Useful Thermal Energy Research Articles

Thermally-stable solar energy absorber structure with machine learning optimization

Major problems that the world is currently confronting include global warming and the energy crisis, and the optimal absorption of solar spectrum radiation is a pivotal stage for a green future for the effective usage of solar thermal energy. The available solar absorbers are temperature sensitive and do not provide perfect absorption for a wide operation range. The major objectives of the proposed paper are to overcome these limitations and present an ultrawideband thermally stable solar absorber. The developed absorber utilizes a high melting point material comprising a Ti reflector element, a Si3N4 dielectric layer, and a pi-shaped top TiN metal layer. Within the spectral range spanning from 200 to 2500 nm, a notable average absorption rate of 97.69 % is attained. This structure has also demonstrated exceptionally under the AM1.5 conditions with a spectral absorption efficiency of 96 %. This work presents a novel optimization approach for solar absorbers, employing K-nearest neighbor (KNN) regression models to enhance design optimization by simulation time reduction with an R2 score of 0.999. The novelty resides in the absorber surface shape, utilization of cost efficient, sustainable, and thermally stable materials, as well as the KNN regression model for optimization of proposed solar absorber structure. Due to the angle and polarization insensitive characteristics, this structure can be potentially utilized for solar energy harvesting and shielding.

An improved dynamic analytical model and the parameter sensitivity analysis of spherical stacking latent thermal energy storage devices

Thermal energy storage technology plays an important role on improving energy usage flexibility for the end users. The spherical stacking latent thermal energy storage devices inherits the advantages of direct thermal energy usage efficiency and simplified practical applications that received widely attentions. However, due to dispersed and multi-layer structural arrangement, the non-ignorable dynamic heat transfer process poses difficulties in the device design and operation control. In this study, an improved analytical model for predicting the transient heat transfer process of spherical stacking devices is developed. After verification, the parameter sensitivity analysis of the device is conducted by using the model. The results show that the dynamic change trend of thermal resistance is distinct for the melting and the solidification process. The developed model can dynamically predict the outlet temperature of heat transfer fluid and the heat transfer efficiency in a good agreement, and the prediction error of outlet temperature during solidification can reach −2.49 %–4.70 %. The correlation between sphere radius and heat transfer rate is negative and reaches a kind of high correlation above 0.8 for solidification process. The inlet temperature and the mass flow rate of heat transfer fluid are the most influential parameters for melting process.

Small-scale district heating system as heat storage for decentralized solar thermal collectors during non-heating period

Solar thermal energy usage in the Baltic countries is currently low, so there is a need to find technically and economically feasible solutions to increase the appeal of this technology. Integration of solar energy into existing district heating systems is a way to increase the share of renewable energy sources while utilizing the existing infrastructure, thereby reducing capital investments, as well as mitigating the risk of solar collector overheating and eliminating the need for local storage tanks in buildings. This study presents a parametric study for evaluating the effectiveness of using a district heating system to store heat produced by decentralized solar thermal collectors and comparing the district solution to the traditional local solution. The TRNSYS 18 model was developed for this purpose. The model investigates the impact of different hot tap water demand profiles as well as pipeline diameters and lengths on system energy efficiency, showing a statistically significant difference (p < 0.05) between installing solar collectors on residential and restaurant or office roofs, and no significant difference (p = 0.24) between restaurant and office. The model shows that solar energy can be shared within a 500 m distance between neighborhoods and that a larger main pipeline diameter can increase overall system efficiency.

Advancing Sustainable Building Practices: Intelligent Methods for Enhancing Heating and Cooling Energy Efficiency

Our work is dedicated to enhancing sustainability through improved energy efficiency in buildings, with a specific focus on heating and cooling control and the optimization of thermal comfort of occupants. With an energy consumption of more than 60% in buildings, HVAC systems are the biggest energy users. By integrating advanced technology, data algorithms, and digital twins, our study aims to optimize energy performance effectively. We have developed a Neural Network-based Model Predictive Control (NNMPC) to achieve this goal. Leveraging technologies such as MQTT communication, Wi-Fi modules, and field-programmable gate arrays will enhance scalability and flexibility. Our findings demonstrate the efficacy of the NNMPC system deployed on the PYNQ board for reducing sensible thermal energy usage for both cooling and heating purposes. Compared to traditional On/Off control systems, the NNMPC achieved an impressive 40.8% reduction in heating energy consumption and a 37.8% decrease in cooling energy consumption in 2006. In comparison to the On/Off technique, the NNMPC demonstrated a 25.6% reduction in annual heating energy consumption and a 28.8% drop in annual cooling energy consumption in the simulated year of 2017. We observed that, across all strategies and platforms, there were no instances where the Predicted Mean Vote (PMV) fell below −0.5. However, a significant proportion of PMV values (ranging from 65% to 83%) were observed between −0.5 and 0.5, signifying a high level of occupant comfort. Additionally, for PMV values between 0.5 and 1.0, percentages ranged from 16% to 33% for both years. Importantly, the NNMPC exhibited notable efficiency in maintaining occupants’ comfort within this range, requiring less energy while ensuring highly satisfactory environments.

Thermal and physiochemical characterization of bricks incorporating date palm fiber for use as insulation materials in buildings

This work presents a new compound to improve thermal comfort and decrease energy usage. The compound is composed of palm fiber, clay, and sand. The purpose of the paper is to assess the impact of combining sustainable and bio-sourced materials into bricks as heat-insulating materials, in addition to embedding the use of biocomposites in buildings. The composites were prepared by adding date palm fibers (size of 0.4 mm) with varying weight concentrations (from 0 wt% to 5 wt%). On the other hand, this biocomposite has been experimentally verified in terms of thermal and physicochemical characterization and energy economy. The TGA and DSC analyses revealed that including DPF impacted the matrix’s thermal properties. The results of FTIR and XRD indicate that fiber inclusion does not influence the chemical structure of the matrix and the non-emergence of new chemicals. This means chemical stability. SEM microscopy images also showed that palm fiber mergins do not affect the matrix. This is due to the excellent blend between palm fiber and clay, which increases the vacuum volume and porosity. Furthermore, the results showed a noticeable decrease in thermal conductivity as the palm fiber weight increased. As well as the energy economy. Hence, DPF has an excellent impact on the thermal and physicochemical properties of the biocomposite. Therefore, adding palm fiber to biocomposites enhances thermal insulation in construction.

A critique on thermal performance and energy usage in&amp;nbsp; government office buildings in Trincomalee and the need for&amp;nbsp; sustainable retrofitting - a typological analysis

Buildings use a large amount of energy during their lifetime and are identified as the main contributors to the increasing energy demand. A proper understanding of the Thermal Performance (TP) parameters can result in a climate-responsive design and reduce indoor overheating. In the construction field, sustainable retrofitting is identified as another important field of research, where new technologies can be introduced to the existing built environment and enhance their efficiency. This paper mainly focuses on how different building typologies of the existing public office buildings are contributing to inefficient TP and energy usage, and how sustainable retrofitting can help to improve their energy performances. 27 existing public office buildings in urban and suburban areas in Trincomalee, were selected for the typology analysis, and with special attention to plan form, one case study under spread-out plan form was selected. The TP of the building was investigated through an on-site Thermal Performance Investigation and Computational Simulation (CS) process. It is proposed that the energy required for cooling a building can be reduced if efficient sustainable retrofitting design strategies can be used to improve the TP. The outcome is beneficial in the formulation of design guidelines for new and existing buildings.

Effect of the Residential Photovoltaic Systems Evolution on Electricity and Thermal Energy Usage in Jordan

Effect of the Residential Photovoltaic Systems Evolution on Electricity and Thermal Energy Usage in Jordan

Constraining the Geochemical Fingerprints of Gases from the UK Carboniferous Coal Measures at the Glasgow Geoenergy Observatories Field Site, Scotland

Usage of thermal energy contained in abandoned, flooded, coal mines has the potential to contribute to low carbon heating or cooling supply and assist in meeting net-zero carbon emission targets. However, hazardous ground gases, such as CH4 and CO2, can be found naturally in superficial deposits, coal bearing strata and abandoned mines. Determining the presence, magnitude, and origin of subsurface gases, and how their geochemical fingerprints evolve within the shallow subsurface is vital to developing an understanding of how to manage the risk posed by ground gases in geoenergy technology development. Here, we present the first CH4 and CO2 concentration-depth profiles and stable isotope (δ13CCH4, δ13CCO2, and δDCH4) profiles obtained from UK mine workings, through analysis of headspace gas samples degassed from cores and chippings collected during construction of the Glasgow Observatory. These are used to investigate the variability of gas fingerprints with depth within unmined Carboniferous coal measures and Glasgow coal mine workings. Stable isotope compositions of CH4 (δ13CCH4 = −73.4‰ to −14.3‰; δ13CCO2 = −29‰ to −6.1‰; δDCH4 = −277‰ to −88‰) provide evidence of a biogenic source, with carbonate reduction being the primary pathway of CH4 production. Gas samples collected at depths of 63–79 m exhibit enrichments in 13CCH4 and 2H, indicating the oxidative consumption of CH4. This correlates with their proximity to the Glasgow Ell mine workings, which will have increased exposure to O2 from the atmosphere as a result of mining activities. CO2 gas is more abundant than CH4 throughout the succession in all three boreholes, exhibiting high δ13CCO2 values relative to the CH4 present. Gases from unmined bedrock exhibit the highest δ13CCO2 values, with samples from near-surface superficial deposits having the lowest δ13CCO2 values. δ13CCO2 values become progressively lower at shallower depths (above 90 m), which can be explained by the increasing influence of shallow groundwaters containing a mixture of dissolved marine carbonate minerals (∼0‰) and soil gas CO2 (−26‰) as depth decreases. Our findings provide an insight into the variability of mine derived gases within 200 m of the surface, providing an important ‘time-zero’ record of the site, which is required in the design of monitoring approaches.

Collective behavior of boreholes and its optimization to maximize BTES performance

Borehole layout strongly affects the behavior of borehole heat exchangers (BHEs) and changes the performance of a borehole thermal energy storage (BTES). This study investigates the existence and importance of the optimum collective behavior of BHEs to maximize the performance of BTES. Charge benefit ratio, storage efficiency and configurational benefit factor are proposed as performance indicators for better and finer performance evaluations of BTES systems. A small-scale BTES consisting of ten boreholes arranged on a concentric double-ring layout is considered as an application. Performance variations with the inner and the outer radii of the borehole field are analyzed for the first five years of operation. The temperature fields of different configurations show the transition from collective to individual behavior of boreholes, which leads to an optimal radial configuration maximizing the performance indicators. It is seen that the indicators strongly depend on both inner and outer radii and they reach their maximums for the same distinct radial configuration. The optimum arrangement can almost double the thermal performance indicators. It is thus of great importance to optimize collective behavior to maximize the usage of stored thermal energy. The results are qualitatively general and represent the common behavioral patterns of BTES systems.

Thermal Performance Assessment of Envelope Retrofits for Existing School Buildings in a Hot–Humid Climate: A Case Study in Chennai, India

This study aims to propose building envelope retrofit packages for existing naturally ventilated school buildings in the hot–humid climatic region of Chennai, India. Indoor thermal parameters were collected through field studies from nine sample classrooms of a selected school building in May 2019, between 9.00 am and 4.00 pm. The thermal performance assessment of the existing building was performed by examining the discomfort hours using the CBE thermal comfort tool. Envelope retrofit strategies gathered from the literature and building standards were applied and studied through simulation. The findings reveal the enormous potential to increase the thermal comfort of existing school buildings through envelope retrofit measures. The results demonstrate that the whole-building temperature can be reduced up to 3.2 °C in summer and up to 3.4 °C in winter. Implementing retrofit measures to the building envelopes of existing buildings will help school owners to increase the comfortable hours of whole buildings by up to 17%. In comparison, annual energy savings of up to 13% for the whole building can be made by enhancing the thermal performance of the building envelope. The findings will also help architects to optimise thermal performance and energy usage with minimal interventions.

Digital Twin of HVAC system (HVACDT) for multiobjective optimization of energy consumption and thermal comfort based on BIM framework with ANN-MOGA

ABSTRACT This study proposes a novel Digital Twin framework of heating, ventilation, and air conditioning (HVACDT) system to reduce energy consumption while increasing thermal comfort. The framework is developed to help the facility managers better understand the building operation to enhance the HVAC system function. The Digital Twin framework is based on Building Information Modelling (BIM) combined with a newly created plug-in to receive real-time sensor data as well as thermal comfort and optimization process through Matlab programming. In order to determine if the suggested framework is practical, data were collected from a Norwegian office building between August 2019 and October 2021 and used to test the framework. An artificial neural network (ANN) in a Simulink model and a multiobjective genetic algorithm (MOGA) are then used to improve the HVAC system. The HVAC system is comprised of air distributors, cooling units, heating units, pressure regulators, valves, air gates, and fans, among other components. In this context, several characteristics, such as temperatures, pressure, airflow, cooling and heating operation control, and other factors are considered as decision variables. In order to determine objective functions, the predicted percentage of dissatisfied (PPD) and the HVAC energy usage are both calculated. As a result, ANN's decision variables and objective function correlated well. Furthermore, MOGA presents different design factors that can be used to obtain the best possible solution in terms of thermal comfort and energy usage. The results show that the average cooling energy savings for four days in summer is roughly 13.2%, and 10.8% for the three summer months (June, July, and August), keeping the PPD under 10%. Finally, compared to traditional approaches, the HVACDT framework displays a higher level of automation in terms of data management.

The significance of exponential space-based heat generation and variable thermophysical properties on the dynamics of Casson fluid over a stratified surface with non-uniform thickness

Stratification is characterized as having applications in a variety of energy storage disciplines, including solar thermal energy usage systems. The effect of heat production, magnetic field, and varied fluid characteristics on the flow of Casson fluid across unstratified and stably stratified paraboloid of revolution is investigated in this work. The velocity index is suitable to describe the fluid flow on an upper horizontal surface of a paraboloid of revolution. It is imperative to mention that the upper horizontal surface of a paraboloid of revolution is likened to the pointed surface of an aircraft which is also described as a surface with variable thickness. The governing partial differential equations are transformed into the nonlinear ordinary differential equations using the similarity transformation. The dimensionless nonlinear ordinary differential equations are solved with the help of the Bvp4c numerical algorithm. The effects of relevant parameters are revealed on various profiles and discussed. It is observed that both the temperature and concentration distributions decrease with increase in thermal stratification and solutal stratification parameters when the velocity index parameter

Literature Review of Energy Management in Combined Heat and Power Systems Based on High-Temperature Proton Exchange Membrane Fuel Cells for Residential Comfort Applications

Combined heat and power technologies represent an efficient way to ensure energy efficiency, as they promote usage of both electrical and thermal energy, something not done by most traditional energy sources, especially in residential environments. In this context, high-temperature proton exchange membrane fuel cells allow the implementation of combined heat and power systems. Additionally, in this environment, fuel cells are more efficient and less polluting than their traditional counterparts. We present a literature review of energy management in residential systems based on this type of fuel cell. In addition, we classify and detail the current state of fuel cell technologies, paying special attention to their characteristics, mathematical modelling and control, as well as combined heat and power systems and energy management strategies.

Assessment of using solar system enhanced with MWCNT in PCM-enhanced building to decrease thermal energy usage in ejector cooling system

In arid climate zones, more than 70% of electricity is used for cooling purposes on hot days of the summer. On the other hand, in these areas, the intensity of radiation is so high that it can be called a stable source of energy for cooling. This study is focusing on the ejector cooling method. Two procedures are employed to reduce energy consumption. In the first procedure, Phase Change Material (PCM) is installed in the building to decline heat transfer of the building and environment. In the second technique, solar system is added to the ejector to reduce much of the energy required by the generator. Then, to make this energy source more effective, multi-walled carbon nanotube (MWCNT) nanoparticles are added to the solar system to improve the solar energy absorption process. Because of adding PCM, energy transfer of the building was dropped by 16.3% in hot in Apr–Sep. Due to installing a solar system and integrating it with ejector, energy usage drops by 94.5 kW h per square meter. In the second procedure, MWCNT at 0.01–0.1 vol% were loaded into collectors and boosted the solar absorption which consequently declined the generator required thermal energy by 18.8%.

Improving the performance of solar membrane distillation processes for treating high salinity feeds: A process control approach for cleaner production

The treatment of high salinity feeds, for example, brines from other desalination technologies such as reverse osmosis, is becoming one of the sought-after applications of solar membrane distillation processes. One of the most appropriate operating methodologies to carry out these treatments is a batch operation. Nevertheless, throughout this operation, the variability of the salinity in the feed water acts as a disturbance causing the optimal operating conditions required to reduce the process’ thermal energy consumption (expressed in kWh/m3 of freshwater production) to change. To face this issue, this study proposes two real-time optimization control approaches, with energy-saving achievements, based on the extremum-seeking control methodology. The first controller reduces the thermal energy consumption of the membrane distillation module by adapting the feed flow rate according to the level of salinity of the operation. The second one is based on the same idea but tries to search for a trade-off solution among energy consumption and water production. Both approaches are simulated under actual process circumstances using data and a validated model of a pilot plant located at Plataforma Solar de Almería (Spain). The results show how the proposed controllers improve the system’s daily operation concerning conventional operational procedures, reducing the system’s mean thermal energy consumption up to 35% (from 993.81 kWh/m3 to 651.52 kWh/m3) in the best case. On the whole, the systematic implementation of the proposed control strategies allows enhancing the sustainability and thermal efficiency of the operation by minimizing unnecessary thermal energy usage. This fact can play a role in solar membrane distillation systems either to lengthen operations or reduce reliance on conventional backup devices in periods with inconstant solar irradiance.

THE USE OF THERMAL ENERGY OF VENTILATION AND HEATING SYSTEMS IN LIVESTOCK PREMISES

In order to save energy resources when managing microclimate in livestock premises, installations and systems based on renewable energy sources are being developed, in particular, regenerative heat exchangers made using heat pipes. Among the well-known designs of heat exchangers using heat pipes, static designs of heat exchangers using heat pipes have become widespread, since they do not have moving parts, their warranty life is 15-20 years. They are easy to manufacture, have a higher thermal and energy efficiency than heat exchangers with intermediate operating fluid, can be used for both heating and cooling without changing their design. (Research purpose) The research purpose is analyzing the use of heat pipes (thermosiphons) in heat recovery plants of agricultural technological processes and developing a heat exchanger circuit using heat pipes with a thermoelectric heat pump. (Materials and methods) Patent search has been made using the websites of the Eurasian Patent Organization, the World Intellectual Property Organization, Rospatent and Google patents. (Results and discussion) The article presents the analysis of the use of heat pipes (thermosiphons) in heat recovery plants of technological processes of agricultural production. The article presents the developed functional and technological schemes of a heat exchanger using heat pipes for livestock premises. The use of a thermoelectric heat pump for additional heating of the supply air was justified in order to overcome freezing of the surface of the heat exchanger instead of using the electric heater. Smooth-walled gravitational heat pipes (thermosiphons) are the most promising in agriculture. (Conclusions) The process of heat utilization from the removed ventilation air is effectively carried out using a regenerative heat exchanger with heat pipes. The usage of thermal energy from the air removed from the room is possible using the proposed design of a heat exchanger on heat pipes with a thermoelectric heat pump.

An Outlook to Six- and Pseudo Six-component Reactions in Organic Synthesis with a Glance at Some Aspects of Green Chemistry

In this review, we focused on the six- and pseudo-six-component transformations in organic syntheses as a class of important and applicable MCRs. Although the MCRs usage in recent years is enhanced the reports for more than five-component MCRs are still rare. In some cases, these kinds of MCRs are the combination of some tandem named reactions that generated a union MCR. Preparation of multi-functionalized heterocycles, prevention of intermediate separation, reaction progressing in a one-pot continuous manner, elevated total yield, high atom economy, and preparation of potent bioactive multi-cycles hetero-organics via the construction of several new bonds are some highlighted features of MCRs. In this article, we classified the mentioned sixcomponent reactions based on reaction media. Another subdivision is applied based on thermal energy usage or ambient temperature. In fact, two aspects of the green chemistry rules have been discussed.

Cold thermal energy storage by encapsulated phase change materials system using hybrid nanofluids as the heat transfer fluid

The comprehensive study of the cascaded latent heat thermal energy storage (LHTES) systems and usage of phase change materials (PCM) are of great interest in the literature. Experimental and numerical measurements have been performed to analyze the performance of LHTES systems employing different PCMs. Overcharging is a known obstacle in the way of deploying a cascaded energy storage system that reduces the stored energy quality and amount. Furthermore, the complicated character of the phase transition of materials conjures up the importance of an accurate model. In the current study, the effects of overcharging a three-stage cascaded cold LHTES through a concentric dispersion model had been analyzed. Three nanoparticles, Al2O3, CuO, and Fe3O4, in the ethylene glycol and water (EG/W) mixture selected as the heat transfer fluid. Also, three eutectic and hydrated salt solutions were chosen as three PCM materials, encapsulated in spherical high density polyethylene shells, and arranged in three stages, namely, PCM-1, PCM-2, and PCM-3, storing high grade, medium grade, and low grade thermal energy, respectively. To overcome the overcharging issue of the system, two different scenarios were introduced. Results indicate that Al2O3, CuO, and Fe3O4 nanoparticles in the EG/W mixture reach their highest charging efficiency at 74.8%, 69.1%, and 75.1%, respectively. Results also revealed that to reach a shorter overcharging time utilizing Al2O3 and CuO nanoparticles, the optimized ratio of the PCM-2 to PCM-1 and PCM-3 to PCM-1 capacity were both 0.55. The optimized ratio of the PCM-2 to PCM-1 and PCM-3 to PCM-1 capacity utilizing Fe3O4 nanoparticles were 0.68 and 0.61, respectively. To maintain the highest charging thermal efficiency, the optimized ratio of the PCM-2 to PCM-1 and PCM-3 to PCM-1 heat capacity was 0.55 for all the three nanofluids.

Evaluation of Thermal Comfort and Energy Usage for an Enclosed Cavity Indifferent Climatic Zones of India

The utilization of energy in building sectors comprises 30–40% of the entire global energy consumption. Most of the energy is being utilized for cooling & heating the buildings. These cooling and heating depend on the nature of climate for different places. In this, the detailed analysis of the building envelope across five areas (viz. Srinagar, Jaisalmer, New Delhi, Thiruvananthapuram and Bangalore) representing different climatic zones had been carried out. Simulations are performed for these locations using eQUEST and ANSYS software. Three of the result output from the eQUEST simulation are used to assess the different cases. These outputs are: total electrical energy consumption of the year, peak cooling load & peak heating load for a particular time of the year. Temperature variations and airflow for a fan with moisture influence are also simulated for five different locations by using the radiation model and shear stress transport in ANSYS. The internal temperature distribution in accordance with an occupant is also compared and discussed for the five regions. Lastly, the predicted mean vote and predicted percentage of dissatisfaction are found to be in the range of −0.50 to −0.99 for all zones that signifies 13% to 30% of people are dissatisfied with the indoor environment.

The Cognition of the Architectural Styles Role on Thermal Performance in Houses of Semi-Arid Climates: Analysis of Building Envelope Materials

The envelope of buildings has an important role in controlling the energy consumption in buildings. The climatic changes and depletion of conventional sources make this fact important. This paper endeavors to estimate the thermal performance (steady-state) condition of a range of houses envelope with different architectural styles in Northern Iraq. The study examines the potential of the building envelope materials to control heat loss/gain through calculating U-Value (Heat transfer coefficient value). The capacity of the building's envelope materials to maintain indoor temperature is a goal to perform thermal comfort and decrease energy usage. The potential of buildings envelope materials for each architectural style in terms of their thermal performance has been identified and the results have been determined. Reconcile the new materials and technologies with old vernacular materials and techniques, would grant effective design potential. Finally, the recommendations to develop new envelopes have been suggested to reduce energy consumption in future houses.