不同型式PV/T一体化系统的对比研究

本文针对热泵型、水冷型、热管型PV/T热水系统的结构特点,建立三种热水系统的数学模型。通过所建的模型,比较三者在南京地区不同典型季节工况下的热效率、电效率以及全年工况下的能量收益。模拟结果表明:在各典型工况下,热泵型PV/T系统热效率、电效率均最高,水冷型PV/T系统热效率高于热管型PV/T系统,但电效率略低于热管型PV/T系统。若用户全年若以供热为主的情况下,则优先采用热泵型PV/T系统。若以发电或节电为目的,宜采用水冷型或热管型PV/T系统。     

PV/T社区用能一体化热泵热水系统的应用研究

为综合利用太阳能资源,搭建了一种基于太阳能光伏光热(PV/T)部件的PV/T社区用能一体化热泵热水系统,并对该系统在夏季的实际运行特性进行测试,通过研究热效率、电效率和系统性能系数(COP)进一步分析其热力性能。测试结果表明:太阳辐射强度对系统运行的影响较大,室外环境温度及室外风速主要影响系统的散热。测试期间,系统平均电效率约为15.98%,系统平均热效率约为42.3%;热泵COP最高可达6.4,平均值约为4.8;系统COP最高可达3.9,平均值约为3.3。该系统可满足社区公共部分的用电和生活热水需求,具有良好的应用前景。     

吹胀微流道式太阳能光伏/光热(PV/T)集热系统春季实验研究

通过吹胀微流道PV/T(photovoltaic/thermal)实验平台实测春季PV/T组件倾斜角、循环水流量因素在减去水泵耗电量和控制相同初始水箱温度在13. 5℃后分析这2种因素对系统实际热/电综合效率的影响。倾斜角从18°增至32°,PV/T平均实际综合效率从44. 6%增至55. 61%,对系统实际综合效率起到正相关作用。循环水流量从60 L/h增至100 L/h,PV/T平均实际综合效率从49. 32%先增至53. 48%后降至46. 53%,效率随水泵功率存在先增后减的规律,而不是一直下降。循环水流量的增加在一定程度上可以提高热效率,当热效率达到阈值后,再增加循环水流量相当于增加额外耗功,导致综合效率的下降。9组实验中较佳运行方式是32°倾斜角,80 L/h循环水流量,比18°倾斜角,100 L/h工况综合效率高18. 06%。即便是在平均辐照最低和综合效率最低2种工况下,单块PV/T板实验期间实际发电量分别是0. 371 k W·h和0. 48 k W·h,均可满足小型直流电器用电需求。本实验目的是在上海地区为太阳能PV/T集热系统春季运行优化提供帮助。     

风冷式PV/T空调系统日间冷电联产性能实验研究

提出了一种风冷式PV/T空调系统，对系统在夏季日间的冷电联产性能进行了实验测试，分析了环境因素、运行参数等对系统发电和制冷性能的影响。结果表明：光伏板温度随太阳辐照度的升高而升高，光伏板输出电效率随光伏板温度的升高而降低；太阳辐照度、室外温度和室外风速都对系统制冷性能有影响，其中室外温度对制冷量和COP的影响最大，当室外温度从23.6℃升高到32.8℃时，制冷量增大1.6倍，COP降低38.8%。该风冷式PV/T空调系统在夏季日间具有一定的冷电联产性能，可进一步优化以拓展其使用时间和应用范围。     

太阳能与空气源双蒸发器热泵复合供能系统性能实验研究

将基于平板微热管阵列的水冷PV/T集热器与双热源热泵相结合,提出1种太阳能与空气源双蒸发器热泵复合供能系统,该系统可实现多种运行模式的切换,以满足复合建筑的供热、供冷、热水和部分电力需求。实验主要针对于冬季制热工况和夏季供冷工况进行实验研究,分别从室外温度、太阳辐照度、热泵COP、制热量、集热效率和发电效率等方面对系统性能进行分析。实验结果表明,冬季制热实验时,空气源热泵制热、PV/T联合水源热泵制热和PV/T联合双热源热泵制热工况下COP分别为2.15、2.5和2.6,均能满足冬季室内的采暖要求。PV/T联合水源热泵制热和PV/T联合双热源热泵制热实验的平均发电效率和集热效率分别为12.1%和48.6%,11.3%和38.8%。空气源制冷实验时,热泵的EER平均为2.08;制冷兼制热水模式实验时,热水作放热源阶段的EER平均2.26,空气作放热源阶段的EER平均为1.96。     

玻璃盖板与光伏板间距对PV/T系统性能的影响

通过对PV/T系统中的光伏板和玻璃盖板进行热平衡分析,探讨光伏板与玻璃盖板之间的板间距对PV/T系统光热效率的影响。根据天津地区典型年气象参数,计算出在不同的板间距不同光伏板温度的情况下,PV/T系统中光伏板散热量和光热效率,对计算结果进行分析。随着板间距变大,PV/T系统的光热效率开始快速升高,达到极大值后随着板间距继续增加,光热效率有所下降,下降到一定程度后又有所上升。PV/T系统中光伏板散热量的变化趋势与此相反。对所分析的两种光伏板温度(40℃、50℃),最佳板间距随着光伏板温度的升高而减小。当光伏板的温度控制在40℃时最佳板间距为6 cm,当光伏板的温度控制在50℃时最佳板间距为5 cm。由于调节板间距容易实现,所以选择合适的板间距对提高PV/T系统的光热效率有实用价值。     

水冷型PV/T系统的高效利用与发展现状

在光伏光热系统(PV/T)中为提高其电效率并高效利用低品位热能,近年来对于冷却工质及其工作方式的研究越来越多。其中,水冷式以其方便直接使用、无需二次换热、良好的光学特性和高热容量等优点,受到了广泛的理论研究和实验测试。通过以效率的视角探究光伏覆盖率、背管分布形式等影响流体冷却能力的因素,并结合相变PV/T、PV/T矩阵等PV/T未来发展新趋势,为今后水冷型PV/T系统进一步高效实验提供了研究方向。     

太阳能光伏光热组件(PV/T)性能评价方法研究

结合对某太阳能光伏光热组件(PV/T)的测试数据,从热力学第一定律、热力学第二定律、发电效率和集热效率的角度对PV/T组件的性能进行了评价,对评价结果进行了分析,给出了PV/T组件性能评价方法。     

风冷式PV/T空调系统夜间制冷性能实验研究

提出了一种新型风冷式PV/T(光伏/光热)空调系统,并测试了系统在夏季夜间的制冷性能,研究了室内外空气温度对系统运行性能的影响。系统冷凝器由风冷式冷凝器和PV/T冷凝器串联组成,可以与周围空气进行对流换热,以及与低温天空进行长波辐射换热,在强化制冷效果的同时节约了冷凝器占地面积,为PV/T空调系统的发展提供新思路。实验结果表明,PV/T冷凝器能有效提高系统过冷度,PV/T冷凝器的冷却效果与冷凝温度呈正相关。风冷式PV/T空调系统制冷性能优于风冷式空调,其COP(性能系数)比风冷式空调高8.6%。当室外空气温度由23℃升高到27℃时,系统COP由3.9降低到3.1。当室内空气温度由20℃升高到24℃时,系统COP由3.1升高到3.5。     

光伏/光热一体化热电性能的实验研究

以上海市独栋住宅建筑屋顶光伏/光热一体化(PVT)系统为研究对象,对系统运行的集热与发电性能进行了实证研究.通过对系统运行参数的连续监测,实证了系统集热量、集热效率、发电量及发电效率等指标.研究结果表明:系统集热效率为33.72％,发电效率为10.33％,平均一次能源效率为66.74％;同时,由于PVT系统的冷却作用,相比于普通的光伏(PV)系统,PVT电池片温度相对较低,发电效率维持在较高的水平;由于技术限制,其单位功率(发电)成本为15.48元/W,相对于单独的光伏和光热系统,经济成本仍偏高.     

Exergetic performance assessment of a solar photovoltaic thermal (PV/T) air collector

In this paper, an attempt is made to evaluate the exergetic performance of a solar photovoltaic thermal (PV/T) air collector. A detailed energy and exergy analysis is carried out to calculate the thermal and electrical parameters, exergy components and exergy efficiency of a typical PV/T air collector. Some corrections are done on related heat loss coefficients. An improved electrical model is used to estimate the electrical parameters of a PV/T air collector. Further, a modified equation for the exergy efficiency of a PV/T air collector is derived in terms of design and climatic parameters. A computer simulation program is also developed to calculate the thermal and electrical parameters of a PV/T air collector. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Finally, parametric studies have been carried out. It is observed that the modified exergy efficiency obtained in this paper is in good agreement with the one given by the previous literature. It is also found that the thermal efficiency, electrical efficiency, overall energy efficiency and exergy efficiency of PV/T air collector is about 17.18%, 10.01%, 45% and 10.75% respectively for a sample climatic, operating and design parameters.     

A heat pipe photovoltaic/thermal (PV/T) hybrid system and its performance evaluation

Building-integrated photovoltaic/thermal (BIPV/T) system has been considered as an attractive technology for building integration. The main part of a BIPV/T system is PV/T collector. In order to solve the non-uniform cooling of solar PV cells and control the operating temperature of solar PV cells conveniently, a heat pipe photovoltaic/thermal (PV/T) hybrid system (collector) has been proposed and described by selecting a wick heat pipe to absorb isothermally the excessive heat from solar PV cells. A theoretical model in terms of heat transfer process analysis in PV module panel and introducing the effectiveness-number of transfer unit (?-NTU) method in heat exchanger design was developed to predict the overall thermal-electrical conversion performances of the heat pipe PV/T system. A detailed parametric investigation by varying relevant parameters, i.e., inlet water temperature, water mass flow rate, packing factor of solar cell and heat loss coefficient has been carried out on the basis of the first and second laws of thermodynamics. Results show that the overall thermal, electrical and exergy efficiencies of the heat pipe PV/T hybrid system corresponding to 63.65%, 8.45% and 10.26%, respectively can be achieved under the operating conditions presented in this paper. The varying range of operating temperature for solar cell on the absorber plate is less than 2.5 °C. The heat pipe PV/T hybrid system is viable and exhibits the potential and competitiveness over the other conventional BIPV/T systems.     

Evaluation of an Active Building Envelope window-system

Active Building Envelope (ABE) systems are a new enclosure technology which integrate photovoltaic (PV) and thermoelectric (TE) technologies. In ABE systems, a PV-system transfers solar energy directly into electrical energy, which can be used to power a TE heat-pump system. ABE-technologies allow for the development of thermal enclosure systems that have the ability to regulate their temperature (cooling or heating) by interacting with the sun. Applications include various enclosures that require thermal control, including building enclosures. This study considers the performance of the overall prototype ABE window-systems, and also includes the PV systems. This paper reports experimental results to establish the efficiency of the ABE system prototype. Computational analysis based upon PV modeling theories are carried out to simulate the performance of the PV system directly connected to a series of TE modules. The number and type of electrical connections for the TE modules is discussed in order to pursue the maximum power point for PV operation.     

Evaluation of a PV-integrated building application in a well-controlled outdoor test environment

This paper presents the assessment of experimental data for electrical and thermal performance evaluation of photovoltaic (PV) systems integrated as cladding components into the building envelope, giving input to modelling and analysis work. From the experience gained in several EU research projects, an improved design for a common Test Reference Environment (TRE) has been developed. This specific design of the PV module and TRE makes it possible to study, through electrical and thermal energy flow analysis, the effect on electrical performance of using different materials for PV modules and the construction design of claddings. The results for a glass–glass PV module with forced ventilation are presented.     

太阳能聚光光伏光热(CPV/T)系统研究

聚光光伏光热(CPV/T)系统将太阳电池与集热器相结合,通过聚光和跟踪太阳提高太阳辐照强度,增加太阳电池的单位面积发电量,集热器在冷却太阳电池的同时回收多余热能,获得电能和热能双重收益。本文研究聚光比、太阳电池效率、组件中电池片的有效覆盖率、热传导率等因素对系统性能的影响。     

石墨填充式PV/T系统光电光热性能试验

设计制作了一种以高导热材料——石墨为填充介质的新型PV/T结构,并搭建了该PV/T系统的光电光热性能综合试验台,在大连地区对其光电光热性能进行了试验研究。研究结果表明：在天气晴朗的情况下,与普通PV板相比,石墨填充式PV/T系统的输出功率相对提高可达120.67%;系统的瞬时热效率可达28.68%;系统水经过一天的循环,可使水箱温度上升至38℃。     

The feasibility of new design of hybrid photovoltaic-thermal system – a theoretical approach

Hybrid photovoltaic thermal (PVT) collectors have been evaluated according to the physical features of commercial photovoltaic (PV) cells; therefore, their commercial application is limited. The Tedlar collector has good electrical insulating properties, resulting in reduction in electrical efficiency. A researcher found that a glazed PVT system without Tedlar was the best among others, showing a significant increase in the overall efficiency. Inspired by this finding, we thought to study, for the first time, the feasibility of a new PVT that has been built by modifying a commercial PV panel and retrofitting it with the integration of two tubes in glass above the PV cell pasted on a thin metal ribbon before PV encapsulation. A heat transfer modelling/simulation in 3D was performed using COMSOL Multiphysics software.

The results show that under the no-cooling situation, the PV cell temperature reaches 74.87°C and the electrical power dropped significantly to 0.113 for electrical efficiency of 0.15 at the reference conditions. The water flow velocity is determined so that the cell can be effectively cooled. The cell temperature variation reaches to 45.9°C for a flow velocity of 0.5m/s, an irradiation of 1000W/m² and ambient temperature equal to 20.15°C.     

Effect of fluid flow and packing factor on energy performance of a wall-mounted hybrid photovoltaic/water-heating collector system

Façade-integrated photovoltaic/thermal (BiPV/T) technology is a relatively new concept in improving the overall energy performance of PV installations in buildings. With the use of wall-mounted water-type PV/T collectors, the system not only generates electricity and hot water simultaneously, but also improves the thermal insulation of the building envelope. A numerical model of this hybrid system was developed by modifying the Hottel–Whillier model, which was originally for the thermal analysis of flat-plate solar thermal collectors. Computer simulation was performed to analyze the system performance. The combined effects of the solar cell packing factor and the water mass flow rate on the thermal and electrical efficiencies were investigated. The simulation results indicated that an optimum water mass flow rate existed in the system through which the desirable integrated energy performance can be achieved.     

Modeling of energy performance of a house with three configurations of building-integrated photovoltaic/thermal systems

A theoretical and experimental study of energy performance of three different open loop air heating building-integrated photovoltaic/thermal (BIPV/T) systems that utilize recovered heat for home heating is presented. The configurations are: Configuration 1: base case of unglazed BIPV with airflow under it; Configuration 2: addition of 1.5 m vertical glazed solar air collector in series with Configuration 1; Configuration 3: addition of a glazing over the PV. The model developed has been verified against experimental data from a solar research house for Configuration 1. Obtained relationships for BIPV/T system exiting air temperature as function of solar irradiance and air speed in PV cavity may be used for developing fan airflow control strategies to achieve desired outlet air temperature suitable for different applications. For Configuration 1, preheated air is suitable for HVAC system and domestic hot water (DHW) preheating. Higher outlet air temperatures of the PV cavity suitable for DHW might be achieved by utilizing Configurations 2 or 3. With Configuration 2, significant outlet air temperatures are achieved in winter along with enhanced thermal efficiency making it suitable for coupling with a rockbed heat storage. Finally, Configuration 3 significantly reduces electricity production and may lead to excessively high PV panel temperatures.     

Theoretical performance assessment of an integrated photovoltaic and earth air heat exchanger greenhouse using energy and exergy analysis methods

In this paper, a simplified mathematical model develops to study round the year effectiveness of photovoltaic/thermal (PV/T) and earth air heat exchanger (EAHE) integrated with a greenhouse, located at IIT Delhi, India. The solar energy application through photovoltaic system and earth air heat exchanger (EAHE) for heating and cooling of a greenhouse is studied with the help of this simplified mathematical model. Calculations are done for four types of weather conditions (a, b, c and d types) in New Delhi, India. The paper compares greenhouse air temperatures when it is operated with photovoltaic/thermal (PV/T) during daytime coupled with earth air heat exchanger (EAHE) at night, with air temperatures when it is operated exclusively with photovoltaic/thermal system (PV/T) and earth air heat exchanger (EAHE), for 24 h. The results reveal that air temperature inside the greenhouse can be increased by around 7-8 °C during winter season, when the system is operated with photovoltaic (PV/T), coupled with earth air heat exchanger (EAHE) at night. From the results, it is seen that the hourly useful thermal energy generated, during daytime and night, when the system is operated with photovoltaic (PV/T) coupled with earth air heat exchanger (EAHE), is 33 MJ and 24.5 MJ, respectively. The yearly thermal energy generated by the system has been calculated to be 24728.8 kWh, while the net electrical energy savings for the year is 805.9 kWh and the annual thermal exergy energy generated is 1006.2 kWh.