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Abstract Thermal performance of three naturally ventilated public buildings in which the wind tower is an important architectural freature is studied. One of the three builidings as well as it's wind tower is instrumented for temperature, relative humidity and airflow velocity measurements, and the other two are instrumented for temperature measurement. The results have led to a discussion concerning the degree of wind tower effectiveness in achieving thermal comfort.

Abstract Molten nitrate salts are widely used as heat transfer and energy storage medium in Concentrated Solar Power (CSP) systems. Solar Salt (60 wt% NaNO3-40 wt% KNO3) is the commercial binary molten nitrate salt, which is the preferred energy storage material with high density, high specific heat, low melting point, high thermal stability, and low vapor pressure. This paper explored the effects of impurity Cl− on the thermophysical properties of Solar Salt, including liquidus temperature, density, viscosity, and thermal stability. The results showed that Cl− can significantly reduce the liquidus temperature, and when Cl− was less than 0.5 wt%, the liquidus temperature of molten salt system decreased within 1 °C. On the other hand, Cl− had little effect on the density, viscosity and thermal stability of the mixed molten salt system at 400 °C, but at high temperature Cl− will promote the volatilization of components. By analyzing the thermostatic stability at 565 °C, it was found that the total mass loss changes less than 0.3% when Cl− was less than 0.01 wt%. After comprehensive analysis, the conclusion is that the upper limit of Cl− is preferably less than 0.1 wt% for keeping good thermal performances of Solar Salt.

Abstract The vacuum solar receiver is the key component of a parabolic trough solar plant, which plays a prominent role in the gross system efficiency. Recently, China’s first high temperature vacuum receiver, Sanle-3 HCE, has been developed and produced by Southeast University and Sanle Electronic Group. Before being utilized in China’s first parabolic trough solar plant, accurately estimating the thermal properties of this new receiver is important. This paper first establishes and optimizes a 1-D theoretical model at Matlab program to compute the receiver’s major heat loss through glass envelope, and then systematically analyzes the major influence factors of heat loss. With the laboratorial steady state test stand, the heat losses of both good vacuum and non-vacuum Sanle-3 receivers were surveyed. Comparison shows the original 1-D model agrees with the ends covered test while remarkably deviating from end exposed test. For the purpose of identifying the influence of receiver’s end to total heat loss, an additional 3-D model is built by CFD software to further investigate the different heat transfer processes of receiver’s end components. The 3-D end model is verified by heating power and IR temperature distribution images in the test. Combining the optimized 1-D model with the new 3-D end model, the comparison with test data shows a good accordance. At the same time the heat loss curve and emittance curve of this new receiver are given and compared with those of several other existing receivers as references.

Abstract A new method of tracking the maximum power point (MPP) of a photovoltaic (PV) module exploiting the effects of the inherent characteristic resistances of the photovoltaic cells is proposed in this paper. An analysis of the mathematical model of the IV characteristic of the PV module revealed a possibility of estimating the MPP from its characteristic parameters such as the open circuit voltage (Voc), short circuit current (Isc), series resistance (Rse) and the shunt resistance (Rsh). The first stage of estimation process, for obtaining the voltage at the MPP, was facilitated by the effects of the series and shunt resistance on the IV characteristic of the PV module and the second stage of estimation process was facilitated by the combined process of the first stage of estimation and the condition for extracting the maximum power from the mathematical model of the pv characteristic of the PV module. The estimated voltage at the MPP in the second stage of estimation was found very close to the true MPP. The effectiveness of tracking the MPP with the proposed method has closely matched with the true MPP. This was validated by the results obtained through simulations and experiments. An analysis of the effects of degradation on the performance of the proposed technique showed that the performance was excellent during the first few years and with the update of characteristic resistances in the proposed algorithm the performance was found to be almost invariant. The successful experimental results obtained with a 100 Wp PV module indicate that the technique can be favourably implemented for standalone PV power systems.

Abstract Exergy analysis is very helpful for reducing irreversibility and rising the efficiency of solar collectors. The major objective of the present study is to organize a review on exergy analysis of different parabolic solar collectors. The effects of various flows and geometrical parameters of parabolic thermal collectors on the exergy efficiency were presented and discussed. In addition, comparative study was carried out to select the best solar thermal system for maximum exergy efficiency with minimal thermal losses. This study indicated that the hybrid nanofluids enhanced the exergy efficiency significantly as compared to without hybrid nanofluids. Passive techniques comprising twisted tape inserts, fins and insertion of swirl devices in the stream for changing the stream patterns causes to interrupt the thermal boundary layer and accordingly high exergy efficiency. This review would also throw light on the scope for further research and recommendation for improvement in the existing solar thermal collectors. Finally, this work will be beneficial for the scholars working on exergy analyses of solar parabolic collectors.

Abstract Cu2BaSn(S,Se)4 (CBTSSe) solar cells are emerging photovoltaic devices due to their high theoretical efficiencies of ~31%, environment-friendly and earth-abundant composition, low density of non-recombination defects, and so on. However, the record efficiency of CBTSSe solar cell is only 5.2%, showing the importance of studying their performance via numerical analysis to further enhance their practical efficiencies. In this paper, the effect of absorber and buffer layers on performances of Cu2BaSnS4 (CBTS) solar cells are firstly systematically studied via the SCAPS-1D software to provide a platform for the study of the effect of MoS2 interlayer on the performances of CBTS solar cells. The highest PCE of CBTS solar cell with a 30 nm CdS buffer layer is 11.87%. The PCE of CBTS solar cell with a 0.8 μm CBTS absorb layer is 12.51%, indicating that the CBTS solar cell is a potential low-cost solar cell due to its large optical absorption coefficient (α > 104 cm−1). The efficiency of CBTS solar cell is improved to 16.47% when the carrier concentration of CBTS is 1016 cm−3. The relationship between the performance of solar cell and the band gap, thickness, donor concentration, acceptor concentration of MoS2 interlayer is systematically investigated on the basis of the optimized efficiency. It is found that MoS2 interlayer plays an important role in the performance of CBTS solar cell. The p-type MoS2 has a beneficial effect on the efficiency improvement while the n-type MoS2 has a negative effect on the efficiency enhancement. The highest PCE of CBTS solar cell is as high as 18.28% when the thickness and the acceptor concentration of MoS2 are 4 nm and 1019 cm−3, respectively. Our simulation result provides a promising research direction to further improve the actual efficiency of the CBTS solar cell.

Abstract Morphology control is critical to achieve high efficiency CH3NH3PbI3 perovskite solar cells (PSC). In this paper, fluorinated perylene diimide (FPDI) was used as novel organic electron transport material in planar heterojunction perovskite solar cells. The perovskite film was fabricated by sequential vacuum vapor deposition, and the film morphology could be controlled by optimizing the FPDI film morphology with short time solvent spin-coating or solvent vapor annealing (SVA). Dense and uniform perovskite film with high substrate coverage could be obtained when the FPDI film was treated by chloroform SVA for half an hour, and the fill factor (FF) of the perovskite solar cell increased from 30.44% to 55.20%, enhancing the power conversion efficiency (PCE) from 3.23% to 7.44%. The PCE of the best device reached 7.93%, which was comparable to that (8.25%) of the conventional ZnO electron transport layer based perovskite device prepared by the same method.

Abstract Bifacial solar cells that can generate electricity from either front or rear side are regarded as advanced photovoltaics for markedly increased photoelectric conversion efficiency. We present here the fabrication of transparent RuSe counter electrodes by an alternating electrodeposition method for bifacial dye-sensitized solar cells (DSSCs). The catalytic and photovoltaics performances are maximized by tuning stoichiometric Ru/Se ratio and bilayer number. Upon irradiation by AM1.5 (100 mW cm−2), the device yields a maximized front efficiency of 8.72% and a rear efficiency of 5.9%, arising from the >80%-transparency of RuSe electrode in visible light region. This strategy provides new opportunities for fabricating high-performance DSSCs.

Abstract In flat-plate PV/T systems, there are some contradictions in the temperature requirements for the heat and electricity acquisition. The widely-used crystalline-silicon solar cells are negatively affected by the high temperature inside the PV/T collector. This paper proposes to use temperature-insensitive solar cells in PV/T and the CdTe used has the advantages of low power temperature coefficient, high photovoltaic efficiency, and low costs. Besides, the sandwich structure that CdTe cells are sealed between two pieces of glass can prevent them from the permeating of moist air. The CdTe-PV/T is experimentally tested and compared with a Poly-Si-PV/T system and it exhibits better instantaneous electrical performance at high operating temperatures and gains more electrical energy throughout the day. Then the influence of cells’ coverage ratio is investigated experimentally and the result shows that a higher coverage ratio is beneficial to the electrical and energy-saving performance. Furthermore, a new quasi-steady-state mathematical model is established and verified. Parametric discussions are conducted for performance optimization. The black TPT coating with higher emissivity performs better than the selective absorption coating of the absorbing plate, contrary to the traditional PV/T collector. The heat transfer mode between the back glass and the absorbing plate is different in different thicknesses of the air gap. Reducing the thickness can effectively improve the system’s performance in terms of thermal, electrical, and temperature. Then an improved CdTe-PV/T eliminating the backglass and air gap is proposed and numerically simulated. This research hopes to provide some ideas for the applicant and the optimization of CdTe-PV/T in hot climates.