Applications In Solar Thermal Systems Research Articles

Design, fabrication and performance analysis of indirect solar dryer

The application of solar thermal systems to preserve and process the agriculture products like fruits and vegetables has found a prominent scope in recent years. In the present research paper, the performance analysis of solar dryer is investigated on the basis of temperature, moisture content (%) and relative humidity. The experiments were performed on onion and garlic. For the complete drying of 1 kg of onion took around 36 h, while it took 188 h for complete drying of 300gm of garlic in an indirect solar dryer. The results were compared with the conventional open sun drying (OSD) method. In the solar dryer, the maximum temperature recorded was 47.6℃. In the open sun drying (OSD) method, the onion and garlic were exposed to direct sun light that diminished the sensory properties (aroma, colour, taste and nutrients). While in case of indirect solar dryer, products were not exposed to direct sunlight and hence retained sensory properties. It is found that within a span of 24 h of experimentation on onion and garlic, the moisture content reduced to 25 % and 60 % while in case of OSD it was recorded 67 % and 63 % respectively. It envisaged that solar dryer is efficient than the conventional OSD method.

A scoping review on recent advancements in domestic applications of solar thermal systems

The rapid growth in smart technology and green energy contributing crucial role in taking our homes into next level. Meanwhile the solar powered thermal systems (STS) are much desired for energy conservation and management of houses. Domestic application of STS will not only reduce electricity consumption but also reduce carbon emission. This paper gives a scoping review on role of various types of STS namely, solar water heating, solar active and passive space heating and cooling, solar thermal water pumping, solar cooking, solar drying, solar distillation, solar green house, solar photovoltaic thermal systems (PVT) and solar thermal energy storage systems in domestic applications. The recent advancements with respect to each type of STS is outlined. Starting from various collectors and materials for STS, each system’s working principle and technological advancements in the view of adopting it to domestic applications are discussed in detail. Also, performance evaluation and role of each different STS in home application is elucidated. The research gaps and potential barriers for adopting STS for domestic homes are explored.

Characterization of Hybrid-nano/Paraffin Organic Phase Change Material for Thermal Energy Storage Applications in Solar Thermal Systems

In this work, the experimental investigations were piloted to study the influence of hybrid nanoparticles containing SiO2 and CeO2 nanoparticles on thermo-physical characteristics of the paraffin-based phase change material (PCM). Initially, the hybrid nanoparticles were prepared by blending equal mass of SiO2 and CeO2 nanoparticles. The hybrid-nano/paraffin (HnP) samples were prepared by cautiously dispersing 0, 0.5, 1.0, and 2.0 percentage mass of hybrid nanoparticles inside the paraffin, respectively. The synthesized samples were examined under different instruments such as field emission scanning electron microscope (FESEM), Fourier transform infrared spectrometer (FTIR), differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), and thermal properties analyzer to ascertain the influence of hybrid nanoparticles on thermo-physical characteristics of the prepared samples. The obtained experimental results proved that the hybrid nanoparticles were uniformly diffused in the paraffin matrix without affecting the chemical arrangement of paraffin molecules. Prominently, the relative thermal stability and relative thermal conductivity of the paraffin were synergistically enriched up to 115.49% and 165.56%, respectively, when dispersing hybrid nanoparticles within paraffin. Furthermore, the hybrid nanoparticles appropriately amended the melting and crystallization point of the paraffin to reduce its supercooling, and the maximum reduction in supercooling was ascertained as 35.81%. The comprehensive studies indicated that the paraffin diffused with SiO2 and CeO2 hybrid nanoparticles at 1.0 mass percentage would yield a better outcome compared to the next higher mass fractions without much diminishing the latent heat of paraffin. Hence, it is recommended to utilize the hybrid-nano/paraffin with 1.0 mass fraction of the aforementioned hybrid nanoparticles for effectively augmenting the thermal energy capacity of low-temperature solar thermal systems.

Enhanced photothermal conversion in nanometric scale MoOx multilayers with Al2O3 passivation layer

An optically selective stack based on molybdenum oxide nanometric layers (Mo/MoOx/Mo/MoO3/Al2O3) was designed using SCOUT reflectance simulations and fabricated using balanced magnetron sputtering for applications in solar thermal systems. The material properties were experimentally optimised by varying the process parameters namely: target power, gas flow rates, and deposition time. In the stack, the bottommost Mo metal layer is used to improve adhesion, reduce diffusion while acting as an infrared reflector, the MoOx layer of the tandem stack acts as the primary light absorbing layer, and the topmost MoO3 + Al2O3 layers act as anti-reflection layers. The individual layers of the optical stack exhibited an amorphous structure as confirmed using X-ray diffraction. The existence of lower oxidation states (+4, +5) of molybdenum in the MoOx layer was revealed by X-ray photoelectron spectroscopy. The stack achieved a high absorptance in the solar spectrum region (α = 0.969) and a low thermal emissivity in the infrared region (ε = 0.15 at 82 °C) at optimal process parameters. The oxidation resistance and thermal stability were evaluated by annealing the samples in vacuum up to 500 °C.

A comprehensive review on phase change material emulsions: Fabrication, characteristics, and heat transfer performance

Phase change material emulsion (PCME) is a latent functionally thermal fluid prepared by dispersing a phase change material into a carrier fluid with the aid of surfactants. The PCME has a high specific heat capacity and enhanced heat transfer performance in the phase change region, and it shows great potential as a novel heat transfer fluid in air-conditioning systems and solar thermal systems. There have been few literature reviews on PCMEs. In this paper, a comprehensive summary of the research on PCMEs, including the fabrication process, thermophysical properties, rheological behavior, heat transfer performance, and applications in solar thermal systems, is presented. Additionally, directions for further studies and applications of PCMEs are proposed.

Experimental performance analysis of low concentration ratio solar parabolic trough collectors with nanofluids in winter conditions

Abstract Applications of solar thermal systems especially for heating are quiet reliable. At present the domestic use of such technologies especially for hot water and space heating applications is limited to flat plate collectors and evacuated tubes. Moreover, commercial use of nano-fluids is also scarce in these applications. The present study is designed to evaluate the experimental performance analysis of a locally developed Parabolic Trough Collector (PTC) system having concentration ratio of 11 for domestic heating applications primarily. Two metallic oxides water based nanofluids i.e. Al2O3/H2O and Fe2O3/H2O are used at three particles concentrations of 0.20%, 0.25% and 0.30% by weight at 1.0, 1.5 and 2.0 L/min flow rates. The experimentation is performed under wide range of operating conditions in terms of solar radiation and ambient conditions at Taxila, Pakistan. The maximum efficiencies achieved with Al2O3 and Fe2O3 nanofluids at 2 L/min are 13% and 11% higher respectively compared to water under same operating conditions. Al2O3 nanofluids seemed more favorable in the enhancement of efficiency of PTC compared to Fe2O3 for domestic applications using PTC. The results offer significant insight from the commercialization aspect for the working of locally developed linear PTC and influence of nano-fluids for space heating application.

Solar cooling system using concentrating collectors for office buildings: A case study for Greece

On a European level there is intense research activity to broaden the applications of solar thermal systems beyond their established domains (hot water, space heating support) and to foster their participation in the energy maps of the EU-Member States. Concentrated Solar Thermal (CST) systems are expected to play a key role in this effort, especially for achieving the medium and high temperatures needed, for electricity generation, for industrial applications but also for hybridized solar heating/cooling and desalination applications.This paper presents a proposal for implementation of a CST system in the building sector, based on a research carried out in the Laboratory of Environmental and Energy Efficient Design of Buildings and Settlements at the University of Thrace. Specifically, an integrated solar cooling system using parabolic trough solar collectors and double-effect chiller is discussed, used to cover the cooling needs of typical office building in Greece.As it was shown, the use of concentrating solar collectors leads to significantly higher output temperatures that can enable the use of two stage absorption chillers with a higher COP. Alternatively, when low or medium temperature heat is required, the use of CST systems takes less space to cope with it than traditional flat plate collectors. The combination of these parameters can contribute to removing key barriers associated with the broader diffusion of solar cooling technology, enhancing the potential to become more competitive to the conventional air conditioning technologies.

Improvement of energy performances of existing buildings by application of solar thermal systems

Improvement of energy performances of the existing buildings in the suburban settlement Konjarnik in Belgrade, by the application of solar thermal systems is the topic presented in this paper. Hypothetical models of building improvements are created to allow the benefits of applying solar thermal collectors to residential buildings in Belgrade climate conditions to be estimated. This case study presents different design variants of solar thermal collectors integrated into a multifamily building envelope. The following aspects of solar thermal systems integration are analyzed in the paper: energy, architectural, ecological and economic. The results show that in Belgrade climatic conditions significant energy savings and reduction of CO2 emissions can be obtained with the application of solar thermal collectors.

Potential application of solar thermal systems for hot water production in Hong Kong

This paper presents the evaluation results of conventional solar water heater (SWH) systems and solar assisted heat pump (SAHP) systems for hot water production in Hong Kong. An economic comparison and global warming impact analysis are conducted among the two kinds of solar thermal systems and traditional water heating systems (i.e. electric water heaters and towngas water heaters). The economic comparison results show that solar thermal systems have greater economic benefits than traditional water heating systems. In addition, conventional SWH systems are comparable with the SAHP systems when solar fractions are above 50%. Besides, analysis on the sensitivity of the total equivalent warming impact (TEWI) indicates that the towngas boosted SWH system has the greatest potential in greenhouse gas emission reduction with various solar collector areas and the electricity boosted SWH system has the comparative TEWI with the SAHP systems if its solar fraction is above 50%. As for SAHP systems, the solar assisted air source heat pump (SA-ASHP) system has the least global warming impact. Based on all investigation results, suggestions are given on the selection of solar thermal systems for applications in Hong Kong.

Public energy performance policy and the effect on diffusion of solar thermal systems in buildings: A Dutch experience

Energy performance policy is an important element in the European Energy Performance of Buildings Directive (Directive 2002/91/EC—in short: EPBD, published 4 January 2003), which the European Commission is now urging all European member states to introduce for the building sector by 2006. One of the expected benefits of energy performance policy is that it can help to introduce innovations such as solar thermal systems. However, few studies have analysed this so far. This paper describes the extent to which the penetration of solar thermal systems in the residential building sector is directly related to energy performance policy in the Netherlands. The concept of energy performance policy is explained and the effects of using energy performance policy for several years in the Netherlands are described, through the results of an empirical study. Statistical analysis appears to show no association between Dutch energy performance policy and the application of solar thermal systems in the domestic sector.