Solar Thermal Energy Applications Research Articles

Enhancing the thermal properties of paraffin wax as latent heat storage material using hybrid nanomaterials

Paraffin wax is the most common phase change material (PCM) that has been broadly studied, leading to a reliable optimal for thermal energy storage in solar energy applications. The main advantages of paraffin are its high latent heat of fusion and low melting point that appropriate solar thermal energy application. In addition to its accessibility, ease of use, and ability to be stored at room temperature for extended periods of time, Nevertheless, improving its low thermal conductivity is still a big, noticeable challenge in recently published work. In this work, the effect of adding nano-Cu2O, nano-Al2O3 and hybrid nano-Cu2O-Al2O3 (1:1) at different mass concentrations (1, 3, and 5 wt%) on the thermal characteristics of paraffin wax is investigated. The measured results showed that the peak values of thermal conductivity and diffusivity are achieved at a wight concentration of 3% when nano-Cu2O and nano-Al2O3 are added to paraffin wax with significant superiority for nano-Cu2O. While both of those thermal properties are negatively affected by increasing the concentration beyond this value. The results also showed the excellence of the proposed hybrid nanoparticles compared to nano-Cu2O and nano-Al2O3 as they achieve the highest values of thermal conductivity and diffusivity at a weight concentration of 5.0 wt%.

Solar energy as a sustainable source of energy for industrial applications in Sri Lanka: a conceptual mini-review

The world’s primary energy demand has increased significantly due to the industrial revolution and population growth, which create the demand for primary energy. The COVID-19 pandemic situation significantly damages the world’s energy network, which critically affects developing countries like Sri Lanka. Therefore, this paper has been developed to discuss an important framework for the use of solar energy as a suitable energy source for various industrial operations. The application of solar thermal energy and solar PV systems into industrial processes can minimize the economic cost of energy usage in the country. The points discussed in this conceptual mini-review can help policymakers identify and explore industrial windows that can be structured with solar energy for a sustainable energy future in Sri Lanka.

A review on solar energy intensified biomass valorization and value-added products production: Practicability, challenges, techno economic and lifecycle assessment

Solar technology is a viable alternative which can be used in place of conventional energy sources. Conversion of biomass to valuable high-end products have also been touted as potential sources of energy which can replace conventional fossil fuel sources. The integration of solar energy in aiding the conversion of biomass to products seeks to completely transform the process into using renewable energy only, without aid of fossil fuel-based electricity. This review discusses the various applications of solar thermal energy and solar photovoltaic energy in various thermochemical processes like solar pyrolysis, hydrothermal liquefaction and gasification. The use of solar energy in production of biodiesel, bioethanol, biohydrogen and biomethane is elucidated on. The integration of all these process into a biorefinery aided by solar technology also has been briefly looked upon, with emphasis on the techno-economic analysis and life cycle analysis of the biorefineries. Finally, opportunities and challenges regarding solar technology has been elucidated with respect to the bioprocess industry.

Experimental investigation to thermal performance of different photo voltaic modules for efficient system design

Due to rapid industrialization, and depletion of fossil fuels, alternative renewable resources are mandatory, where solar thermal energy is one of the promising alternate. In this study, an experimental investigation was conducted to analyze the thermal performance of different photovoltaic-modules under varying climate conditions. These include thin plate Copper indium diselenide, mono-crystalline silicon, micro crystalline silicone, amorphous silicon and poly-crystalline silicon. The analysis was concentrated on the evaluation of module efficiency, solar irradiance absorption rate, maximum power output, performance ratio, normalized power output efficiency and temperature effect on each module at real operational outdoor conditions. Mono-crystalline silicon module showed high average efficiency of 20.8% and average performance ratio 1.21 compared to the other PV modules. It was observed that all types of modules have higher average temperature in summer season and showed low performance ratio and low module efficiency as compared to winter season. Average normalized power out of mono-crystalline silicon 56.2% more efficient than the other modules. The increased thermal performance of mono-crystalline silicon was related with its high absorption rate and high conduction rate. Thus, mono-crystalline silicon PV module is the best potential candidate for solar capturing technique to be utilize in diverse solar thermal energy applications.

Performance of a collector-storage solar air heating system for building mechanical ventilation preheating in the cold area

The application of solar thermal energy to preheat cold fresh air for mechanical ventilation could save a lot of energy and ensure the stable operation of the ventilation system. In this paper, a kind of collector-storage solar air heating system (CSSAHS), in which the thermal storage unit (TSU) is characterized by a dual S-channel for heat transfer, is proposed and the mathematical model for the integrated system was established. The model including the TSU, solar air collector, heat recovery device, and the fan was verified by an experimental study set up in a typical cold city in China. The model has been verified by experiments. The simulation results demonstrate that fresh air is the most important factor affecting storage/release efficiency. The increasing rate of heat release efficiency in the range of fresh air temperature -6–18°C is about 1.58%/°C. The solar heat collector area and the size of the TSU suitable for representative cities in cold regions are optimized based on multi-condition simulation analysis. The CSSAHS can preheat fresh air for 5 h after heat storage and the release efficiency is between 52 and 74%. Compared with other systems, the energy-saving rate of the CSSAHS is 26.5–33.3% in cold winter, and the heat supply ratio of the TSU is 24.4–35.1%.

Thermally induced flexible phase change composites with enhanced thermal conductivity for solar thermal conversion and storage

Organic phase change materials (PCMs) composites with thermally induced flexibility, lower interfacial thermal resistance, excellent stability, photo-absorption, higher thermal conductivity, good photo-thermal conversion and storage properties present better prospects in solar thermal application. This research prepared flexible PCMs composite by taking palmitic acid (PA) as PCMs, olefin block copolymers (OBC) as carriers and graphene nanoplatelets (GNP) as additive by blending and hot-pressing method. The unique block structure of OBC, excellent performance of GNP and interaction between GNP and PA provide OBC/GNP/PA composites good flexibility, excellent stability and thermal reliability. GNP as effective solar trap and thermal conductive additive are attribute to the sunlight capture, high solar energy conversion and transportation. The photo-thermal conversion efficiency of OBC/GNP/PA PCMs composites with 4 wt % GNP reaches 86.21%. The thermal conductivity is 155% higher than PA/OBC. The phase change enthalpy is 145.52 J/g for adsorbing 77.6 wt% PAand 4 wt% GNP. PCMs composites show excellent energy storage properties. Practical and easy preparation method and excellent performances of OBC/GNP/PA composites provide a good idea and more possibility for flexible PCMs composites with enhanced thermal conductivity in low and medium temperature solar thermal application. • Thermal induced flexible PCM composites with enhanced thermal conductivity for high-efficiency solar thermal conversion and storage is developed. • The OBC/GNP/PA composites exhibit excellent thermally induced flexibility, good shape stability and thermal reliability. • The highest efficiency of photo-thermal conversion is up to 86.21%. • The thermal conductivity is 155% improvement over PA/OBC. • High photo-thermal energy storage and practical preparation show huge potential for solar thermal-energy applications.

Ultra-broadband and polarization-insensitive metasurface absorber with behavior prediction using machine learning

The solar spectrum energy absorption is very important for designing any solar absorber. The need for absorbing visible, infrared, and ultraviolet regions is increasing as most of the absorbers absorb visible regions. We propose a metasurface solar absorber based on Ge2Sb2Te5 (GST) substrate which increases the absorption in visible, infrared and ultraviolet regions. GST is a phase-changing material having two different phases amorphous (aGST) and crystalline (cGST). The absorber is also analyzed using machine learning algorithm to predict the absorption values for different wavelengths. The solar absorber is showing an ultra-broadband response covering a 0.2–1.5 µm wavelength. The absorption analysis for ultra-violet, visible, and near-infrared regions for aGST and cGST is presented. The absorption of aGST design is better compared to cGST design. Furthermore, the design is showing polarization insensitiveness. Experiments are performed to check the K-Nearest Neighbors (KNN)-Regressor model’s prediction efficiency for predicting missing/intermediate wavelengths values of absorption. Different values of K and test scenarios; C-30, C-50 are used to evaluate regressor models using adjusted R2 Score as an evaluation metric. It is detected from the experimental results that, high prediction proficiency (more than 0.9 adjusted R2 score) can be accomplished using a lower value of K in KNN-Regressor model. The design results are optimized for geometrical parameters like substrate thickness, metasurface thickness, and ground plane thickness. The proposed metasurface solar absorber is absorbing ultraviolet, visible, and near-infrared regions which will be used in solar thermal energy applications.

Solar Photovoltaic Technology In Brazil

In recent years, the use of solar systems has been increasing worldwide in an accelerated rate, with perspective of staying among the main sources of renewable energy for the following decades, along with wind power. The photovoltaic energy in Brazil currently represents 4,5 GW (2,5% of the national electric matrix). Solar thermal energy is called when solar radiation is used to transfer energy to a medium, usually water or air. It is a renewable, sustainable and environmentally friendly source of energy. The number of solar thermal energy applications is very extensive when considering all temperature levels and energy demands. In this context, the present work shows the evolution of solar photovoltaic energy in Brazil, bringing a discussion regarding to solar power characteristics, working principles and different technologies of solar cells, as well as aspects of operation and maintenance of the photovoltaic panels. Investments in research for the development of new technologies and valuation of existing ones for solar energy should also be prioritized, as well as for better planning and sustainable use of photovoltaic energy, given the advantages for the economy, society and the environment provided by this renewable and clean source.

Thermal Stability of Ionic Liquids: Effect of Metals

We investigated the thermal stability and corrosion effects of a promising ionic liquid (IL) to be employed as an advanced heat transfer fluid in solar thermal energy applications. Degradation tests were performed on IL samples kept in contact with various metals (steel, copper and brass) at 200 °C for different time lengths. Structural characterization of fresh and aged IL samples was carried out by high-resolution magic angle spinning nuclear magnetic resonance and Fourier transform infrared spectroscopic analyses, while headspace gas chromatography–mass spectrometry was employed to evaluate the release of volatile organic compounds. The combination of the above-mentioned techniques effectively allowed the occurrence of degradation processes due to aging to be verified.

Solar thermal energy application to dry reforming of methane on the open-cell foam to enhance the energy storage efficiency of a thermochemical fluidized bed membrane reformer: modelling and simulation

The hydrodynamic characterization of the solar-driven CO2 reforming of methane through b-SiC open-cell foam in a fluidized bed configuration is performed by reacting Methane (CH4) with carbon dioxide (CO2). The mathematical modelling is important to design and optimize the reforming methods. Usually, the reforming methods's application through b-SiC foam bed improves the heat transfer and mass transfer due to high porosity and surface area of the b-SiC foam. Fluidized Bed Membrane (FBM) Reformers can be substantially studied as a promising equipment to investigate the thermochemical conversion of CH4 using CO2 to produce solar hydrogen. This work has as main objective a theoretical modelling to describe the process variables of the solar-driven CO2 reforming of methane in the FBM reformer. The FBM reformer is filled with b-SiC open-cell foam where the thermochemical conversion is carried out. The model variables describe the specific aims of work and these objectives can be identified from each equation of the developed mathematical model. The present work has been proposed to study two specific aims as (i) The effective thermal conductivity's effect of the solid phase and (ii) molar flows of chemical components. The endothermic reaction temperature's profiles are notably increased as the numeral value of the effective thermal conductivity's effect of the solid phase. is rised. The solar-driven CO2 reforming method is suggested to improve the Production Rate (PR) of H2 regarding the PR of CO.

The Emergence of Phase Change Material in Solar Thermal Energy: A Scientometric Review

Phase change material (PCM) features an attractive option due to its solar thermal storage capability to assist the cooling/heating process especially during night operation, thus contributing to the reduction of energy cost and carbon footprint. This study aims to analyse the emergence of PCM in the application of solar thermal energy. Subsequently, to envisage Technology Readiness Level (TRL) and commercialisation opportunity based on historical and contemporary research trends. This review encompasses of peer-reviewed literatures from Scopus database for one decade between 2010 and 2019. Based on the review, there is a moderate growth on the research related to PCM-solar thermal at 22% of emergence rate from the past one decade. China has dominated in this research development by concurring approximately 22% from the number of research articles published globally. It can be concluded that the application of PCM in solar thermal energy system is at TRL 5 which reflects research and development (R&D) progress is at intermediate prototypical development based on the trend of academic publication. Furthermore, based on the review, PCM features great potential in commercialisation opportunity due to its vital contribution as a frontier material/substance in overcoming the challenges of energy and environmental insecurity.

Three-Dimensional Interpenetrating Network Phase-Change Composites with High Photothermal Conversion and Rapid Heat Storage and Release

Solar thermal energy conversion and storage have gained more attention for solving energy crisis and environment issues. Phase-change materials with excellent thermal conductivity, high photothermal conversion efficiency, rapid heat storage and release, and good stability are required for solar thermal applications. In this study, three-dimensional (3D) interpenetrating network phase-change composites are fabricated by taking graphene-oxide (GO) aerogel (GA) containing a small amount of carbon nanotubes (CNTs) and carbon spheres (CSs) as support materials and vacuum impregnation melting polyethylene glycol (PEG) as the phase-change material. The 3D structure and abundant functional groups greatly improve the stability of phase-change composites. The addition of CNTs and CSs greatly increases the thermal conductivity and photothermal conversion capability of PCMs. Compared with pure PEG, thermal conductivity is increased by 181.58%, and photothermal conversion efficiency reaches 89.3%. Simulated results also confirm that GA-based phase change composites exhibit better thermal conductivity. Less thermal conductivity fillers and more phase-change material (96.4%) exhibit excellent thermal conductivity, high photothermal conversion efficiency, and a greater energy-storage density. The 3D phase-change composites are also applied for thermoelectric generation and show a stable output voltage of 35 mV for 300 s after removing the light source. The 3D interpenetrating network form-stable phase change composites based on black GA shows broad prospects in solar thermal energy applications.

Techno feasibility analysis of a concentrating solar thermal cooling systems at a university complex

Concentrating solar thermal (CST) energy applications are growing worldwide, especially in combined cooling, heat, and power processes. Building upon the analysis of a building’s thermal comfort, and software simulations for CST, the current study evaluates a solar conditioning system integrated with absorption systems. The cooling system is equipped with single-, double- and triple-effect configurations cycle, production parameters, and thermal storage. The required fraction of auxiliary energy for the system operation is estimated. The results indicate that the double effect system is the best configuration for the adopted location in Brazil. The system’s annual auxiliary energy demand is, approximately, 20%. Triple-effect systems require less energy at higher temperatures due to local direct radiation, which then leads to an intermittent operation and greater auxiliary energy demands. The methodology applied in this work could be adopted in different locations, with an emphasis on the possibility of testing smaller scale systems in small buildings.

High-energy and light-actuated phase change composite for solar energy storage and heat release

Phase change materials (PCMs) show great potential for solar thermal energy application due to the large latent heat and high efficiency. However, it is difficult to implement long-term storage because of the sensitive phase-transition to environment temperature. Here, we report a high-energy organic phase change composite (PCC) by introducing long-chain azobenzene molecule (AZO) into low-cost tetradecyl alcohol (TA) for light-regulated solar energy storage and release. The photo-switch azobenzene can install a new energy barrier and form a supercooling in liquid-phase charged PCC via molecular photo-isomerization and enhanced intermolecular interactions. Moreover, the charged PCC reveals a large latent heat of 239 J g−1 and a high power density of 594 W kg−1 with a suitable degree of supercooling (3.33–7.67 °C) for energy storage near room temperature. It is noted that the optically-controlled energy release by blue light and excellent cycling stability can be obtained. This kind of PCC is a promising candidate for smart and convenient solar energy storage application.

Experimental study on combined sensible-latent heat storage system for different volume fractions of PCM

Renewable energy sources are unable to provide continuous energy because of their sporadic nature. To counter this, in the case of solar thermal energy applications, there is a need for effective thermal energy storage. The concept of single tank thermocline storage is considered as a potential cost-optimized approach for medium thermal applications. Although, one of the major disadvantage of this design is greater degradation of the thermocline during the discharge cycle, which results in poor performance. In the present work, a novel combined sensible-latent TES system is proposed to combat these problems. A combined sensible-latent TES system is designed by incorporating the PCM spherical capsules above the concrete spheres in the same storage tank. An experimental study has been performed to investigate the effect of four different volume fractions of PCM on the performance of the proposed TES system during charge and discharge cycles. The increase in volume of PCM has a significant impact on the performance of the system. The higher volume fractions of PCM have greater energy storage, extraction and cumulative energy transfer than the lower volume fractions. The volume fraction of 80% and 60% shows better performance than the 40% and 20% volume of PCM. Based on the results, it is recommended that charging at higher flow rates provides faster charging and discharge at lower flow rates provides better utilization of energy for a longer duration of time in case of solar thermal applications.

High temperature stability of transparent silica aerogels for solar thermal applications

Solar thermal energy systems combined with low-cost thermal storage provide a sustainable, dispatchable source of renewable energy. One approach to increase the attractiveness of these systems is to use high-performing solar transparent, thermally insulating silica aerogel to significantly increase efficiency. Several past works have proposed using these ultra-nanoporous materials to reduce thermal losses in the receiver, but only recently have aerogels reached the high solar transparency necessary to be considered for concentrated solar applications (>97%). However, the durability and stability of optically transparent silica aerogels at the operating conditions of solar-thermal receivers has not been examined. Here, we investigate the high temperature stability of transparent silica aerogel for use in concentrated solar thermal energy applications. Transparent samples (visible transmission >95% at 4 mm thickness) were annealed for several months at 400, 600, and 800 °C to investigate the relative change in nanostructure, solar transparency, and effective thermal conductivity. Results showed that at 400 and 600 °C, the temperature-dependent changes reach a plateau within 30 days of continuous annealing, but at 800 °C, samples are structurally unstable. A simple receiver efficiency model was used to show stable performance at 400 and 600 °C temperatures, even after months of exposure. This work validates that transparent silica aerogels can be used in solar thermal receivers below 800 °C, yielding appreciable increases in efficiency for solar energy harvesting operation.

Experimental investigation on a novel triple heat sources-driven absorption heat pump system

This paper presents a novel triple heat sources-driven absorption heat pump system. The exhaust gas is used as the heat source for a high-pressure generator. The superheated refrigerant vapor generated by the high-pressure generator is used for heating the solution in the low-pressure generator 1 by releasing the latent and sensible heat. The low-temperature solar thermal energy serves as the heat source of the low-pressure generator 2. The geothermal energy supplies heat to the evaporator. Heat discharged from the condenser and the absorber is supplied to the air conditioner heat medium water. The high- and low-pressure generators are coupled to each other through an ejector. The introduction of the ejector reduces the pressure of the low pressure generator 2 below the condensing pressure so that the lower temperature solar thermal energy can be utilized. An experimental setup for this heat pump cycle is built, and an experimental investigation is carried out. The influences of the independent variables on the key internal operating parameters and heating performance have been investigated. Experimental studies show that when the hot air temperature is 213 °C and the temperature of the hot water is 43.5 °C, a heating capacity of 26.6 kW can be achieved with a heating performance coefficient greater than 1.7. In this way, an efficient and full use of waste heat is realized, and the results can provide an important basis for the design and wide application of low-temperature solar thermal and geothermal energy.

Monitoring investigation of solar diffuse fraction in Taiwan

Global solar radiation, which passes through the atmosphere and arrives on earth’s ground, is composed of two constituents, that is, beam and diffuse radiation. It is agreed that the beam radiation is the only effective part for use of solar energy in concentrating either photovoltaic or solar thermal energy application, which concentrates the incident sunlight to attain high performance of either electrical power or high-temperature thermal energy generation, respectively. Information of beam radiation quantity incident upon an absorbing surface is, thus, a prerequisite for the performance evaluation of concentrating optic device. However, very few data of diffuse fraction, defined as the ratio of diffuse radiation to global radiation, is available in Taiwan. A long-time monitoring investigation in the main island (Taiwan proper) and one offshore islet (Penghu) were conducted over recent years. It was found that the annually averaged diffuse fractions, calculated with the time duration from sunrise to sunset, in the east (Taitung) and west (Tainan) sides of the main island were about 0.49 and 0.53, respectively, while about 0.50 in the offshore islet (Penghu). Seasonal variations due to geographical/topographical effects on diffuse fraction are also reported and discussed. It is found that Northeast Monsoon has remarkable effects on increment of diffuse fraction in Taitung and Penghu, while insignificant effect in Tainan.

Modeling the Feasibility of Using Solar Thermal Systems for Meeting the Heating Requirements at Corn Ethanol Production Facilities

While ethanol use as a vehicle fuel has been promoted as a renewable alternative to fossil fuels, current production methods of ethanol from corn feedstock rely heavily on the combustion of nonrenewable fuels such as natural gas. Solar thermal systems can provide a renewable energy source for supplying some of the heat required ethanol production. In this paper, a model to analyze the feasibility of using solar thermal energy to reduce natural gas consumption in ethanol production is described and applied. Sites of current ethanol production facilities are used to provide a realistic analysis of the economic feasibility of using solar thermal energy in the ethanol production process. The results show that it is not reasonable to expect to replace all of the natural gas consumption in the heating processes in ethanol production but that application of solar thermal energy can be applied to a specific subsystem such as the preheating of boiler makeup water. Profitability of systems for replacing a fraction of the natural gas is analyzed. It is found that both location and local natural gas prices are important in determining whether to pursue such a project and that solar thermal systems should have long-term profitability.

Solar Thermal Energy Utilization for Medium Temperature Industrial Process Heat Applications - A Review

The paper presents a review of solar thermal utilization to various commercial and industrial process applications. The current trend around the world has shown that the growth of solar thermal energy for Industrial use is slow compared to domestic applications due to higher temperature requirement and available solar system’s low efficiency. An extensive research on solar thermal applications in various process industries along with systems have been discussed in research papers. The aim of this review work is to identify the trend on solar thermal energy applications to various process industries with various solar thermal systems available in the market. It also focuses on the challenges on appropriate solar collector selection based on type of process industries and temperature range on which it operates. Therefore the current paper aims to fill the gap between available solar thermal energy systems and their process integration based on type of process industry aiming to enhance the practical application of these systems without sacrificing on the performance and economic feasibility of the systems