•The combination of solar collector and LNG based on cascade ORC is innovative.•The proposed equivalent efficiency is original and significant.•An equivalent efficiency of 5.99% is achieved with ...isopentane/R125 and ETC.•The hybrid system has a faster return on solar power investment than a solar ORC.
A cascade organic Rankine cycle (ORC) system utilizing solar energy and liquefied natural gas (LNG) for thermal power generation is proposed. Energy from solar collectors drives the evaporation of working fluid in the top cycle (I). The heat released by cycle I facilitates the evaporation of working fluid in the bottom cycle (II). LNG is the cold source of cycle II. The system is optimized with respect to a new index, i.e., the equivalent efficiency, which denotes the ratio of the extra electricity produced by adding collectors and the received solar irradiation. Its advantages are clarified in comparison with existing indices like thermal efficiency, cold energy efficiency, and exergetic efficiency. The effects of working fluids on the system performance are investigated. Flat plate collectors (FPC) and evacuated tube collectors (ETC) are exemplified. It is shown that the equivalent efficiency is the most suitable index to embody the effectiveness of combination of solar collectors and LNG. A maximum equivalent efficiency of 5.99% can be obtained on the use of isopentane/R125 and ETC. The volume ratio for each expander in the cascade ORC is much smaller than that in single-stage ORC, thereby resulting in easier design and manufacture of the expanders.
In this work, microwave-assisted steam distillation (MASD) extraction method followed by gas chromatography/electron capture detection (GC/ECD) was developed for the determination of organochlorine ...pesticides (OCPs) and pyrethroids in the Chinese teas. MASD is a combination of microwave-assisted extraction (MAE) and steam distillation techniques. Water vapor generated by microwave irradiation is used to accelerate desorption of the analytes from the sample, and the nonpolar organic solvent used for trapping the analytes is kept from direct contact with the sample by the water. Therefore, relatively clean extracts were obtained compared to the method directly using organic solvent as extraction solvent, such as ultrasonic extraction (USE). Microwave power of 200
W and irradiation time of 2
min was found to be the optimum conditions for the MASD process, and
n-heptane was chosen as the analyte-trapping solvent in the study. Five OCPs (α-HCH, γ-HCH, dicofol,
p,
p′-DDE,
p,
p′-DDT) and two pyrethroids (bifenthrin, fenvalate) were determined using this extraction method in the tea samples. The relative standard deviation (R.S.D.) of the analytes varied from 2.2 to 8.4%, and the method detection limits (MDLs) found were lower than 0.23
μg/kg. The recoveries of the seven compounds in the Jasmine tea sample were between 84.04 and 110.1%. Comparative results obtained by MASD and USE were also discussed in the study.
The blind is an effective device for controlling solar heat gain through the window. However, the usage of it exists the issues of overheating in summer and low heat gain in winter. Meanwhile, ...formaldehyde is a common indoor gaseous pollutant in buildings. Here, we proposed a novel double-skin ventilated window integrated with air-purifying blind, which could improve the overheating issue in summer and the solar thermal efficiency in winter while realize formaldehyde degradation at the same time. Then the system heat and mass transfer model was developed and verified, the impacts of various parameter on system performance were analyzed. Finally, the performance comparison of the double-skin ventilated window with air-purifying blind and shading blind applied in Hefei was performed. Main results were: (1) The model had the high accuracy in terms of thermal transfer, optical behavior and air purification. (2) The optimal slat angle and position of blind applied in winter and summer were 20° and 50o, 0.3 m and 0.7 m, respectively. (3) Compared with shading blind, the double-skin ventilated window with air-purifying blind could improve the thermal and visual comfort, and the saved thermal energy was 23.9 kWh/m2 in winter and 78.8 kWh/m2 in summer.
•A novel double-skin ventilated window integrated with air-purifying blind.•The developed and verified thermal, mass transfer and purification coupled model.•The optimal slat angle and position of air-purifying blind.•The excellent performance of double-skin window with air-purifying.
This paper aims to study the preparation and viscoelastic properties of asphalt binder modified by tetrahydrofuran soluble fraction (THFS) extracted from direct coal liquefaction residue. The ...modified asphalt binders, which blended with SK-90 (control asphalt binder) and 4%, 6%, 8% and 10% THFS (by weight of SK-90), were fabricated. The preparation process for asphalt binder was optimized in terms of the orthogonal array test strategy and gray correlation analysis results. The properties of asphalt binder were measured by applying Penetration performance grade and Superpave performance grade specifications. In addition, the temperature step and frequency sweep test in Dynamic Shear Rheometer were conducted to predict the rheological behavior, temperature and frequency susceptibility of asphalt binder. The test results suggested the optimal preparation process, such as 150 °C shearing temperature, 45 min shearing time and 4000 rpm shearing rate. Subsequently, the addition of THFS was beneficial in increasing the high-temperature properties but decreased the low-temperature properties and resistance to fatigue. The content analysis of THFS showed the percentage of 4~6% achieved a balance in the high-and-low temperature properties of asphalt binder. The asphalt binder with higher THFS content exhibited higher resistance to rutting and less sensitivity to frequency and temperature.
Building integrated photovoltaic (BIPV) glazing is currently regarded as a promising building material with a wide range of benefits. Photovoltaic combined vacuum glazing is a relatively new ...innovative concept in BIPV glazing. On the other hand, photovoltaic combined hybrid vacuum glazing (PVCHVG) is a rarely studied topic in which an air gap exists between vacuum glazing and photovoltaic glazing to form an insulated glazing unit. This paper investigates the overall energy-saving performance of a CdTe-based semi-transparent PVCHVG. A dynamic simulation model was developed and validated with an outdoor experiment to explore the energy-saving performance of the PVCHVG under five different climate conditions in China, and the results were compared with commonly used window systems. The results indicated good insulation properties against both heat loss and heat gain due to the combined action of vacuum glazing and semi-transparent photovoltaic glazing. Compared to clear single-glazing and double-glazing window systems, PVCHVG can save overall energy consumption up to 59.39% and 39.97% in heating-dominated region, and 76.33% and 73.766% in cooling-dominated region, respectively. Furthermore, the PVCHVG window system generated electricity with a good performance ratio and total system efficiency ranging from 85.7% to 85.78% and 7.45%–7.55%, respectively, considering five climate conditions.
•A CdTe-based STPV glazing combined hybrid vacuum glazing is investigated.•A dynamic simulation model is developed and validated with an outdoor experiment.•It poses inferior heat loss and heat gain in 5 distinct climate conditions in China.•The energy-saving potential is better in cooling than heating-dominated regions.•Key performance parameters for the window PV system are discussed.
The effects of using fumed SiO
2, MCM-41, and SBA-15 as supports for Ru and Ni catalysts on ammonia decomposition were investigated. It was found that the supported catalysts on these siliceous ...materials are more active than those supported on ordinary silica. In general, the supported Ru catalysts are more active than the Ni catalysts, and MCM-41 is the best support material for Ru and Ni. Significant enhancement in activity was observed when the supported Ru catalysts were modified by KOH, but such effect was minimal in the cases of supported Ni catalysts. The results of N
2 adsorption and transmission electron microscopy studies revealed that the Ni particles of Ni/MCM-41(TIE) prepared by template-ion exchange (TIE) method are largely located inside the pores of MCM-41. Compared with the Ni/MCM-41(IMP) catalyst prepared by impregnation method, the Ni/MCM-41(TIE) catalyst exhibited appropriate Ni dispersion and weaker Ni/support interaction, and consequently higher catalytic activity. In terms of the remarkable changes in turnover frequency (TOF) with Ni dispersion on different catalysts, it was demonstrated that NH
3 decomposition over Ni is significantly structure sensitive. Some unique metal clusters similar to B5 active sites should be responsible for the catalytic activities. Preparation methodology has a substantial influence on metal dispersion. For the supported Ni catalysts prepared by the TIE method, the generated metal particles are very small and the constitution of unique active sites becomes unfavorable, which accounts for the apparently lower TOF values.
This paper presents an experimental investigation on the flame shape and length under the ceiling of a channel, and altogether 48 experiments with four experimental setups were performed. The ...experimental setups include fires in the open space, flush with a wall without ceiling, at the longitudinal centerline of a channel and flush with the sidewall of a channel. Results showed that the flame extending under the ceiling presented a circular shape when the fire is located at the longitudinal centerline of channel, whereas for fire placed flush with sidewall, it is a half ellipse. As heat release rate (HRR) increases, the long axes of the ellipse changes from perpendicular to the sidewall plane to parallel to it, resulting from the competition between air entrainment enhancement of generated vortices and air entrainment restriction of the corner structure above fire source. Additionally, the total flame extension as a lump of the vertical flame height and horizontal flame length is quantified using dimensional analysis. The total flame extensions for fire at the longitudinal centerline are proportional to 2/5 power of dimensionless heat release rate , while for fire flush with sidewall, the total flame extensions in longitudinal and transverse directions are proportional to 1/2 and 2/5 power of , respectively. The critical (transient) dimensionless heat release rate can be calculated as 0.60, under which the longitudinal and transverse flame lengths are identical.
This study presents a detailed performance analysis of a novel concentrated system which consists of a photovoltaic/thermal (PV/T) module with phase change material (PCM) and a solar thermal (ST) ...collector with thermoelectric generators (TEG) connected in series. While considerable electrical energy is acquisitive, enhanced high-temperature thermal energy is also achieved. In this system, the PV/T module generates both photoelectric power generation and low-temperature thermal energy, and the secondary heated water and the secondary thermoelectric output are obtained through the ST module and TEG on ST. Theoretical investigations find that, the system of the PV/T module and the ST module in series (PV/T-ST) performs well in terms of thermal performance and comprehensive performance. During the all-day operation, compared with the PV/T-PV/T system, the final temperature of the water tank in the PV/T-ST system is about 5 °C higher. Also, the electrical efficiency and the thermal efficiency are 10.65% and 65.22% respectively at 12:30 when using the 1.1-m2 Fresnel lens. Where, TEG converts some thermal energy into electrical energy, increasing the amount of high-grade energy of the system by about 321.53 kJ in the daytime. Additionally, the discussion from different perspectives on the impact of different parameters is also carried out.
•A novel concentrated system that connects PV/T and ST in series is proposed.•Both electricity and low-temperature heat can be generated by PV/T.•Reheated water and secondary electrical output are achieved through ST with TEG.•PCM placed in PV/T absorbs heat in the daytime to reduce the temperature of PV.•The discussion on the impact of different parameters is carried out.
The investigation on the impact of various factors of thermoelectric generator (TEG) & structure on the performance of TEG & system was carried out in this paper, which is essential to improve the ...system performance, optimize the system design, and match better TEG parameter. Results represent that a larger figure of merit Z (or ZT¯) may still lead to a reduction in system performance. When Z = 0.0016, the TEG conversion efficiency is 2.96% which is higher than 1.31% in the system with Z = 0.0028 under 800 W/m2 because the output is influenced by not only Z (orZT¯) but also ΔT/Th. The COPPVT and exergy efficiency of the system with Z = 0.0016 could be 7.35 and 29.18% which are lower than 7.52 and 29.77% in the system with Z = 0.0012. The exact influence of each parameter of Z is also explored. The TEG efficiency decreases from 2.05% to 0.83% with the rise of λ while the PV efficiency increases from 26.48% to 27.55%, but the COPPVT is changeless at 7.54. However, on the total performance, s and σ have more significant effects than λ. Running for 822 min with real environmental conditions, the average electrical efficiency and COPPVT could reach 28.10% and 6.84.
•A larger figure of merit Z (orZT¯) may still lead to a reduction on the performance.•The output of TEG is influenced by not only Z (orZT¯) but also ΔT/Th.•Thermal conductivity has a larger impact on TEG/PV, but has little impact on system.•A higher CR elevates the TEG performance but deteriorates the PV performance.•The mean electrical efficiency/COPPVT could be 28.10%/6.84 under real environment.
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