Types Of Solar Thermal Collectors Research Articles

Integration of solar thermal collectors and heat pumps with thermal energy storage systems for building energy demand reduction: A comprehensive review

Solar energy, coupled with innovative technologies, holds the promise of propelling buildings towards net-zero and carbon neutrality. In this regard, this review explores the integration of solar technologies, heat pumps, and thermal energy storage systems to reduce building energy demand. It thoroughly examines various types of solar thermal collectors (STCs), including both concentrating devices like compound parabolic concentrators and parabolic troughs, as well as non-concentrating designs such as flat plate and evacuated tube collectors. It examines innovative strategies for enhancing STC performance, such as alternative profiles for compound parabolic concentrators and the insertion of thermal fins in absorber tubes. Furthermore, the review categorizes solar-assisted heat pumps (SAHPs) into indirect expansion (IDX) and direct expansion (DX) systems, describing their advantages and limitations. It performs a comparison between IDX-SAHPs and DX-SAHPs, explaining their effectiveness and applicability. Eventually, the review explores thermal energy storage materials, categorizing them into sensible heat storage, latent heat storage, and thermochemical heat storage (TCHS). It discusses the advantages and disadvantages of each category, as well as notable materials within them. A comparative examination between open and closed systems for TCHS further enriches the discussion. Throughout the review, recent advancements and key findings from relevant studies are summarized in separate tables, offering valuable information into practical strategies for sustainable building energy systems. Regarding the provided sections, this review plays a crucial role in introducing scholars to practical methods employed in recent years to integrate the STCs with heat pumps and thermal energy storage systems.

A review of recent developments in the application of machine learning in solar thermal collector modelling.

Over the past few decades, the popularity of solar thermal collectors has increased dramatically because of many significant advantages like being a free, natural, environmentally friendly and permanent energy source. Today, developing and optimising different solar thermal energy systems are more important than before. Thus, there are various methods for investigating the performance of these systems, such as experimental, numerical and mathematical methods. One of the cutting-edge methods is artificial intelligence, which can predict key and effective parameters in solar collector efficiency. This review identified recent machine learning modelling, including multilayer perceptron artificial neural network (MLP-ANN), group method of data handling (GMDH), radial basis function (RBF), artificial neuro-fuzzy inference system (ANFIS), support vector machine (SVM) and studies regarding different types of solar thermal collectors, namely non-concentration and concentration. Furthermore, it investigated the effect of various essential factors on the accuracy, potential issues and challenges facing the application of artificial intelligence in these systems. Finally, it will also be recommended opportunities for future research.

A Comparative Thermal Performance Assessment of Various Solar Collectors for Domestic Water Heating

Growing population, depleting fossil fuels, economic expansions, and energy intensive life style demand are resulting in higher energy prices. We use energy as of heat and electricity, which can directly be obtained from sun using thermal collectors and solar cells. Solar thermal systems are gaining attention for water and space heating applications due to green aspects of solar energy. A solar thermal collector is a vital part of solar thermal energy system to absorb radiant energy from the sun. In this study, a solar water heating (SWH) system has been designed and simulated in the TRNSYS ® software using thermal and chemical properties of heat transfer fluids using REFPROP for dwellings located on ±31° latitudes (+31 Lahore in Pakistan and -31° Perth in Australia). We present an efficiency parametric optimization-based model for water and space heating. Simulation results for four types of solar thermal collectors are presented, and performance is analyzed on the basis of output temperature ( T out ), solar fraction ( f ), and collector efficiency ( η ). This study evaluates the comparative performance of evacuated tube collector (ETC), flat-plate collector (FPC), compound parabolic concentrator (CPC), and thermosiphon-driven systems. Our findings conclude the evacuated glass tube collector achieves the highest solar fraction, i.e., 50% of demand coverage during August in Pakistan and February in Australia, with an overall average of 43% annually.

Solar assisted heat pump system for high quality drying applications: a critical review

Solar assisted heat pump (SAHP) system integrates a solar thermal energy source with a heat pump. This technique is a very fundamental concept, especially for drying applications. By combining a solar thermal energy source such as solar thermal collectors and a heat pump dryer will assist in reducing the operation cost of drying and producing products with high quality. Many review papers in the literature evaluated the R&D aspects of solar-assisted heat pump dryers (SAHPD). This critical review paper studies some of the researches conducted in this field to understand and provides an update on recent developments in SAHPD. Also, a detailed explanation of principles and operation for SAHPD and its applications are presented. The used types of solar thermal collectors, as well as various heat pump dryers, are all discussed in this article. Finally, it is concluded that there is clear lack of research in the techno-economic and environmental evaluati0on, while most of SAHPD studies focused on the performance study of the system.

Application of support vector machine for prediction of electrical and thermal performance in PV/T system

In photovoltaic–thermal (PV/T) system analysis, solar collectors with numerous design concepts have been used to purvey the thermal and electrical energy effectively. In this study, two types of solar thermal collectors in PV/T system are proposed and fabricated called design A and design B respectively. In order to investigate the effects of collector type on the system performance a thin flat metallic sheet (TFMS) and fins were introduced as an effective heat absorber and heat sink in the collectors. Extensive experiments were carried out for different conditions under indoor solar simulator. Then PV/T thermal and electrical efficiency were calculated by using data obtained from experiments. Here, support vector machine (SVM) model is designed to estimate the thermal and electrical output which predicts the values for some input variables. For this purpose, three SVM models namely SVM coupled with the discrete wavelet transform (SVM-Wavelet), the firefly algorithm (SVM-FFA) and with using the radial basis function (SVM-RBF) were analyzed. The estimation and prediction results of these models were compared with each other using statistical indicators i.e. root means square error, coefficient of determination and Pearson coefficient. The experimental results show that a significant improvement in predictive accuracy and capability of generalization can be achieved by the SVM-Wavelet approach. Moreover, the results indicate that proposed SVM-Wavelet model can adequately predict the electrical and thermal efficiencies of PV/T system. In the final analysis, a proper sensitivity analysis is performed to identify the influence of considered input elements on performance prediction of PV/T system.

Process intensification and integration of solar heat generation in the Chinese condiment sector – A case study of a medium sized Beijing based factory

Over the last decade, energy prices in China have risen dramatically. At the same time, extensive use of coal fired energy provision systems in industry has led to serious environmental and economic problems translating to an economic damage of an estimated 10% of the Gross Domestic Product. This has led to increasing awareness in the process industries of the need to save energy whilst replacing conventional energy sources with renewable ones.An energy audit was conducted for a soy sauce production facility in Beijing, which aimed to reduce its thermal energy demand through process intensification and to integrate renewable energy. Their current supply of thermal energy came directly from a district steam network, which was both directly consumed and downgraded via heat exchangers. It was determined that the best two solar integration locations would be in the pre-heating/mixing of raw ingredients to 60°C and the subsequent direct steaming of the mixture to 120°C.Three different systems for supplementing steam were investigated: (1) a traditional solar thermal heating system; (2) a system consisting of mono crystalline photovoltaic panels coupled with either a resistance heater or electric steam generator; and (3) a cascading system consisting of two types of solar thermal collectors, photovoltaic panels, and an electric steam generator. Comparisons of systems 1 and 2 were made for the heating of mixing water, and systems 1, 2, and 3 for saturated steam generation.Results showed that for the heating of process water, flat plate solar collectors performed best with an estimated 20year Levelised Cost of Energy of 0.063€/kWh. Steam generation was most cost effective with a cascade system of photovoltaic and flat plate collectors, with an estimated 20year Levelised Cost of Energy of 0.145€/kWh. The model predicts that integration of this technology would lead to a reduction of 14% in heating utility demand.

Design and experimental optimisation of a novel flat plate solar thermal collector with trapezoidal shape for facades integration

For developing solar–thermal facades, new efficient flat plate solar thermal collectors are required, fulfilling the prerequisites of efficiency and architectural acceptance, with new shapes and/or new colours. A new flat plate solar–thermal collector, with isosceles trapeze shape was developed and stepwise optimised focussing on the insulation, the bonding between the tubes and the absorber plate, the meander tube length and diameter, and the glazing. The results show that the improved contact between the tubes and the absorber plate has a significant effect on the experimental conversion efficiency, as also the tubes with larger diameters have. A self-cleaning coating applied on the outer side of the glazing, deposited through a simple cold-spraying process has a beneficial effect on the collector's functionality, without significant efficiency losses. To support architectural integration, a concept of a multi-coloured absorber plate is formulated and tested. Eight types of solar thermal collectors were tested and the optimised version reached a 60.7% efficiency on an indoor testing rig, corresponding to a 62.38% maximum conversion efficiency estimated based on steady-state experimental conditions. Outdoor testing of the optimal collector is reported for a sunny day that includes 2 h with solar radiation in the same range as on the indoor testing rig when efficiencies of 61.85% were obtained.

A dynamic thermal performance model for flat-plate solar collectors based on the thermal inertia correction of the steady-state test method

In determining the dynamic thermal performance of a flat-plate solar collector, when the instantaneous solar irradiance changes sharply at one moment, most of the existing models cannot accurately predict the momentary thermal characteristics of outlet temperature and useful heat gain. In the present study, an analytical model in the form of series expansion is put forward to depict the momentary thermal characteristics of flat-plate solar collectors. The analytical model reveals that, instantaneous useful heat gain of a solar collector at one moment consists of the steady-state useful heat gain and corresponding thermal inertia correction. The model is then validated by the experimental data. It indicates that the analytical model can properly predict the dynamic thermal performance of the solar air collector. Besides, the model pertains to other types of solar thermal collectors, if they can be tested by the steady-state test method.

Review of Materials and Environment Management for Solar Thermal Collectors

To cover the main contributions and developments in solar thermal collectors through focusing on materials, heat transfer characteristics and manufacturing challenges. A range of published papers and internet research including research work on various solar thermal collectors (flat plate, evacuated tubes, and heat pipe tube) were used. Evaluation of solar collectors performance is critiqued to aid solar technologies make the transition into a specific dominant solar collector. The sources are sorted into sections: finding an academic job, general advice, teaching, research and publishing, tenure and organizations. Provides information about types of solar thermal collectors, indicating what can be added by using evacuated tube collectors instead of flat plate collectors and what can be added by using heat pipe collectors instead of evacuated tubes. Focusing only on three types of solar thermal collectors (flat plate, evacuated tubes, and heat pipe tube). Useful source of information for consultancy and impartial advice for graduate students planning to do research in solar thermal technologies. This paper fulfils identified information about materials and heat transfer properties of materials and manufacturing challenges of these three solar thermal collectors. Describes some changes made to improve the environment which have had unforeseen and adverse effects on safety and the reasons why we need more case histories. Also discusses the reasons why there are no permanent solutions to safety problems and the reasons why senior managers should become more involved in safety problems.

Performance Analysis of Solar Evacuated Tube Collector

The high temperature operation of Evacuated Tube Collectors (ETC) and their very low radiant heat losses make them ideal for solar water heating, solar space heating, desiccant air conditioning, thermal driven cooling and industrial process heating applications. The work temperature of common ETC can reach 100~ 250°C. The vacuum tube envelope minimizes heat loss and ensures high collector durability and steady performance. This paper investigates different types of solar thermal collectors and compared them so that the result which the heat loss of ETC is least is obtained. The thermal analysis and performance of ETC are investigated as well.

Review of Materials for Solar Thermal Collectors

To cover the main contributions and developments in solar thermal collectors through focusing on materials, heat transfer characteristics and manufacturing challenges. A range of published papers and internet research including research work on various solar thermal collectors (flat plate, evacuated tubes, and heat pipe tube) were used. Evaluation of solar collectors performance is critiqued to aid solar technologies make the transition into a specific dominant solar collector. The sources are sorted into sections: finding an academic job, general advice, teaching, research and publishing, tenure and organizations. Provides information about types of solar thermal collectors, indicating what can be added by using evacuated tube collectors instead of flat plate collectors and what can be added by using heat pipe collectors instead of evacuated tubes. Focusing only on three types of solar thermal collectors (flat plate, evacuated tubes, and heat pipe tube). Useful source of information for consultancy and impartial advice for graduate students planning to do research in solar thermal technologies. This paper fulfils identified information about materials and heat transfer properties of materials and manufacturing challenges of these three solar thermal collectors.

Review of materials for solar thermal collectors

PurposeTo cover the main contributions and developments in solar thermal collectors through focusing on materials, heat transfer characteristics and manufacturing challenges.Design/methodology/approachA range of published papers and internet research including research work on various solar thermal collectors (flat plate, evacuated tubes, and heat pipe tube) were used. Evaluation of solar collectors performance is critiqued to aid solar technologies make the transition into a specific dominant solar collector. The sources are sorted into sections: finding an academic job, general advice, teaching, research and publishing, tenure and organizations.FindingsProvides information about types of solar thermal collectors, indicating what can be added by using evacuated tube collectors instead of flat plate collectors and what can be added by using heat pipe collectors instead of evacuated tubes.Research limitations/implicationsFocusing only on three types of solar thermal collectors (flat plate, evacuated tubes, and heat pipe tube).Practical implicationsUseful source of information for consultancy and impartial advice for graduate students planning to do research in solar thermal technologies.Originality/valueThis paper fulfils identified information about materials and heat transfer properties of materials and manufacturing challenges of these three solar thermal collectors.

The effect of diffuse/indirect light on the energy gain of solar thermal collectors

An extension of previous studies, which did not treat quantitatively possible effect of diffuse skylight on the enhancement of energy gain of solar thermal collectors when sun-tracking instead of fixed position is used, involved consideration of possible contribution of the former to the overall solar power and energy received on the ground under different conditions (time of a year, degree of overcast). The effect on the efficiency of two types of solar thermal collectors: a standard (fixed) one and one of adjustable orientation, is considered. Also, possible advantage of orienting adjustable-position collectors towards maximum light (light-tracking) instead of the astronomic position of the sun (sun-tracking) was discussed, as to conclude that little is to be gained and even that only at the sky totally covered by clouds. Some experimental proof of the validity of conclusions is presented.

Development of solar desal, a code for modeling, simulation and design of solar desalination systems

A computer code has been developed as a tool to aid design work of wind-powered and solar-powered desalting plants. The code accommodates for various solar energy sources deliver systems and RO and ED processes. In this paper flow charts are presented with detailed description of the code, capability and limitations. The SOLAR DESAL program could also be used to simulate desalination units of RO and ED which employ diesel generators. The program has been structured to allow the interchange, substitution, and elimination of major subsystems, a flexibility necessary for tradeoff analyses and parameter studies. Reliability considerations are included in the code calculations by the computation of times of failure and of repair. Program logic is based upon the availability of a particular component/ subsystem in addition to the usual temperatures, flow rates, etc. The desalination code simulated the production of water from a wind energy conversion system powered reverse osmosis plant. The plant included pretreatment, battery storage, backup diesel generator, and water storage and demand simulations. This is in addition to solar thermal collectors, photo voltaics, a second desalination subsystem, heat engine, waste pond, recovery turbine, and various minor subsystems and components such as heat exchangers piping, pumps, chiller, etc. Program modifications include the TRNSYS 10.1 solar radiation processor to compliment the existing distribution functions, including Weibul, found in the code. Actual insolation data may be read in and patched directly into the solar radiation processor. The code has the capability of two different types of solar thermal collectors, two different photovoltaic cells, and two different, or two similar, desalination stages. Solar energy calculations are made for basic units such as a row of thermal collectors connected together to provide the necessary temperature and mass flow, or photovoltaic modules connected in series and/or parallel to obtain sufficient voltage and current. The basic unit can be sized upwards by combining similar units to allow for virtual unlimited array size.