季节性蓄热太阳能地板供暖系统的性能研究

本文建立了季节性蓄热太阳能地板供暖系统的数学模型,以上海一栋别墅建筑为实例,给出了系统中蓄热水箱的平均水温变化。同时分析了太阳能集热器面积、蓄热水箱容积、建筑热损失系数及地板供暖系统每天运行时间对系统性能的影响,为该系统的优化设计提供参考。     

太阳能地面采暖系统蓄热水箱容积分析

通过分析太阳能采暖系统所需蓄热鼍与建筑热负荷、太阳能集热量日变化规律之间的关系,得出太阳能采暖系统所需蓄热水箱容积的理论算式.根据拉萨、银川、西宁、西安等地的太阳辐射强度及建筑热负荷的日变化规律,模拟得出系统所需蓄热量变化规律;并对各种蓄热温差下对应的蓄热水箱容积进行了模拟分析,结果表明:太阳能采暖系统所需蓄热量随太阳集热器的集热量与建筑热负荷之间的差值增大而增加;蓄热水箱容积随蓄热温差增大而减小,当蓄热水温达到80℃时,在各种地面采暖系统取水温度下,单位集热器面积所需蓄热水箱容积趋于相等.     

蓄热水箱水温和水箱体积对太阳能集热系统的性能影响分析

采用实验和模拟计算方法对太阳能集热系统蓄热水箱的水温和水箱体积影响因素开展探究，分析日有用得热量、集热器功率和水箱内平均温度等参数随水箱初始温度和水箱体积的变化规律。研究结果表明：水箱初始温度从10.34℃增加到29.88℃时，日有用得热量减少了19.52%；换算成日太阳辐照量为17MJ/m2时的储热水箱中水的温升值下降了17.66%，储热水箱结束水温下降了10.73%；单位面积日有用得热量减少了17.64%。通过TRNSYS模拟软件，分析出太阳能集热系统全年运行工况时的水箱变量参数对系统性能的影响，获得了日有用得热量、集热器功率和水箱内平均温度的变化规律。通过选取不同月份的若干个时段进行对比分析，得出水箱体积对太阳能供热系统的影响较水箱初始温度大；当下调水箱初始温度和缩小水箱体积时，日有用得热量提升，但集热器功率降低；当上调水箱初始温度和缩小水箱体积时，水箱内平均温度升高；且随着太阳能集热系统运行时间的累加，水箱初始温度和水箱体积对上述各性能参数的影响减弱。日有用得热量、集热器功率和水箱内平均水温随着季节变化明显，秋季和冬季气候下的日有效得热量，集热器功率和水箱内平均水温均低于春季和夏季。     

基于插栓流模型的太阳能供热系统的研究

采用蓄热水箱的多节点模型,对典型太阳能供热系统进行全年逐时模拟计算.计算数据表明,相比于完全混合的蓄热水箱,水箱温度分层可较大幅度提高太阳能集热器的平均效率和太阳能保证率.同时还分析了不同集热器类型、供水温度、供回水温差等条件下.蓄热水箱温度分层对太阳供热系统性能提高程度的影响.     

太阳能、蓄热与地源热泵组合系统的应用与实验

在天津地区针对某建筑物设计建成太阳能、蓄热与地源热泵组合系统(SGCHPSS)的示范工程与数据采集系统.结合建筑特点与用途,设计太阳能热利用与蓄热利用,将夏季丰富的太阳能储存于地下土壤中,提高土壤冬季热源温度,以提高地源热泵效率,实现太阳能的转移利用.初步实验得到夏季蓄热时集热器进、出口温度,日蓄热时间,蓄热功率及系统耗功等.     

太阳能相变蓄热复合土壤源热泵系统的研究

叙述了以太阳能相变蓄热装置蓄热,且与蒸发器进口处换热的辅助热泵系统,用20号蓄热专用石蜡,通过板式换热器与蒸发器进水管进行热量传递的实验。指出,利用太阳能集热器在白天升高蒸发器侧的温度提高热泵效率,利用储存在蓄热装置中的热量夜晚可对蒸发器的进水增温,以此实现太阳能相变蓄热装置与复合土壤源热泵系统的良好结合,提高整个系统的供热效率。     

严寒C区太阳能热水采暖系统设计参数匹配的研究

以太阳能热水采暖系统蓄热水箱的容积与太阳能集热器的集热面积的匹配关系为研究对象,通过数值模拟的方法,以严寒C区的赤峰地区为例,参考赤峰地区的逐时气象数据,以太阳能热水采暖系统的集热效率、太阳能贡献率为优化目标,对蓄热水箱的容积与太阳能集热器的集热面积的比值(RVA)、蓄热水箱保温层厚度等设计参数进行了优化研究.研究结果...     

浅议太阳能+蓄热+辅助热源供热方式——以西藏巴青县供热为例

简述了适用于西藏高原及大风地区的太阳能集热器,以西藏巴青县城供热项目为例,介绍了太阳能+蓄热+辅助热源供热的控制方式,该供暖系统可满足巴青县供暖工程的需要。     

一种太阳能相变蓄热沙发采暖系统分析

介绍一种把太阳能热利用、相变蓄热与局部采暖技术结合的新型太阳能相变蓄热沙发采暖系统，阐述该系统的组成和工作原理，并给出沙发散热量、蓄热材料用量、集热器面积等关键设计参数的计算方法。     

太阳能热泵供热系统实验台的设计及误差分析

开发新能源和节能是寻找能源出路的两大途径,太阳能热泵系统以其显著的节能性和环保性具有广阔的发展前景。介绍了太阳能热泵供热实验台集热器、蓄热器等设备的设计,分析了集热器集热效率的测试误差,指出太阳能热泵供热实验台测试数据准确、可靠,为太阳能热泵供热系统的设计、安装和运行提供了有价值的参考依据。     

Modeling of the CSU heating/cooling system

This paper resents a thermal simulation of the Colorado State University solar house. A computer model of the solar energy system was developed and computer runs were made using one year of meteorological data to determine the important design features. The system consists of a flat plate solar collector, main storage tank, service hot water storage tank, auxiliary heater, absorption air conditioner with cooling tower and heat exchangers between the collector and storage, storage and service hot water tank and storage and residence. This system very closely models the CSU house in operating mode one.The results are in the form of monthly integrated values for the pertinent energy quantities. In addition, results are presented which show the effect on the system performance of the collector tilt, collector area and number of covers.     

Experimental investigation of a domestic solar water heater with solar collector coupled phase-change energy storage

Phase change materials (PCMs) have good properties such as high thermal capacity and constant phase change temperature. Their potential use in solar energy storage is promising. Tests of exposure and constant flow rate are performed to investigate the thermal performance of a domestic solar water heater with solar collector coupled phase-change energy storage (DSWHSCPHES). Due to the low thermal conductivity and high viscosity of PCM, heat transfer in the PCM module is repressed. The thermal performance of the DSWHSCPHES under exposure is inferior to that of traditional water-in-glass evacuated tube solar water heaters (TWGETSWH) with an identical collector area. DSWHSCPHES also performs more efficiently with a constant flow rate than under the condition of exposure. Radiation and initial water temperature have impacts on system performance; with the increase of proportion of diffuse to global radiation and/or initial water temperature, system performance deteriorates and vice versa.     

Energy analysis and modeling of a solar assisted house heating system with a heat pump and an underground energy storage tank

An analytical model is presented and analyzed to predict the long term performance of a solar assisted house heating system with a heat pump and an underground spherical thermal energy storage tank. The system under investigation consists of a house, a heat pump, solar collectors and a storage tank. The present analytical model is based on a proper coupling of the individual energy models for the house, the heat pump, useful solar energy gain, and the transient heat transfer problem for the thermal energy storage tank. The transient heat transfer problem outside the energy storage tank is solved using a similarity transformation and Duhamel’s superposition principle. A computer code based on the present model is used to compute the performance parameters for the system under investigation. Results from the present study indicate that an operational time span of 5–7 years will be necessary before the system under investigation can attain an annually periodic operating condition. Results also indicate a decrease in the annually minimum value of the storage tank temperature with a decrease in the energy storage tank size and/or solar collector area.     

A case study of underground thermal storage in a solar-ground coupled heat pump system for residential buildings

This paper presents a case study of underground thermal storage in a solar-ground coupled heat pump system (SGCHPS) for residential buildings. Based on the experimental results, the operation performance is simulated by the unit modelling. The results show that the performance of underground thermal storage of SGCHPS depends strongly on the intensity of the solar radiation and the matching between the water tank volume and the area of solar collectors. Compared with the solar radiation, the variations of the water tank temperature and the ground temperature raise lag behind and keep several peaks during the day time. In the present study, the experimental efficiency of underground thermal storage based on the absorbed solar energy by the collectors reaches 76%. For the similar design of SGCHPS, it is suggested that the optimal ratio between the tank volume and the area of solar collectors should range from 20 to 40 L/m².     

An analysis of solar heating systems that use vapor-compression cycles

This paper analyzes the technical and economic performance of solar heating systems that use vapor-compression cycles, circulating a compressible fluid as the working fluid. With conventional solar heating systems that use water or as their working fluid, the collector inlet temperature is equal to that of the storage outlet temperature. Operating the system on a cold day can result in large thermal losses to the surroundings and, thus, low useful heat gains. A vapor-compression cycle may be attractive because it allows the collector inlet temperature to be lowered so that the heat gain of the collector can be increased. Such a system is simulated and a preliminary economic analysis performed. The results indicate that the vapor-compression system can collect almost 50% more solar energy than a conventional system if the collector area of the two systems are the same.     

A computational model of a domestic solar heating system with underground spherical thermal storage

This theoretical study deals with a domestic heating system assisted by solar energy stored in an underground spherical container. The system includes a heat pump. The analytical model employed calculates the water temperature in the storage vessel, as well as the temperature distribution in the surrounding geological structure, by using the monthly-average solar radiation and ambient temperature. Storage temperature, collector efficiency, performance coefficient of the heat pump (COP) and annual solar fraction are computed and presented in various graphs. The importance of seasonal solar energy storing in the ground is demonstrated.     

Performance simulation of solar-boosted ocean thermal energy conversion plant

Ocean thermal energy conversion (OTEC) is a power generation method that utilizes small temperature difference between the warm surface water and cold deep water of the ocean. This paper describes the performance simulation results of an OTEC plant that utilizes not only ocean thermal energy but also solar thermal energy as a heat source. This power generation system was termed SOTEC (solar-boosted ocean thermal energy conversion). In SOTEC, the temperature of warm sea water was boosted by using a typical low-cost solar thermal collector. In order to estimate the potential thermal efficiency and required effective area of a solar collector for a 100-kWe SOTEC plant, first-order modeling and simulation were carried out under the ambient conditions at Kumejima Island in southern part of Japan. The results show that the proposed SOTEC plant can potentially enhance the annual mean net thermal efficiency up to a value that is approximately 1.5 times higher than that of the conventional OTEC plant if a single-glazed flat-plate solar collector of 5000-m² effective area is installed to boost the temperature of warm sea water by 20 K.     

太阳能-土壤源热泵联合供暖系统优化研究

针对严寒地区的气候条件,选取哈尔滨地区某居民住宅小区作为研究对象,利用TRNSYS软件对太阳能-土壤源热泵联合供暖系统(SGCHP)进行计算分析。结果表明:太阳能-土壤源热泵联合供暖系统中太阳能集热器对热泵机组的进水温度和COP以及节电量等方面有改善作用;对太阳能-土壤源热泵联合供暖系统中太阳能集热器面积与地埋管管长的最佳配比的优化结果表明,1 m~2太阳能集热器可保证17～27 m长的地埋管取热平衡。并继续模拟了沈阳地区,并以哈尔滨地区为基准,给出严寒地区该参数的推荐值。     

Solar water heaters with phase change material thermal energy storage medium: A review

Latent heat thermal energy storage is one of the most efficient ways to store thermal energy for heating water by energy received from sun. This paper summarizes the investigation and analysis of thermal energy storage incorporating with and without PCM for use in solar water heaters. The relative studies are classified on the basis of type of collector and the type of storage used i.e. sensible or latent. A thorough literature investigation into the use of phase change material (PCM) in solar water heating has been considered. It has been demonstrated that for a better thermal performance of solar water heater a phase change material with high latent heat and with large surface area for heat transfer is required.     

Analysis and performance of a low-cost solar heater

One of the alternatives to reduce the consumption of electricity for heating water is by popularizing the use of solar energy. This work contributes with studies on a Low-Cost Solar Heater (LCSH), a new concept of solar water heater made entirely of polymeric materials, which requires a relatively low investment and is user-assembled. The solar collector, which absorbs solar energy and transfers it to water in the form of heat, is composed of uncovered flat panels of rigid PVC. The storage tank that holds the water heated during the day is made of polyethylene coated with polystyrene. The results of the LCSH were compared with those of a conventional solar heater composed of a glass-covered copper collector and a stainless steel storage tank. The efficiency of the systems was evaluated by measuring the incident solar radiation and water temperature with the systems operating naturally (thermosiphon). The heat loss in the hot water storage tanks was measured to estimate the thermal performance of the solar heaters. Considering that the target temperature for the heated water is slightly above the ambient temperature, the results indicated that the LCSH showed a satisfactory global heat transfer coefficient for storage tanks and that it attained an excellent thermal performance, although it is not as efficient as the conventional heater.