Energy Simulation Program Research Articles

Monte Carlo Workflow Unification for Nuclear Reactor Analysis with Metamodel-Driven Modeling

Monte Carlo (MC) transport codes are a cornerstone of nuclear reactor analysis frameworks, providing reference solutions and multigroup cross sections, and even as core components in multiphysics couplings. These applications can be seen in toolkits from the Nuclear Energy Advanced Modeling and Simulation program and the U.S. Nuclear Regulatory Commission’s BlueCRAB (Comprehensive Reactor Analysis Bundle). Contrary to their ubiquitousness in reactor physics modeling and simulation, popular MC codes, such as MCNP, Serpent, and KENO, are still reliant on antiquated textual input formats. These input languages use a plethora of keywords with terse syntax to specify all facets of a model, including its geometry, materials, physics settings, and tally options. This poses a steep learning curve and a poor user experience. Being tied to unique text-based input formats also significantly complicates programmatic input generation or modification that may be desired and/or required within a multiphysics framework. This work demonstrates how the development of programmatic interfaces for MC codes can support model unification and translation activities. Building on the Python application program interface (API) development of MCNPy, similar capabilities are being implemented for Serpent that are able to support model translation. In future work, the Serpent API capabilities will be made more robust and the work will be further expanded to include translations with KENO.

High-Fidelity Multiphysics Modeling of a Heat Pipe Microreactor Using BlueCrab

Researchers who are actively developing nuclear microreactors are planning to employ innovative designs and features using traditional commercial modeling tools that may be inadequate for their design and licensing activities. The codes developed under the U.S. Department of Energy Office of Nuclear Energy Advanced Modeling and Simulation (NEAMS) program provide flexibility in terms of geometry modeling and multiphysics coupling and are particularly well suited for modeling novel microreactor concepts. To test the maturity of these codes, this paper introduces a conceptual heat pipe microreactor (HP-MR) designed to gather various technologies of interest to microreactor developers such as control drums, heat pipes, and hydride moderators. The objective of this effort is to demonstrate NEAMS tools capability to perform high-fidelity multiphysics simulations, using coupled neutronics (via the Griffin code), heat conduction (via the BISON code), heat pipe modeling (via the Sockeye code), and hydrogen redistribution in hydride metal moderator (via the SWIFT code). Codes are coupled in-memory through the Multiphysics Object-Oriented Simulation Environment (MOOSE) framework, which permits flexible multiphysics data transfer schemes. The analysis confirmed two key aspects of the HP-MR concept: (1) its ability to follow the power load requested from the heat pipe and (2) its ability to avoid heat pipe cascading failure unless designed with high power close to operating failure limits of its heat pipes. The developed computational model was distributed publicly on the Virtual Test Bed for training purposes to accelerate adoption by industry and to provide a high-fidelity multiphysics solution for benchmarking against other tools. Additional multiphysics analyses including other transients and coupled physics were identified as necessary future work, together with a focus on validating multiphysics behavior against experiments.

Modeling a solar shading system that controls heat gain by using solar energy to change louver slat angles

In this study, we propose a model for a passive louver system that adjusts slat angles using solar heat energy. The model is structured in two stages: predicting the surface temperature of a solar collector plate and using this temperature to determine the slat angles. The system was installed and monitored in a building in Okinawa, Japan, to validate the model’s accuracy with field measurements. The validation showed that while the model accurately predicted the daily opening and closing times of the louvers, it faced limitations in minute-by-minute variations, making it less suitable for scenarios requiring instantaneous state evaluations, such as lighting environment assessments. Additionally, predicting the temperature for the double-skin façade was challenging and could affect overall model accuracy. Despite these issues, the model effectively achieved its primary goal of predicting annual energy consumption by accurately forecasting the daily opening and closing times of the louvers. The model’s fast computation speed and simplicity make it particularly suitable for annual energy simulations and easy to integrate with existing energy simulation programs. Further research is needed to enhance minute-by-minute reproducibility and integrate temperature predictions for double-skin façades, ensuring a comprehensive evaluation of both thermal and lighting environments.

A study on the impact of using a subchannel resolution for modeling of large break loss of coolant accidents

The nuclear industry is investigating the feasibility of transitioning from 18- to 24-month fuel cycles because of the positive impact it would have on the operational costs for the current fleet of light-water reactors. A challenge to making this change is the increased risk of fuel fragmentation, relocation, and dispersal (FFRD) due to the known potential for ceramic fuel to pulverize into fine particles at the higher discharge burnups. Previous work has been performed by the Nuclear Energy Advanced Modeling and Simulation program to assess FFRD risk in high-burnup cores using the BISON fuel performance code and a coarse mesh thermal hydraulics (T/H) solution for a loss-of-coolant accident (LOCA) using the TRACE system T/H code. Because of the importance of the T/H solution for FFRD assessment, this study seeks to investigate the impact of using higher-fidelity subchannel techniques for modeling of the LOCA transient. CTF was used to model a subregion of a high-burnup core that was depleted by the Virtual Environment for Reactor Applications (VERA) multiphysics core simulator. Both coarse-mesh and pin-resolved models were created in CTF, and a consistent coarse-mesh TRACE model was also developed to allow for benchmarking the code results. A large-break loss-of-coolant accident (LBLOCA) reflood transient was simulated using these three models, and results were compared. Results showed some consistent differences between the CTF and TRACE coarse models, including a higher peak cladding temperature (PCT) prediction in CTF and later quenching in CTF; however, the transient clad temperature behavior was similar, and these differences are likely due to post-critical heat flux heat transfer modeling differences and minimum film boiling temperature model differences. The pin-resolved results indicate that the PCT in the lumped model is often under-predicted by as much as 70 °C and that PCT occurs at a different location than the high-power pin in the assembly. The lumped model predicts a difference of 10 °C or less between the average and hot pins in the assembly, whereas the pin-resolved model predicts a range of over 100 °C. These results indicate that higher-fidelity T/H results may have an impact on predicted core behavior during LOCA, which may be important to consider when assessing FFRD risk.

Toward a high-fidelity tritium transport modeling for retention and permeation experiments

Tritium Migration Analysis Program version 8 (TMAP8), the latest version of TMAP, was developed within the framework of the Multiphysics Object-Oriented Simulation Environment (MOOSE). Created at Idaho National Laboratory (INL), MOOSE is an open-source, dimension-agnostic, fully coupled, and fully implicit multiphysics platform featuring massively parallel computation capabilities. Using TMAP8, tritium transport in a divertor monoblock was analyzed to elucidate the effects of pulsed operation (up to fifty 1,600 s plasma discharge and cool-down cycles) on the tritium in-vessel inventory source term and ex-vessel release term (i.e., tritium retention and permeation) for safety analysis. With its built-in Message Passing Interface capability, TMAP8 can, in under 2 h, simulate tritium transport in three different layered materials (i.e., tungsten, copper, and copper-chromium-zirconium alloy) in 2D geometry, using a single device/computer with 10 cores. The MOOSE-based TMAP8 code can leverage other MOOSE tools developed under the Nuclear Energy Advanced Modeling and Simulation program to perform tritium and thermal transport in complex geometries and multiphysics environments. And via its massively parallel computation, MOOSE will enable the fusion pilot plant designers to conduct high-fidelity multiphysics modeling for the design of the divertor and blanket systems as well as for the safety analysis.

Incidence of circular refurbishment measures on indoor air quality and comfort conditions in two real buildings: Experimental and numerical analysis

The application of Circular Economy to construction sector is a key to attain carbon neutrality, since it is responsible of 40 % of natural resource consumption. In this frame the importance of an efficient building refurbishment process throughout recycled material and renewable energy is fundamental. From an overview about building refurbishment emerges the need to investigate aspects related to Indoor Environmental Quality and the comparison between in-field measurements with output of dynamic simulation models. The present study aims to fill these two gaps by means an energy renovation of two real buildings in Greece. The work develops within the European project “Drive 0″, born to promote deep environmentally friendly retrofitting by means of circular renovation concepts. The methodological approach involves on-site monitoring of a series of parameters describing the energy, microclimate environmental and air quality, before and after the energy requalification. In addition, a numerical model developed in Building Energy Simulation program is calibrated and a Computational Fluid Dynamics is developed. From the in-field measurements emerges that, on one hand, the refurbishment of heating system shows a great improvement of indoor thermal conditions, with Total Volatile Organic Compounds concentration that sometimes exceed 3.0 mg/m3; on the other hand an integrated thermal insulation reduces infiltrations and changes the envelope behaviour, with a global energy saving of 30 % during winter and autumn periods.Another result of the study shows that a numerical model developed in Building Energy Simulation program and calibrated on energy consumption can greatly fit the local thermal comfort distribution of the occupant zone and predict the indoor air quality, if it outputs are used as input data in a Computational Fluid Dynamics study. These results can be beneficial to decision makers and designers for evaluating emitters positioning, opening design and mechanical ventilation strategies, aimed at reducing energy costs.

Assessing energy saving potential of wavelength-dependent passive daytime radiative cooler implemented with EnergyPlus by a roof model

The Passive Daytime Radiative Cooler (PDRC) exhibits potential in enhancing building energy conservation due to its high emissivity in wavelength between 8 μm and 13 μm. However, current building energy simulation programs, e.g., EnergyPlus, generally adopt a constant emissivity. To implement the wavelength-dependent PDRC model into EnergyPlus, a roof model was introduced to couple it with EnergyPlus to assess the energy saving potential of PDRC more reasonably. To assess the PDRC roofs, the impact of buildings constructed in different eras, building heights, and climatic conditions in China on building energy saving was investigated. The results showed that more energy was saved in regions with high cooling demands e.g., Shanghai and Guangzhou. Applying PDRC on roofs of buildings constructed pre 2001 in severe cold regions increased building energy consumptions. Furthermore, buildings with well insulated roofs coated by PDRC were not equally beneficial for reducing cooling demands in summer compared to buildings with non-insulated roofs, but heating demands in winter could be reduced. With an increase in building height, the energy saving potential of PDRC roofs was reduced. Therefore, a comprehensive analysis was imperative considering the local climates as well as the building itself when PDRC is to be applied.

Nearly zero energy building design and optimization: A residential building transformation in Türkiye

In this study, the energy performance analysis of a representative residential building located in Izmir, Turkey, was carried out, utilizing the DesignBuilder energy simulation program. Heating, ventilation, and air conditioning systems are modeled as detailed in Design Builder in order to consider parameters such as thermal properties of materials, duct layout and airflow dynamics of the system in detail in the analysis. The technical and economic analysis of transforming the building into a nearly zero energy building (NZEB) was performed for eight different retrofit scenarios, including passive and active energy efficiency measures. The most effective scenario, Scenario 8 (S8), reduced the building's annual net primary energy consumption by 96.08% to 7.45 kWh/m²/year. S8's annual CO2 emissions decreased by 100.07% compared with the reference scenario, resulting in −0.042 kg CO2/m²/year. The overall energy performance class of the building was determined using Turkey's national calculation program for the preparation of the energy identity certificate. The energy performance class of the reference building was determined as D, and the class of the building designed according to S8 as A. Investment evaluations were carried out for the retrofit scenarios, revealing that the investment cost for S8, having the lowest net primary energy consumption, amounted to USD 17,565.87. This finding establishes S8 as a more financially viable option in the short term. This study demonstrates the potential of NZEBs in reducing greenhouse gas emissions and achieving sustainable development goals.

Natural ventilation in high-rise office building – Comfort and energy performance

AbstractThe application of natural ventilation strategies in high-rise office buildings is considered one of the most promising trends to address high energy performance and enhance the indoor thermal comfort levels in interior office spaces. In this regard, this study attempts to assess the potential of natural ventilation strategies of a specific, previously investigated, envelope design of a high-rise office building located in a temperate climate zone. Different summer natural ventilation approaches were tested using the building energy simulation program IDA ICE 4.8, evaluating thermal comfort and energy demand. The findings indicated that considerable energy savings can be achieved, compared to conventional mechanical ventilation and air conditioning systems.

Container farms: Energy modeling considering crop growth and energy-saving potential in different climates

Container farms (CFs), integrating plant factories into mobile prefabricated buildings, are emerging as a novel decentralized food production system to fortify sustainable urban development. However, the high energy demand needs to be optimized to promote wider CF application. This study investigates the energy efficiency of CFs in various climates, covering eight ASHRAE climate zones. The CF energy model was developed in the building energy simulation program EnergyPlus, fed with plant (lettuce) growth data measured from a real case. Four energy-saving methods were evaluated, with how different climates impact their potential. The results show that, in colder climates, the CF energy demand is lower and energy-saving methods are more effective. Air-side economizers reduce CF cooling demand by 3.5–58.3% from the hottest to coldest regions. Shifting lighting schedules into nocturnal lighting, as a cost-free method, reduces HVAC energy demand by up to 19.4% and can further reinforce the effectiveness of air-side economizers. The optimal envelope U-values should be among 0.5–3 W/m2-K, without being either poorly or overly insulated. Improving lighting efficacy can save over 20% total energy demand by reducing intense lighting power. We conclude that locating CFs in colder climates presents greater potential in energy conservation along with benefits for improving urban sustainability. The results can support decision-making for cleaner CF design and operation, and the methodology could be replicated to other indoor food production systems.

Façade typology development in high-rise office building envelope

AbstractThe design of the envelope in high-rise office buildings is a task of great importance as it can impact the entire building's energy performance. The study presented in this paper is an extension of a previous work reporting on the optimization of the façade and the shading systems of an east-west facing high-rise office building. This study aims to investigate the façade geometry design factors for other potential orientations, e.g., south, south-east, and south-west directions. The IDA ICE 4.8 complex dynamic building energy simulation program was used to assess thermal and lighting simulations. The optimization results revealed the best-performing façade configurations, appropriate for each orientation examined in terms of thermal comfort, visual comfort, and energy consumption.

Design and implementation of a bioclimatic housing prototype for the Bolivian highlands

The Mechanical - Electromechanical Engineering research institute, made up of a multidisciplinary team, designs and implements a bioclimatic housing prototype for the Bolivian highlands, located near the Andes Mountains at an altitude of 3,000 to 4,000 meters above sea level. This project was developed and implemented with financing from the Swiss Cooperation for Bolivia, within the Climate Change Adaptation projects.
 The design process includes: the sociocultural study of the inhabitants of the region, where direct information is collected from the peasants on the conception of housing in their culture and ancestral construction characteristics of their houses. Subsequently, the climate of the region (temperatures, solar radiation, winds and relative humidity) is characterized with the help of a meteorological station, which provided historical records of 5 years. Those data were sufficient to be able to carry out a reliable characterization, with which the Typical Meteorological Year is determined. Likewise, local construction materials that may be useful in the design are studied, analyzing their thermal and mechanical properties in the laboratory.
 Finally, with all the information described, an architectural design is carried out taking into account bioclimatic aspects, ways of harnessing solar energy, distribution of the room and a viable construction cost for the economic reality of the region. The developed architectural model is optimized in an energy simulation program (Siter Vs. 1.2), achieving energy savings of 65%. The software used is owned property of the research institute
 The house has been monitored with temperature sensors for about a year and six months, to date it shows good results, where the correct functioning of the elements and constructive forms is evidenced, reflecting a temperature inside the house of around 10 °C above room temperature 24 hours a day.

Potential and Benefit of Green Roof Energy Renovation of Existing Residential Buildings with a Flat Roof in Belgrade

Green roofs are considered to be one of the optimal tools for saving energy and protecting the environment in developed countries. In this paper, an analysis of the possible application of green roofs on existing residential buildings with flat roofs is presented. In the economic analysis, models of existing buildings in Belgrade, with two different types of green roofs, are studied. A key indicator of investment profitability in this investigation is the net present value (NPV) of the green roof project. Besides the private economic impact, other aspects of green roof applications, significant for sustainable development, have been highlighted. The values of the reductions in the annual energy needed for heating and cooling are compared for different scenarios. A maximum energy saving of 22% in the heating season is determined in the building energy simulation program for the model with an intensive green roof. Life cycle profit analysis was based on the probabilistic approach. The corresponding variance-based sensitivity analysis determined the impact of various parameters on the final result. In all models, the first order sensitivity index, which measures the impact of the number of residential units on the NPV, ranges from 12.2% to 63.6%. Sensitivity analysis showed that the benefit of property value increase has the highest influence on the calculated NPV in scenarios that account for this benefit. The obtained results in those scenarios indicate that the most probable NPV at the end of the life cycle is EUR 43/m2 and EUR 82/m2 for extensive and intensive green roofs, respectively.

Güneş enerjisi destekli ısıtma sistemlerinde güneş kolektörü ve sıcak su deposu kapasitesi seçimi için parametrik analiz

In this study, a study was carried out on integrating solar assisted systems into heating systems in a building. For the study, an existing building was modeled with the DesignBuilder building energy simulation program. The scenarios were created on the model to determine the number of solar collectors and the capacity of the water tank used in solar assisted heating systems. The primary energy consumption, global costs and payback periods of the scenarios created were obtained by parametric analysis. According to the results obtained, the solution that reduces primary energy consumption the most is SYS20, the solution that reduces the global cost the most is SYS1 and the optimum solution is SYS7. Considering the payback periods, SYS1 was determined as the most appropriate solution to be applied in the study since it was the solution with the minimum payback period. At the end of the study, it was seen that primary energy savings could be reduced by up to 47% with solar energy assisted heating system. Thanks to the study, a reference source for the number of solar collectors and water tank capacity selection in Isparta and provinces with similar climates has been created.

Experimental and numerical investigations on the heat transfer characteristics of a real-sized radiant cooled wall system supported by machine learning

Despite the extensive utilization of radiant air conditioning units in rooms, challenging points of design associated with the calculation of cooling load are still present. Except for the radiant wall cooling studies aimed at conducting heat transfer-focused analyses carried out by the authors of this investigation, neither experimental nor computational studies exist in the related literature. The current experimental and computational study aims to address the deficiencies in the radiant-cooled wall problem. Differing from other conditioned rooms, the heat is exposed through the back surface of the analyzed wall, whose heat flux range lies between 1.60 and 10.84 W/m2. The total, radiative, and convective heat transfer coefficients of 7.78, 5.13, and 2.52 W/m2.K are acquired as values for use in building energy simulation programs. Seven different artificial neural network models are designed to estimate the total, radiative, and convective heat transfer coefficients and heat transfer rates. Dependency analyses are also performed using various inputs in the investigated numerical models. The margin of deviation values computed for six different output factors are found below −1.80%, the mean square error values are less than 1.51E-04, the R values are greater than 0.98, and the data points do not surpass the 10% deviation line. Artificial neural networks have been found to outperform well-known correlations in estimating experimental results. Extensive measured experimental data are presented for the sake of other researchers numerical modelling and validation issues. Building energy simulation software designers and engineers in the field of thermal comfort are thought to benefit from these findings.

Residential Building Energy Conservation in Mediterranean Climate Zone by Integrating Passive Solar and Energy Efficiency Design Strategies

Residential buildings have a list of functions, and one of the top priories is the thermal comfort of its occupants. Thermal comfort can be one of the measurements of successful building performance, and it can be addressed in various ways to provide a good quality indoor climate. The way to address the need for thermal comfort determines the consumption and conservation of energy. Adapting passive strategies and thermal mass to a building can reduce energy consumption significantly. Applying these strategies to a building does not need additional investment from the initial capital, and renovating a building to implement the strategy will cut the energy usage of a building and save the additional financing of new technology for heating and cooling, ventilation, and so on. In this study, two residential buildings located in North Cyprus with the same geographical location, climate zone, and different construction materials were studied. The study aimed to make a technical test to reduce energy consumption and improve energy conservation in the building by applying passive solar and energy efficiency design strategies (PSEEDS). The thermal mass has been used and discussed as an improbable energy technique alongside other insulation materials and shading devices. The article discusses and compares the energy consumption and thermal comfort of traditional Mediterranean houses with contemporary houses. The study uses 2D drawings, 3D modeling, and energy simulation programs to evaluate energy consumption in both real and assumed scenarios. The study finds that traditional Mediterranean homes, with their thick walls and built-in shading mechanisms, require less energy for heating and cooling than contemporary houses. The implementation of passive solar energy efficient design strategies (PSEEDS) significantly reduces energy consumption in both types of houses, but traditional Mediterranean houses still show more efficiency due to their higher thermal mass. The research demonstrates that improving windows, examining the orientation of the structure, altering shade devices, and decreasing infiltration rates can reduce overall energy consumption by up to 34.71% To sum up, in this study, PSEEDS, the performance of thermal mass, and pre-design measures significantly decrease energy consumption. In addition, implementing passive strategies during a renovation of a building also compensates for the investment and lifecycle cost of new technologies and energy usage.

Origins of whole-building energy simulations for high-performance commercial buildings: Contributions of NATEOUS, SHEP, TACS, CP-26, and RESPTK programs

Previous studies have traced the earliest origins of today’s whole-building energy simulation programs, such as EnergyPlus, eQUEST, DOE-2.1E, TRNSYS, TRACE, and HAP, to two public simulation programs in the early 1970’s, including: the Post Office program and the NBSLD program. However, in the 1960’s, there were earlier public simulation programs that had a significant influence on developments of the Post Office and NBSLD programs and are therefore related to many of the today’s whole-building energy simulation programs but were not discussed in previous studies, including: the NATEOUS program, the SHEP program, and the TACS program. In addition, there were public supplementary calculation programs that also contributed to developments of the Post Office and NBSLD programs, including: the CP-26 program and the RESPTK program. Therefore, the purpose of this study is to further clarify the earliest origins of today’s whole-building energy simulation programs based on the analysis of these early computer programs. This study extends the previous research (Oh and Haberl 2016) that discussed the origins of today’s whole-building energy simulation programs for high-performance commercial buildings and the thermal analysis methods used in these programs.

MOOSE Reactor Module: An Open-Source Capability for Meshing Nuclear Reactor Geometries

The U.S. Department of Energy (DOE) Nuclear Energy Advanced Modeling and Simulation (NEAMS) program has developed numerous physics solvers utilizing the open-source Multiphysics Object-Oriented Simulation Environment (MOOSE) framework for multiphysics reactor analysis. These solvers require input finite element meshes representing the discretized spatial domain. Typically, reactor analysts turn to licensed tools for the creation of reactor geometry meshes. Recently, open-source functionality has been added to the MOOSE framework to mesh common reactor geometries and improve MOOSE-based nuclear reactor application user workflows. The new functionality is primarily contained in the new Reactor module of MOOSE and includes support for hexagonal pins, assemblies, and cores, extended Cartesian geometry support, options for modeling static and rotating control drums within a hexagonal assembly, core periphery triangulation, and automatic tagging of pin, assembly, plane, and depletion regions for easier post processing of physics results. A set of reactor geometry mesh builder objects further streamlines the construction of hexagonal and Cartesian cores and allows mapping of materials to regions during mesh generation. The meshes produced with the MOOSE Reactor module may be used directly within MOOSE-based applications or exported as Exodus II files for use in other finite element solvers. The tools have been demonstrated and verified using a variety of NEAMS physics solvers on a range of reactor applications, including a sodium-cooled fast reactor core analysis using Griffin, a fast reactor assembly thermal deformation analysis using MOOSE Tensor Mechanics, and a heat pipe–cooled microreactor coupled analysis using Griffin, Bison, and Sockeye. MOOSE’s Reactor module provides significant advantages compared to the use of external meshing tools when analyzing Cartesian and hexagonal reactor lattices using MOOSE-based applications: immediate accessibility (open-source) to the end user, low barrier to entry for new users, speed of mesh generation, volume preservation of meshed fuel pins, and simplification of analysis workflow when used in conjunction with MOOSE-based applications.

The Virtual Test Bed (VTB) Repository: A Library of Reference Reactor Models Using NEAMS Tools

With the next generation of nuclear reactors under development, modeling and simulation tools are being developed by the U.S. Department of Energy to support their design, licensing, and future operation. Mirroring the physical test beds currently under construction (i.e., Demonstration and Operation of Microreactor Experiments, known as DOME, and Laboratory for Operating and Testing in the United States, known as LOTUS), the Virtual Test Bed was launched by the National Reactor Innovation Center in collaboration with the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program to support the advanced reactor community. This collaborative effort, which involves multiple teams at both Idaho National Laboratory and Argonne National Laboratory, aims to use state-of-the-art simulation tools to model a wide range of reactor designs. These models are automatically tested to ensure their continued functionality as the tools are further developed. Examples are extensively documented, each acting as a tutorial for applying the relevant NEAMS tools to that reactor design. Currently, five advanced reactor types (with a total of 12 specific design subvariants) are simulated by a variety of models. These models range from steady-state, core multiphysics simulations to integrated plant analysis during loss-of-flow transients. To our knowledge, this is the first publicly available library of multiphysics advanced reactor models distributed with extensive documentation and maintained through continuous integration.

Reducing energy consumption of heat pumps by introducing a thermal energy storage system

We proposed a short-term thermal energy storage system by applying Phase Change Materials (PCMs) in air ducts connected to an indoor air conditioning unit within a ceiling space. PCM tubes were arranged in a staggered layout in the air duct and cooled by chilled air from the air conditioning unit during “charging” mode, whereas the PCM tubes released cold energy to the room space without operation of the compressor during “discharging” mode. The charging mode allowed for an increase in the partial load ratio of the heat pump to prevent low-efficiency operation at <20% load, which can increase seasonal energy efficiency. We constructed an energy simulation program, where the heat exchange coefficient between the PCM tubes and air was varied with airflow rate and the temperature difference between the PCM and air, in accordance with results from CFD analysis. Switching between the charging and discharging modes was based on the outlet temperature (Tout) and 30% of the rated capacity of the indoor unit (Lr). The heat balance between the charging and discharging modes was improved by this change to the system control. A higher load factor and higher COP resulted in a 7.6% reduction in energy consumption.