The properties, fatty acid composition and degree of saturation of palm oil are believed to be altered when subjected to repeated high temperature during frying. This work compares the properties and fatty acid composition of neat palm oil and waste palm oil samples. Neat palm oil (NPO), waste palm oil used to fry fish and chips (WPOFC) and another waste palm oil used to fry sausage and chips (WPOSC) were collected at the point of disposal and subjected to property determination and pyrolysis gas chromatography-mass spectrometer (PYGCMS) analysis. Repeated high temperature frying was found to trigger the change of congealing temperature, density, viscosity @ 40 oC of NPO from – 10.25 oC, 919.48 kg/m3 and 27.96 mm2 /s respectively to 12.3 oC, 904.3 kg/m3 and 44.25 mm2 /s for WPOFC and 14.7 oC, 913.4 kg/m3 and 38.41 mm2 /s for WPOSC respectively. Also, the 76 % polyunsaturated fatty acid in NPO became 77 % and 80 % saturated fatty acid for WPOFC and WPOSC respectively. The results of the WPO samples validate the suitability of waste palm oil as a feedstock for biodiesel production and other industrial purposes but unsafe for human consumption.
This study investigated the thermal performance and passive cooling effect of an extensive green roof based on an experiment conducted on sunny days in the summer of 2007, for a room with a green roof and a room with a bare roof under air-conditioned and nonair-conditioned states. Three different heat transfer scenarios in terms of average heat flux inside the green roof are defined: (1) heat transfer from indoor space to the green roof when the indoor-outdoor air temperature difference is relatively small, (2) heat transfer from the green roof to the indoor space when the indoor-outdoor air temperature difference is large, (3) ideal thermal equilibrium scenario that heat flux between green roof and indoor space equal to zero. “Cooling flux” is proposed to explain and qualify the passive cooling effect from evapotranspiration on sunny days. A simple method to approximate the “cooling flux” is purposed. The result shows at least 27.4% of the heat flux was absorbed by the passive “cooling flux“ under air conditioned status.
Binary nitrate (NaNO3-KNO3)/expanded graphite (EG)/ nano-SiO2 composite heat storage materials, used as high-temperature thermal energy storage materials, were prepared by mechanical dispersion method, and the effects of EG and nano-SiO2 additives on thermal properties of compound salts were investigated by SEM (scanning electron microscope), STA (Simultaneous Thermal Analysis) and LFA (Laser Flash Apparatus). The results showed that the specific heat capacity of the composites increased first and then decreased with the increase of EG mass fraction. When the mass fraction of EG was 15%, the specific heat of the composite was 3.92J/(g·K), which was 2.58 times higher than that of pure binary nitrate, and the thermal conductivity of the composite was 8.46W/(m·K), which was 16.2 times higher than that of pure binary nitrate. Compared with NaNO3-KNO3/EG(15%wt) composite, the average specific heat capacity and thermal conductivity of the NaNO3-KNO3/EG(15%wt)/nano-SiO2 composite material increased by 15.98% and 42.91% respectively. The preparation process was simple, and the NaNO3- KNO3/EG/nano-SiO2 composite had a broad application prospect in high-temperature energy storage system.
As the test cycle used for evaluating the fuel consumption and emission characteristics of the heavy-duty commercial vehicle in China will be replaced from C-WTVC to CHTC in a round 2020, the investigation on the variation of fuel consumption and emission test results after the replacement is well needed for further vehicle’s development and calibration. In this paper, the fuel consumption and emission characteristics of a China VI coach under these two test cycles have been discussed and compared. Results showed that fuel consumption, CO, HC and NOx emissions of the test coach all increased after changing the test cycle from C-WTVC to CHTC, which were due to the low rotation speed and low torque operating points, and the aggressive and frequent acceleration under CHTC. In addition, Acceleration driving condition contributed most to the deterioration of fuel consumption, CO, HC and NOx emissions under CHTC, which attention should be especially paid in the further vehicle calibration.
In the current paper, we investigated the phase change material (PCM) volume fraction for three-layers thermocline thermal energy storage (TES) tank system by using spherical capsules filled with high temperature PCM of different thermo-physical properties. A transient one-dimensional dispersion-concentric (D-C) model is modified to calculate the phase change process within capsules so as to determine the temperature distribution. Detailed characteristics of heat transfer between molten salt and the PCMs capsules are discussed, and various numerical results are presented, including the temperature distributions of molten salt and exit temperature. The results show that the volume fraction has a significant impact on the stored/recovered time energy. As the volume fraction of bottom PCM increases, the time required to discharge the thermocline TES tank increases.
With the extensive integration of high penetration renewable energy sources and electric vehicles, frequency regulation service is required to eliminate the impact of uncertainty of load and distributed generation on system frequency. The community integrated energy station (CIES) is an effective way to participate in the service. To realize the optimal configuration of CIES, a method for the planning of CIES for participating in the auxiliary service of the distribution networks is presented. First, the model of frequency regulation and energy station planning is established. Then, the model is solved by the mixed integer linear programing (MILP). Case studies are conducted under different scenarios and results show that participating in the frequency regulation service can effectively reduce the annual total cost of CIES.
Hybrid electric aircraft are developed to reduce emission and save energy. However, the thermal efficiency of turbo-electric aircraft and the endurance of battery-electric aircraft are both limited, respectively. Aircraft powered by fuel cells can achieve long endurance, low emission, and fuel consumption reduction. Solid oxide fuel cell hybrid electric jet engines without turbines for unmanned aerial vehicles was proposed in our previous work in which compressors are powered by fuel cells instead of the turbines. The hybrid electric jet engine combining the merits of a turboelectric engine and a fuel cell powered engine. To avoid component malfunctions and engine performance deterioration, determination of safe operation zone is necessary.
In this study, the performance analysis model of the hybrid electric jet engine is built and the main conclusions are as follows. The off-design performance of the hybrid electric jet engine is achieved by adjusting the mass flow of fuel injected into the reformer. The safe operating zone of the hybrid engine is not restricted by turbine inlet temperature. Under low fuel flow and low air flow, too low reforming temperature zones or too low SOFC open voltage zones exist. Additionally, the unbalanced energy zone exists under high fuel flow and low air flow. The power produced by the SOFC is over the one consumed by the compressor. In the safe zone, the hybrid engine has a characteristic of high specific thrust (837.6 N/kg.s-1 ) and high thermal efficiency (70.43%) with high rotational speed, vice versa.
A present experimental study demonstrates the visual characteristics of the liquid-solid interface during the melting process in the Latent Heat Thermal Energy Storage System (LHTES) system. The instantaneous morphology of liquid-solid interface and temperature are directly obtained at the different locations in the enclosure when heated at an isothermal temperature condition. The visualization of the phase front and temperature field shows the significance of fins to alleviate the melting phenomenon by the formation of thermal plumes above the top surface of the fins. The role of natural convective transport as a governing mechanism for the phase change process in the partial assisted enclosure is also discussed.
Linear equation solver of real-time simulators for active distribution networks (ADNs) requires significant computation power. Field programmable gate array (FPGA) has many merits such as highly parallel hardware structure and programmable characteristics, which shows great potential for the real-time solving of linear equations. Considering the sparsity of the linear equation, a parallel solver is designed in this paper based on block triangular form (BTF) matrix block algorithm. The design of off-line processing on host PC and online calculation on FPGA are proposed in detail. Simulation results are compared with PSCAD/EMTDC to validate the correctness and effectiveness of the parallel solver design.
The uncertainty of distributed photovoltaic (PV) output brings difficulties to reactive power optimization of power system. A robust reactive power optimization model for power system considering the uncertain output of PV is proposed. The probabilistic model of PV output is used to solve the problem that the robust optimization solution is too conservative. The effectiveness of the proposed model is verified by an example.