Successive lumped analysis simulation of solar energy collection systems

A methodology for deriving an analytical, simplified solar system performance prediction model is presented. Factors related to system design can be examined; for example, storage tank temperature variations, solar system turn-on and turn-off times and system ‘memory’. A simple domestic water heating type system is used as a basis for illustrating derivation of performance models. Predicted performance results are in good agreement with results obtained from another design method. A generalized procedure is described for deriving new system models. The lumped analysis simulation may prove useful for non-standard applications where other simplified design methods are not defined and where detailed simulation capability is not available.     

A new TRNSYS component for parabolic trough collector simulation

This study describes and evaluates a new simulation component for parabolic trough collectors (PTCs). The new simulation component is implemented in the TRNSYS software environment by means of new Type that is suitable for integration into the calculation of a whole concentrating solar thermal plant, in order to evaluate the energy production of a PTC. The main advantage of the new Type is that is derived from experimental data available on efficiency Test Reports, according to the current European and International standards, rather than the theoretical approach considered in the existing parabolic trough component of TRNSYS library. The performance of the new Type has been validated with real experimental data obtained from the DISS solar test loop in Plataforma Solar de Almería, Spain. The paper describes the modelling approach, presents the comparison of simulation results with measurements taken at the DISS facility and evaluates the results.     

Dynamic multiphysics model for solar array

An approach to model the solar cell system with coupled multiphysics equations (photovoltaic, electro-thermal, direct heating and cooling processes) within the context of the resistive-companion method in the Virtual Test Bed computational environment is presented.. Appropriate across and through variables are defined for the thermal terminal of the system so that temperature is properly represented as a state variable, rather than as a parameter of the system. This allows enforcement of the system power conservation through all terminals, and allows simultaneous solutions for both the electrical potentials and the system temperature. The thermal port built accordingly can be used for natural thermal coupling. The static and dynamic behaviors of the solar array model based on the approach are obtained and validated through comparison of simulation results to theoretical predictions and other reported data. The electro-thermal modeling method developed here can be generally used in the modeling of other devices, and the method to define the across and through variables can also be generalized to any other interdisciplinary processes where natural coupling is required     

Multi-objective optimization of integrated solar absorption cooling and heating systems for medium-sized office buildings

Integrated solar absorption cooling and heating (SACH) systems, which use solar energy to provide space heating, space cooling, and water heating, represent a promising substitute to reduce the earth's carbon emissions. SACH systems currently are designed based on engineering experience for the most part and few systematic methodologies are available to identify the key optimal parameters for SACH systems, such as the slope of the solar collectors, the area of the solar collectors, and the volume of the storage tanks. As a result, the established systems usually are not capable of yielding the greatest returns on investment. Motivated by the above facts, this study investigates a formal method for SACH system optimization by incorporating simultaneously a system's performance related to its economic, energy, and environmental aspects. The proposed method includes central composite design, regression, and multi-objective optimization. Central composite design (CCD) is used to select the significant experimental data generated by energy system simulation and life cycle analysis. Linear regression models are used to predict the functional relationship between system performance and the key system parameters using data sets. A multi-objective optimization model is then formulated and solved based on the Weighted-Tchebycheff metric approach. The proposed approach is applied to medium-sized office buildings located in Phoenix, Los Angeles, Atlanta, and Chicago; and the results suggest that the approach can provide a systematic mechanism to optimally design SACH systems.     

Modelling and simulation of elements for solar heating and daylighting

Through the development of highly efficient transparent insulation materials (TIM), new opportunities are appearing in the field of daylighting and passive solar space heating. The simulation program WANDSIM, developed at the Fraunhofer-Institut für Solare Energiesysteme (ISE), models the dynamic performance of three important elements for daylighting and passive solar space heating: window glazing; transparently insulated masonry; transparently insulated glass wall. Selected simulation results of each type are represented and compared under thermal and daylighting aspects. The advantages of the transparently insulated glass wall, a new combined passive space heating and daylighting system, in economy and comfort are verified.     

Simulation of solar heating systems—an overview

Process simulation has become an accepted tool for the performance, design, and optimization of thermal processes. Solving the mathematical models representing solar heating process units and systems is one of the most tedious and repetitive problems. Nested iterative procedures are usually needed to solve these models. To tackle these problems, several researchers have developed different methods, techniques, and computer programs for the simulation of very wide verity of solar heating process units and systems.It is of interest in this work to characterize and classify these methods, techniques, and programs in order to better understand their relations, types, structures, and procedures.The simulation problems are outlined; the simulation programs are grouped into two main types; special purpose, and general-purpose programs. Sequential and simultaneous computational sequences are illustrated. Simulator structure, program evaluation, and numerical techniques are summarized.By considering the unit and/or system entropy generation as well as the energy and material balances equations, more realistic models can be obtained. Also, rapid development of computer hardware and software will suggest new techniques and programs to be considered. These progress directions are noted.     

Thermal performance assessment of recyclic double-pass flat and V-corrugated plate solar air heaters

Double-pass solar air heaters occupy an important place among solar air heating systems, because of minimal heat loss and maximum thermal efficiency with marginal heater size and cost. In the present work, investigations related to the thermal performance predictions have been carried out for double-pass flat and V-corrugated absorber plate solar air heaters under recycle operation. The mathematical models proposed herein are solved using an analytical approach that uses an iterative solution procedure. Furthermore, based on simulation results obtained from the analytical study, the optimum value of the recycle ratio, the mass flow rate, the absorptivity and the emissivity at which the heaters yield the maximum value of the thermal efficiency have been identified and presented using response surface methodology (RSM). The results of RSM revealed that the mathematical models are significant. In addition, results of the present study are validated and compared with previous studies. A reasonable agreement and significant improvement have been achieved.     

太阳能地板辐射采暖系统的实验与数值模拟分析

介绍了上海交通大学太阳能实验室的太阳能地板辐射采暖系统的实验情况，通过实验对该系统在连续循环运行模式下对室内热环境所产生的影响进行了研究，并与非采暖房间进行了比较。同时对整个采暖系统建立了数学模型，通过数值计算得到地板表面温度及室内空气温度动态变化，模拟结果与实验基本吻合。     

A design procedure for solar air heating systems

A natural extension of the design procedure for liquid-based solar space and water heating systems is a similar analysis for solar heating systems using air as the heat transfer fluid. In this paper, a solar air heating system incorporating a flat-plate air heater and packed bed thermal storage is described and a simulation model for the system is developed. The results of many simulations of the air heating system are used to establish the relationship between system performance and the system design and meteorological variables. The results are presented in analytic and graphical form, referred to as an f-chart for solar air heating systems. The results of simulations in several widely different climates suggest that the information presented in the f-chart is location independent. Methods of estimating the performance of air heating systems having a collector air capacitance rate and a storage capacity other than those used to generate the f-chart are included. A comparison of the performance of air and liquid based systems is afforded by a comparison of their respective f-charts. The air system is shown to perform better at high load fractions supplied by solar energy than a liquid-based system with the same collector thermal performance parameters.     

Stochastic modelling of temperatures affecting the in situ performance of a solar-assisted heat pump: The multivariate approach and physical interpretation

Box-Jenkins-based multivariate stochastic modelling is carried out using data recorded from a domestic heating system. The system comprises an air-source heat pump sited in the roof space of a house, solar assistance being provided by the conventional tile roof acting as a radiation absorber. Multivariate models are presented which illustrate the time-dependent relationships between three air temperatures—at external ambient, at entry to, and at exit from, the heat pump evaporator. Using a deterministic modelling approach, physical interpretations are placed on the results of the multivariate technique. It is concluded that the multivariate Box-Jenkins approach is a suitable technique for building thermal analysis. Application to multivariate model-based control is discussed, with particular reference to building energy management systems. It is further concluded that stochastic modelling of data drawn from a short monitoring period offers a means of retrofitting an advanced model-based control system in existing buildings, which could be used to optimise energy savings. An approach to system simulation is suggested.     

A method of simulation of solar processes and its application

TRNSYS, a program for simulating the dynamic thermal behavior of transient systems, is a general program for solving sets of differential and algebraic equations which describe solar energy systems. It is based on a modular approach which enables the user to readily simulate a wide variety of systems. The program consists of component models (for collectors, controls, storage tanks, heat exchangers, furnaces, building loads, integrators, recorders, etc.) and an executive routine.The designer selects both his components and the design parameters describing the components and specifies, in a simple fashion, the way in which the components are interconnected. The whole process is analogous to specifying an experimental system. The designer also selects the information he wants from the simulation, again in a manner analogous to a physical experiment, and includes the appropriate instrument components in his simulation.The use of the program is illustrated by a comparison of methods of operating a solar heating system.     

Improved control strategy for forced flow solar water heating systems

The solar water heating system functioning on a fixed temperature control (FTC) mode, rather than a differential temperature control (DTC) mode (continuous water flow rate), has appreciable advantages for saying parasitic power consumption and reducing the maintenance cost. A computer simulation model, using a numerical analysis method, has been developed to study a forced flow solar water heating system taking into account the realistic conditions of operations. It is noted that the most critical parameter in designing such types of system is the water flow rate. The results are obtained, corresponding to a solar water heating system of 4000 1/day capacity working at an average temperature of 60°C.     

小型太阳能热泵地板供暖系统的优化研究

建立了太阳能热泵地板供暖系统的能量分析、可用能分析数学模型,模拟了上海供暖期的气候条件,给出了系统各部件的可用能损失情况。着重从太阳能集热器并联的组数出发对系统进行了优化研究,并给出了系统供暖性能系数和可用能效率,为该系统的设计及应用提供参考。     

Integration of solar air collector with phase change material wall for a heating system

可再生能源的高效利用是降低建筑能耗的有效方法。将相变储能墙与太阳能热风相结合,可改善太阳能热风采暖的不稳定性,从而提高太阳能的利用效率。通过试验和ANSYS模拟软件对复合系统的分析,确定相变储能墙体的储热特性和合理用量,研究复合采暖系统的室温变化和传热规律,分析相变储能墙对采暖系统的贡献率。结果表明：与未采暖房间相比,复合采暖系统可以使室内平均温度提高7~15℃,该复合采暖系统具有一定的应用前景;当太阳能空气集热器的送风口温度在37~77℃时,相变材料能够充分利用,相变墙整体的相变比例约为40%,从线性回归比例看,复合采暖效果要比太阳能热风采暖效果好。     

Thermal and economical analysis of a central solar heating system with underground seasonal storage in Turkey

Thermal performance and economic feasibility of two types of central solar heating system with seasonal storage under four climatically different Turkey locations are investigated. The effects of storage volume and collector area on the thermal performance and cost are studied for three load sizes. The simulation model of the system consisting of flat plate solar collectors, a heat pump, under ground storage tank and heating load based on a finite element analysis and finite element code ANSYS™ is chosen as a convenient tool. In this study, the lowest solar fraction value for Trabzon (41°N) and the highest solar fraction value for Adana (37°N) are obtained. Based on the economic analysis, the payback period of system is found to be about 25–35 years for Turkey.     

Numerical simulation and experimental validation of indirect expansion solar-assisted multi-functional heat pump

A novel indirect expansion solar-assisted multi-functional heat pump (IX-SAMHP) system which composes of the multi-functional heat pump system and solar thermal collecting system is proposed and studied in this paper. This system can fulfill space heating, space cooling and water heating with high energy efficiency by utilizing solar energy. For solar water heating mode and solar space heating mode, a dynamic model is presented and validated with the experimental results. The simulation results show good consistency with the experimental data, and the established model is able to predict the system performance at a reasonable accuracy (with the root mean square deviations less than 5%). On this basis, the performances of the IX-SAMHP system are investigated under different parametric conditions. For solar water heating mode, simultaneously operating the solar thermal collecting system and multi-functional heat pump system can be an energy efficiency method. With the solar irradiation rising from 0W/m² to 800W/m², the COP increases from 2.35 to 2.57. In solar space heating mode, the effect of the mass flow rate of water in evaporator is investigated. To balance the heating capacity and COP, the mass flow rate of water should be adjusted according to different temperature demands and heat load.     

Optimization of the heat exchanger in a flat plate indirect heating integrated collector storage solar water heating system

Due to the environmental impact of energy usage, consumers need to be encouraged to use renewable energy sources such as solar energy. The indirect heating flat plate integrated collector storage solar water heating system is one of the compact systems for domestic water heating. It incorporates the collection of a solar energy component and a hot water storage component in one unit. The objectives of this study were to investigate the effect of different parameters on the thermal performance of this system with the aim of reducing both the initial and the running costs. The outlet service water temperature was used as a measure of performance, because it is an indicator of the energy acquired from the solar radiation. The continuity, momentum and energy equations of the fluids involved in the system were numerically solved in a steady state condition, using FLUENT software. Three-D CFD models were developed and validated using previous experimental results. A standard k–ω turbulent model was used in the optimization of the heat exchanger because it produced good agreement with the experimental results. The surface-to-surface radiation model was included. The effect of single and double row heat exchangers with different lengths was investigated. Circular and elliptic cross-section pipes were also examined. Mass flow rates of 500 and 650 L/h were chosen. The results showed that the single row HX of 10.8 m length for both the elliptical and type B tube gave high service water outlet temperature (acceptable for heat exchanger design) and with low pumping power. This resulted in an increase in the thermal efficiency and a significant reduction in both the initial and the operating costs of the system.     

基于PVT集热/蒸发器的补气增焓热泵性能分析

传统直膨式太阳能辅助热泵系统在低温环境适应性欠佳,影响其在寒冷地区使用,通过采用补气增焓技术可以有效提高其低温条件下的供热能力。以所提出的采用PVT集热/蒸发器的补气增焓热泵系统为研究对象,计算分析环境条件、太阳辐射强度、注入蒸汽质量流量对该热泵系统性能的影响。研究结果表明： 当环境温度为-10℃,太阳照强度为500 W/m²时,性能系数（COP）可达4.3,比使用补气增焓（VI）循环的空气源热泵（ASHP）系统高63.6%。以当量热价（LCOH）作为指标与其他3种供热系统进行比较,所提出的系统经济性也具有一定的优势,可为补气增焓热泵系统在寒冷气候地区的应用提供新思路。     

Dynamic study of the thermal behaviour of solar thermochemical refrigerator: barium chloride-ammonia for ice production

The results of the theoretical thermodynamic analysis and the dynamic behaviour of the solar heating system of a thermochemical refrigerator, which operates on a heterogeneous solid–gas reaction between barium chloride and ammonia, are presented in this work. The thermodynamic analysis of the barium chloride–ammonia system shows that after energy and mass balance, the global efficiency coefficient (COP) varies very little. The theoretical relative low temperatures of dissociation in this system which are between 50°C and 60°C need simple heating systems such as flat plate collectors are needed, with an advantage over traditional liquid/vapour absorption systems. A simulation of the annual dynamic behaviour of the solar heating system for the operation of a solid-gas reactor is also presented. For an ice production specific cooling load, calculations are made of the different solar fractions of different areas of solar caption as well as the monthly variations of the efficiencies of the refrigeration systems.     

太阳能与空气源热泵复合式供暖系统在西安地区的应用特性分析及评价

以西安地区的某个房间为研究对象,采用TRNSYS软件针对该房间分别应用太阳能集热系统、空气源热泵系统及太阳能与空气源热泵复合式供暖系统进行供暖时的情况进行了分析.首先,建立了太阳能与空气源热泵复合式供暖系统的仿真模型,并对其正确性进行了实验验证;其次,对比分析了在3种运行模式下各个系统的运行特性;最后,以系统能耗及能效...