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Abstract A new formulation for the evaporation, flashing, condensation processes taking place in the effects of thermal desalination systems which simulates the operation of both forward and parallel/cross configurations is coupled with an exergo-economic model based on the SPECO method. The thermo-economic model uses accurate properties for the seawater, brine, pure water and vapour and is solved with an equation solver which does not require the development of a specific solution algorithm as in most previous studies. This flexible model is used to analyze the influence of the number of effects N and the temperature difference ΔT e between effects on the technical and economic performance of multi-effect desalination systems with ejector vapour compression. In particular, it is shown that the performance calculated by an earlier black-box approach is not attainable by technically and economically realistic systems. It is also shown that for each feed configuration and a given number of effects there exists an optimum value of ΔT e which minimizes the cost of the produced potable water. This last result forms the basis of a procedure that combines black-box results with the optimum value of ΔT e and can be used to select the appropriate system for any specific application.

Abstract In this paper, energy and exergy analyses of the geothermal-based hydrogen production via thermochemical water decomposition using a new, four-step copper–chlorine (Cu–Cl) cycle are conducted, and the respective cycle energy and exergy efficiencies are examined. Also, a parametric study is performed to investigate how each step of the cycle and its overall cycle performance are affected by reference environment temperatures, reaction temperatures, as well as energy efficiency of the geothermal power plant itself. As a result, overall energy and exergy efficiencies of the cycle are found to be 21.67% and 19.35%, respectively, for a reference case.

This paper presents different Maximum Power Point Tracking (MPPT) methods belonging to different classes as well as two overviews. The first was about the procedures used in the test and evaluation of MPPTs. The second is an overview of Fuzzy Logic Controller (FLC) MPPTs and improved MPPTs. Conventional MPPTs such as Perturb and Observe (P&O), Hill Climbing (HC) and Incremental Conductance (InCond); Improved MPPTs (are the modified versions of conventional MPPTs) such as Improved Incremental Conductance (Improved-InCond) and intelligent MPPTs such as FLC have been implemented and tested under two different levels of irradiance and temperature. A detailed description about the hardware and software implementation platforms (designed and built in our laboratory) is provided. Based on measured data, the MPPTs under consideration have been evaluated and compared in terms of different criteria, showing the advantages and disadvantages of each one. The comparison results showed that Improved-InCond gives a fast convergence to the MPP(Maximum Power Point). Whereas, FLC is able to adapt to the variation of irradiance and temperature levels. Thereby, a good performance is obtained wherein the MPP is reached in a short time as well as the power ripples are very small.

Abstract Biomass materials are renewable sources that abundant worldwide due to natural plants and living organisms. Lignocellulosic biomass can be categorized as hardwood, softwood, agricultural wastes, and grasses. Agricultural residues those which of them have importance due to being produced in huge amounts in the worldwide annually. Food wastes and agricultural wastes are utilized either alternative use such as generating energy, fuels or disposal. However, disposal of these residues is follow out either scraping or burning way. This study aims to convert industrial agricultural origin biomass by using hydrothermal carbonization method to carbon-based material having high conductivity for use in supercapacitor production by using different activating chemicals. Hydrothermal carbonization was applied to different biomass samples such as nutshell, hazelnut shell, and corn cob. The elemental analysis of the obtained biochar was carried out and it was determined that the highest source of biomass was corn cob. The selected biochar has been chemically activated with different chemicals such as KOH, NaOH, H3PO4 and, ZnCl2. Advanced carbonization of activated biochar was carried out at 500, 600, 700 and 800 °C with 1, 1.5 and 2-h retention times. The resulting carbon-based products were mixed with KBr and identical pellets were prepared and their electrical conductivity values were measured. Electrical conductivity results, NaOH-800 °C-2h and ZnCl2-700 °C-1.5 h obtained from the process prepared from the biocidal pellets were determined to have the highest conductivity value. Brunauer–Emmett–Teller (BET) and Scanning Electron Microscope (SEM) analyses of the samples with the highest conductivity values were performed and surface morphologies were examined.

Abstract Oxy-combustion with a circulating fluidized bed (Oxy-CFBC) can facilitate the separation of high CO2 concentration and reduce emissions by biomass co-firing. This study investigated Oxy-CFBC characteristics such as temperature, solid hold-up, flue gas concentrations including CO2, pollutant emissions (SO2, NO, and CO), combustion efficiency and ash properties (slagging, fouling index) with increasing input oxygen levels (21–29 vol%), and biomass co-firing ratios (50, 70, and 100 wt% with domestic wood pellet). The possibility of bio-energy carbon capture and storage for negative CO2 emission was also evaluated using a 0.1 MWth Oxy-CFBC test-rig. The results show that combustion stably achieved with at least 90 vol% CO2 in the flue gas. Compared to air-firing, oxy-firing (with 24 vol% oxygen) reduced pollutant emissions to 29.4% NO, 31.9% SO2 and 18.5% CO. Increasing the biomass co-firing from 50 to 100 wt% decreased the NO, SO2 and CO content from 19.2 mg/MJ to 16.1 mg/MJ, 92.8 mg/MJ to 25.0 mg/MJ, and 7.5 mg/MJ to 5.5 mg/MJ, respectively. In contrast to blends of sub-bituminous coal and lignite, negative CO2 emission (approximately −647 g/kWth) was predicted for oxy-combustion only biomass.

Abstract The aim of this work is to determine the optimum operating conditions for the process of preparing anode electrocatalysts for direct sodium borohydride fuel cell (DSBHFC). Pt–Au/C electrocatalysts were studied as the anode catalysts while Pt/C were chosen as a cathode catalyst. Anode electrocatalysts were produced by the precipitation method. In this work, pH, temperature, drying time and Pt/Au ratio were selected as independent process parameters and their effects on dependent parameters, such as power density and hydrogen production rate, were investigated using response surface methodology (RSM). Based on this methodology, it was found that the maximum power density and the minimum hydrogen production rate were 354.4 mW cm−2 and 30 ml min−1 respectively. These findings were obtained at 90 °C, 9.27 pH, 61.07 h of drying time, and 93.54% Au ratio to total metal ratio.

Abstract The urges of reducing energy use and carbon footprint in buildings have prompted the developments of regenerative evaporative coolers (RECs). However, the physical dimensions of RECs have to be designed enormous in order to deliver a large amount of supply airflow rate and cooling capacity. To tackle the issue, this paper develops a large-scale counter-flow REC with compact heat exchanger through dedicated numerical modelling, optimal design, fabrication and experimentation. Using modified e-NTU method, a finite element model is established in Engineering Equation Solver environment to optimise the cooler's geometric and operating parameters. Based on modelling predictions, the cooler's experimental prototype was optimally designed and constructed to evaluate operating performance. The experiment results show that the cooler's attained wet-bulb effectiveness ranges from 0.96 to 1.07, the cooling capacity and energy efficiency ratio from 3.9 to 8.5 kW and 10.6 to 19.7 respectively. It can provide sub-wet bulb cooling while operating at high intake channel air velocities of 3.04–3.60 m/s. The superior performance of proposed cooler is disclosed by comparing with different RECs under similar operating conditions. Both the cooler's cooling capacity per unit of volume and per unit of airflow rate are found to be 62–108% and 21.6% higher respectively.

A dual-mode seasonal solar thermochemical sorption energy storage system using working pair of expanded graphite/SrCl2-NH3 was constructed and investigated. Solar thermal energy is transformed into chemical bonds in summer, and the stored energy is released in the form of chemical reaction heat in winter. Two working modes are performed to produce heat with expected temperature according to the different ambient temperatures in winter. The direct heating supply mode is adopted at a relatively high ambient temperature. The effective energy storage density is higher than 700kJ/kg and the corresponding system COP is 0.41 when the heat output temperature and ambient temperature are 35oC and 15oC, respectively. The specific heating power increases with the decrease of heat output temperature for a given ambient temperature. The temperature-lift heating supply mode is adopted to upgrade the heat output temperature at a low ambient temperature below 0oC. It can produce heat with a temperature above 70 oC although the ambient temperature is as low as -15oC. It is desirable to further improve the system performance using low mass ratio and high global conversion. Experimental results showed the advanced dual-mode thermochemical sorption energy storage technology is feasible and effective for seasonal solar thermal energy storage.