Long-Term Performance Analysis of Solar 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.

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.

The paper analyses the performance of a spherical solar collector compared to the efficiency of a flat-plate solar collector, which is the type of solar collector that does not use a tracking system in collecting solar radiation for energy conversion. Spherical solar collector benefits from a constant value of the angle of incidence, which optimizes the solar radiation that strikes the absorber of the solar device and maximizes the energy collection. Besides, the spherical geometry has a larger area for equal dimensions, width, and length. The combined effect of a larger surface and a higher value of the effective solar radiation onto the surface of the absorber increases the energy collection and the performance of the solar device. We developed a theoretical analysis to obtain the algorithm to determine the collected solar energy, which increases when using the spherical solar collector. A simulation runs to calculate the predicted values. We developed experimental tests in a spherical solar collector of 1.05 m in diameter, and in a flat-plate solar collector of 1.94 m × 1.025 m. to validate the simulation. The comparative analysis shows that a spherical solar collector generates more energy than a flat-plate one of the same absorbing surface by a factor of 2.09, and 7.75 times more if the width and height of the flat-plate collector equals the diameter of the spherical one.

The performance of the Flat Plate Collector (FPC) and Evacuated Tube Collector (ETC) for domestic hot water applications under Jordan climate conditions was theoretically investigated using TRNSYS software. The presented simulation model can provide a long-term evaluation of system performance at different weather conditions. This simulation was carried out during 24 hours in 21 June, is considered as a hot climate and 21 January is considered as a cold climate; under the meteorological conditions of both Irbid and Aqaba cities in Jordan. The inlet water temperature of the first collector, collector area, water flow rate and tilt angle were considered 15℃, 2.04 m2, 0.0139 kg/s and 45 degrees respectively. The outlet temperature of each collector was considered as the inlet of the previous collector. Three collectors in series were applied to increase the output temperature up to 90-100℃. The results showed that TE increased with the decrease in the inlet temperature, which means the useful energy gain (Qu) of the first collector is greater than the 2nd and the 3rdcollector. The useful energy gain (Qu) of ETC is greater than of FPC, and the useful energy gain (Qu) of cold climate is less than hot climate. The output temperature of ETCs is greater than that of FPCs for Irbid city in cold and hot climate. Furthermore, for Aqaba in cold climate and in hot climate the outlet temperature of ETCs is higher than FPCs. Additionally, the daily thermal performance of the ETCs is significantly better than the FPCs in cold climate. Meanwhile, thermal performance of both collectors are close in a hot climate.

In this paper, a parametric study on the thermal performance of a solar air collector with a v-groove absorber has been investigated. In this single-cover collector, the air flowing in the channel formed by the v-groove absorber and the bottom plate—which is flat and insulated—is along the groove, aiming at enhanced heat transfer rate between the air and the absorber by increasing the heat transfer surface area, which is crucial to the improvement of thermal performance of a solar air collector. To quantify the achievable improvements with the v-groove absorber, a flat-plate solar air collector where both the absorbing plate and the bottom plate are flat, is also considered. The thermal performance of these two types of solar air collectors is analyzed and compared under various configurations and operating conditions. The results show that the v-groove collector has considerably superior thermal performance to the flat-plate collector. It is also found that to achieve better thermal performance, it is essential to; use a small size of the v-groove absorber for the v-groove absorber collector and to maintain a small gap between the absorber and the bottom plate for the flat-plate collector; to use selected coatings that have a very high absorptivity of solar radiation but a very small emissivity of thermal radiation on the absorber and glass cover; to maintain an air mass flow rate above 0.1kg/m2s; and to operate the collectors with the inlet fluid temperature close to that of the ambient fluid.

Heating of water for domestic purpose by making use of solar energy is essential and it is one of the effective ways of utilizing solar energy. Initial cost of solar water heating (SWH) system is high, but the operation cost is zero. This paper discusses on improving the performance of a flat plate solar energy collector by changing the design parameters of the number of riser tubes and the arrangement of riser tubes in zig-zag pattern from the existing flat plate collector system (FPC) and using the different working nanoparticles with base fluids like aluminium oxide mixed with water. Experiments were conducted using copper tube in headers and risers with two different configurations and maintain the same dimensions. The performance comparison was made for all the two types of collectors in closed loop. The performance shows that the efficiency of FPC with zig-zag arrangement of tubes (Z-Configuration) is higher than that of conventional FPC. Thus the newly presented FPCs system produces higher efficiency than the existing conventional flat plate collector system.

Cosmic power is one of the numerous renewable energy sources that can use in a Photovoltaic (PV) system or Thermal. Solar collectors play a crucial role in solar thermal systems. They convert solar radiation into heat and transfer the heat to working fluids Such as water or air. The Flat-plate collectors are the numerous common type of solar collectors and typically used as a water heater or air heater. These collectors have low efficiency and low outlet temperature. Recently, many scientists have attempted to improve the efficiency and performance of flat-plate collectors via different methods. This review paper describes the results of the experimentation carried out to study and compare the performance of the modified flat plate collector having increasing riser tube diameter and reducing riser tube length with the conventional ISI marked solar liquid flat plate collector. To study, the comparative performance characteristics of a modified flat plate collector with ISI flat plate collector operated under natural circulation mode. The suggested design found to be better than the existing ISI design of the absorber plate from an efficiency point of view. The actual useful heat gain (Qu) in the suggested design understudy found to be more by 30% than that in the case of ISI collector. However, the modified flat plate collector found to operate at a relatively lower exit temperature than the conventional ISI marked 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.

Renewable energy systems such as wind, solar and biomass are significantly more land intensive than traditional fossil fuels. Renewable energy increases diversity of energy supplies and can replace diminishing fossil fuel resources over the long run; their use in place of fossil fuels can substantially reduce greenhouse gases and other pollutants. Application of solar energy for domestic and industrial heating purposes has become more popular. In this paper, reduced land use of flat plate collectors for same output with solar point collector is analysed. However the effectiveness of presently used flat plate collectors is low due to the moving nature of the energy source. So the performance of solar flat plate collector is effectively improved by using a novel system called solar point collector. Also an attempt has been made to compare the performance of flat plate collector with that of solar point thermal energy collector by conducting experiments. Experiments were conducted for a week during which the atmospheric conditions were almost uniform and data was collected both flat plate collector and solar point collector for various flow conditions.

This comprehensive investigation has been executed to compare the thermodynamic performance and optimization of LiCl–H2O and LiBr–H2O type absorption system integrated with flat-plate collectors (FPC), parabolic-trough collectors (PTC), evacuated-tube collectors (ETC), and compound parabolic collectors (CPC). A model of 10 kW is analyzed in engineering equation solver (ees) from thermodynamic perspectives. Solar collectors are integrated with a storage tank which fueled the LiCl–H2O and LiBr–H2O vapor absorption system to produce refrigeration at 7 °C in evaporator for Gujarat Region of India. The main objective includes the evaluation and optimization of critical performance and design parameters to exhibit the best working fluid pair and collector type. Optimum heat source temperature corresponding to energetic and exergetic aspects for LiCl–H2O pair is lower than that of LiBr–H2O pair for all collectors. Simulation shows that FPC has lowest capital cost, exergetic performance wise PTC is optimum, and ETC requires lowest collector area. On the basis of overall evaluation, solar absorption cooling systems are better to be powered by ETC with LiCl–H2O working fluid pair.

A comparison between flat-plate and evacuated tube solar collectors in terms of energy and exergy analysis by using nanofluid

Techno-economic analysis of a hybrid district heating with borehole thermal storage for various solar collectors and climate zones in Pakistan

Solar water heating is one of the most efficient solar technologies in the domestic sector. The most important component of the solar thermal systems is the solar collector, which converts solar radiation to useful thermal energy. There are many types of solar collectors, which are categorized based on the operating temperature (low, medium and high temperatures) or the working fluid (gas or liquid). One of the newest types of solar collectors is direct absorption solar collector in which solar radiation is absorbed through the working fluid, unlike other collectors that use the surface absorber or indirectly absorb the solar radiation. The common working fluid for DASC is the suspension of metal, metal oxide or carbon nanomaterials in solar common fluids (water, EG, PG and Therminol VP-1). In this review paper, the effect of design and operating parameters on the thermal performance of low-temperature direct absorption solar collector is summarized. Using the numerous studies done in this field, the efficiency enhancement of DASC by variation of the collector geometric properties, the flow properties (the flow rate and Reynolds number), the working fluid properties (the base fluid, the nanoparticle material and size, and the nanofluid concentration), and the collector design is identified. This paper also identifies the current challenges facing the direct absorption solar collectors and the future recommendations for developing and commercializing these collectors.

During the past few decades, a wide range of studies have been performed to improve the performance of flat plate solar collectors by either reducing the heat loss from a collector or by increasing the amount of solar radiation absorbed by the absorber plate. Examples of these studies include adding transparent honeycomb to fill the air gap between the glazing and absorber plate to reduce convective heat loss, replacing the air in the gap by other gases such as Argon, Krypton, Xenon and Carbon Dioxide, or adding a chemical coating such as Copper Oxide to increase absorbtance and reduce the emittance of the absorber plate. While these methods improve the collector’s efficiency, they focus primarily on limiting the natural convection that occurs in the collector cavity, or on improving the optical properties of the absorber or glazing. None of these studies have addressed the problem of heat loss due to forced convection to the surrounding ambient air in any detail. Yet, research has shown that forced convection will contribute significantly to the heat loss from a collector. Windbreaks have traditionally been used to direct wind to protect farmland, and to direct wind drifts and sand dunes. Windbreaks also have been shown to provide protection for homes from winter winds which result in reduced heating costs for buildings. While windbreaks have been traditionally used for large scale applications, there is reason to believe that similar benefits can be expected for scaled down applications such as adding a windbreak along side of a flat-plate solar collector. In this paper, we examine the feasibility of using a windbreak to provide a flat plate solar collector protection from the wind in order to improve its performance. A series of experiments were performed wherein the thermal performance of two flat-plate collectors — one without a windbreaker and one with a windbreaker — were measured. The results of these experiments are reported in this paper and the need for further studies to explore different windbreak configurations is discussed.

Solar thermal energy is a renewable, convenient source and environmentally benign energy resource. Flat-plate solar collectors are the most common and cost-effective devices for exploiting and converting solar energy into heat and transfer the heat to a medium. However, the efficiency of these systems is not favorable due to the poor thermo-physical properties of working fluid. Using nano-fluid is proposed as an efficient method in order to improve the heat transfer properties of the working fluid. Adding nanoparticles to base fluid, leads to enhancement in thermal properties of working fluid. Thermo-physical properties of base fluid depend on several parameters including particle concentration and size. In this study, the effect of these parameters is theoretically investigated on the thermal performance of a flat-plate solar collector. In addition, the collector efficiency is evaluated for different shapes of the cross-section of the riser pipe. It is observed that increase in nanoparticle volume fraction, enhances the efficiency of a flat-plate collector and the maximum obtained value was approximately 80%. Reversely, particle size increase from 20 nm to 80 nm, causes more than 3% reduction in the efficiency. In addition, for different shapes of the pipe cross-section, including circle, square, and triangle; circular cross sections leads to the highest efficiency in a flat-plate solar collector