Energy-saving Technology of Vent in Passive Solar Wall of Rural House of Severe Cold Region

This paper aims at solving the problems of low thermal collection rate,inconvenient maintenance,hindering indoor using during the application of passive solar technologies in rural houses in severe cold region.All these defects prevent the passive solar houses' further development. This paper chooses trombe wall,which has higher thermal efficiency of the passive solar house,as research object. The traditional vent is improved into a new type of ventilation device. This improvement overcomes the shortcoming,which traditional vent loses huge heat,and simplifies the construction of vent. Comparing with traditional trombe wall,the energy saving rate is 15. 69%.

Designing an Automatic Control System for the Improved Functioning of a Solar Wall with Phase Change Material (PCM)

Solar walls constitute an important green architectural feature that positively contributes to energy saving in buildings. Different configurations may be proposed, such as, solar wall with Phase Change Material (PCM), composite solar wall, photovoltaic solar wall, zigzag solar wall, and solar hybrid wall. Being environmentally friendly, these passive solar components can provide thermal comfort and help save energy. Their disadvantages include principally unpredictable heat transfer, heat losses by night for some systems or inverse thermo-siphon phenomenon. Appropriate energy management techniques can be used to control and optimize the performances of solar walls. An experimental study for energy management of a PCM based solar wall is described in this paper. The experimental results show the effectiveness of the proposed automatic control system in regulating the capture of solar energy.

Steel-Tinplate as a Solar Wall Panel and Its Effectiveness

The aim of the research was to investigate black colored steel-tinplate use for absorber and covering material of the collector and compare the efficiency of three types of air heating collectors. This heated air can be exploited for drying of agricultural products, room ventilation and room heating etc. 0.1 × 0.5 × 1.0 meter long FPC （fiat-plate collector） with a sun following platform was built. Air velocity at the experiments was v = 0.9 m/s. Collectors of insulated and un-insulated surfaces with steel-tinplate absorber as a covering material warmed the ambient air up to 10-12 and 5-6 degrees correspondingly （at irradiance 800 W/m^2）. This difference indicates the great importance of insulating the collector body. It can be explained with intense heat exchange between the absorber and ambient air which reduces the efficiency of the collector. There was good correlation with irradiance and the air heating degree. The investigations showed that more effective FPC had the collector with absorber tinplate in the middle of the collector body. At favorable weather conditions the heating degree of the ambient air at the outlet reaches 6-8 degrees more that at the outlet of the insulated collector covered by steel-tinplate.

SOLAR WALL SYSTEM, THE SUN-CENTERED APPROACH TOWARD ECOSYSTEM

Energy costs are continuing to rise as the Earth’s fossil fuel resources diminish. In addition, the population of the earth is increasing, meaning that the use of these scarce resources will increase at a faster rate than in the past. Inevitably, the result will be continuing increases in the Earth’s temperature, resulting in widespread climate change that could have devastating environmental impacts. Thus, as the Earth is moving rapidly toward an energy crisis, sustainable architecture with enhanced energy efficiency takes on great importance in seeking to establish a reasonable balance between human needs and the environment. To achieve this balance, it is essential that we use every available means to manage and reduce people’s basic needs-such as heating or cooling of living spaces-in order to minimize our use of non-renewable energy sources. The Sun is one of the largest and cheapest sources of energy. This tremendous resource has the ability to meet a large portion of human needs. In recent decades, solar energy has been used extensively to achieve environmental sustainability. One of these applications is the use of solar energy to provide warm air in buildings. The purpose of this paper is to investigate renewable energy sources, particularly solar energy and the solar systems currently in use around the world. By assessing their positive and negative attributes, we also intend to propose an alternative solar wall for producing warm air in buildings. Thus, in addition to addressing the weaknesses of previous products and approaches, we intend to augment the energy savings and decrease the costs associated with such systems by combining the positive attributes of several different systems to produce more efficient air heating, lighting, air circulation, and air purification.

Numerical Study of Classical and Composite Solar Walls by TRNSYS

The laboratory LAMTI has worked for several years on the study and the optimization of the thermal performances of passive solar walls like solar Trombe wall. These components of the buildings envelope have very complex behaviour because they are the seat of various coupled heat transfers modes and are subjected to the random variations of the meteorological parameters. Using the finite difference method （FDM） and starting from experimental results recorded during several years, a simulation model was developed and validated concerning the ＂composite＂ Trombe wall. In order to make this work more accessible to the community of the heat engineers, it appears interesting to build a simulation model which can be integrated into the library of elements of the TRNSYS software. A ＂Type＂ was thus carried out and the results obtained compared with those of the FDM model. In this work we compare the obtained results with these two numerical ways. The assumptions and the results of simulations are also confronted with those of an existing module in TRNSYS （Type 36） established for the ＂classical＂ Trombe wall. The study shows that the models that we developed are very precise and that certain assumptions must be used with a lot of precautions. The advantages of the composite Trombe solar wall compared to the Classical Trombe wall are highlighted for cold and/or cloudy climates.

Lattice Boltzmann Simulation for Complex Flow in a Solar Wall

In this letter,we present a lattice Boltzmann simulation for complex flow in a solar wall system which includes porous media flow and heat transfer,specifically for solar energy utilization through an unglazed transpired solar air collector(UTC).Besides the lattice Boltzmann equation(LBE) for time evolution of particle distribution function for fluid field,we introduce an analogy,LBE for time evolution of distribution function for temperature.Both temperature fields of fluid(air) and solid(porous media) are modeled.We study the effects of fan velocity,solar radiation intensity,porosity,etc.on the thermal performance of the UTC.In general,our simulation results are in good agreement with what in literature.With the current system setting,both fan velocity and solar radiation intensity have significant effect on the thermal performance of the UTC.However,it is shown that the porosity has negligible effect on the heat collector indicating the current system setting might not be realistic.Further examinations of thermal performance in different UTC systems are ongoing.The results are expected to present in near future.

Determination and Analysis on Heat of Trapezoidal Soil Wall in Solar Greenhouse

Solar greenhouse with trapezoidal soil wall is widely used due to its good heat retaining property and cost efficiency.In this study, solar irradiance, heat flux and the temperature 0.05 and 0.3 m from the inner surface of the wall at the upper,middle and lower measured positions were determined to study the thermal condition of the trapezoidal soil wall in solar greenhouse. The results showed: first, both the solar irradiance and the temperature increased from the upper to the lower measured position. Second, the heat absorption also increased from the upper to the lower measured position. In clear day, the heat absorption at the three measured positions accounted for 31.4%, 32.6% and 36.0% of the total amount of heat absorption of the whole wall. In cloudy day, the heat absorption at the three measured positions were 0.249, 0.370 and 0.440 MJ/m^2, which accounted for 23.5%, 35.0% and 41.4% of the total amount of heat absorption of the whole wall. When P<0.05, the heat fluxes were strikingly different between the upper and lower measured positions. But when P<0.01, the heat flux had no big difference among the three measured positions. Third, in clear day, the heat emission was the biggest at the middle measured position and smallest at the upper measured position. The heat emission at the three measured positions accounted for 27.5%, 36.7%and 35.8% of the total amount of heat emission of the whole wall. And the heat emission between the middle and lower measured position was not strikingly different. In cloudy day, the heat emission was the biggest at the lower measured position and smallest at the upper measured position. The average heat emission at the three measured positions accounted for 26.1%,36.4% and 37.4% of the total amount of heat emission of the whole wall. Fourthly, correlativity, the solar irradiance directly influenced the heat absorption and had close relation with heat emission. And heat emission again had close relation with the temperature in the greenhouse. Solar irradiance directly influences the thermal condition of a solar green house. It is hoped that this study can be referred to optimize trapezoidal structure and to improve the thermal conditions of the solar greenhouse.

CFD Simulations of Wind Effect on Net Solar Heat Gain of South Walls with Internal Insulation

Computational fluid dynamics( CFD) techniques are used to investigate effects of both wind direction and wind speed on net solar heat gain of south wall with internal insulation in winter.Results show that wind effect has a significant influence on the net solar heat gain,where the impact of wind direction is stronger than that of wind speed. For regions in lower reaches of the Yangtze River,difference of their average net solar heat gains( NSHGS) is about 20% due to various wind speeds and wind directions.Buildings in districts with a dominant wind direction of north achieve the highest solar energy utilization.

Preparation of Multi-Wall Carbon Nanotubes/Graphene Composites with Cadmium Sulfide in Dye-Sensitized Solar Cells (DSSCs)

In the present work, Dye Sensitized Solar Cells (DSSCs) have been fabricated by utilizing a dense layer of photoelctrode cadmium sulfide thin film (CdS) as n-type, which prepared by spray coating, while p-type electrode was multi-wall carbon nanotubes/graphene (MWNT-G) composites. The experimental results showed the higher energy conversion efficiency for CdS/MWNT-G was 0.056% in comparison with the others, which were CdS/MWNT with 0.044% and CdS/G with 0.037% respectively, which referred to improvement in the conductivity by using MWNT-G. The microstructure and nanostructure of CdS, MWNT, G, and MWNT-G nanocomposite were carried out by employing Scanning Electron Microscopy (SEM). X-Ray Diffraction (XRD) has been used to get crystal size of CdS, Raman scattering, and optical absorption also used for characterizations the samples. This study promised to increase and enhance the conversion efficiency of photovoltaic devices.

A Study of Passive Solar House Design

This paper deals with the investigation of the principles of passive solar house design, passive solar systems, and techniques for solar house design. It is expected that the research is to be of momentous significance to the design and construction of passive solar house, and may make contribution to the massive energy efficient housing construction in our country.

不同集热蓄热墙集热情况模拟研究

集热蓄热墙式建筑的研究方向主要是百叶型集热蓄热墙和多孔型集热蓄热墙等。使用Fluent软件,采用RNGk–ε方程湍流模型和太阳辐射模型模拟不同类型被动太阳能集热蓄热墙与室内的传热情况,建立了两种集热蓄热墙和传统集热蓄热墙的模型,模拟了在沈阳冬季和夏季条件下,两种不同集热蓄热墙与传统式集热蓄热墙的墙体内、外壁面温度和室内温度等参数。通过分析比较3种模型的模拟结果得出,百叶型被动太阳能集热蓄热墙在冬季集热性能比其他类型墙体好,室内温度较对比模型提高了3℃,在夏季,有效降低了墙体向室内的热负荷。本研究对集热蓄热墙的建筑改造及进一步的研究有一定的参考价值。

光伏建筑一体化光伏幕墙体系与经济性研究

在当今全球能源转型的大背景下,建筑行业作为主要能源消费领域,其能源消费模式的革新对于实现国家层面的可持续发展目标至关重要。鉴于此,显著削减建筑领域对化石燃料的依赖,并积极拓宽可再生能源的利用渠道,成为了推动绿色建筑革命的重要策略。光伏建筑一体化(BIPV)技术,作为一种将高效光伏发电系统与现代化建筑设计、建造工艺深度融合的创新实践,不仅展现了太阳能这一清洁、可再生资源的巨大应用潜力,而且也预示着未来建筑领域在能源自给自足方面广阔的发展蓝图。为了探究光伏建筑一体化的现状,文章对光伏建筑一体化的背景及常用的应用场景进行研究,通过案例分析光伏幕墙增量成本,并采用静态投资回收期和效益费用比两个参数对薄膜类光伏幕墙、晶硅类光伏幕墙、薄膜类光伏采光顶三种光伏方案的经济性进行分析,为后续光伏建筑一体化中光伏幕墙的经济性提供参考。

装配式柔性墙体日光温室联合储热系统蓄放热特性

增设多蓄热介质联合主动蓄放热系统是解决装配式柔性墙体日光温室“重保温、轻蓄热”问题的有效方法,但当前对于“土壤-空气-水”多介质联合储热系统蓄放热特性和加温效果尚不明确,针对此问题,该研究以配备“空气源地中热交换-水源后墙循环换热”联合储热系统的装配式柔性墙体日光温室为研究对象,采用现场跟踪测试和能量转移测算,对联合储热系统各自和组合的蓄放热特性进行研究。结果表明,配有联合储热系统的装配式柔性墙体日光温室室内夜间最低空气温度维持在10℃以上,室内外最大温差达26.5℃。0~50 cm的土壤层是该温室主要蓄热介质,晴天土壤层蓄热量最高占总蓄热量的63.5%。地中热交换系统最高占土壤蓄热量的54.4%。水循环系统蓄热量可达424.04 MJ,最高占总蓄热量的45.1%,通过循环蓄热可将储水池内8 m3水的温度提高到35℃。连阴天时,通过引入蓄放热比指标,对联合储热系统的运行效果进行定量评价,发现水循环系统具有蓄放热速度快的特点,蓄放热比绝对值最高可达1.62,是当天土壤蓄放热的1.8倍。但从总量上看,土壤仍是连阴天主要放热来源,在北京地区联合蓄放热系统能够维持3个连阴天的热量需求。水循环系统平均性能系数(coefficient of performance,COP)为9.16,地中热交换系统平均COP为6.82,联合蓄放热系统综合COP为8.85,对比热泵,其节能率达60.26%。研究结果为联合储热系统蓄放热机理研究提供了理论依据。

不同日光温室墙体结构热性能分析

[目的]探索不同日光温室在杨凌地区的保温性能,寻找适宜在杨凌地区推广的新型、适宜建造、标准化程度高的日光温室。[方法]对传统后墙主动蓄热温室(G1)、相变固化土后墙主动蓄热日光温室(G2)、现浇筑混凝土后墙主动蓄热温室(G3)和模块化素土后墙主动蓄热日光温室(G4)的墙体热结构性能进行对比分析。[结果]在典型晴天条件下,4座温室平均气温分别为15.68、15.83、16.52、18.44℃;在典型阴天条件下,4座温室平均气温分别为8.09、11.12、10.97和11.21℃。[结论]G4模块化后墙的主动蓄热能力使温室在冬季夜间保持较高温度,为作物越冬提供了更适宜的环境条件。模块化日光温室以其独特的施工工艺和可就地取材、施工周期短、标准化建设、机械化等优势,在杨凌及西北地区具有推广价值。

玻璃幕墙建筑中入射太阳辐射逃逸性计算

太阳发出的辐射能量由于地表建筑物的吸收、再辐射等过程,部分能量未能有效捕获而逃逸到空间中。传统建筑中假设入射进入室内太阳辐射不能再次通过窗户逃逸,但这一假设不适用于玻璃幕墙建筑。为了计算太阳辐射逃逸率,文章基于辐射度照射法建立了太阳辐射模型,使用Matlab软件进行了模拟计算,计算并分析了在不同时间尺度上的太阳辐射逃逸率变化规律。数值计算结果表明,不同时间的逃逸太阳辐射率随太阳辐射入射角变化而变化,日墙方位角越小,太阳辐射逃逸率越小。南朝向房间夏至日太阳辐射逃逸率变化范围为8.88%~10.29%,全年太阳辐射逃逸率呈周期性波动,秋季与冬季的波动较大,波幅达6.8%,而夏至日时全天变化仅为1.4%。通过加权平均计算,得到太阳辐射逃逸率夏季最大为9.26%,其次是过渡季,冬季最小为8.12%。

基于裸土地面的日光温室室内温湿度预测模型构建

为探究日光温室热湿环境形成机理和规律,认识其内部多物理场耦合的复杂物理现象,根据日光温室的结构特性、外部环境条件等参数,应用传热传质学理论,基于日光温室围护结构内表面热量平衡关系式、空气热量及湿量平衡关系式,考虑墙体湿传递、土壤蒸发等作用建立日光温室室内温湿度预测模型。该模型借助Matlab软件,利用迭代法求解微分方程组得到室内温湿度,并与实验值进行对比及验证分析。结果表明:连续两日内室内空气温度及湿度的预测值与实测数据相对误差分别为5.11%、4.17%;一致性指数分别为0.98、0.94;预测值和实验值之间不存在显著性差异。理论预测值与实验测定值相对误差小,模型一致性高、可靠性强,考虑墙体湿传递和土壤蒸发的影响后可使裸土地面的日光温室室内温湿度的预测模型更加准确。

分频北墙结构对日光温室内光热环境的影响

日光温室为中国特有的一种栽培设施结构,非对称的结构形式造成温室内南北光环境分布不均匀,一般墙体结构冬季夜间保温不能满足多数作物的生长需求。为构建具有保温蓄热能力、反射补光能力的多功能墙体结构,该研究设计了一种直接吸收太阳能的红外分频补光板(infrared frequency divided and supplementary light panel,IFDSLP),可对室内光热环境进行调节。合成了基于氧化锡锑(antimony tin oxide,ATO)-三氧化钨(tungsten trioxide,WO_(3))的水基纳米流体,将该纳米流体补充进IFDSLP内腔,作为传热分光工质。当IFDSLP集热面积为7.2 m^(2),光程为10 mm、体积分数为0.005%时,该流体工质在300~800 nm的植物光合有效波段中的平均反射率为79.6%,在近红外光波段中的平均吸收率为85.4%。该结构在增加温室北侧作物光照的同时,兼具温室夜间升温能力。IFDSLP系统的太阳能总利用率为71.9%,光热转换效率为36.4%,相比传统砖墙光辐射增加25%~28%,夜间空气温度平均提高1.5~2.0℃。该系统依托于现有日光温室结构,进一步改善了温室内的光热环境,是提高温室北墙全光谱利用率的有效途径。

新型主动蓄放热墙体改善日光温室内热环境的数值研究

针对日光温室砌块承重墙体存在热稳定层,限制利用日间免费得到的太阳能用于夜间加热,致使室内空气昼夜温差大,不利于作物生长的问题,该文构建一种带重力循环环形管的新型主动蓄放热复合墙体,利用传热学理论建立该墙体非稳态传热模型,耦合室内空气热平衡方程,借助Matlab进行数值模拟。结果表明:在寒冷地区的冬季,新型主动蓄放热墙体夜间可使室内空气温度提高1.21℃,相比无重力循环环形管墙体提高13.12%;日有效积温提高7.88℃·h,相比提高4.84%;日平均热负荷可降低4769.24 W/d,相比降低17.35%。该墙体能增强主动蓄放热能力,将更多太阳能转移到夜间使用,可有效降低日间过高室温、提升夜间过低室温,减小室内气温日较差,有利于作物“四段变温管理”,促进冬季作物快速生长。

相变材料在装配式复合墙体日光温室中的应用研究

为进一步提高日光温室墙体的蓄热能力,改善室内热环境,对石蜡-膨胀珍珠岩复合相变材料(paraffin-expanded perlite composite phase change material, PCM-PE)在温室中的应用进行研究。利用TRNSYS(transient system simulation program)建立装配式复合墙体日光温室的模型,用晴天和阴天的实测数据验证模型准确性,利用该模型分析温室的北屋顶、侧墙、北墙等结构内表面分别添加PCM-PE后室内温度的变化和单位成本,及温室北屋顶、侧墙和北墙均添加PCM-PE时的最佳厚度。结果表明:温室不同结构内表面添加PCM-PE均对室内平均温度有明显提升作用,侧墙内表面添加PCM-PE使晴天时室内平均温度提高1.32℃,单位成本最低,为2 094元/℃;北屋顶、侧墙、北墙均添加PCM-PE时,其最佳厚度为50 mm,晴天室内平均温度和北墙平均温度分别提升3.9和3.7℃,阴天分别提升2.2和2.3℃;添加50 mm PCM-PE后,温室墙体传热系数较试验温室降低了15%,热阻提高了9.9%,对维持室内温度、降低温室能耗具有积极作用。分析温室不同结构应用PCM-PE的效果,同时考虑单位成本,可为建造经济性好、蓄热性能强的温室提供参考。

新型动态保温相变Trombe墙体热性能的实验研究

通过测试一间有一面是相变材料另一面是保温材料的新型动态Trombe墙体的房屋全尺寸模型,对该墙体的热性能进行实验研究。以墙体和房间的空气温度以及通过墙体的热流量和气流速率来评估其性能。结果表明:在相变过程中,温度变化相对平缓;墙体从玻璃获得的热量占其获得总热量的26.2%,且利用其储存的90.1%的热量对房间进行加热;在相变材料放热期间,该墙体可降低室内温度的分层且房间中部的温度至少比室外温度高3.2℃。