Efficiency of Model Induction Motor Using Various Non-Oriented Electrical Steels

The performance of a 3-phase 6-pole 400 W inverter-drive induction motor was investigated using a variety of non-oriented electrical steels for stator core at PWM inverter fundamental wave frequencies of 30 to 300 Hz. There existed an optimum Si content of the material depending on the tooth flux density. Both reduction of material thickness and stress-relief annealing of the stator core improved the motor efficiency. The influence of Si content on the efficiency was small at lower PWM frequencies, while at higher frequencies the motor efficiency increased with increasing Si content. The Cu loss WC increased and the Fe loss Wi counteractiveiy decreasedwith increasing Si content at lower frequencies; while at higher frequencies Wi had dominant effect on the efficiency. Newly developed materials RMA, having lower Fe losses after stress-relief annealing and higher flux densities with lower Si contents, showed motor efficiencies superior to conventional J1S grade materials with comparable Fe losses.

Measurements of the Electrical Incidence Angle Modifiers of an Asymmetrical Photovoltaic/Thermal Compound Parabolic Concentrating-Collector

Reflector edges, sharp acceptance angles and by-pass diodes introduce large variations in the electrical performance of asymmetrical concentrating photovoltaic/thermal modules over a short incidence angle interval. It is therefore important to quantify these impacts precisely. The impact on the electrical performance of the optical properties of an asymmetrical photovoltaic/thermal CPC-collector was measured in Maputo, Mozambique. The measurements were carried out with the focus on attaining a high resolution incidence angle modifier in both the longitudinal and transversal directions, since large variations were expected over small angle intervals. A detailed analysis of the contribution of the diffuse radiation to the total output was also carried out. The solar cells have an electrical efficiency of 18% while the maximum measured electrical efficiency of the collector was 13.9 % per active glazed area and 20.9 % per active cell area, at 25 °C. Such data make it possible to quantify not only the electrical performance for different climatic and operating conditions but also to determine potential improvements to the collector design. The electrical output can be increased by a number of different measures, e.g. removing the outermost cells, turning the edge cells 90°, dividing each receiver side into three or four parts and directing the tracking, when used, along a north-south axis.

Analysis and Economic Evaluation of Hourly Operation Strategy Based on MSW Classification and LNG Multi-Generation System

In this study,a model of combined cooling,heating and power system with municipal solid waste(MSW)and liquefied natural gas(LNG)as energy sources was proposed and developed based on the energy demand of a large community,andMSW was classified and utilized.The systemoperated by determining power by heating load,and measures were taken to reduce operating costs by purchasing and selling LNG,natural gas(NG),cooling,heating,and power.Based on this system model,three operation strategies were proposed based on whether MSW was classified and the length of kitchen waste fermentation time,and each strategy was simulated hourly throughout the year.The results showed that the strategy of MSW classified and centralized fermentation of kitchen waste in summer(i.e.,strategy 3)required the least total amount of LNG for the whole year,which was 47701.77 t.In terms of total annual cost expenditure,strategy 3 had the best overall economy,with the lowest total annual expenditure of 2.7730×108 RMB at LNG and NG unit prices of 4 and 4.2 RMB/kg,respectively.The lower heating value of biogas produced by fermentation of kitchen waste from MSW being classified was higher than that of MSW before being classified,so the average annual thermal economy of the operating strategy of MSW being classified was better than that of MSW not being classified.Among the strategies in which MSW was classified and utilized,strategy 3 could better meet the load demand of users in the corresponding season,and thus this strategy had better thermal economy than the strategy of year-round fermentation of kitchen waste(i.e.,strategy 2).The hourly analysis data showed that the net electrical efficiency of the system varies in the same trend as the cooling,heating and power loads in all seasons,while the relationship between the energy utilization efficiency and load varied from season to season.This study can provide guidance for the practical application of MSW being classified in the system.

Dust Deposition’s Effect on Solar Photovoltaic Module Performance:An Experimental Study in India’s Tropical Region

A solar PV panel works with maximum efficiency only when it is operated around its optimum operating point or maximum power point.Unfortunately,the performance of the solar cell is affected by several factors like sun direction,solar irradiance,dust accumulation,module temperature,as well as the load on the system.Dust deposition is one of the most prominent factors that influence the performance of solar panels.Because the solar panel is exposed to the atmosphere,dust will accumulate on its surface,reducing the quantity of sunlight reaching the solar cell and diminishing output.In the proposed work,a detailed investigation of the performance of solar PV modules is carried out under the tropical climatic condition of Chennai,India,where the presence of dust particles is very high.The data corresponding to four different dust samples of various densities at four solar irradiation levels of 220,525,702,and 905 W/m^(2)are collected,and performance analysis is carried out.Based on the analysis carried out,the maximum power loss is found to be 73.51%,66.29%,65.46%,and 61.42%,for coal,sand,brick powder,and chalk dust respectively.Hence,it can be said that coal dust contributes to the maximum power loss among all four dust samples.Due to heat dissipation produced by dust deposition,the performance of solar PV modules is degraded as the temperature rose.

Numerical Study of Mixed Convection in a Photovoltaic Trombe Wall Channel Coupled with a Solar Chimney Integrated into a Building for Habitats Passive Cooling

The solar chimney can generate airflow through the living space of the building to provide cooling. Hence, solar energy represents the best renewable, environmentally friendly source of energy that can be used for heating and cooling of houses. The present paper reports the numerical study of the performance of the mixed convection in the associated hybrid Photovoltaic/Thermal chimneys integrated into building for natural habitat ventilation. The front side glass plate of the chimneys is heated by a non-uniform daily solar radiation flux. Air is considered to be the cooling fluid. The stream fucntion-vorticity formulation with a finite difference numerical discretization solution scheme has been adopted. The system of algebraic governing equations is solved by Thomas algorithm method. The aim of the present paper is to study and to predict the dynamic fields and particularly of the mass flow rate of the air thermosiphon drawing in the associated hybrid Photovoltaic-Thermal chimneys integrated into a building for passive cooling in the habitats. The effects of the governing parameters, namely Reynolds number (30 ≤ Re ≤ 200), Rayleigh number (103 ≤ Ra≤ 105), the integrated chimney width on the fluid flow and the heat transfer characteristics, are studied in detail. The local Nusselt number, streamlines, isotherms, PV cells electrical efficiency and the outlet velocity at the top of the channels are the results represented versus the above controlling parameters.

A comparative study of hybrid electric vehicle fuel consumption over diverse driving cycles

Environmental pollution and declining resources of fossil fuels in recent years,have increased demand for better fuel economy and less pollution for ground transportation.Among the alternative solutions provided by researchers in recent decades,hybrid electric vehicles consisted of an internal combustion engine and an electric motor have been considered as a promising solution in the short-term.In the present study,fuel economy characteristics of a parallel hybrid electric vehicle are investigated by using numerical simulation.The simulation methodology is based on a fast forward facing simulation model of a parallel hybrid and an internal combustion engine powertrains.The objective of this study is to present the main parameters which result in an optimum combination of hybrid powertrain components in order to obtain a better fuel economy of hybrid powertrains regarding different driven cycles and hybridization factors.Then,the fuel consumption of the parallel hybrid electric vehicles are compared considering various driven cycles and hybridization factors.The results showed that the better fuel economy of hybrid powertrains increases by decreasing average load of the test cycle and the point of the best fuel economy for a particular average load of the cycle moves towards higher hybridization factors when the average load of the test cycle is reduced.

Impact of Electricity Shortages on Productivity: Evidence from Manufacturing Industries

Electricity shortages present a significant constraint on manufacturers,who rely on electricity as an important input into production.In China,electricity supply has been growing rapidly.However,the rapid industrialization sometimes makes the power supply still unable to meet the demand.Using a survey of 1673 Chinese manufacturing firms,this paper explores how firms response to electricity shortages and its impact on productivity.We find that self-generation of electricity and investment in Research and Development(R&D)have significant positive relationships with electricity shortages.Further investigations reveal that self-generation is the most common way to deal with electricity shortages.However,it aggravates productivity loss.Though investment in Research and Development can promote productivity,it cannot offset the negative impact of electricity shortages on productivity.Analyses on subsamples show heterogeneity in the impacts of electricity shortages across firms.In particular,large firms are more inclined to invest in R&D than small and medium-sized firms are.They are also the one who suffer significant productivity loss due to self-generation of electricity.Though it is possible for medium-sized firms to reduce productivity loss through R&D,they are not likely to invest in R&D as a response to electricity shortages.This study illustrates that firms can hardly have effective solutions to electricity shortages,and policy makers should take great efforts to increase electricity supply.

Energy Management Strategy for Hybrid Electric Vehicle Based on System Efficiency and Battery Life Optimization

A novel method to calculate fuel-electric conversion factor for full hybrid electric vehicle（HEV）equipped with continuously variable transmission（CVT）is proposed.Based on consideration of the efficiency of pivotal components,electric motor,system efficiency optimization models are developed.According to the target of instantaneous optimization of system efficiency,operating ranges of each mode of power-train are determined,and the corresponding energy management strategies are established.The simulation results demonstrate that the energy management strategy proposed can substantially improve the vehicle fuel economy,and keep battery state of charge（SOC）change in a reasonable variation range.

Comparison Study of a Novel Tank PV/T Hot Water System and a Heat Pipe PV/T System

A novel tank-Photovoltaic-thermal(PV/T) system is presented in this paper, and its energy performance has been compared with a traditional heat pipe PV/T system. The novel tank PV/T system combines photovoltaic cell, heat absorbing plate and hot-water storage tank which expands the heat exchange area, shortens the heat transfer path and saves the module installation space. A prototype system is constructed and tested in a cold weather condition and then compared with a heat pipe PVT system. The experimental results indicate that during the 10 days’ testing, the electrical, thermal and overall efficiency of the tank PV/T system ranges from 14.3% to 15.6%, 38.6% to 43.8% and 53.1% to 58.1%, respectively, while the heat pipe PVT system ranges from 10.9% to 12.2%, 39.3% to 41.2% and 50.5% to 53.4%, respectively. Based on these data, the electrical and thermal efficiency curve of the system with the novel tank-PVT system and heat pipe PVT system were generated. According to the comparison result, it shows that the novel tank-PVT system has a better thermal and electrical efficiency. This system provides a new design method for the development of the PV/T systems, which has a potential for PV/T systems building integration in the future.

Effects of LED light quality on the growth of pepper seedling in plant factory

The extensive environment,especially low temperature and weak lighting in winter and spring,which limits the growth of pepper(Capicum annuum L.)seedlings,the use of plant factory with artificial lighting technology can effectively control the lighting environment to produce high-quality seedlings.In this study,white LED lamps with R:B ratio of 0.7(L0.7)and 1.5(L1.5)and red-blue LED lamps with R:B ratio of 3.5(L3.5)were used to cultivate seedlings of“CAU-24”pepper in the light intensity of 250μmol/m^(2)·s and photoperiod of 12 h/d,white fluorescent lamps with R:B ratio of 1.7(F1.7)was used as control.The results showed that plant height,stem diameter,hypocotyl length,biomass accumulation,light energy use efficiency(LUE)and electric energy use efficiency(EUE)of pepper seedling under L1.5 were the highest.After 36 days of sowing,the dry weight of shoot reached 302.8±45.2 mg/plant.Leaf area reached maximum value of 153.5±22.0 cm^(2) under L0.7.The contents of chlorophyll a,chlorophyll b and total chlorophyll of pepper seedling leaves under all kinds of LED light were greater than F1.7,but there was no significant difference in net photosynthetic rate.The total dry weight with lamp electric power consumption of L1.5 were 3.0 g/(kW·h)which was 1.5,2,and 3 times greater than that of L3.5,L0.7,and F1.7,respectively.Therefore,compared with fluorescent lamp and other LED lamps,the white LED light quality with R:B ratio of 1.5 is suitable for pepper seedling production in plant factory because of the high LED lighting efficiency,greater LUE and EUE.

Charged ultrafine particle filtration through vehicular cabin air filters

Understanding the effectiveness of cabin air filters is important for assessing human exposure to ultra- fine particles （UFPs） of vehicular origin. The filtration efficiency of vehicular UFPs with electric charges was investigated for different electric charge characteristics （charge state, charge polarity）. The average filtration efficiency increased ~10% as the electric charge state on the particles changed in distribution from lightly charged to highly charged. The enhancement of filtration efficiency due to electric charge was different at various filter-face air velocities. As electric charges increased, the filtration efficiency increased 12% and 9% at low air velocity （0.1 m/s） and high air velocity （0.S m/s）, respectively. The filter fiber material poses somewhat effect on the filtration efficiency change due to the electric charge. The effects of filter usage and charge polarity on filtration efficiency due to the electric charge were negligi- ble. A coefficient was empirically derived and successfully accounts for the electric charge effect on UFP filtratinn efficiency.