Improved Electricity Production Research Articles

Sediment Microbial Fuel Cells with Algae-Assisted Cathodes for Electricity Generation and Bio-Treatment of Sewage Sludge

In this study, an algal–bacterial symbiotic consortium was integrated with the sediment microbial fuel cell (SMFC) to construct an algal–bacterial cathode SMFC (AC-SMFC) for excess sewage sludge treatment and electricity generation. A bacterial cathode SMFC (BC-SMFC) and a static settling system (SS-system) were used as controls. Electrochemical analysis confirmed that the algal–bacterial biofilm on the cathode improved electricity production. The maximum power density of AC-SMFC was 75.21 mW/m2, which was 65.70% higher than that of the BC-SMFC (45.39 mW/m2). After 60 days of treatment, AC-SMFC achieved much higher removal efficiencies of the total chemical oxygen demand (TCOD) (59.60%), suspended solids (SS) (62.42%), and volatile suspended solids (VSS) (71.44%) in the sediment, compared to BC-SMFC and the SS-system, exhibiting an effective degradation of the organic matter in the sediment sludge. Moreover, the lower concentration of total nitrogen (TN) and total phosphorus (TP) in the overlying water of AC-SMFC demonstrated that the algae on the cathode could inhibit the accumulation of nitrogen and phosphorus released from the sediments. The three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy revealed that the tryptophan protein and aromatic protein in the loosely bound extracellular polymeric substances (LB-EPS) of the sediment sludge in the AC-SMFC were significantly decreased. Additionally, the abundance of functional microbiota in the AC-SMFC increased, such as Trichococcus, Alphaproteobacteria, and Clostridia, which contributed to electricity generation and sludge degradation. The combined application of microalgae and the SMFC provided a promising approach for excess sludge reduction and energy recovery.

Enhanced power generation with disordered porous carbon-modified foam iron–nickel anode in human urine-driven microbial fuel cell

Microbial fuel cell is a promising way for renewable energy recovery. The direct conversion of urine into electricity through MFC has been tested, considering that urine has rich organic substances and high conductivity, demonstrating dual benefits for electricity generation and urine treatment as a feasible method. However, it still suffers from several constraints relating to anodes, including limited bacterial loading capacity and inferior extracellular electron transfer efficiency. Substantial efforts have been made to improve electricity production, especially to develop new anodes. In this study, we prepared a new composite anode (SC-FeNi) and used it in an MFC reactor to recover energy from urine. The power density of the SC-FeNi anode could reach 524.93 mW·m−2 when using synthetic urine and increased to 1720.1 mW·m−2 when replaced with undiluted human urine, which was the highest power density in monomer MFC fueled with urine to the best of our knowledge. SC-FeNi had high conductivity (12.29 S·m−1), large specific surface area (1236.417 m²·g−1), and enriched high microorganism density (312.04 ± 15.4 mg·cm−³). The stable power generation period in batch mode reached 288 h. This experiment verified that combining foam metal and disordered porous carbon as MFC electrode materials could generate energy from human urine waste with high efficiency and durability.

Equivalent circuits studied by means of electrochemical tests employing different inoculum and simultaneous treatment during bioelectricity production in a single chamber-microbial fuel cell

Microbial fuel cells (MFC) have attracted the attention of scientists due to their capacity to improve electricity production and to employ wastewater as substrate. This duality results in a source of clean energy and degradation of the organic matter. The use of catalysts such as platinum make the implementation of these technologies difficult, therefore, it is a challenge to find economically feasible options and strategies carry out studies. Stream sediments (SS) and anaerobic granular sludge (AGS) were compared in a single chamber-MFC. Reactors constructed with Plexiglas contained carbon cloth cathode treated with polystyrene, graphite felt anode, and acetate as substrates. The voltage was measured with a digital multimeter, whereas power density and Coulombic efficiency were calculated based on Ohm’s law. The electrochemistry impedance spectroscopy analysis was determined with an equivalent circuit model resistances. AGS-MFC produced 1.35 mW/m2 and 30 mA/m2, while SS-MFC produced 1.25 mW/m2 and 20 mA/m2 of power density and current density, respectively. AGS-MFC showed a 10% greater Coulombic efficiency compared to the one obtained from the SS-MFC. In this research, the effect of the inoculum on power density in an MFC was evaluated with the objective of finding sources of microorganisms with better capacities for electricity production and organic matter degradation. The equivalent circuit model showed that AGS-MFC obtained the lowest charge transfer resistance value and the highest constant phase elements values. AGS was the inoculum that showed the best performance in the MFC in terms of voltage and power density.

Enhanced degradation of Metronidazole by the coupling of photocatalytic and microbial fuel cell: Mechanism and electrochemistry characteristic

In this study, the attempt was made to enhance the degradation of the typical antibiotics, metronidazole (MNZ) by coupling three-electrode photocatalytic and microbial fuel cell systems (PMFC). The PMFC reactor was constructed, and the photocatalytic bioanode, attached with TiO2, was synthesized and characterized using SEM, EDS, XPS methods. The stability of microbial on bioanode was tested during acclimatization process. Electrochemical characteristics, including power density, CV and EIS curve, were analyzed to explore the advantage of power generation and higher electron transfer interaction in the PMFC. Compared with the traditional MFC system, the improved degradation and enhanced mineralization of MNZ were achieved, and the 1.30 and 1.24-fold increase in MNZ and TOC removal were realized, respectively. The three degradation pathways of MNZ were identified by LC-MS in the coupling PMFC, and the intermediates were more easily to further degrade and mineralize. The structure of the microbial community was demonstrated, and the functional species consisted of MNZ degradation bacteria, exoelectrogens, hydrocarbon removal bacterial, and nitrogen removal bacterial, were largely enriched in the PMFC, contributing to the improved electricity production, MNZ degradation and photoelectric effect. Moreover, the photoelectric played the selective role in the enrichment of functional microbial. The study provides a promising and environmentally approach for the treatment of containing antibiotics wastewater in the practical application.

Wind energy potential assessment for co-generation of electricity and hydrogen in the far North region of Cameroon

The fast increase of Cameroon population growth rate and the actual shortage of electricity plaguing the country, particularly in remote areas, give rise to great challenges in the energy generation sector. Nowadays, renewable and clean energy sources are used to foster and improve electricity production via hydrogen generation with water electrolysis. This paper therefore scrutinizes the wind energy potential alongside the electricity and hydrogen generation from wind energy for the cities of Kousseri, Kaele, Maroua, Mokolo, Mora and Yagoua in the Far North Region of Cameroon using wind speed data recorded at 10 m, 40 m and 70 m heights for the years 2011–2021. Several performance indicators including the wind power density, wind turbines power output, wind turbines capacity factor, hydrogen production, cost of produced electricity and hydrogen and payback period are utilized to evaluate the techno-economic viability of the system. This assessment was carried out employing twenty-two commercially accessible wind turbines. Our findings revealed that, Kousseri displays the best hydrogen output with yearly hydrogen production ranging from 3.5054 to 53.232 tons of hydrogen. The annual compressed hydrogen to be saved in this region was found to be in the range of 92.5049 to 1404.70 m3. Enercon E-48/800 turbine records the highest capacity factor in all the chosen locations with the lowest cost of energy varying from 0.0578 $/kWh at Kousseri to 0.0838 $/kWh at Mora. The lowest cost of hydrogen was found to be 4.3865 $/kg for Kousseri, 5.5284 $/kg for Kaele, 5.7160 $/kg for Maroua, 5.9439 $/kg for Mokolo, 6.5065 $/kg for Mora and 6.3354 $/kg for Yagoua employing GE 1.5SL turbine. The highest annual energy output of 3193.9, 2738.1, 2488.4, 2393.9, 2153.3 and 2323.1 MWh was acquired at Kousseri, Kaele, Maroua, Mokolo, Mora and Yagoua, respectively. The shortest payback period was found to be 2.9 years which was related to the case where Enercon E-48/800 wind turbine was assumed to be installed at Kousseri. Finally, the maximum CO2 emission minimization to be achieved if electricity produced by wind turbine is utilized in place of oil burning power plant and power plant that burns natural gas as fuel was 885.36 tons of CO2 and 641.60 tons of CO2, respectively.

Novel feedwater preheating system for parabolic trough solar power plant

Several improvements in the referenced parabolic trough power plant (PTPP) model (Andasol II) have been implemented by APROS software. The main advantage of this novel feedwater preheating system is to improve electricity production and evening operation hours at a low cost for modifying an existing PTPP in Spain. This in turn leads to less dependence on fossil fuels during the evening and cloudy periods. The reference model is improved by an increase in the collector loops in the reference solar field (SF) model to 208 loops rather than 156 loops to increase the absorbed thermal power, increasing the capacity of the thermal storage system (TSS) from 1017 MWth h to 1,360 MWth h to improve the night operating period, replacing the Feedwater/Steam circuit with a Feedwater/HTF circuit using five shell and tube counter-current heat exchangers that are used instead of condenser heat exchangers. The HTF enters the fifth low-pressure preheater with 128 kg/s and 393 °C in the daytime and 377 °C at night. The main advantage of this improvement is to use the entire generated steam within the steam turbine and not to heat the feedwater in the feedwater circuit. In addition, the control circuits are modified and added new controllers with new limitations for controlling the new operating conditions. This development is the first attempt in the field of research to use a Feedwater/HTF circuit in the PTPP in order to enhance performance. This improvement (optimization 1) in turn leads to a raise in the total HTF mass flow and the quantity of stored molten salt, as well as increasing the mass flow of HTF to the power block (PB). According to optimization 1, no steam will be taken out of the HP and LP-turbine toward the feedwater circuit. Therefore, the feedwater fed through new preheaters is heated by thermal oil instead of steam extractions. The predictions obtained from this optimization are compared to the simulated results that were previously extracted from the reference model on clear and cloudy days for evaluation of the behaviour of the optimized PTPP. It should be mentioned here that it can be used the same turbine and generator in the actual power plant to achieve this increase in the performance of the power plant, according to the technical data of manufacturers. Finally, an economic study of the cost was conducted for referenced and the optimized PTPP depending on the levelized energy cost (LEC). The findings reveal that the levelized energy cost of the optimized PTPP with storage energy is about 10.5% lower than that of the referenced PTPP.

Thermodynamic analysis on a novel bypass steam recovery system for parabolic trough concentrated solar power plants during start-up processes

Most concentrated solar power plants undergo daily start-up and shut-down processes, which consume much energy. If the start-up energy losses can be recovered, the power plant efficiency may be enhanced. The energy loss of bypass steam is one of the major start-up energy losses, but the method to recover bypass steam is absent. Therefore, we proposed a novel system to recover bypass steam by integrating a steam accumulator, and the recovered bypass steam was used to replace the extraction steam of regenerative heaters. The dynamic models of the bypass steam recovery system were developed, and the design parameters and discharging strategy of the steam accumulator were optimized. Results show that simultaneously increasing the initial pressure and volume of the steam accumulator can increase recovered exergy, and switching the regenerative heater received steam during the steam accumulator discharging process can improve electricity production. The optimal initial pressure and volume of the steam accumulator are 2.6 MPa and 246.4 m3, respectively, by balancing the tradeoff between the annual electricity production and the steam accumulator volume. Integrating the steam accumulator with optimal design parameters can improve the annual electricity production by 1.1 GWh (0.55%) for a 50 MW parabolic trough concentrated solar power.

Improved electricity production and nitrogen enrichment during the treatment of black water using manganese ore-modified anodes

The decline of fossil fuel availability is calling for alternative energy such as electricity produced by degradation of waste in microbial fuel cells. The performance of microbial fuel cells is controlled by the anode because microorganisms grow and attach on the anode. Here, we prepared carbon felt electrodes modified with manganese ore based on the hypothesis that manganese and silicon oxides would improve the cell performance to treat simulated black water. We compared properties of the manganese ore-modified electrodes with properties of classical carbon felt electrodes modified with magnetic ferroferric oxide. We also studied the removal of the chemical oxygen demand and the enrichment in ammonia nitrogen. Results show that the maximum voltage of the manganese ore-modified carbon felt electrode is 1.7 times higher than that of the magnetic ferroferric oxide-modified carbon felt electrode. The start-up time to reach the maximum voltage is reduced by 68%. The removal of chemical oxygen demand reached 91.2%. Up to 68.0% of ammonia nitrogen can be enriched at the cathode, implying that ammonia nitrogen can be highly reduced in the effluent. Overall, the manganese ore-modified carbon felt electrode showed excellent redox performance, excellent corrosion resistance and low electron transfer resistance.

Reconstruction of a Genome-Scale Metabolic Network for Shewanella oneidensis MR-1 and Analysis of its Metabolic Potential for Bioelectrochemical Systems.

Bioelectrochemical systems (BESs) based on Shewanella oneidensis MR-1 offer great promise for sustainable energy/chemical production, but the low rate of electron generation remains a crucial bottleneck preventing their industrial application. Here, we reconstructed a genome-scale metabolic model of MR-1 to provide a strong theoretical basis for novel BES applications. The model iLJ1162, comprising 1,162 genes, 1,818 metabolites and 2,084 reactions, accurately predicted cellular growth using a variety of substrates with 86.9% agreement with experimental results, which is significantly higher than the previously published models iMR1_799 and iSO783. The simulation of microbial fuel cells indicated that expanding the substrate spectrum of MR-1 to highly reduced feedstocks, such as glucose and glycerol, would be beneficial for electron generation. In addition, 31 metabolic engineering targets were predicted to improve electricity production, three of which have been experimentally demonstrated, while the remainder are potential targets for modification. Two potential electron transfer pathways were identified, which could be new engineering targets for increasing the electricity production capacity of MR-1. Finally, the iLJ1162 model was used to simulate the optimal biosynthetic pathways for six platform chemicals based on the MR-1 chassis in microbial electrosynthesis systems. These results offer guidance for rational design of novel BESs.

Electricity Consumption and Economic Growth: Evidence from South Asian Countries

The purpose of this study is to shed light on the nexus between electricity supply and economic growth in South Asian countries during 1990–2018. The study employs Pedroni’s panel cointegration test as well as Dumitrescu and Hurlin’s (DH) causality test for panel data. The empirical results confirm a long-term relationship between electricity supply and economic growth. We fail to reject the non-causal relationship between electricity supply and economic growth for the panel, thereby affirming the neutrality hypothesis. Single country causality analysis reveals the growth hypothesis in the case of Pakistan. These results have a number of policy implications. For example, governments can introduce measures to improve energy efficiency in Bangladesh, India and Sri Lanka without fear of harming economic growth. The results for Pakistan may also imply that fostering green energy generation would lead to a positive effect on economic growth via improved electricity production. The government may use various policy tools to stimulate adoption of renewable energy, such as fiscal incentives, low interest loans, or grants for rural populations to speed up the green energy transformation.

Bacterial Competition for the Anode Colonization under Different External Resistances in Microbial Fuel Cells

This study investigated the effect of external resistance (Rext) on the dynamic evolution of microbial communities in anodic biofilms of single-chamber microbial fuel cells fueled with acetate and inoculated with municipal wastewater. Anodic biofilms developed under different Rext (0, 330 and 1000 ohms, and open circuit condition) were characterized as a function of time during two weeks of growth using 16S rRNA gene sequencing, cyclic voltammetry (CV) and fluorescence microscopy. The results showed a drastic difference in power output of MFCs operated with an open circuit and those operated with Rext from 0 to 1000 ohms. Two steps during the bacterial community development of the anodic biofilms were identified. During the first four days, nonspecific electroactive bacteria (non-specific EAB), dominated by Pseudomonas, Acinetobacter, and Comamonas, grew fast whatever the value of Rext. During the second step, specific EAB, dominated by Geobacter and Desulfuromonas, took over and increased over time, except in open circuit MFCs. The relative abundance of specific EAB decreased with increasing Rext. In addition, the richness and diversity of the microbial community in the anodic biofilms decreased with decreasing Rext. These results help one to understand the bacterial competition during biofilm formation and suggest that an inhibition of the attachment of non-specific electroactive bacteria to the anode surface during the first step of biofilm formation should improve electricity production.

Life cycle assessment of molten carbonate fuel cell system for power plants

This study evaluated the environmental impacts of a 2.5 MW molten carbonate fuel cell (MCFC) system on impact categories such as climate change (CC), abiotic resource depletion (ARD), acidification (AC), and eutrophication (EU) using a life cycle assessment (LCA) methodology with the functional unit of 1 kWh electricity. Because MCFC systems produce electricity and heat simultaneously, the allocation was performed based on the amounts of exergy contents between electricity and heat (0.636 and 0.364, respectively). The impact on CC, expressed in global warming potential (GWP), was estimated as 3.53E-01 kg CO2 eq./kWh, while the impact on ARD was 1.90E-03 kg Sb eq./kWh, the impact on AC was 3.05E-04 kg SO2 eq./kWh, and the impact on EU was 1.35E-05 kg PO43− eq./kWh. The main cause for the impact on CC was found to be the reforming of liquefied natural gas in the operation stage. For the other categories (ARD, AC, and EU), the contributions of the operation stage were also over 80%. A comparison of the MCFC system with the Korean grid mix showed that the environmental impacts of the grid mix were larger than those of the MCFC system. Several improvement strategies were simulated to reduce the GWPs. First, to improve the efficiency of the heat exchanger, instead of using the heat generated by the MCFC system to produce high-temperature steam as is currently done, the generated heat was proposed to be used to produce medium or low-temperature water. This change reduced the GWPs of the MCFC by approximately 1.72E-02 kg CO2 eq./kWh. Second, this study simulated with an improved electricity production efficiency, with an increase from its current level (45%) to the theoretical maximum value of 60%. This improvement achieved a reduction of approximately 4.00E-02 kg CO2 eq./kWh. Finally, the electricity production efficiency was further increased using unreacted hydrogen, resulting in a reduction of 2.70E-02 kg CO2 eq./kWh.

Finding 10% hidden electricity in crystalline Si solar cells using PDMS coating and three‐dimensional cell arrays

AbstractOver the decades, solar cells have been developed to achieve higher energy conversion efficiency. However, the fabrication of modules has resulted in electricity production loss, but this has not attracted as much attention as the solar cells. As a result, the improved performance of solar cells has not been fully revealed at the panel scale. Furthermore, the standard testing conditions, such as 1 sun, AM1.5, which is very strong incident light, does not fully reflect the electricity production capabilities of solar panels because of performance degradation under oblique and weak illumination. Simple modification of the module fabrication process, including poly‐dimethylsiloxane (PDMS) coatings and three‐dimensional (3‐D) structured modules by one‐directional angled arrays of each cell, has revealed 13.4% extra hidden electricity in solar panels with some types of crystalline silicon (Si)‐based solar cells through high transmission to short wavelength light, recapture of the light reflected from Si solar cell surface textures by the PDMS coating and enhanced power production under oblique incident light or scattered light through a 3‐D module. Further studies to find hidden electricity should be followed by the development of solar cell device structures to improve electricity production, rather than being restricted to optimizing energy conversion efficiency.

Enhancing copper recovery and electricity generation from wastewater using low-cost membrane-less microbial fuel cell with a carbonized clay cup as cathode

Abstract The recovery of low concentrations of copper in wastewater for industrial reuses meets the goals of circular economy. This work develops a modified clay cup (MCC) that can be used as a cathode in a membrane-less microbial fuel cell (ML-MFC) because of its porosity, adsorption and conductivity. The ML-MFC was then used to treat copper-containing wastewater and generate electricity. Cu2+ is removed from wastewater and electricity produced primarily by the adsorption of Cu2+ in the wastewater onto the MCC, reducing its inhibitory effects on biodegradation. Cu2+ in wastewater can be reduced in an MFC to form copper-containing compounds on the surface of the MCC. Cu2O can be used as a catalyst to modify the cathode to improve electricity production. In seven days ML-MFC with a power density of 113.7 mW/m2 removed 96.5% of the Cu2+. At neutral pH, Cu2O was observed on the surface of the MCC and modification of cathode reduced the internal resistance of the ML-MFC by 30%, increasing the output voltage. Cyclic voltammetry revealed a redox peak current at pH 7 that was 1.11–5.45 times under other conditions. This work demonstrates the feasibility of using an MCC cathode to increase the recovery of Cu2+ and the generation of electricity by an MFC.

Construction of Efficient Bio-Electrochemical Devices; An Improved Electricity Production from Cyanobacterium (Leptolyngbia sp.) Based on π-Conjugated Conducting Polymers/Gold Nanoparticles Composite Interfaces

In this study, the electrochemical communication of Lyptolyngbia sp. (CYN82) were accomplished using two different DtP type conducting polymers 4-(4H-Dithieno[3,2-b:2’,3’-d]pyrrole-4-yl)aniline, P(DtP-Py-NH2) and 5-(4H-dithieno [3,2-b:2’,3’-d]pyrol-4-yl) naphtalene-1-amine, P(DtP-Nptyl-NH2) via electropolymerization. After that, p-aminothiophenol and 2-mercaptoethane functionalized AuNPs were cross-linked to DtP polymers modified GE as a result of electropolymerization. Bioelectrodes were obtained by attaching of Leptolyngbia sp. onto the conducting polymer/AuNP modified GEs and stabilized on the electrode surface by using a dialysis membrane. These electrode structures were generated enhanced photocurrent due to high wiring capacity and high electron transfer ability. Electrons are formed as a result of oxidation in CYN82 by photosynthesis in water under visible light is easily transferred to the GE by DtP/AuNP structure (Figure 1). Photocurrent experiments were proved the transfer of electrons were achieved and the effect of P(DtP-Py-NH2) and P(DtP-Nptyl-NH2) polymers reveal that the photocurrent obtained from the electrode using polymer is almost eight-fold greater than the electrode without using polymer. This result indicates that the polymer is highly effective in electron transfer. Another important point in obtaining the enhanced photocurrent is the use of gold nanoparticles in the electrode structure. Results clearly show that the photocurrent measured from the electrodes with AuNP is higher than the other electrodes (without AuNP). Conductivity of AuNP and oligoaniline bridges serves a very suitable surface for fast electron transfer from CYN82 to the gold electrode. A 25 nA cm-2 photocurrent was observed by GE/Leptolyngbia sp.. After the electrode modifications, a significant improvement in the photocurrent up to 630 nA cm-2 was achieved. Bioelectrodes P(DtP-Py-NH2)/AuNP/CYN82 and P(DtP-Nptyl-NH2)/AuNP/CYN82 were tested with diuron, clorpyrifos and atrazine which are the important pesticides as by the decrease in photocurrent which is resulted from inhibition of photosynthesis by pesticides [1].

Construction of efficient bioelectrochemical devices: Improved electricity production from cyanobacteria (Leptolyngbia sp.) based on π-conjugated conducting polymer/gold nanoparticlecomposite interfaces.

In this study, gold electrodes (GE) were coated with conducting polymers to obtain a high photocurrent using cyanobacteria from a novel bioelectrochemical fuel cell. For this purpose, 4-(4H-ditiheno[3,2-b:2',3'-d]pyrol-4-yl) aniline and 5-(4H-dithieno[3,2-b:2',3'-d]pyrol-4-yl) napthtalane-1-amine monomers were coated on GE by performing an electropolymerization process. After that, gold nanoparticles (AuNP) were specifically modified by 2-mercaptoethane sulfonic acid and p-aminothiophenol toattach to the electrode surface. The conducting polymers GE coat was modified with functionalized AuNP using a cross-linker. The resulting electrode structures were characterized by cyclic voltammetry and chronoamperometry under on-off illumination using a fiber optic light source. Cyanobacteria Leptolyngbia sp. was added to the GE/conducting polymer/AuNP electrode surface and stabilized by using a cellulose membrane. During the illumination, water was oxidized by the photosynthesis, and oxygen wasreleased. The released oxygen was electrocatalytically reduced at the cathode surface and a 25 nA/cm 2 photocurrent was observed inGE/ Leptolyngbia sp. After the electrode modifications, a significant improvement in the photocurrent up to 630 nA/cm 2 was achieved.

Green roof and photovoltaic panel integration: Effects on plant and arthropod diversity and electricity production

The combination of green roofs with photovoltaic (PV) panels has been proposed to provide synergistic benefits as the panel is cooled by the presence of the vegetation, and thus produces more electricity, while the solar panel enhances growing conditions for vegetation, and increases abiotic heterogeneity, resulting in higher plant diversity. We tested these hypotheses in a non-irrigated green roof in a Mediterranean climate with replicated plots including green roofs only, green roofs with a PV panel, and a conventional roof surface with a PV panel. We found that presence of a panel resulted in higher heterogeneity in substrate moisture, but there was no effect on plant diversity. Plant species showed enhanced growth in plots with PV, including greater growth of Sedum sediforme and longer flowering time of annual species. On the other hand, arthropod diversity was lower during part of the year, and abundance of some arthropod taxa was lower in green roof plots with PV. The presence of the green roof also did not improve electricity production by the panels. We conclude that in a Mediterranean climate, it would be appropriate to examine the use of irrigation in green roofs with PV panels, including effects on the plant community and on electricity production.

Application of Adaptive Time Delay Model in Optimal Control of a Hydropower Cascade

Small hydropower plants (SHP) are increasingly constructed in recent years as a substitution of the use of conventional energy materials such as wood and fossil fuel in remote rural regions. Besides new constructed plants, upgrading operational strategies of existed systems for increasing electricity productivity is also significant. Motivated by this issue, a combination of two techniques, simulation and optimization based on models is frequently used to improve the operation regimes of coordinated reservoir cascades. However, the application of a complex hydraulic model consumes a huge computation time. Hence, this paper proposes a replacement for the complex hydraulic model by an adaptive time delay (ATD) model. The cutting- edge point is that the ATD model is able to quickly predict the system dynamics both in simulation and optimization. This ATD model consists of only two parameters: time constant and time delay which are functions of unsteady flow and can be easily derived from complex hydraulic models (HECRAS, MIKE11), or from physical parameters of rivers (flow rate, roughness, bed slope, cross section). The integration of the ATD model into the simulation and optimization techniques will be demonstrated by a case study of a cascade of SHPs. In terms of optimization, a non-linear constrainted optimization algorithm is applied to improve electricity production to meet the scheduled demand.

The potential of SO2 for reducing corrosion in WtE plants

Due to the high-temperature boiler corrosion induced by chloride-rich fly ash deposits, steam generation in today’s Waste-to-Energy (WtE) plants is typically designed only for 40 bar/400 °C as an economic compromise between acceptable corrosion rate and maximum power generation. The high-corrosive metal chlorides in the fly ash can react with SO2 forming low-corrosive sulfates. The sulfation efficiency is enhanced by high SO2 levels and sufficient residence time of the flue gas at high-temperatures (700–900 °C). The fly ash sulfation was tested in full scale in a Swedish WtE plant by applying the economic sulfur recirculation method. Probes of several alloys (16Mo3, Inconel 625, Sanicro 28) were exposed for 1000 h at controlled material temperatures in the superheater position, at normal and during sulfating operation respectively. Analyses of the fly ash showed that the molar Cl/S was decreased to values well below 1 and the corresponding corrosion rates of the individual material samples were less than half when sulfur recirculation was in operation. These positive findings demonstrate that the sulfur recirculation process has high potential for low-corrosive high-temperature steam generation (T ≈ 500 °C) and improved electricity production. Further steam superheating can be realized by staged superheating using small amounts of secondary fuel.

Institutional Capacity Building and Legal Reform in Iraq: Toward Innovation and Public Administration Modernization

AbstractIraq is often cited as a test case as to whether “nation-building” can work. Since 2003, the U.S. government has been advancing institutional capacity development with Iraq’s national government. Now 10 years later, it is clear that the program, the largest such as U.S. government program since the Vietnam War, has been a success. Tangible durable institutional reforms are now in place to professionalize the civil service, improve electricity production, make public procurement more transparent and efficient, and upgrade budget formulation and execution. The program, known locally as USAID/Tatweer, worked across executive branch agencies, to improve government performance and expand institutional capacity development. Its accomplishments, so far almost entirely unrecognized by the media, will continue to advance democratic change in Iraq for generations to come.