A thermodynamic model of a solar assisted heat pump system with energy storage

In this study, a thermodynamic model of a solar assisted heat pump system with energy storage was developed. The model consists of thermodynamic correlations concerning the fundamental equipment in the system such as solar collector, energy storage tank, compressor, condenser and evaporator. Some model parameters of the system were calculated by using experimental results obtained from a pilot plant. Simulation studies were performed to assess the importance of some design factors on the system performance and economy.     

Experimental investigation of thermal performance of a solar assisted heat pump system with an energy storage

An experimental solar assisted heat pump space heating system with a daily energy storage tank is designed and constructed, and its thermal performance is investigated. The heating system basically consists of flat plate solar collectors, a heat pump, a cylindrical storage tank, measuring units, and a heating room located in Gaziantep, Turkey (37.1°N). All measurements are automatically collected as a function of time by means of a measurement chain feeding to a data logger in combination with a PC. Hourly and daily variations of solar radiation, collector performance, coefficient of performance of the heat pump (COP_HP), and that of the overall system (COP_S) are calculated to evaluate the system performance. The effects of climatic conditions and certain operating parameters on the system performance parameters are investigated. COP_HP is about 2.5 for a lower storage temperature at the end of a cloudy day and it is about 3.5 for a higher storage temperature at the end of a sunny day, and it fluctuates between these values in other times. Also, COP_S turns out to be about 15–20% lower than COP_HP. Copyright © 2004 John Wiley & Sons, Ltd.     

Numerical simulation of solar assisted ground-source heat pump heating system with latent heat energy storage in severely cold area

Solar assisted ground-source heat pump (SAGSHP) heating system with latent heat energy storage tank (LHEST) is investigated. The mathematical model of the system is developed, and the transient numerical simulation is carried out in terms of this model. The operation characteristic of the heating system is analyzed during the heating period in Harbin (N45.75°, E126.77°). From the results of the simulation, the average coefficient of performance (COP) of the heating system is 3.28 in heating period. In the initial and latter heating period, the COP of the heating system is higher, and the highest value is 5.95, because the system can be operated without heat pump. During the middle heating period the COP of the heating system and the operation stability of the system are improved due to solar energy and soil alternately or together as the heat source of heat pump. LHEST is a very important role in operation of the system. The system can be operated more flexibly, effectively, and stably by the charge and discharge heat of LHEST, and the effect becomes especially obvious in the initial and latter heating period.     

First and second law analysis of a solar assisted heat pump based heating system

We propose a model for the heating system of an ecological building whose main energy source is solar radiation. The most important component of the heating system is a vapour compression heat pump. Both the first law and the second law were used to analyse the heat pump operation. The state parameters and the process quantities were evaluated by using, as input, the building thermal load. The second law analysis emphasised that most of the exergy losses occur during compression and condensation. Preliminary results show that the photovoltaic array can provide all the energy required to drive the heat pump compressor, if an appropriate electrical energy storage system is provided.     

Design parameters for a solar heating system with an underground cylindrical tank

We have performed a theoretical analysis of a solar heating system with an underground cylindrical tank. A two-dimensional ground-temperature distribution is used around the tank. Heat-transfer problems are solved by application of complex, finite Fourier-transform technique and a finite difference method. A 25- and a 100-house community are considered for the performance calculation. The effects of collector area, tank volume, number of houses, and depth of the tank have been investigated for stanbul (40°N). Isotherms of the ground around the tank are illustrated in graphical form.     

The performance of a solar assisted heat pump water heating system

Analytical and experimental studies were performed on a solar assisted heat pump water heating system, where unglazed, flat plate solar collectors acted as an evaporator for the refrigerant R-134a. The system was designed and fabricated locally, and operated under meteorological conditions of Singapore. The results obtained from simulation are used for the optimum design of the system and enable determination of compressor work, solar fraction and auxiliary energy required for a particular application. To ensure proper matching between the collector/evaporator load and compressor capacity, a variable speed compressor was used. Due to high ambient temperature in Singapore, evaporator can be operated at a higher temperature, without exceeding the desired design pressure limit of the compressor, resulting in an improved thermal performance of the system. Results show that, when water temperature in the condenser tank increases with time, the condensing temperature, also, increases, and the corresponding COP and collector efficiency values decline. Average values of COP ranged from about 4 to 9 and solar collector efficiency was found to vary between 40% and 75% for water temperatures in the condenser tank varying between 30°C and 50°C. A simulation model has been developed to analyse the thermal performance of the system. A series of numerical experiments have been performed to identify important variables. These results are compared with experimental values and a good agreement between predicted and experimental results has been found. Results indicate that the performance of the system is influenced significantly by collector area, speed of the compressor, and solar irradiation. An economic analysis indicates a minimum payback period of about two years for the system.     

相变储能太阳能热泵系统的试验研究

文章建立了相变储能太阳能热泵系统试验平台,介绍了系统的运行方式以及各个部分的运行原理,选取典型日进行试验,并对试验数据进行分析。分析结果表明:相变储能太阳能热泵系统能够满足北方农村的供暖需求,可以保证白天室内的温度达到22℃,COP的最大值为6.3;太阳能热泵系统停止工作后,相变储能箱可以保证室内温度达到供暖的需求温度7 h,起到了"削峰填谷"的作用,运行费用显著降低;相变储能太阳能热泵系统解决了单纯电加热供暖方式费用高、能耗高的问题,具有显著的节能性。     

太阳能热泵地板辐射供暖系统

太阳能热泵低温地板辐射供暖系统是将太阳能、水源热泵和地板供暖结合在一起的新型采暖方式。介绍了太阳能热泵低温地板辐射供暖系统的工作原理和构成,并以青岛地区为例,设计了太阳集热器、蓄热器、地板换热盘管等设备,探讨了系统的设计方法。     

Optimization of a community solar heating system with a heat pump and seasonal storage

The optimization of a district solar heating system with an electric-driven heat pump and seasonal heat storage is discussed. The optimization process comprises thermal, economic and system control analyses. Thermal and economic optima have been derived for collector area and storage volume simultaneously. The effects of different collector types and building loads are also investigated. Summertime charging of the storage by off-peak electricity has been applied to avoid severe peaking of auxiliary in the winter and to reduce the yearly energy cost. The thermal co-storage of electric energy is emphasized with systems which fail to supply heat for the heat pump during the winter heating season.‡ It has been found that system cost-effectiveness is only slightly affected as storage volume is increased beyond the optimum size. Large variations in the optima for different system configurations were found. The minimum cost of heat supplied in an optimal 500-unit community with 90% solar fraction was estimated at 8.9 ¢ kWh⁻¹.     

太阳能供暖二级水箱变容积蓄热系统能量及?分析

太阳能供暖系统中的固定容积单水箱蓄热系统,在太阳能波动供给和建筑热负荷波动需求之间存在不匹配及灵活性不足的问题。为更高效地利用太阳能,本文对二级水箱温度分层变容积蓄热太阳能供暖系统建立了MATLAB数学模型,包括集热循环、充热循环、取热循环和供热循环四部分及相应的控制策略,并运用Trnsys进行了模型验证。提出了在某时间段内,实际参与充热、取热或同时充热与取热的水箱体积为有效蓄热体积的概念。定义了集热比、有效蓄热体积平均温度、水箱热量取充比和热损比等参数对系统进行了分析与评价。研究表明:与传统的太阳能供暖固定容积单水箱温度分层蓄热系统相比,在整个供暖季,二级水箱变容积蓄热系统的热损失减少了17.2%,取充比增加了6.3%,?效率提高了6.6%,辅热能耗减少了9.5%;在供暖初期,二级水箱变容积蓄热系统的水箱温度响应时间缩短了54.9%,可更灵活快速地用于供热。二级水箱变容积蓄热系统有利于调节供暖季不同时期的供需匹配,具有良好的节能效果,可进一步为太阳能供暖系统的设计与应用提供指导。     

A simulation study on a solar heat pump heating system with seasonal latent heat storage

Solar heating systems with seasonal energy storage have attracted an increasing attention over the past decades. However, studies of such systems using a phase change material (PCM) as seasonal storage medium have not been found in the open literature. In this paper a solar heat pump heating system with seasonal latent heat thermal storage (SHPH–SLHTS) is firstly described. This is followed by reporting the development of a simplified mathematical model for a SHPH–SLHTS system. Using the model developed, the operational performances of a SHPH–SLHTS system which provided space heating to a villa building have been investigated by simulation, and simulation results are reported in this paper.     

Net energy analysis of district solar heating with seasonal heat storage

A net energy analysis of district solar heating using seasonal heat storage has been performed. The use of seasonal heat storage is of great importance in northern latitudes when the solar contribution is to be increased. Different system alternatives were considered. Net energy ratios for the most favourable options were found to be between 3 and 5.     

Heat pump house heating system with phase change heat storage in the place of auxiliary heating

A house heating system consisting of an “energy roof” (unglazed collector), a heat pump, and medium-term phase change heat storage in the place of auxiliary heating was studied using a simple computer model. The least required storage volume is calculated and discussed as a function of the significant parameters. The choice of water for the storage medium is justified by showing the closeness of its phase change temperature to the economic optimum. The system appears technically feasible and permits minimum fossil fuel consumption together with the associated environmental benefits. Its economic position will depend on future price developments.     

An experimental analysis of a solar assisted absorption heat pump with earth seasonal storage

A plant composed of an energy roof, a seasonal earth storage and an absorption heat pump has been experimented. The purpose was to study the behaviour of the various components and their interaction. The surveys were carried out over a two year period. The following operations were considered: the charging of the earth storage by the energy roof and the working of an absorption heat pump connected either to the energy roof or to the earth storage.     

蔬菜大棚利用太阳能地下蓄热实践分析

对蔬菜大棚利用太阳能增温进行试验测试、分析和研究.试验结果表明:12个测温点的温室内土壤温度的月平均温度比没有安装太阳集热模块的高2～3℃.土壤温度的升高有利于蔬菜的生长,提高了温室大棚的经济效益.     

蓄热型太阳能-地源热泵耦合系统设计

以所设计的新型蓄热太阳能-地源热泵耦合系统为研究对象进行了现场模拟实验,太阳能集热器具有季节性蓄热功能,蓄热水箱可在冬季高品质供暖,夏季实现高效制冷。通过实验研究和经济分析结果显示,系统中地埋管换热器和蓄热水箱间歇运行,有利于地下温度场的恢复,延长地埋管的使用寿命,提高地源热泵工作效率及使用年限,具有明显的经济效益。     

直膨式太阳能热泵系统的数学建模及验证

文章建立了直膨式太阳能热泵系统的数学模型,其中包括有盖板的平板太阳能集热蒸发器数学模型、压缩机数学模型、冷凝器数学模型以及膨胀阀数学模型,并从两种角度对该数学模型进行求解,同时建立了实验平台,以实验数据来验证模型的正确性。结果表明,实验计算所得COP为6.18、集热效率η为0.65,模型的两种求解所得COP分别为7.11和6.95、集热效率η分别为0.71和0.68,将模型求解结果与实验计算结果进行对比,同时考虑理论与实际所允许的差距,可得该文建立的模型是正确的。     

Thermal performance of a solar-assisted heat pump drying system with thermal energy storage tank and heat recovery unit

Thermal performance parameters for a solar-assisted heat pump (SAHP) drying system with underground thermal energy storage (TES) tank and heat recovery unit (HRU) are investigated in this study. The SAHP drying system is made up of a drying unit, a heat pump, flat plate solar collectors, an underground TES tank, and HRU. An analytical model is developed to obtain the performance parameters of the drying system by using the solution of heat transfer problem around the TES tank and energy expressions for other components of the drying system. These parameters are coefficient of performances for the heat pump (COP) and system (COPs), specific moisture evaporation rate (SMER), temperature of water in the TES tank, and energy fractions for energy charging and extraction from the system. A MATLAB program has been prepared using the expressions for the drying system. The obtained results for COP, COPs, and SMER are 5.55, 5.28, and 9.25, respectively, by using wheat mass flow rate of 100 kg h⁻¹, Carnot efficiency of 40%, collector area of 100 m², and TES tank volume of 300 m³ when the system attains periodic operation duration in fifth year onwards for 10 years of operation. Annual energy saving is 21.4% in comparison with the same system without using HRU for the same input data.     

太阳能单罐蓄热系统的数值模拟与性能分析研究

文章以太阳能单罐蓄热系统为研究模型,以新型三元熔融盐KNO3-Na NO3-Na NO2为传热、蓄热介质,利用Fluent软件对熔融盐在斜温层蓄热单罐中的流动规律和传热特性进行数值模拟研究。研究结果表明:随着熔融盐入口流速的增大,斜温层厚度逐渐增加,蓄热效率逐渐降低,但过低的入口流速会延长蓄热周期;冬季、夏季工况下,应对罐体进行保温,并减少蓄热进程的中断,以降低热损失,提高蓄热单罐的蓄热效率。研究结果为单罐蓄热系统蓄热效率的提高指明了一条新思路,并为更加复杂的单罐传热以及蓄热模型的改进与研究奠定基础。     

太阳热水器与空气源热泵辅助加热集中供热水系统的工程设计

结合实例论述宾馆用太阳热水器与空气源热泵辅助集中供洗浴热水系统的工程设计方法,并着重介绍了空气源热泵的配置、布局、安装和控制.