太阳能PV/T系统电热输出性能及其Matlab仿真研究

建立了太阳能PV/T(Photovoltaic/Thermal)系统的热电模型,编制了Matlab程序,采用迭代法对电热参数进行耦合求解。研究了PV/T系统在呼和浩特不同季节下的热电效率,电池温度和性能曲线的变化,通过与实验数据对比,验证了该模型具有较高的精度。实验结果显示了环境温度、风速、入射辐射量对太阳能PV/T系统热、电以及综合性能的影响:PV/T系统夏季的日平均电效率、热效率及正午组件最大功率分别为14.1%、34.5%和180.8 W,冬季的日平均电效率、热效率及正午组件最大功率分别为16.1%、24.8%和190.3 W。     

浅谈电热锅炉用管状电热元件

1前言随着国家电力工业的迅速发展和城市对环保要求的提高，工业锅炉的使用也在发生着一定的变化由于电热锅炉与其它锅炉相比，有其优越性，因而该产品发展迅速，社会需求量较大，甚至在特殊的地区必须以电热锅炉取代其它工业锅炉。为了保证电热锅炉的基本功能、安全性能的实现，对电热锅炉发热心脏—金属管状电热元件质量提出了较高的要求，现予以探讨如下。2金属管状电热元件的结构及特点2.1产品设计原理金属管状电热元件的电原理是将电能变为热能其工作原理是元件通电产生热量，并通过导热性能好、绝缘性能高的氧化镁传递给管外壳，最终…     

一种改进型槽式聚光电热联供系统的性能研究

提出一种改进型的槽式聚光电热联供系统,该系统在电热联供系统的基础上增加一个金属腔体再热级,实现输出高品质电能的同时输出较高温位的热能。构建改进型槽式聚光电热联供系统实验装置,通过测试实验,发现改进型系统的电输出性能和热输出性能均有所提高。分析改进型槽式聚光电热联供系统与单晶硅平板光伏系统、太阳能热水系统三者之间的经济效益,结果表明,改进型系统的经济性能高于单晶硅平板光伏系统,低于太阳能热水系统。     

固体蓄热式电锅炉蓄热模拟及实验

研究一种新型的蓄能装置——固体蓄热式电热锅炉。该设备利用低谷电加热穿插在蓄热体耐火砖孔道中的电热丝,蓄热体吸收电热丝释放的热量并暂时贮存起来,在需要的时候通过二次换热释放出来,供用户使用。采用AN-SYS进行蓄热体温度场的三维数值模拟,得到了不同时刻的温度分布。为了验证ANSYS模拟温度分布的正确性,在260~900℃范围内进行了试验测试。其结果表明,在此温度范围内,两者误差小于10%,在7 h谷电期间,蓄热温度可达900℃。实验样机表明,锅炉热效率可达97.4%。研究表明:此型固体蓄热式电热锅炉具有蓄热能力高,结构紧凑,运行安全、高效节能及无大气污染等特点,对固体蓄热式电热锅炉的应用推广具有一定的指导意义。     

节能电热元件—电热膜加热管的研制

本文介绍了一种节能电热元件－电热膜加热管，讨论了电热膜加热管研制中有关技术问题。该加热管可广泛用于连续加热水等流体，具有电热转换效率高、加热快、寿命长和寿命安全的特点。     

聚光太阳能热电系统的实验研究

利用所设计的2m~2槽式聚光热电联供系统,对晶硅阵列和砷化镓电池阵列进行性能测试实验,结果表明:砷化镓电池阵列的聚光特性优于晶硅电池阵列。优选出一定聚光比作用下性能较好的砷化镓电池阵列建立10m~2槽式太阳能聚光热电系统,实验表明:10m~2系统的电池阵列电效率为23.21%,系统光电效率和光热效率分别为9.88%和49.84%,系统(?)效率为13.48%,比基于槽式聚光加热真空管系统(?)效率高158%,比平板光伏发电系统(?)效率高16%。对采用空间太阳电池阵列的10m~2聚光热电系统性能分析表明,槽式聚光热电联供系统发电成本已与平板的持平,且每年还可提供4838.38MJ热量供用户使用。     

变压器油纸绝缘电热联合老化机理研究

变压器油纸绝缘系统在运行中需要承受电、热等共同作用,目前一般研究工作重点在电故障、热故障以及电或热老化对油纸的特性影响,而电热联合老化特性研究较少。该文通过研究油纸绝缘电热联合老化,对不同老化阶段油纸结构的聚合度,抗张强度和频域介电谱特性进行测量和研究。研究结果得到了电热联合老化条件下的聚合度的二阶模型以及聚合度与抗张强度的拟合公式。进一步研究频域介电谱发现随着老化时间的增加,在低频区εr和tan δ随频率的减小而有不同的增大趋势。在10-3,10-1Hz频率区εr和tan δ与绝缘纸老化状态有明显的相关关系,拟合得到在10-3、10-2及10-1Hz特征频率处的εr和tan δ值与绝缘纸聚合度的指数函数关系。该研究将为油纸绝缘在电热联合作用下的老化机理及应用FDS无损评估变压器油纸绝缘状态提供方案。     

电炉文摘

WJ83374 《电—82》展览会上的国外电热设备——《Электротехн.пром—сть》83.№6.26—27(俄)本文介绍1982年7月在苏联莫斯科举办的第三届国际《电—82》展览会上展出的电热设备,着重介绍了国外大容量(125吨)炼钢无心感应炉,炼铁的无心和有心感应炉,各种外形坯件加热用感应加热装置及其优点,精制单晶体用的电炉。简单介绍感应炉各种变频器的结构型式和性能,以及控制计算装置的元件和微处理机的使用。     

膨胀剂对面板坝混凝土减缩抗裂性能的影响

为验证和提高堆石面板坝面板混凝土的抗裂性能,以云南省某水库堆石坝面板混凝土为例,对比研究了3种典型膨胀剂(Ⅰ型和Ⅱ型硫铝酸钙类膨胀剂、氧化镁膨胀剂)对面板混凝土强度发展、早期非接触收缩、早期抗裂、干燥收缩和限制膨胀率的影响。结果表明,3种膨胀剂在面板混凝土中的膨胀性能发挥差异较为明显,其中使用Ⅱ型膨胀剂的补偿收缩效果最显著,混凝土早期收缩率降低75.8%且未开裂、28 d干缩率减小50.9%、42 d限制收缩率减小83.3%,说明其膨胀历程与混凝土性能发展协调性较好(且混凝土56 d抗压强度提高23.6%)。该研究可为实际工程配合比优化、减少面板混凝土开裂风险提供借鉴。     

基于电热耦合效应的锂电池荷电状态与温度状态联合估计

准确估计电池的荷电状态(SOC)和内部温度可以提高电池的性能和安全性。其中,电池模型的准确性和估计算法的适用性是关键。为了解决这两个问题,本文建立了圆柱形锂离子电池的多参数电热耦合模型。模型考虑电池SOC与温度变化之间的耦合关系,并且利用改进的熵热系数实验获得电池运行中产生的可逆热与不可逆热,通过可变遗忘因子最小二乘算法(VFFRLS)进行参数辨识,并对比独立的电模型与热模型的SOC与内部温度估计结果,验证了多参数电热耦合模型的准确性,结果证明所提模型相比较于单独的电热模型,估计精度提高了70%以上。最后,设计了一种基于奇异值分解的卡尔曼滤波(SVD-AUKF)算法来同时在线估计SOC和内部温度,并在改进的动态测试(DST)工况下对所提方法进行实验验证。结果表明：所提方法相较于扩展卡尔曼滤波(EKF)与无迹卡尔曼滤波(UKF)算法,能实现更高精度的SOC和温度估计,SOC与内部温度的平均误差分别是5%和0.2℃。     

New proposal for photovoltaic-thermal solar energy utilization method

One of the most effective methods of utilizing solar energy is to use the sunlight and solar thermal energy such as a photovoltaic-thermal panel (PV/T panel) simultaneously. From such a viewpoint, systems using various kinds of PV panels were constructed in the world. In these panels, solar cells are set up at an absorber collecting solar thermal energy. Therefore, temperature of solar cell increases up to the prescribed temperature of thermal energy use, although it is lower than the cell temperature when using only solar cell panel. For maintaining cell conversion efficiency at the standard conditions, it is necessary to keep the cell at lower temperature. In this paper, electric and thermal energy obtained from a PV/T panel is evaluated in terms of energy. Based on this evaluation, the method of not to decrease cell conversion efficiency with collecting solar thermal energy was proposed.     

Field study of various air based photovoltaic/thermal hybrid solar collectors

In the present work a comparative study for thermal and electrical performance of different hybrid photovoltaic/thermal collectors designs for Iraq climate conditions have been carried out. Four different types of air based hybrid PV/T collectors have been manufactured and tested. Three collectors consist of four main parts namely, channel duct, glass cover, axial fan to circulate air and two PV panels in parallel connection. The measured parameters are, the temperature of the upper and the lower surfaces of the PV panels, air temperature along the collector, air flow rate, pressure drop, power produced by solar cell, and climate conditions such as wind speed, solar radiation and ambient temperature. The thermal and hydraulic performances of PV/T collector model IV have been analyzed theoretically based on energy balance. A Matlab computer program has been developed to solve the proposed mathematical model.The obtained results show that the combined efficiency of collector model III (double duct, single pass) is higher than that of model II (single duct double pass) and model IV (single duct single pass). Model IV has the better electrical efficiency. The pressure drop of model III is lower than that of models II and IV. The root mean square of percentage deviations for PV outlet temperature, and thermal efficiency of model IV are found to be 3.22%, and 18.04% respectively. The calculated linear coefficients of correlation (r) are 0.977, 0.965 respectively.     

Performance and costs of a roof-sized PV/thermal array combined with a ground coupled heat pump

A photovoltaic/thermal (PVT) panel is a combination of photovoltaic cells with a solar thermal collector, generating solar electricity and solar heat simultaneously. Hence, PVT panels are an alternative for a combination of separate PV panels and solar thermal collectors. A promising system concept, consisting of 25 m² of PVT panels and a ground coupled heat pump, has been simulated in TRNSYS. It has been found that this system is able to cover 100% of the total heat demand for a typical newly-built Dutch one-family dwelling, while covering nearly all of its own electricity use and keeping the long-term average ground temperature constant.The cost of such a system has been compared to the cost of a reference system, where the PVT panels have been replaced with separate PV panels (26 m²) and solar thermal collectors (7 m²), but which is otherwise identical. The electrical and thermal yield of this reference system is equal to that of the PVT system. It has been found that both systems require a nearly identical initial investment.Finally, a view on future PVT markets is given. In general, the residential market is by far the most promising market. The system discussed in this paper is expected to be most successful in newly-built low-energy housing concepts.     

Design and analysis of a CPV/T solar receiver with volumetric absorption combined spectral splitter

Spectral beam splitting is a promising technology to achieve the maximum electrical and thermal outputs from concentrating photovoltaic/thermal (CPV/T) systems simultaneously. In this article, a novel CPV/T receiver is proposed by incorporating a fluid based filter together with a solid absorptive filter. The geometry of the receiver is developed for a designed linear flat mirror concentrator. According to the optical transmittance of both fluid based filters and solid absorptive filters, as well as their corresponding merit functions, four fluid filters and two solid filters are determined to be the candidates of the combined filter for the silicon concentrator solar cell. Then, a complete solar radiation propagation process from concentrator to the designed CPV/T receiver is simulated using ray tracing software-LightTools. The results show that the surface illumination uniformity of the PV module filtered by each combined filter under the linear flat mirror concentrator is higher than 96%. Using 5 g/L CoSO₄ solution and HB650 as the combined filter, 33.67% of the concentrated light can be directed to the PV module with the remainder collected by the filter as thermal energy and the silicon CPV cells can convert 27.06% of this energy into electrical power. This contributes to the fact that 92.43% of the light striking the PV module is within 650-1100 nm, which is the spectral response range of the cell can work efficiently. The total efficiency of 49.88% can be achieved with such a filter and the electrical efficiency is 9.1% with respect to the total incident power on the receiver.     

Hybrid photovoltaic/thermal solar systems

We present test results on hybrid solar systems, consisting of photovoltaic modules and thermal collectors (hybrid PV/T systems). The solar radiation increases the temperature of PV modules, resulting in a drop of their electrical efficiency. By proper circulation of a fluid with low inlet temperature, heat is extracted from the PV modules keeping the electrical efficiency at satisfactory values. The extracted thermal energy can be used in several ways, increasing the total energy output of the system. Hybrid PV/T systems can be applied mainly in buildings for the production of electricity and heat and are suitable for PV applications under high values of solar radiation and ambient temperature. Hybrid PV/T experimental models based on commercial PV modules of typical size are described and outdoor test results of the systems are presented and discussed. The results showed that PV cooling can increase the electrical efficiency of PV modules, increasing the total efficiency of the systems. Improvement of the system performance can be achieved by the use of an additional glazing to increase thermal output, a booster diffuse reflector to increase electrical and thermal output, or both, giving flexibility in system design.     

Off-grid solar powered charging station for electric and hydrogen vehicles including fuel cell and hydrogen storage

This paper designs an off-grid charging station for electric and hydrogen vehicles. Both the electric and hydrogen vehicles are charged at the same time. They appear as two electrical and hydrogen load demand on the charging station and the charging station is powered by solar panels. The output power of solar system is separated into two parts. On part of solar power is used to supply the electrical load demand (to charge the electric vehicles) and rest runs water electrolyzer and it will be converted to the hydrogen. The hydrogen is stored and it supplies the hydrogen load demand (to charge the hydrogen-burning vehicles). The uncertainty of parameters (solar energy, consumed power by electrical vehicles, and consumed power by hydrogen vehicles) is included and modeled. The fuel cell is added to the charging station to deal with such uncertainty. The fuel cell runs on hydrogen and produces electrical energy to supply electrical loading under uncertainties. The diesel generator is also added to the charging station as a supplementary generation. The problem is modeled as stochastic optimization programming and minimizes the investment and operational costs of solar and diesel systems. The introduced planning finds optimal rated powers of solar system and diesel generator, operation pattern for diesel generator and fuel cell, and the stored hydrogen. The results confirm that the cost of changing station is covered by investment cost of solar system (95%), operational cost of diesel generator (4.5%), and investment cost of diesel generator (0.5%). The fuel cell and diesel generator supply the load demand when the solar energy is zero. About 97% of solar energy will be converted to hydrogen and stored. The optimal operation of diesel generator reduces the cost approximately 15%.     

Experimental and numerical studies of a U-shaped solar energy collector to track the maximum CPV/T system output by varying the flow rate

In the last decade, no comprehensive numerical and experimental analyses have been performed to find the maximum possible power generation from a concentrated photovoltaic thermal (CPV/T) system by varying the flow rate of the fluid. This paper describes numerical and experimental studies of a U-shaped solar energy collector model of a CPV/T system, with the goal of determining the maximal thermal and electrical power outputs against a specific volumetric flow rate also called an optimum flow rate. The CPV/T system was based on the union of 8 triple junction solar cells, 8 SOG Fresnel lenses, effective dual-axis tracking, and a forced cooling system. Analyses were performed by changing the flow rate of the working fluid at a considered solar irradiation and ambient temperature. The thermal and electrical power outputs also varied with changes in the ambient temperature and available solar radiation. The relatively high value of CPV/T power was observed against the optimum flow rate at a given irradiation and ambient temperature. Analysis of the energy of the U- shaped solar energy collector system was evaluated experimentally. The numerical results and experimental measurements of the U-shaped solar energy collector model showed great harmony, with minimal deviations of <7% between them.     

Second law analysis of the 160 Wp standalone solar photovoltaic system

The demand for solar photovoltaic (SPV) systems is growing all over the world due to the continuous increase in the cost of conventional means of power. India has the advantage of around 300 clear sunny days in a year. However, the biggest problem is conversion efficiency. In this paper, an attempt has been made for evaluating the second law efficiency of 160?Wp stand-alone SPV systems installed in RKGIT Ghaziabad premises. The performance of a SPV system depends on climate conditions like temperature, air velocity and a number of sunny days. The solar energy striking the solar panels gets converted into electric and thermal energy. In this work, we have considered the effect of ambient temperature and air velocity on the efficiency of solar panels. The average second law efficiency of SPV systems was found to be 10.7%, whereas maximum second law efficiency was 13.8% at 9am on the same day. The efficiency of the SPV system can be improved by maintaining the temperature of the module.     

Performance Optimization of Water-Cooled Concentrated Photovoltaic System

In this paper, a three-dimensional computational fluid dynamics model is developed to predict the thermal and electrical performance of a water-cooled concentrated photovoltaic (CPV) system. Based on the good agreement between the numerical results and experimental data from literature, an attempt was made to improve this system performance. Indeed, as the developed model is able to predict the thermal behavior of the different system components, many hot spots were detected in the cell module. In order to avoid this disadvantage while promoting solar cell cooling, the number of water cooling pipes of the CPV module was first increased and then a rectangular channel was employed. Numerical simulation results indicate the potential of the different modified systems for reducing these hot spots and the CPV module temperature, thus providing increased electrical and thermal efficiencies. The optimum design, which presents a solar cell temperature of 315.15 K and respectively a thermal and combined (thermal plus electrical) efficiency of 74.2% and 83.5%, is also evaluated.     

Detailed analysis of the energy yield of systems with covered sheet-and-tube PVT collectors

Solar cells have a typical efficiency in the range of 5-20%, implying that 80% or more of the incident solar energy can be harvested in the form of heat and applied for low-temperature heating. In a PVT collector one tries to collect this heat. In this work, the electrical and thermal yield of solar domestic hot water systems with one-cover sheet-and-tube PVT collectors were considered. Objectives of the work were to understand the mechanisms determining these yields, to investigate measures to improve these yields and to investigate the yield consequences if various solar cell technologies are being used. The work was carried out using numerical simulations.A detailed quantitative understanding of all loss mechanisms was obtained, especially of those being inherent to the use of PVT collectors instead of PV modules and conventional thermal collectors. The annual electrical efficiencies of the PVT systems investigated were up to 14% (relative) lower compared to pure PV systems and the annual thermal efficiencies up to 19% (relative) lower compared to pure thermal collector systems. The loss of electrical efficiency is mainly caused by the relatively high fluid temperature. The loss of thermal efficiency is caused both by the high emissivity of the absorber and the withdrawal of electrical energy. However, both the loss of electrical and thermal efficiency can be reduced further by the application of anti-reflective coatings. The thermal efficiency can be improved by the application of a low-emissivity coating on the absorber, however at the cost of a reduced electrical efficiency.