Electrospray‐deposited nickel ferrite thin film electrode for hydrogen production in PV‐assisted water electrolysis system

Nanocrystalline Ni ferrite thin film was prepared by electrospray deposition technique and characterized by different analytical techniques at different annealing temperatures. All these films were studied by photovoltaic‐assisted water electrolysis system for solar to hydrogen production efficiency measurement. Highly dense and uniform surface morphology was observed in as‐deposited film, which changed into agglomerated nanocrystalline grains of irregular size and shape with change in annealing temperature. The X‐ray photoelectron spectroscopy study showed that the as‐deposited film was a mixture of an oxyhydroxide form of iron and an Ni₂O₃ form of nickel, whereas it changed into ferrite phase with change in annealing temperature. The as‐deposited film was observed to be of amorphous phase, which changed to crystalline cubic spinel structure with change in annealing temperature. The solar to hydrogen production efficiency was found to increase in a film with an increase in annealing temperature. The film annealed at 500°C showed a high solar to hydrogen production efficiency (8.29%) with constant performance of up to initial 500 h. Thereafter, the performance slowly declined by 11% when up to 1000 h. Copyright © 2011 John Wiley & Sons, Ltd.     

Stability Studies of Ozonized Sunflower Oil and Enriched Cosmetics with a Dedicated Peroxide Value Determination

Ozonized oils have interesting applications in the cosmetic industry and several patents on enriched products were developed in the last years. Ozonides are known for their high reactivity and stability data are required for enriched cosmetic products during storage. In this paper a dedicated determination of Peroxide Value (PV) was performed on ozonized sunflower oil (Neozone 4000) and on some enriched cosmetics, in order to control their stability during storage. The optimal conditions of the PV method were determined, following the decomposition reaction of ozonides with KI utilizing ¹H-NMR and GC/MS techniques.     

Integrated standalone hybrid solar PV,fuel cell and diesel generator power system for battery or supercapacitor storage systems in Khorfakkan,United Arab Emirates

Renewable energy resources play a very important rule these days to assist the conventional energy systems for doing its function in the UAE due to high greenhouse gas (GHG) emissions and energy demand. In this paper, the analysis and performance of integrated standalone hybrid solar PV, fuel cell and diesel generator power system with battery energy storage system (BESS) or supercapacitor energy storage system (SCESS) in Khorfakkan city, Sharjah were presented. HOMER Pro software was used to model and simulate the hybrid energy system (HES) based on the daily energy consumption for Khorfakkan city. The simulation results show that using SCESS as an energy storage system will help the performance of HES based on the Levelized cost of energy (LCOE) and greenhouse gas (GHG) emissions. The HES with SCESS has renewable fraction (68.1%) and 0.346 $/kWh LCOE. The HES meets the annual AC primary load of the city (13.6 GWh) with negligible electricity excess and with an unmet electrical load of 1.38%. The reduction in GHG emissions for HES with SCESS was 83.2%, equivalent to saving 814,428 gallons of diesel.     

Design optimization of grid-connected PV-Hydrogen for energy prosumers considering sector-coupling paradigm: Case study of a university building in Algeria

Integrating sector coupling technologies into Hydrogen (H₂) based hybrid renewable energy systems (HRES) is becoming a promising way to create energy prosumers, despite the very little research work being done in this largely unexplored field. In this paper, a sector coupling strategy (building and transportation) is developed and applied to a grid-connected PV/battery/H₂ HRES, to maximise self-sufficiency for a University campus and to produce power and H₂ for driving electric tram in Ouargla, Algeria. A multi-objective size optimization problem is solved as a single objective problem using the ε-constraint method, in which the cost of energy (COE) is defined as the main objective function to be minimized, while both loss of power supply probability (LPSP) and non-renewable usage (NRU) are defined as constraints. Particle swarm optimization and HOMER software are then employed for simulation and optimization purposes. Prior to the two scenarios investigated, a sensitivity study is performed to determine the effects of H₂ demand by tram and NRU on the techno-economic feasibility of the proposed system, followed by a new reliability factor introduced in the optimization, namely loss of H₂ supply probability (LHSP). The results of the first scenario show that by setting NRU^max = 100%, the system without H₂ provides the best solution with COE of 0.016 $/kWh that reaches grid parity and has 13% NRU. However, by setting NRU^max = 1% in the second scenario, an optimized configuration consisting of grid/PV/Electrolyzer/Fuel cell/Storage tank is obtained, which has 0% NRU and COE of 0.1 $/kWh. In the second scenario, it is also observed that an increased number of trams (i.e. increased H₂ demands) causes a significant reduction in LHSP, COE, NRU and CO₂ emissions. It is thus concluded that the grid/PV combination is the optimal choice for the studied system when considering economic aspects. However, taking into account the growing requirements of future energy systems, grid-connected PV with H₂ will be the best solution.     

An online optimum voltage estimation and real‐time MPP tracking for a PV system

In this paper, a photovoltaic system topology incorporating a new maximum power point tracking (MPPT) controller method is presented. This method uses an autotuning estimator and a PI controller to make the system work in the maximum power point. The controller is formulated based on the bijectivity in the photovoltaic generator characteristic; therefore, if the optimal voltage is reached, this means that the maximum of power is obtained. The proposed MPPT algorithm is implemented on a dSpace DS1104 controller board. In order to demonstrate the efficiency of the proposed algorithm in real time, an experimental setup using a boost converter connected to a resistive load is successfully implemented and studied. The obtained experimental results prove the validity of the proposed MPPT algorithm.     

Effect of partial shading conditions on off-grid solar PV/Hydrogen production in high solar energy index regions

In present work, the effect of partial shading on off-grid solar PV/hydrogen production in solar energy has been studied. The study was designed to stimulate future work in this area and to help demonstrate PV/hydrogen production. Four different electrodes in the study were coated and used in PV/Hydrogen Production. Pt anode and four different cathode materials which were Cu, Cu/Ni, Cu/NiBi and Cu/NiMo were used in the study. Data obtained from 105 W PV panel via automation system installed at ATU University, Adana, in Turkey were used for data of days representing different seasons by electrolysis experiment. The experiments were carried out between 08:00 and 16:00. The main contribution of this study is to produce hydrogen by using a part of the electrical energy gained from the solar panels, and at the same time to reveal the effect of the electrical energy produced by the partial shading of the panels on the hydrogen production. Furthermore, the effect of cathode material type was investigated for the impact of partial shading on hydrogen production. Results showed that Cu/NiMo has better hydrogen production efficiency than Cu/Ni, Cu/NiBi. The lowest efficiency was observed in the bare Cu electrode.     

Power quality assessment in 3-Ф grid connected PV system with single and dual stage circuits

This paper addresses the assessment of power quality (PQ) in 3-Ф grid connected photovoltaic (PV) system that consists of single and dual stage power extraction circuits. The single stage circuit comprises of Z-source inverter (ZSI) controlled by space vector pulse width modulation (SVPWM), while dual stage is traditional boost based voltage source inverter controlled by sinusoidal pulse width modulation. The PQ of signals in both the circuits is analyzed during transient variations like solar intensity and load conditions, with/without use of hybrid filter. The simulation and experimental results suggest an improved smooth sinusoidal waveform available at PCC in case of ZSI based circuit using hybrid filter, if power quality improvement is of prime importance with both linear and nonlinear load connected in the system.     

Research on the influence of PV cell to thermal characteristics of photovoltaic/thermal solar system

In the paper, we analyzed internal thermal transmission characteristics of water‐heating photovoltaic/thermal (PV/T) solar collector covered by photovoltaic (PV) cell, established photothermal conversion model of PV/T solar system, and analyzed the influence of PV cell coverage to photothermal characteristics of PV/T solar system. Results show that the thermal efficiency of PV/T solar system by optimizing PV cells coverage can reach 68%. In addition, by designing four water‐heating PV/T solar system prototypes with PV cell coverage of 0.4, 0.56, 0.7, and 0.82, respectively, we conducted experimental researches for the four prototypes and found that the four prototypes can achieve thermal efficiencies of 58%, 51%, 64%, and 67%, respectively, in heating 250 L of water to 50°C. The experiment results are consistent with theoretical analysis results, indicating that it is feasible to improve thermal characteristics of PV/T solar system by optimizing PV cell coverage. Copyright © 2017 John Wiley & Sons, Ltd.     

Fire behaviour and external flames in corridor and tunnel‐like enclosures

This work investigates how the inflow, the burning and the outflow develop in a corridor open to one end having a fire at either the closed or open end. The situation of a corridor fire having a fire source at the close end is a situation similar to a tunnel having a fire source at the centre of the tunnel without ventilation. A gaseous propane burner is used to produce the fire at a prescribed fuel flow rate in a long corridor of aspect ratio up to 6:1 having a rectangular cross section and varying door‐like openings. Gas temperatures using thermocouple trees, heat fluxes in the corridor and on its façade, flame heights of emerging flames and total heat release rates (HRRs) are measured as the fuel flow rate of propane increases gradually and linearly with time to a preset maximum value. For over‐ventilated conditions, the flames remain near the fire source at the closed end of the corridor. Unexpectedly, it is established for under‐ventilated conditions that the inflow of air is not affected by the aspect ratio of the corridor or the location of the burner in the corridor and that the vertical distribution of gas temperatures inside the enclosure is nearly uniform with height everywhere. In addition, the flame heights and heat fluxes on the façade are the same as those for aspect ratios of the corridor from 1:1 to 3:1 examined in previous work. Moreover, as the conditions changed from over‐ventilated to under‐ventilated conditions, the flames migrated in a ghostly manner from the closed end to the open end of the corridor as soon as under‐ventilated conditions were established. The speed of migration of the flames from the back to the front has also been inferred from the thermocouple tree measurements, which also indicate that the flow conditions ahead and after the passing of the front are changed. These results can be applied to interpret some of the observed behaviours of fires in long corridors or tunnels without ventilation. Copyright © 2012 John Wiley & Sons, Ltd.     

Measuring the rebound effect: A case study of residential photovoltaic systems in San Diego

This study examines the effect of solar photovoltaic system installation on the electricity consumption in residential households across various geographic regions in San Diego. Using meter-level data, the electricity consumption for residential households is calculated before and after installation to assess whether there are any significant rebound effects in usage. Results reveal significant variations in the change in electricity usage depending on geographical location. The findings are relevant to regional resource planning and climate response, as the failure to account for the rebound effect may result in significant overestimation of the energy and emissions benefits of distributed renewable energy adoption.