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Abstract The optimal sizing of a hybrid system of renewable electricity is an important phase in its design. As long as the cost of the capital equipment is the major component in the price of renewable electricity. This paper presents the application of one of the latest swarm intelligence algorithms, namely Grey Wolf Optimizer (GWO) which is inspired from grey wolves. The GWO algorithm mimics the leadership hierarchy and hunting mechanism of grey wolves in nature. The proposed strategy is applied for optimal design and minimizes the total cost of the hybrid power generation system in isolated rural village in south Algeria named “Djanet”. A power system consisting of a photovoltaic array panel, diesel generator, Battery banks and load is considered for tested the proposed approach. The results obtained by this new method are compared with Particle Swarm Optimization (PSO) algorithm; there are shows that the proposed methodology finds the optimal number of PV panels, diesel generators and battery banks easily with fast convergence, lower cost and the superior capabilities of this proposed method are demonstrated.

Abstract The previous researchers have developed a variety of liquid thermal solar collectors designs for water heating. It was reported by the other authors, that metal heat pipes applications to liquid solar collectors, especially to evacuated glass tube ones, is an efficient solution for water heating plants. However, the majority of thermal solar collectors do not meet the requirements on small weight, easy assembly and installation, versatility, scalability, and adaptability of the design, which are particularly important when they are facade integrated. Very high hydraulic resistance, from 2000 Pa to 20,000 Pa, in liquid solar collectors and low thermal efficiency of some of them, less than 0.5, also are the problems to be solved by the developers. Current research is proposing to apply extruded aluminum alloy made heat pipes of original cross-sectional profile with wide fins and longitudinal grooves in order to avoid the above-mentioned drawbacks of liquid thermal collectors. Absorber plate of flat collectors could be composed of several fins. Fins at the opposite end of the heat pipe serve as a heat sink surface. Multiple tests proved that new lightweight and inexpensive heat pipes show high thermal performances. Maximum heat transfer power of one heat pipe is up to 210 W; and its thermal resistance is very low – from 0.02 to 0.07 °C/W. Hydraulic resistance of flat plate solar collector and evacuated one utilizing aluminum profiled heat pipes, could be reduced to less than 100 Pa, at the same time their thermal efficiency is rather high, up to 0.72. In the issue of authors study, the feasibility of the developed aluminum profiled heat pipes application to thermal solar collectors was proved; and they can be successfully integrated to building facades and roofs.

Abstract The paper was motivated by the need to extend the utility of a solar water heating system by adjusting a heat exchanger in the hot water tank. An approximate dynamic model, composed of two linear differential equations, is used in an attempt to describe the transient performance of the system. This model is digitized in time, the result being in the form of a set of finite difference equations. Using experimental data the parameters of the model are identified by linear regression. These parameters are computed for various flow rates of the feed water through the heat exchanger in order to obtain a global representation of the system. The theoretical results were tested by simulation and were proved to be sufficiently close to the experimental ones.

Abstract In this work, we used solar energy converted via photosynthesis into chemical energy of the biomass of the fast-growing perennial herb Miscanthus × giganteus for the manufacture of nanocellulose (NC) films, which are biodegradable alternative to common petroleum-based polymer substrates used in flexible electronics. To create the NC substrates, we applied an environmentally friendly method of organosolv delignification of plant raw materials carried out at a low temperature and in a relatively short time. Then by means of the low-temperature cheap and scalable method Successive Ionic Layer Adsorption and Reaction (SILAR) we deposited copper iodide (CuI) film of 0.72 µm thickness on both sides of the 12 µm thick NC substrate, and thus obtained light-weight and flexible biodegradable nontoxic thermoelectric material CuI/NC. Crystal structure, morphology, chemical composition, and optical, electrical and thermoelectric properties of the CuI/NC have been researched. Studies have shown that nanostructured p-type semiconductor CuI film in the CuI/NC TE material is quite dense and completely covers the NC surface. It has typical optical direct band gap ≈ 3.0 eV, is single-phase γ-CuI with crystallite sizes in the 19–25 nm range, with moderate dislocation density of (1.6–2.8) × 1015 lines/m2, and tolerable microstrains e of (4–9) × 10−3 a.u. The determined value of the Seebeck coefficient S is ~228 μV K−1, at that, S is constant in the temperature range 290–335 K. Together with the thermoelectric power factor ≈ 36 μW·m−1·K−2it is favorable for the use of CuI/NC as new thermoelectric material for an in-plane design of biodegradable flexible thin film thermoelectric generator (TEG). At temperature gradient of 50 K, the single p-CuI thermoelectric leg made from CuI/NC strip of 3 cm long and 0.5 cm wide generates open circuit voltage 8.4 mV, short circuit current 0.7 µA and maximum output power 1.5 nW. It corresponds to the output power density 10 µW/m2, and thus confirms the suitability of CuI/NC to obtain electricity by the harvesting the waste environmental heat.

Abstract Here we applied solar energy converted into biomass to produce efficient biodegradable flexible hydrophobic thermoelectric (TE) material with nanocellulose (NC) film as environmentally friendly functional substrate. We used fast-growing perennial herb Miscanthus × giganteus to manufacture flexible 12 µm thick NC film with stable monoclinic cellulose structure (Iβ), high crystallinity index (CI = 78%) and average crystallite size 3 – 4 nm. Through the low-temperature cheap and scalable method Successive Ionic Layer Adsorption and Reaction (SILAR) we deposited copper iodide (CuI) films on NC substrates and thus obtained non-toxic TE materials CuI/NC, which can be water-repellent, as their contact angles reach 140°. In the most efficient TE sample CuI/NC, the obtained via SILAR 0.39 µm thick nanostructured CuI film consists of cubic (1 1 1)-oriented γ-CuI crystals with faceted surfaces of ~200–300 nm. The high electrical conductivity (σ) and shape of the σ vs. temperature (T) curve of this CuI/NC sample is realized through suppression of grain boundary scattering due to tunneling currents in CuI. The CuI/NC material has large thermoelectric power factor (PF) that grows with increasing temperature and reaches value 140 μW·m−1·K−2 at T = 333 K. This PF is the record for biodegradable flexible thermoelectric materials. At ΔT = 40 K the CuI/NC-based single p-CuI thermoelectric leg generates open circuit voltage 3.5 mV, short circuit current 4 µA, and power 3.8 nW, and these output parameters can be further improved through a thickening the CuI film in CuI/NC by increasing the number of SILAR cycles.

Abstract In this work we present utilization of solar energy for a creation of biocompatible, biodegradable, and renewable thin film transparent materials that can protect against overabundant ultraviolet (UV) radiation and high energy visible (HEV) light of solar spectrum. From biomass of herbaceous plants Miscanthus × giganteus and Phragmites australis we obtained nanocellulose suspensions NCm through acid hydrolysis and NCp through TEMPO oxidation, respectively. These suspensions transformed into corresponding transparent flexible NCm and NCp nanocellulose films and used as substrates for 0.17 – 0.23 µm thick nanostructured layers of wide band gap semiconductor CuI deposited via wet chemical method Successive Ionic Layer Adsorption and Reaction (SILAR) to obtain promising visibly transparent UV- and HEV-shielding materials CuI/NCm and CuI/NCp. Under this investigation, we compare UV- and HEV-shielding properties of transparent NCm, CuI/NCm, NCp, and CuI/NCp flexible samples depending on structure, surface morphology, chemical composition, optical properties, and thickness. It is shown that the best CuI/NCp sample with 0.23 µm thick CuI film and 8 µm thick NCp substrate has optical transmittance up to 82% for visible light at wavelengths above 500 nm, blocks 65% of high-energy visible radiation, and has excellent sun protection factor (SPF = 112).

This study presents an analysis of the effect of the transport delay which occurs in solar flat-plate collector fields and how to include its behavior in dynamic models suitable for control purposes. This investigation has been carried out using simplified models based on dynamic energy balances and models based on step response methods and experimental tests. The solar flat-plate collector field encompasses parallel absorber pipes inter- twined with pipelines which act as several first-order plus dead time systems in parallel. The effect is an apparent delay observed at the outlet temperature that must be included in the dynamic model in order to reduce the error between the real measurement and the model prediction. The main contribution of this paper is the procedure to evaluate the apparent delay to obtain adequate dynamic models aimed to be used for control purposes.

Abstract This paper outlines the development of models of a solar field designed to provide thermal energy to a Multi-Effect Desalination (MED) plant. The dynamic model can be used both for simulation and control purposes. Some of these models have been developed based on static and dynamic energy and mass balances, and some others are based on step response methods (experimental tests). The solar field comprises a flat-plate collector field, an air cooler, a heat exchanger and the corresponding pipelines and interconnections. The main purpose of the solar field is to feed the MED unit with hot water within a specific temperature range using two thermal storage tanks as input buffers to the MED system. The main achievement of this paper is that the developed model provides an adequate tradeoff between complexity and performance.

Abstract In this paper, a solar water heating system (SWHS) based on 4 m2 flat plate collectors is integrated to an office building to ensure the heat demand. The SWHS is equipped with Labview software and a multichannel digital card that makes the system control and data acquisition automatic. A TRNSYS model is developed and validated against experimental data and then used for optimization purposes. A sensitivity approach based on the Design of Experiments method and dynamic simulations is proposed to optimize the solar fraction. For this purpose, 134 simulations have been carried out. Metamodels of the solar fraction have been then established for three ranges of the collector area; namely, [2–10] m2; [10–20] m2 and [20–30] m2. The results have shown that the solar fraction is highly dependent on the collectors’ area and the storage volume. Furthermore, the impact of the pump control strategy on the solar fraction has increased with larger systems. Finally, optimum design parameters have been obtained using the fitted models to achieve the targeted solar fraction of 60%. The proposed approach could be used for the optimization of solar heating systems design.