfill biogas: An italian case

The study considers the “renovation” (as defined by Italian legislation) of an electricity-generating plant using biogas produced in a managed landfill as the primary energy source. The landfill, located in the Marche region (central Italy), receives about 100 kt y⁻¹ of urban and industrial residues. The plant is endowed with two 470 kW (e) internal combustion engines and has been in operation since 1998. At the end of its lifecycle it is scheduled for decommissioning. Public incentives for energy production from renewable sources, which the plant enjoyed in the first eight years of activity, have also expired. The study examines the main legal, technical and economic options available to the landfill management, in particular considering the new Italian and EU incentives for energy generation from renewable sources.Five configurations are considered for the replacement of the existing engines, three at the original site (a single combustion engine with/without incentives, and a plant with microturbines), and two involving the construction of new plants at a separate site (a cogeneration plant with a combustion engine and one with microturbines).The study provides data that may be a useful basis for other similar cases and for simulations.     

Potential for biofuels from the biomass of prickly pear cladodes: Challenges for bioethanol and biogas production in dry areas

Prickly pear is a term used to refer to several species of cactus belonging primarily to the genus Opuntia. In general, these species present an exceptional ability to produce biomass in soil and climate conditions unfavorable for most plant species, in part due to their high water use efficiency. Given the current increase demand for renewable energy and the future prospect of more limited water resources, the potential use of prickly pear cladodes for biofuel production deserves to be investigated. The objectives of this study were to gather information on the chemical composition of prickly pear biomass from the most cultivated varieties in NE Brazil, discuss the potential of processing biomass for ethanol and biogas production and to point out gaps in know-how and priorities for research on this topic. We quantified in the tree varieties studied significant amounts of uronic acids (10.7%) and oxalic acid (10.3%), confirming the reports of high amounts of pectin and calcium oxalate in cladodes of prickly pear. The estimated potential of ethanol production for prickly pear (1490–1875 L ha⁻¹ yr⁻¹) was low when compared to traditional biomass sources (sugarcane and sugar beet, for example). However, it appears that prickly pear stands out as a biomass with potential for high production rates of methane (3717 m³ ha⁻¹ yr⁻¹), being comparable to traditional energy crops. Further studies are needed to assess more consistently both the sustainability of biomass production as the potential for ethanol, and biogas production, specially for newly released varieties of prickly pear.     

Prospects and challenges of using hydropower for electricity generation in Lebanon

In a region characterized by low water resources, Lebanon stands as an exceptional country in the Middle East. Several waterways present ample opportunity for utilization of hydropower. Before the civil war, several projects were undertaken to generate electricity through hydropower. A total installed capacity of 283 MW has aided Lebanon in supplementing its need of electricity from local renewable sources, thus reducing the overall bill of imported energy. The available hydropower generation constitutes currently 4–7% of the electricity generation depending on rainfall, with future plans expected to install another 205 MW of capacity. This use is in competition with water diversion for irrigation. Four different scenarios were analyzed to indicate the share of hydropower in the total production of electricity, with and without future irrigation and power projects, indicating that, by 2020, hydropower's share of electricity generation will vary between a maximum of 6.9% and a minimum of 1.2% depending on government plans regarding water use. Current value of potential energy available when water from the Litani river is used for hydropower is estimated to be around 20 cents per m³. Water uses planned should take this value into account.     

Lanthanum doped copper oxide nanoparticles enabled proficient bi-functional electrocatalyst for overall water splitting

The need for a clean and an environmentally non-degrading sustainable energy resource has grown worldwide due to the huge depletion of other fuel sources, as a result, production of hydrogen by electrochemical water splitting is considered as a potential answer to this pertaining need. However, development of low-cost electrocatalyst as a replacement for Pt and RuO₂ for both Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) remains a significant challenge for the production of hydrogen at a larger scale. This study presents the synthesis of non-noble metal-based lanthanum doped copper oxide nanoparticles as a potential bi-functional electrocatalyst for overall water splitting in alkaline electrolyte. The optimized 1% lanthanum (La) doped CuO electrocatalyst exhibits outstanding OER and HER activity in 1.0 M KOH electrolyte posting a potential of 1.552 V vs RHE for OER and −0.173 V vs RHE for HER at a current density of ~10 mAcm⁻². Significantly, the functional bi-catalyst exhibits a low cell voltage of 1.6 V to achieve overall water splitting at a current density of 10 mAcm⁻² along with long-term stability of 13.5 h for a cell voltage of 2.25 V at a constant current density of 30 mAcm⁻² with only 20% initial current lose after 13.5 h. The results demonstrate that the incorporation of the rare-earth element onto CuO nanoparticles has made it a viable high-end non-noble electrocatalyst for overall water splitting.     

Multi-objective technoeconomic optimization of an off-grid solar-ground-source driven cycle with hydrogen storage for power and fresh water production

Utilizing renewable sources integrated with thermodynamic cycles has been gaining attention in recent years due to being economical and environment-friendly, among which, renewable-energy driven water and power generation systems have shown promising outcomes. In the field of renewable-energy based multi-generation systems (MGS), many recent works have focused on energy analysis or simple optimization. Therefore, in this study, an off-grid solar-geothermal cogeneration system which is able to produce power by Kalina cycle, hydrogen by proton exchange membrane electrolyzer (PEMEC), and freshwater by a multi-effect desalination (MED) unit, was investigated and optimized in terms of economic and energy viewpoints. Unlike previous studies, in this work, a comprehensive multi-objective optimization (MOO) was employed on the system in order to find the optimal working condition. The decision variables of the optimization include flat plate collector area, water mass flow, and ammonia concentration of the Kalina cycle, and the objective functions were levelized cost of electricity (LCOE), payback period (PBP), the overall energy efficiency of the system, and freshwater production of MED unit. Final results show that the system, in its optimum condition, is able to produce 182.09 m³.day⁻¹ fresh water, with energy efficiency, PBP, and LCOE equal to 6.23%, 5.19 years and 0.238 $.kWh⁻¹, respectively.     

Performance of a PEM electrolyzer using RuIrCoOx electrocatalysts for the oxygen evolution electrode

The Proton Exchange Membrane Water Electrolyzer (PEMWE) can be coupled to renewable energy sources (solar radiation and wave energy), which produce the necessary electricity for splitting the water. In this work the performance of a PEMWE using RuIrCoO_x as anodic electrocatalyst had been examined. The oxide powder was synthesized using a chemical reduction method, followed by thermal oxidation. The electrochemical properties of the electrocatalysts were examined by cyclical and lineal voltammetry in 0.5 M H₂SO₄. It was found that RuIrCoO_x oxide electrodes present a stable performance for OER. The PEMWE was designed and in-home built. Chrono-potentiometric experiments were recorded in the current range of 0.25 mA cm⁻² to 75 mA cm⁻² at 300 s. The current pulses length is chosen to be sufficiently long so that the voltage remains constant. Their intrinsic electrocatalytic activity in combination with their large surface area and stability are quite promising for the development of economically feasible electrocatalysts for (PEMWE).     

Energy use patterns and econometric models of grape production in Hamadan province of Iran

This paper examines the energy use patterns and relationship between energy input and yield for grape production in Malayer region of Hamadan Province. Data from 50 farmers were collected using a face-to-face questionnaire method. In the surveyed vineyards, average yield and energy consumption were calculated as 18,530 kgha⁻¹ and 45,213.66 MJha⁻¹, respectively. Among input energy sources, fertilizers, electricity and farmyard manure contained highest energy shares with 37.25%, 19%, and 17.84%, respectively. The energy ratio and energy productivity were found to be 4.95 and 0.42 kgMJ⁻¹.Three econometric models were developed to estimate the impact of energy inputs on yield. The results revealed that impact of chemical, fertilizer and water on yield were significant at 1% probability level. Also, indirect and non-renewable energies were found to be rather high. Sensitivity analysis indicated that among the inputs, chemical has the highest MPP value of energy inputs. RTS (returns to scale) values for grape yield was found to be 2.15; thus, there prevailed an IRS of grape for estimated model. The net return was found to be positive as 2810.56 $ha⁻¹ for grape. The benefit-cost ratio was calculated as 2.08.