Thermal Energy Systems Research Articles

Development and characterization of eutectic phase change material for thermal energy storage system

The most efficient way to store thermal energy is the latent heat energy storage method because of its high energy storage density and almost constant freezing/melting temperature. The present study deals with the preparation of eutectic Phase change material (PCM) which is the mixture of myristic acid and Polyethylene glycol (PEG) of molecular weight 10000. The mixture was prepared in different weight fractions via facile incorporation method. The thermal and chemical properties of the eutectic mixture is characterized by DSC and FTIR technique. A mixture of 50% PEG 10000 and 50% myristic acid possess the maximum latent heat of 188.96 kJ/kg among all prepared samples and the final melting temperature achieved is 58.61 °C. The experimental results shows that the developed eutectic mixture possess good thermal energy storage capacity and can be a potential material for the thermal energy system applications.

Environmental Impact of the High Concentrator Photovoltaic Thermal 2000x System

High Concentrator Photovoltaic Thermal (HCPV/T) systems produce both electrical and thermal energy and they are efficient in areas with high Direct Normal Irradiance (DNI). This paper estimates the lifecycle environmental impact of the HCPV/T 2000x system for both electrical and thermal functionalities. Process-based attributional method following the guidelines and framework of ISO 14044/40 was used to conduct the Life Cycle Assessment (LCA). The midpoint and endpoint impact categories were studied. It was found that the main hotspots are the production of the thermal energy system contributing with 50% and 55%, respectively, followed by the production of the tracking system with 29% and 32% and the operation and maintenance with 13% and 7%. The main contributor to the lifecycle environmental impact category indicators was found to be the raw materials acquisition/production and manufacturing of the thermal energy and tracking systems. The results indicate that the lifecycle environmental impact of the HCPV/T 2000x system is lower compared to fuel-based Combined Heat and Power (CHP) and non-Renewable Energy Sources (non-RES) systems.

Evaluation of photothermal properties for absorption of solar energy by Co3O4 nanofluids synthesized using endophytic fungus Aspergillus nidulans

An attempt has been made to compare the optical properties of cobalt oxide (Co3O4) nanoparticles using experimental values and theoretical predictions. Optical transmittance of the nanoparticles obtained was higher than 65% in 550–850 nm containing visible spectrum and the experimental results were in accordance with the predictive datum. The absorption coefficient peak observed is close to the predictive value and is present in the visible region of the light. In addition, there was an excellent agreement between theoretical and experimental results in extinction coefficient and refractive index. Besides, this work proposes and validates a novel idea of using Co3O4 nanofluids to enhance solar thermal conversion efficiency. Co3O4 nanofluids synthesized using endophytic fungus Aspergillus nidulans isolated from a medicinal plant, Nothapodytes foetida has been used to illustrate the energy storage capacity of nanofluids. Experimental results reveal that Co3O4 nanofluids have good specific absorption rate (SAR) and better photo-thermal conversion efficiency than water. Nanofluid exhibited a greater temperature gradient than pure water, which is desired. Thus the good absorption ability of Co3O4 nanofluids for solar energy indicated that it is suitable for direct absorption solar thermal energy systems.

Phase change materials integrated solar thermal energy systems: Global trends and current practices in experimental approaches

Abstract Solar thermal systems (STSs) are gaining boom in the globalized market since last two decades to combat the menace of global warming. Considerable research has been carried out in the field of solar thermal system for efficiency enhancement. Improvement in terms of efficiency and performance would make solar thermal systems a better option for replacing the conventional energy systems. Phase change Materials (PCMs) have emerged as an alternative to enhance the performance of the solar heating systems by acting as thermal storage batteries. In this review article an attempt has been made to consolidate the global trends and practices that has been underwent incorporating Phase change materials (PCMs) in solar thermal systems. Research on PCM based solar cooker has found to be extinct. PCM based PCM based high temperature power plant applications are on current trends of research. Application of phase change materials for low, medium and high temperature solar thermal systems are comprehensively reviewed and discussed in this article. As well the environmental benefits in terms decline in CO2 emission, due to the use of STS in day-today life and the economic analysis of PCM based STS in terms of cost and payback period is presented.

Solar fuel production by developing an integrated biodiesel production process and solar thermal energy system

To diminish the consumption of fossil fuels and their subsequent pollutions, biodiesel plays an important role in the transportation section. Biodiesel production processes can be coupled with renewable energy sources to achieve higher energy efficiency and higher renewability. Also, employing a sub-system to produce power simultaneously increases the process performance as well. In the present study, a new integrated cogeneration process for the production of biodiesel and power using solar energy is proposed and analyzed. Methanol, fresh oil, and sodium hydroxide, at 25 °C and 100 kPa, enter into the biodiesel production unit as feed. Yazd city in Iran, located between 31.88 N and 54.28 E, is considered as base region for simulating the parabolic trough solar collector. To design a cogeneration plant, the organic Rankine cycle is combined with the solar system to supply the required process power. The proposed system produces 991.42 kg/h of biodiesel with a yield of 94.42% and 1718 kW net power simultaneously. The total energy efficiency is 60.83%, showing the capability of the proposed process for biodiesel and power cogeneration from renewability and environmental perspective. Also, the exergy analysis applied to evaluate the proposed plant’s thermodynamic performance. The total exergy efficiency of the system is 74.38% when the highest exergy destruction rate takes place inside the parabolic trough solar collectors.

Perfect grating-Mie-metamaterial based spectrally selective solar absorbers

Spectrally selective solar absorbers are widely employed in solar thermal energy systems. This work theoretically investigates thermal radiative properties of metamaterials consisting of 1-D and 2-D grating-Mie-metamaterials (tungsten nanoparticles embedded in alumina) on top of multilayered refractory materials (tungsten-silicon nitride-tungsten) as a promising selective solar absorber. The proposed metamaterial shows high absorptance from the ultraviolet to near-infrared lights, while exhibiting low emittance in the mid-infrared regime owing to Mie-resonances, surface plasmon polaritons, and metal-dielectric-metal resonance. The optical properties of designed metamaterial solar absorbers are angular independence of up to 75° and polarization insensitive. The total absorptance of 1-D and 2-D grating-Mie-metamaterials are 90.59% and 94.11%, respectively, while the total emittance are 2.89% and 3.2%, respectively. The photon-to-heat conversion efficiency is theoretically investigated under various operational temperatures and concentration factors. Thermal performance of grating-Mie-metamaterials is greatly enhanced within a one-day cycle, and the stagnation temperature under different concentration factors manifests the potential feasibility in mid and high-temperature solar thermal engineering.

A review on potentials of coupling PCM storage modules to heat pipes and heat pumps

A large portion of world’s final energy consumption is employed in thermal form. The proper techniques can be used to improve the efficiencies of thermal energy systems and decrease the energy consumption. Phase change material (PCM) storage modules can be coupled with different thermal systems to improve their thermal efficiency. This paper reviews the real potentials of coupling PCM storage modules to heat pipes and heat pumps in terms of energy saving and thermal energy management. The different systems suggested by researchers are described, and the main findings of the studies are provided. The advantages and disadvantages of these combined systems are discussed, and some suggestions for future studies are provided. The results show that heat pipes show great heat transfer ability and have good efficiency in improving heat transfer within PCMs. Moreover, heat pipes can be incorporated into PCMs to decrease the thermal resistance. The purpose of PCM coupled with heat pipe is to incorporate the large thermal conductivity of heat pipe with the large latent heat capacity of PCM. PCMs have ability to balance the unconformity between supply and demand in heat pumps and decrease the size of storage tank used in a heat pump module.

Effect of thermoelectric materials in electrical and thermal performance of photovoltaic thermal (PVT) collector

A photovoltaic integrated thermal (PVT) collector with thermoelectric material has been proposed in this communication, where a channel or duct has been used below the photovoltaic module in which air has been circulated to extract the heat taken by the photovoltaic module. Hence in PVT system, electrical energy from photovoltaic and thermal energy from duct are taken at the output. In this collector, thermoelectric (TE) is used to change the thermal energy by removing the waste heat of photovoltaic module into electric energy. In proposed PVT with thermoelectric system, TEs are generally appended at the back of the photovoltaic to improve the efficiency of PVT collectors. Thermal modelling has been presented for PVT collector with thermoelectric. The effect of thermoelectric material has been analysed for PVT collector. The electrical energy gain for photovoltaic collector and overall electrical energy gain with thermoelectric has been theoretically calculated. From the computed results, the overall electrical output is observed of PVT system with thermoelectric material; it is higher than only PVT system due to thermoelectric. As PVT system without thermoelectric generates only electrical energy due to PV and thermal energy but PVT system with thermoelectric generates electrical energy due to PV and thermoelectric both as well as thermal energy so overall exergy of PVT system with thermoelectric is higher than only PVT system. Hence PVT system with thermoelectric shows better results than only PVT system in respect of electrical, thermal and overall exergy gain.

Cogeneration optimisation for locally integrated energy systems

Energy Efficiency is proven to be a significant opportunity for industry, cities and society, in general, to save energy costs and harmful gaseous and particulate emissions. Locally Integrated Energy System (LIES) was introduced to promote symbiosis between industry and local area to enhance their overall system energy efficiency. LIES extends Total Site Heat Integration (TSHI) to optimise the energy system for multiple industrial processes as well as other process heat demands in proximity. This paper integrates the TSHI methodology with Power Pinch Analysis (PoPA) to sequentially optimise the thermal and electrical energy in a LIES. A Power Cogeneration Estimation Table is used to systematically identify and determine the amount of power that the thermal energy system potentially generates via backpressure and condensing steam turbines. This work evaluated the thermal and power system based on total utility cost, where the thermal requirement is fulfilled by the industrial boiler system with the potential of outsourced power demands. A case study is performed for verifying the proposed methodology. Results found that LIES with Heat and Power Integration and battery storage is recommended for low utility cost operation without the need for a heat storage system.

Opportunities for Local Energy Supply in Norway: A Case Study of a University Campus Site

Neighbourhoods can contribute to climate change mitigation by supplying and/or facilitating renewable energy sources (RES). In this context, we evaluate opportunities related to the energy system of a Norwegian university campus, Campus Evenstad, by quantifying monetary value of local energy resources like solar photovoltaics (PV) and a bio-based combined heat and power (CHP) plant in a cost analysis. Environmental value is discussed regarding operational control of energy units to minimize emissions. Using mixed integer linear programming (MILP), we also present results from an investment analysis for local thermal and electric energy system to achieve different levels of emission compensation. Results show that local electricity supply generates most monetary value through saved costs related to reduced power grid import, and that solar PV is the most cost-efficient resource to achieve compensation of GHG emissions.

Thermo Physical Properties of Nanofluids

Nanofluids are new generation of thermo fluids. Researchers are attracted towards their application in various thermal energy systems. Before employing nanofluids in the heat exchangers, it is necessary to ensure superior thermo physical properties of nanofluids. In the present work, different thermo physical properties of nanofluids like thermal conductivity, viscosity, specific heat and density have been studied for a wide range of volume concentration (0.25-2.0 %) and temperature (30-60°C). TiO2/ H2O and CeO2/ H2O nanofluids show good stability for 0.25-2.0 volume %. The temperature range 30-60°C is considered because above 60°C the convection heat transfer may affect the accuracy of measurements. De-ionized water (D.I. water) is considered as base fluid. TiO2/H2O and CeO2/H2O nanofluids show superior thermal properties as compared to D.I. water.

보일러 열에너지 이용 및 시스템 효율 향상을 위한 습식 분무 응축 열교환 개념 적용 가능성 연구

보일러 열에너지 이용 및 시스템 효율 향상을 위한 습식 분무 응축 열교환 개념 적용 가능성 연구

Analysis of a Residential Photovoltaic-Thermal (PVT) System in Two Similar Climate Conditions

Photovoltaic-thermal (PVT) panels combine solar thermal and photovoltaic technologies and generate simultaneously both heat and electricity. This paper looks at the potential of integrating these systems into small domestic prosumer households for the climates of Bucharest, Romania, and Strasbourg, France. First, some brief background information on PVT systems and the concept of prosumers is introduced, highlighting their features as well as the solar energy market setting in Romania and France. Next, a PVT system is proposed for a given household consumer in Strasbourg and Bucharest with the variable weather conditions corresponding to the two locations. The PVT system and the coupled consumer are modelled in TRNSYS (v17, Thermal Energy System Specialists, Madison, USA). A performance analysis is carried out in order to establish the daily instantaneous energy output and the annual energy production. The results indicate a 10–12% better performance in Bucharest compared to Strasbourg due to slightly better weather conditions. The system efficiency was assessed through various methods (first law efficiency and primary energy saving). Depending on the method used, the location and time of year, the results vary from 15% for the first law efficiency to 90% for the primary energy saving efficiency. The most suitable efficiency assessment method for this study was found to be the primary energy saving method, as it takes into account the regional differences in energy production. This study concludes that the Romanian PVT market has a good potential for adopting the technology, especially since it is currently less mature than in France.

Energy and exergy analysis of a desiccant cooling system integrated with thermal energy storage and photovoltaic/thermal-solar air collectors

This paper presents an energy and exergy analysis of a desiccant cooling system integrated with an air-based thermal energy storage (TES) unit using phase change materials (PCMs) and a photovoltaic/thermal-solar air collector (PV/T-SAC). The PV/T-SAC was used to generate thermal energy for desiccant wheel regeneration and space heating, and the TES was used to solve the mismatch between thermal energy supply and demand. The performance of this system was evaluated using a simulation system developed using TRNSYS. The effects of several key parameters on solar thermal contribution, specific net electricity generation, and the exergy destructions of individual components and overall system were investigated. It was found that the system exergy destruction was mainly resulted by the PV/T-SAC. Both the exergy performance and energy performance of this system were significantly influenced by the length and PV factor of the PV/T-SAC used. The results obtained from this study could be potentially used to guide the optimal design of desiccant cooling systems integrated with thermal energy storage and solar energy systems.

Dynamic economic dispatch with demand-side management incorporating renewable energy sources and pumped hydroelectric energy storage

This paper recommends chaotic fast convergence evolutionary programming (CFCEP) for solving real-world dynamic economic dispatch (DED) with demand-side management (DSM) incorporating renewable energy sources and pumped-storage hydroelectric unit. Here, solar–wind–thermal energy system has been considered taking into account pumped-storage hydroelectric unit and uncertainty of solar and wind energy sources. DSM programs reduce cost and boost up power system security. To investigate the upshot of DSM, the DED problem is solved with and without DSM. In the recommended technique, chaotic sequences have been applied for acquiring the dynamic scaling factor setting in FCEP. The efficiency of the recommended technique is revealed on two test systems. Simulation outcomes of the suggested technique have been matched against those acquired by fast convergence evolutionary programming (FCEP), colonial competitive differential evolution and heterogeneous strategy particle swarm optimization. It has been observed from the comparison that the recommended CFCEP technique has the ability to give better-quality solution.

Impact of ultra‐capacitor on automatic generation control of electric energy systems using an optimal FFOID controller

Automatic generation control (AGC) acts as a significant part in alleviating dynamic oscillations and sustaining constancy in frequency and scheduled tie-line power to establish the reliable, secure, and stable operation of electric energy systems under dynamic conditions. AGC needs energy storage system (ESS) and elevated expert, intelligent, and flexible control strategies to ensure generation-demand balance in modern complex structured energy systems following inconsistent load demands. Hence, this paper utilizes a new fuzzy fractional order integral derivative (FFOID) controller along with ultra-capacitor (UC) ESS to solve AGC issue in energy systems effectively. The imperialist competitive algorithm is employed to tune the output scaling factors like integral, derivative, and noninteger order of integrator/derivative of FFOID controller using ISE performance index. Initially, the technique is applied on a one-area nonreheat thermal system. Then, to demonstrate its competency and scalability, the study is boosted to prevalent two-area nonreheat thermal, two-area multisource multi-unit hydrothermal, and three-area reheat thermal energy system models. The advantage of the proposed controller is demonstrated by juxtaposing the outcomes with those offered by various best claimed intelligent control approaches expressed in the contemporary literature and fuzzy proportional integral (FPI)/fuzzy FO PI (FFOPI) controller. The UC with the FFOID controller outperforms other methods. The robustness analysis proves that parameters of the utilized controller acquired at nominal situation are healthy enough and necessarily not needed to retune under broad alterations in the system loading/parameters, size/position of load perturbation, and under the appearance of system constraints and random load pattern with/without noise.

Technical and economic feasibility of solar flat-plate collector thermal energy systems for small and medium manufacturers

Manufacturing industries require process heating for a wide variety of operations, such as drying, cooking, washing, and sterilizing. Studies of industrial energy consumption have shown that more than 50% of industrial heating demand is in the low (<60 °C), medium (60–150 °C), and medium-high (<250 °C) temperature ranges. A significant fraction of this low temperature thermal energy could be generated by commercially available solar flat-plate collector thermal energy systems, which would reduce the use of fossil fuels, energy cost volatility, and carbon emissions. However, manufacturing industries have not been able to take advantage of solar flat-plate collector systems for two main reasons: First, information is not readily available about when and what flat-plate collector system sizes can be economically applied and, second, manufacturers often do not have appropriate personnel or analysis tools to make decisions about installation of solar flat-plate collector systems. The goal of this research is to provide design decision support to small- and medium-sized manufacturers in conducting feasibility analysis for the application of solar flat-plate collector systems in their operations. The ϕ‾,f-chart method and modified ϕ‾,f-chart design method are used to predict the amount of energy collected by solar flat-plate collectors. A simplified model is proposed to assess the cost of solar flat-plate collector energy systems. To demonstrate the presented feasibility analysis methodology, a decision support software application is developed. What-if scenarios are presented for several geographic locations of varying climates. A sensitivity analysis of savings-to-investment ratio (SIR) was performed by changing selected input parameters by ±30% from the base case. It was found that SIR is sensitive to natural gas price, followed by collector area dependent cost, discount rate, cost of the auxiliary gas heater, and cost of the preheating system.

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 (&amp;gt;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 &amp;gt;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.

An Assessment of Airport Sustainability: Part 3—Water Management at Copenhagen Airport

Sustainable water management is critical for airports as they consume substantial volumes of water to maintain their infrastructure and operations. Airports also generate large volumes of surface and waste waters. The aim of this study was to examine Copenhagen Airport’s sustainable water management strategies and systems from 2006 to 2016. The study used a longitudinal qualitative research design. The annual water consumption at Copenhagen Airport has risen from 2006 to 2016 in line with the increased passenger volumes and aircraft movements. Drinking water is sourced from the Taarnby and Dragør municipal water works. Non-potable water is used wherever possible and is sourced from a local remedial drilling. Copenhagen Airport uses two separate sewer systems for handling surface and wastewater. These waters are not discharged to same system due to their different nature. To mitigate environmental risks and impacts on soil, water, and local communities; the quality of drinking, ground, and surface water are regularly monitored. The airport has implemented various water saving initiatives, such as, an aquifer thermal energy system, to reduce water consumption. The strategies, systems, and the water-saving initiatives have successfully underpinned Copenhagen Airport’s sustainable water management.

Self-assembly of 3D-graphite block infiltrated phase change materials with increased thermal conductivity

Abstract: Expanded graphite based composite phase change materials is a good candidate for latent thermal energy storage system, while suffering large volume expansion in the phase changing process. In this work, a self-assembly method is presented to build novel 3D-graphite block, and phase change composite based on the block is prepared via casting way. The new phase change material exhibits large thermal conductivity and low volume expansion. The continuous 3D-graphite network of the carbon skeleton leads to high thermal conductivity of 15.6 W m−1·K−1 and volume expansion lower than 1%. The SEM characterization, XRD patterns, impact strength and electrical conductivity results reveal that the 3D block has network interaction and percolating threshold. Then, a new model is proposed to predict the thermal conductivity of new composite. The new phase change material has great thermal energy charging/discharging performance, which has promising application foreground as heat capacitance in thermal energy systems.