A thermo-economical optimization of a domestic solar heating plant with seasonal storage

In this study, the thermo-economic optimization analysis to determinate economically optimal dimensions of collector area and storage volume in domestic solar heating systems with seasonal storage is presented. For this purpose, a formulation based on the simplified P₁ and P₂ method is developed and solved by using MATLAB optimization Toolbox for five climatically different locations of Turkey. The results showed that the required optimum collector area in Adana (37 °N) for reaching maximum savings is 36 m²/house and 65 m²/house in Erzurum (39 °N) for same storage volume (1000 m³). The effects of collector efficiency on solar fraction and savings are investigated. The simulation results showed that the solar fraction and savings of the selective flat plate collector systems are higher than the other black paint flat plate collector systems.     

Review on solar air heating system with and without thermal energy storage system

In order to produce process heat for drying of agricultural, textile, marine products, heating of buildings and re-generating dehumidify agent, solar energy is one of the promising heat sources for meeting energy demand without putting adverse impact of environment. Hence it plays a key role for sustainable development. Solar energy is intermittent in nature and time dependent energy source. Owing to this nature, PCMs based thermal energy storage system can achieve the more popularity for solar energy based heating systems. The recent researches focused on the phase change materials (PCMs), as latent heat storage is more efficient than sensible heat storage. In this paper an attempt has been made to present holistic view of available solar air heater for different applications and their performance.     

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.     

Simulation of a solar domestic water heating system using a time marching model

This paper presents the modelling and simulation of a solar water heating system using a time marching model. The results of simulations performed on an annual basis for a solar system, constructed and operated in Yugoslavia, which provides domestic hot water for a four-person family are presented. The solar water heater consists of a flat-plate solar collector, a water-storage tank, an electric heater, and a water-mixing device. The mathematical model is used to evaluate the annual variation of the solar fraction with respect to the volume of the storage tank, demand hot water temperature required, difference of this temperature and preset storage tank water temperature, and consumption profile of the domestic hot water demand. The results of this investigation may be used to design a solar collector system, and to operate already designed systems, effectively. The results for a number of designs with different storage tank volumes indicate that the systems with greater volume yield higher solar fraction values. The results additionally indicate that the solar fraction of the system increases with lower hot water demand temperature and higher differences between the mean storage water and the demand temperatures. However, when a larger storage tank volume is used, the solar fraction is less sensitive to a variation of these operation parameters.     

国内外家用分离式太阳能热水系统浅析

通过国内外分离式太阳能热水系统形式及部件对比,阐述了国内外分离式太阳能热水系统的差异。     

Thermal performance of PCM thermal storage unit for a roof integrated solar heating system

The thermal performance of a phase change thermal storage unit is analysed and discussed. The storage unit is a component of a roof integrated solar heating system being developed for space heating of a home. The unit consists of several layers of phase change material (PCM) slabs with a melting temperature of 29 °C. Warm air delivered by a roof integrated collector is passed through the spaces between the PCM layers to charge the storage unit. The stored heat is utilised to heat ambient air before being admitted to a living space. The study is based on both experimental results and a theoretical two dimensional mathematical model of the PCM employed to analyse the transient thermal behaviour of the storage unit during the charge and discharge periods. The analysis takes into account the effects of sensible heat which exists when the initial temperature of the PCM is well below or above the melting point during melting or freezing. The significance of natural convection occurring inside the PCM on the heat transfer rate during melting which was previously suspected as the cause of faster melting process in one of the experiments is discussed. The results are compared with a previous analysis based on a one dimensional model which neglected the effect of sensible heat. A comparison with experimental results for a specific geometry is also made.     

相变蓄热式太阳能木材干燥供热系统设计

设计了一种具有相变蓄热的太阳能木材干燥供热系统，介绍了系统的组成、工作流程和特点。利用太阳能作为能源干燥木材，有利于木材加工企业节能降耗，也有利于保护自然环境。     

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.     

Comparison of energy and exergy efficiencies of an underground solar thermal storage system

In this experimental study, solar energy was stored daily using the volcanic material with the sensible heat technique. The external heat collection unit consisted of 27 m² of south‐facing solar air collectors mounted at a 55° tilt angle. The dimensions of the packed‐bed heat storage unit were 6 × 2 × 0.6 m deep. The packed‐bed heat storage unit was built under the soil. The heat storage unit was filled with 6480 kg of volcanic material. Energy and exergy analyses were applied in order to evaluate the system efficiency. During the charging periods, the average daily rates of thermal energy and exergy stored in the heat storage unit were 1242 and 36.33 W, respectively. Since the rate of exergy depends on the temperature of the heat transfer fluid and surrounding, the rate of exergy increased as the difference between the inlet and outlet temperatures of the heat transfer fluid increased during the charging periods. It was found that the average daily net energy and exergy efficiencies in the charging periods were 39.7 and 2.03%, respectively. The average daily net energy efficiency of the heat storage system remained nearly constant during the charging periods. The maximum energy and exergy efficiencies of the heat storage system were 52.9 and 4.9%, respectively. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of storage thermal behavior in seasonal storage solar heating systems

An analytical methodology has been developed to investigate the effects of storage operational strategies (or, equivalently, stratification) on the performance of a seasonal storage solar heating system with a water storage. The method is based on a relative comparison between a thermally stratified and well-mixed storage system representing probable extreme outcomes of the subsystem-to-storage loop control strategies. The effects are incorporated into a set of performance reduction factors that describe maximum changes in the solar collector yield, storage losses and solar fraction due to storage operational mode. The study indicates that the storage thermal behavior could in the worst case affect the yearly solar fraction by a factor of 2, but most likely a maximum value from 1.35 to 1.6 could be expected.     

家用太阳热水系统标准探讨

家用太阳热水系统性能检测的国家标准主要有GB/T 18708-2002、GB/T 19141-2003,因测试目的不同,两个标准之间以及与其他各相关标准之间存在一些差异,针对热性能测量系数对各相关的国内外标准进行对比分析,对家用太阳热水系统某些参数测量提出改进建议。     

Dynamic response of a packed bed thermal storage system—a model for solar air heating

A mathematical model for simulating the dynamic temperature response of a packed column to an arbitrary time-dependent inlet air temperature is developed. The model includes axial thermal dispersion as well as intra-particle conduction, features that have usually been neglected but can be important in solar energy applications. Solutions, presented in terms of moments of the temperature response to an impulse of heat at the inlet, can be evaluated by simple numerical quadrature. Results of the model compare favorably with experimental data found in the literature. The model is used to optimize heat storage in a rock bin system subject to a realistic transient inlet temperature.     

A computational study on the performance of a solar air-conditioning system with a partitioned storage tank

This paper reports the performance of a modified solar powered air-conditioning system, which is integrated with a partitioned storage tank. In addition, the effect of two main parameters that influence the system performance is presented and discussed. The study shows that by partitioning the storage tank, the solar cooling effect can be realized much earlier and could attain a total solar cooling COP of 12% higher compared to the conventional whole-tank mode. Simulation results also indicate that there exists an optimum ratio of storage tank volume over collector area.     

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.     

Computational simulation of district solar heating systems with seasonal thermal energy storage

A computational simulation model for determining the thermal performance of large-scale community solar heating systems with interseasonal heat storage is described. Special attention has been paid to the mathematical formulation of the storage unit. It comprises an uninsulated stratified hot water tank excavated in rock. The storage capacity of the surrounding ground may also be utilized by vertical heat exchanger pipes. Comparisons of theoretical system performance predictions with recent experimental measurements from a full-scale prototype installation are presented and found to be in reasonable agreement. The simulation program is also used to evaluate the thermal performance of various district solar heating system configurations for northern cold climatic conditions (60°N).     

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.     

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.     

A cost-optimal solar thermal system for apartment buildings with district heating in a cold climate

Finding the global optimal combination of the main components for a solar thermal energy system is an important topic in utilising solar radiation in a cost-effective way. However, selecting an optimal solar thermal system in a cold climate condition is a challenging task due to the dependency on the heat demand and the limited availability of solar radiation. This research presents several sets of optimum combinations of a solar thermal collector and a hot water storage tank regarding energy efficiency and the life cycle cost. Since domestic hot water consumption forms the significant part of the heat demand in new energy efficient apartment buildings, the applied consumption information were extracted precisely according to measured data. The solar thermal system with cost-optimal component sizes was able to save district heat energy consumption up 24% to 34% and made 4 €/m^2 to 23 €/m^2 in financial profit.     

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.     

Life cycle analysis of a solar thermal system with thermochemical storage process

Solar energy itself is generally considered as environmentally friendly, nevertheless it is still important to take into consideration the environmental impacts caused by production of thousands of solar thermal systems. In this work the standard LCA methodology has been extended to analyse the total environmental impacts of a new more efficient solar thermal system SOLARSTORE during its whole life cycle. This system is being developed by a 5th Framework EC project. The LCA results show that to produce 1 GJ energy with SOLARSTORE system will result in global warming potential of 6.3–10 kg CO₂, acidification potential of 46.6–70 g SO₂, eutrophication of 2.1–3.1 g phosphate and photochemical oxidant of 0.99–1.5 g C₂H₄. The raw material acquisition and components manufacturing processes contribute 99% to the total environmental impacts. In comparison with traditional heating systems, SOLARSTORE system provides a considerably better solution for reduction of negative environmental impacts by using solar energy more efficiently.