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Abstract This paper presents a theoretical and experimental study of the transient adsorption characteristics of vertical packed porous bed. The theoretical model describes the effect of independent parameters (time and vertical distance through the bed) on the vertical gradient of adsorbable fluid in the bed. A simplified analytical solution, for specific operating conditions, is also presented. In the experimental study, porous granules of burned clay are applied as a desiccant carrier in the fixed bed. The granules of the packed bed are impregnated with liquid calcium chloride solution to form the porous adsorbing surface. The isothermal adsorption of water vapour from atmospheric air using the prepared bed is experimentally studied. Transient values of the mass of adsorbed water vapour, solution concentration and vapour pressure through the bed layers are evaluated from the experimental measurements. The model output, which show the effect of dimensionless relative time (Tr) on the potential ratio (C−C ∗ )/(C−C ∗ 0 ) , is compared with the experimental results and good agreement is found.

Abstract Ever-growing energy demands and unacceptable emissions from fossil fuel combustion are major driving forces for expanding alternative, green energy sources. Hydro-power is one promising ecological alternative to meet these energy requirements. Such systems do not require any weir or dam and, thus, can be employed with minimum ecological impact. However, available designs are not yet suitable as efficient water energy converters, in particular for conditions corresponding to low water speeds (as mostly found in practice), due to low power output. Savonius turbines are particularly robust and cost-efficient, but show a poor efficiency. This article aims at maximizing the output power of a hydraulic Savonius turbine by modifying the blade profile. The main difference in this work compared to previous studies is that the blade shape of the concave and convex sides evolve independently from each other (no constant blade thickness). Twelve geometrical parameters are involved during shape optimization. To obtain optimal conditions, many transient computational fluid dynamics (CFD) simulations are performed using the industrial flow simulation code Star-CCM+, driven by the in-house optimization library OPAL++ relying on evolutionary algorithms. The optimization process takes into account the output power coefficient ( C p ) as a target function. Compared to the traditional Savonius turbine, a relative increase of C p by almost 12% is obtained at a tip speed ratio of 1.1. The performance of the optimal geometry was compared to the standard design over the whole range of operation. This comparison revealed additionally that the performance was improved by almost 15% at a tip speed ratio of 1.2. The performance of the optimal design is superior for the whole range of operation, particularly at a tip speed ratio exceeding 0.8. Finally, it was checked that the optimal design is still self-starting.

Abstract In terms of supercapacitor electrode materials, biomass derived carbon electrodes are gaining much attention as a viable option for practical applications. Obtaining unique carbon nanostructures can significantly promote the electrochemical performance. Waste potato peel (WPP) derived hierarchical porous carbon materials with heteroatoms doping can boost the development of efficient and economical electrodes with improved charge storage capabilities. Here, we report sulfur and phosphorus co-doped porous activated carbon (S, P/PAC) as an effective supercapacitor electrode material with a large specific surface area. More importantly, the S, P/PAC not only acquires dual heteroatoms doping for promoting capacitive performance but also possesses fascinating porous features which are beneficial to shorten ion adsorption distances and enlarge the contact area. The electrode exhibits a high specific capacitance of 323 F g−1 at 1 A g−1, acceptable rate capability and good cycling stability after 5000 cycles. The constructed symmetric supercapacitor device with a wide operational potential window of 1.6 V achieves a maximum energy density of 45.5 Wh kg−1 at a power density of 800 W kg−1 with an improved long cycle life (94.3 retention after 10 000 consecutive cycles).

The valorisation of lignin is being increasingly recognised to improve the economics of pulp and paper making mills. In the present study, an integrated lignin–glycerol valorisation strategy is introduced with an overarching aim for enhancing the process value chains. LignoBoost kraft lignin was subjected to base-catalysed depolymerisation using glycerol as a co-solvent. The generated bio-oil was used as a renewable additive to biodiesel for enhancing the oxygen stability. The influence of three independent parameters including temperature, time and glycerol amount on lignin depolymerisation was investigated. Response surface methodology was applied to design the experiments and to optimise the process for maximising the yield and antioxidant impact of bio-oil. The results showed that glycerol has a positive qualitative and quantitative impact on the produced bio-oil, where an enhancement in the yield (up to 23.8%) and antioxidant activity (up to 99 min induction period) were achieved using the PetroOxy method (EN16091). The addition of 1 wt% bio-oil on biodiesel led to an improvement in the oxidation stability over a neat sample of up to ∼340%, making it compliant with European standard (EN14214). The proposed process presents a biorefinery paradigm for the integrated utilisation of waste cooking oil, lignin and glycerol.

Abstract Dust accumulation on glass plates with different tilt angles and associated reductions in solar transmittance have been experimentally investigated over a period of 1 year under the climate conditions of the Minia region, middle of Egypt. The glass plates were never cleaned during the experiment duration of 1 month to allow dust to accumulate. The results showed that the fractional reduction in glass normal transmittance depends strongly on dust deposition in conjunction with plate tilt angle, as well as on the exposure period and site climate conditions. Based on the data obtained, an empirical correlation, accurate to ±6%, is developed which allows for the calculation of the reduction in glass transmittance for a given tilt angle after a number of days of exposure to the atmosphere. For design purposes and in the absence of any specific data, the literature comparisons encourage the use of the correlation for other neighboring regions along the desert belt that extends from the Atlantic Ocean to the Persian Gulf. For moderately dusty places, weekly cleaning of the glass covers of solar panels is strictly recommended as part of the maintenance routine, but equipment should be cleaned immediately after a dust storm to retain nominal operating efficiency.

Abstract The foam-mat drying technique is used to dry fruit syrups into powder. Literature has indicated that solar energy has not yet been used in this field. Thus, it is the object of the present work to dry the foamed syrups of different fruits in a solar energy augmented drying unit. This leads to a saving in both energy and environmental pollution. An auxiliary heater, along with a control unit, is used to ensure drying at constant temperature. Foaming is effected by suitable edible additives and in some cases a stabilizer is needed as well. New techniques concerning the concentration and neutralization of fruit syrup were reached. The drying experiments were run on orange, lemon, grapefruit, tomatoes, strawberry, guava and apple. The results showed that foaming decreased the time of drying by 30.8–41.5% in the case of direct sun drying and by 47.1–73.2% in the case of solar drying compared to the drying time of unfoamed syrup. The present study showed that the solar-augmented foam-mat drying technique proves to be of sufficient efficiency and acceptability to replace spray drying which is known to be a highly complicated and energy-consuming technique.