Energy Storage Systems In Buildings Research Articles

A methodical approach for the design of thermal energy storage systems in buildings: An eight‐step methodology

AbstractRecent research focuses on optimal design of thermal energy storage (TES) systems for various plants and processes, using advanced optimization techniques. There is a wide range of TES technologies for diverse thermal applications, each with unique technical and economic characteristics. Matching an application with the most suitable TES system remains challenging. This study proposes an eight‐step design methodology guiding the process from describing the thermal process to defining the most appropriate TES based on constraints and requirements. The steps include specifying the thermal process, system design parameters, storage characteristics, integration parameters, key performance indicators, optimization method, tools, and design robustness. Seven already‐designed TES systems are evaluated to assess the methodology's effectiveness, where the design procedures have been adapted to the proposed steps. Case studies involve various applications with both sensible and latent TES systems, demonstrating the applicability of the proposed design procedure. A significant diversity exists among the design cases regarding the design objective, input, design, and output parameters. Nevertheless, the design procedure in each case can be deconstructed into the outlined design steps. The last design step has been excluded from all case studies due to insufficient information regarding the robustness of the design process. The paper demonstrates how a methodical approach can be applied to examine the TES design and the integration. The design steps proposed in this study can serve as a foundation for developing a more systematic approach for designing TES systems in future works, resulting in simplifying the design process.

Load decomposition: A conceptual framework for design and control of thermal energy storage systems in buildings

This work proposes a load decomposition framework for the characterization of thermal energy storage systems (TES) in buildings. This conceptual framework makes it possible to rapidly obtain an estimate of the required rating for the primary equipment and the storage device. The proposed approach employs mathematical methods from signal processing to break down the building load signal into two sub-signals: (a) a primary load provided by the primary production system, and (b) a balancing load provided by the storage system. This information is used to form a Pareto set of solutions that expresses the trade-off between the storage capacity and the primary system size, and hence, comprises the peak shaving potential of any given configuration. A simple decomposition method based on the concept of ”moving average” is tested within this framework on a representative energy model of an office building in the region of Montréal, Québec (QC). The Pareto set is shown to offer a wide range of design and operation solutions for peak shaving, from small water tanks to large underground reservoirs. The results provide clear evidence that TES system not only contributes to peak shaving and load shifting, but also to significantly reduce the primary production unit size.

Effect on the Thermal Properties of Building Mortars with Microencapsulated Phase Change Materials for Radiant Floors

The use of slag silicate cement mortar as a thermal mass layer for radiant floor heating systems holds significant potential for active thermal energy storage systems in buildings. The main objective of this article is to experimentally test the thermal performance of slag silicate cement mortar thermal storage blocks after the addition of phase change materials. The present study focuses on investigating the thermal performance of thermal storage blocks made of slag silicate cement mortar that incorporates a microencapsulated phase change material (mPCM). The mPCM consists of particles of paraffin-coated resin, which are uniformly distributed in the mortar. The analysis revealed that the introduction of mPCM particles into the mortar decreases the bulk density by approximately 9.4% for every 5% increase in mPCM particles ranging from 0% to 20%. The results obtained utilizing the Hot Disk characterization method demonstrate that the mPCM particles significantly affect the thermal properties of the mortar. Particularly, the thermal conductivity and thermal diffusion coefficient of the SSC30 mortar with a 17.31 wt.% mass of mPCM particles decreased by 59% and 69%, respectively. The results of this study provide a basis for the application of RFHS end-use thermal storage layers.

Thermophysical characterization of paraffin-based PCMs for low temperature thermal energy storage applications for buildings

Trustworthy information about the thermophysical properties of phase-change-materials (PCMs) is vital for designing low temperature thermal energy storage systems for buildings and for modelling their thermal behaviour. However, data provided by manufacturers are recurrently optimistic, insufficient and/or uncertain for developing reliable numerical approaches, which requires further investigation. This paper aims to assess the key thermophysical properties of ten paraffin-based PCMs: microencapsulated and bulk paraffins.The melting/solidification peak temperatures, the enthalpy of fusion/solidification and the specific heat capacity were measured by Modulated-Differential-Scanning-Calorimetry. The Transient-Plane-Source-method was used to estimate the variations of the thermal conductivity/diffusivity with temperature. The thermal stability was assessed by High-Resolution-Thermogravimetric-Analysis. The microstructures of the microencapsulated PCMs were examined via Scanning-Electron-Microscopy.It was concluded that some information provided in the datasheets is roughly corroborated by the experimental results. However, in some cases, it was too optimistic (particularly the enthalpy of fusion/solidification), incoherent (mainly the melting/solidification peak temperatures) or scarce (e.g., the values of the thermal conductivity and the specific heat of the solid/liquid phases). The major contribution of this work is a reliable dataset for upcoming numerical modelling, saving time and resources in future studies. The results can also be used as a reference for future inter-laboratorial comparison studies.

Electricity Consumption Optimization Using Thermal and Battery Energy Storage Systems in Buildings

Energy storage system (ESS) plays a key role in peak load shaving to minimize power consumption of buildings in peak hours. This paper proposes a novel energy management unit (EMU) to define an optimal operation schedule of ESSs by employing metaheuristic and mathematical optimization approaches. The proposed EMU uses a thermal energy storage system (TESS) and a battery energy storage system (BESS) to store the energy in off-peak periods and discharge it in high load demands. We formulate the charging/discharging schedule of TESS and BESS as an optimization problem. Then, particle swarm optimization (PSO) is employed to obtain the optimal schedule due to its computational time efficiency. The mathematical approach is also applied to prove the convexity of the problem and the uniqueness of the solution. Due to the different characteristics of the building loads, this paper divides the total load into shiftable and fixed loads. Moreover, to model the building components and loads, grey-box modeling is adopted. Results show that employing a combination of TESS and BESS achieves peak load shaving while reducing 42.2% of the required BESS capacity compared with the case where the BESS is only used. In addition, the results indicate the effectiveness and robustness of the proposed algorithm.

Electric tariffs and thermal energy storage systems for buildings

Thermal energy storage systems are systems that can be an alternative to the systems used especially in residential heating in our country. These systems are systems that reduce CO2 emissions, are efficient and can reduce consumption by shifting electricity demand to night. In this study, the ten-year price changes of the fuels used for heating in our country, the change in the real electricity consumption of a province over time, the electricity tariffs were examined and cost calculations were made in case of heating a space. It is seen that fuel prices have increased significantly in recent years, and thermal energy storage systems (TES) are 20-40% less costly than other systems until 2020, and 40-55% less costly than natural gas in 2021 and 2022.

Life-cycle economic analysis of thermal energy storage, new and second-life batteries in buildings for providing multiple flexibility services in electricity markets

More energy flexibility is required to alleviate the stress of power systems caused by intermittent and weather-dependent solar and wind power. The utilization of demand-side flexibility (e.g., flexibility management strategies and distributed storage technologies) can be considered a win-win approach for demand-side users and power grids. However, the economic benefits of distributed energy storage systems in buildings are usually underestimated without considering the full-scale flexibility utilization, which may impede storage investments. Meanwhile, the disposal problem of retired EV batteries is becoming more serious. Repurposing these batteries for stationary applications in buildings seems cost-effective and eco-friendly. Therefore, this study first proposes novel optimal dispatch strategies for different storage systems in buildings to maximize their benefits from providing multiple grid flexibility services simultaneously, and then conducts a comparative life-cycle economic analysis on thermal energy storage, new and second-life batteries. The optimal configuration of hybrid storage systems is also analyzed to facilitate the decision-making of building owners/operators. Test results show that thermal energy storage and electrical energy storage can increase the economic benefits by 13% and 2.6 times, respectively. Battery storage may no longer be an expensive option for building-scale investment due to downward trends in capacity costs and environmental impacts.

Uncertainty and simulation‐based cost analyses for energy storage systems used in green buildings

Energy storage systems (ESS) provide buildings with the ability to store electricity generated from renewable energy sources (eg, solar photovoltaics), increasing building operational flexibility and reliability. Previous studies on ESS in buildings often make assumptions about key input parameters (eg, installation factor, roundtrip efficiency, etc.) being fixed, overlooking potential performance risks due to uncertainty or variations in these parameters. The goal of this paper is to quantify the impact of uncertainty in technical and financial parameters on the economic performance of Li-ion batteries (LIB), proton-exchange membranes reversible fuel cells (PEM RFC), and reversible solid oxide cells (RSOC). The analysis is conducted on three medium-sized office buildings located in three different climate zones of the United States: 2B (Phoenix, AZ), 3B-Coast (Los Angeles, CA), and 4C (Seattle, WA). Two metrics are used to evaluate the economic viability of the selected technologies, namely the levelized cost of electricity (LCOE) and the levelized cost of energy storage (LCOS). While the results of the LCOE and LCOS differed in value between those cities, the cost breakdown for LCOS in all locations shows that capital cost is the biggest cost contributor, followed by electricity cost. A Monte-Carlo simulation was also conducted to assess the impact of uncertainty in input parameters on the LCOS model. The simulation results allowed us to generate probable ranges and probability tables for the LCOS.

Performance evaluation of a dynamic wall integrated with active insulation and thermal energy storage systems

Thermal energy storage systems in buildings can store cooling/heating energy during non-peak load hours or when renewable energy sources are available for later use when demanded. Using the building envelope as a thermal battery can help to shave the peak load, reduce the burden in electric grids, and enhance the occupant's thermal comfort. Sensible energy storage on wall systems such as thermally activated building systems can provide an active thermal storage strategy. However, most of the stored energy is used through passive means directed by the thermal lag, which can impede the on-demand release of the stored energy. Integrating active insulation systems with building thermal storage systems can increase the flexibility of charging and discharging time and duration. In this study, a wall system equipped with an active insulation system and thermally activated storage system was designed, and its performance on active cooling energy contribution was studied. The performances of energy storage (charging), release (discharging) of the thermal energy storage energy, and the active insulation system were studied separately and together as an integrated system. Results showed that the thermal properties of the thermal energy storage core material and the pipe spacing of both embedded pipes in the thermal energy storage and hydronic pipes used in the active insulation system affected the wall performance the most out of all the tested wall system parameters. During discharging, the heat flux into the wall was as high as 81.92 W/m2. The active insulation system's dynamic R-value varied between less than 1ft2•°F•h/BTU (0.18 m2•K/W) to 98% of the equally thick foam insulation's R-value.

Life Cycle Assessment (LCA) of an Innovative Compact Hybrid Electrical-Thermal Storage System for Residential Buildings in Mediterranean Climate

The buildings sector is one of the least sustainable activities in the world, accounting for around 40% of the total global energy demand. With the aim to reduce the environmental impact of this sector, the use of renewable energy sources coupled with energy storage systems in buildings has been investigated in recent years. Innovative solutions for cooling, heating, and domestic hot water in buildings can contribute to the buildings’ decarbonization by achieving a reduction of building electrical consumption needed to keep comfortable conditions. However, the environmental impact of a new system is not only related to its electrical consumption from the grid, but also to the environmental load produced in the manufacturing and disposal stages of system components. This study investigates the environmental impact of an innovative system proposed for residential buildings in Mediterranean climate through a life cycle assessment. The results show that, due to the complexity of the system, the manufacturing and disposal stages have a high environmental impact, which is not compensated by the reduction of the impact during the operational stage. A parametric study was also performed to investigate the effect of the design of the storage system on the overall system impact.

Function and practice of photovoltaic building energy storage system with low-voltage DC power supply

Function and practice of photovoltaic building energy storage system with low-voltage DC power supply

Enhancing building energy performance by effectively using phase change material and dynamic insulation in walls

Deploying phase change materials (PCMs) in building envelopes can be effective in reducing space heating/cooling loads and providing load shedding and shifting capacity. However, the full potential of PCM-integrated envelopes can only be harnessed if the PCM undergoes phase change using free ambient heating/cooling, and the stored energy is effectively transferred between the exterior and the interior environments. Traditional thermal insulation (with a fixed thermal resistance) limits PCM utilization, which restrains the energy saving potential of a PCM-integrated envelope to a small percentage. Proposed dynamic insulation material and system (DIMS) provides the option of varying its thermal resistance based on the indoor and outdoor conditions. Although it has been established that employing PCM as well as DIMS in building envelopes separately improves buildings’ energy performance, no prior studies that analyzed the combined influence of both technologies were identified. In this study, we examine a novel wall design, comprising a layer of PCM between two layers of DIMS. We note that the PCM-DIMS-integrated wall provides significantly higher energy saving potential than the DIMS-only integrated wall or the PCM-only integrated wall in all the climates and wall orientations analyzed in this study. Depending on the climate, the PCM-DIMS-integrated wall could provide 15–72% reduction in annual heat gain and 7–38% reduction in annual heat loss. The analysis presented in this study supports the need to develop scalable dynamic insulations combined with thermal energy storage systems for buildings.

Validation of different numerical models with benchmark experiments for modelling microencapsulated-PCM-based applications for buildings

This paper assesses the thermal performance of four microencapsulated-PCM-based samples that can be used in the design of new thermal energy storage systems for buildings: a PCM-enhanced plasterboard; three different fin-enhanced aluminium containers filled with the PCM. The methodology covers: the thermophysical characterization of the PCM-based products; the development of charging and discharging experiments to provide data for numerical validation purposes; the numerical modelling considering five different methods dispersed in literature, and a new-improved method. The main goals are to validate the numerical predictions against reliable experimental results and to find out which method is preferable for future simulations. The 3D numerical simulations were based on the effective heat capacity (EHC), additional heat source (AHS) and enthalpy (H-P) approaches. The first two methods were implemented in ANSYS CFX®; the other in ANSYS FLUENT®. For the EHC method, four different ways to specify the variation of the effective specific heat with temperature were assessed. While the H-P commercial code already implemented in ANSYS FLUENT® was used, the other two methods implemented in ANSYS CFX® were developed and validated for the purpose of this study.Good agreement between numerical and experimental results was achieved for all numerical approaches. In fact, it was concluded that the six numerical methods can be used to simulate heat diffusion with solid-liquid phase-changes. However, it was verified that the EHC method with the triangular or the self-adjusted triangular profiles is preferable for both charging and discharging simulations, since it can be drawn based on few information about the PCM-based products; it ensures good predictions of both charging/discharging kinetics and stored/released energy; it can be used without compromising computation time in comparison to other methods. The EHC method with the rectangular profile, recurrently used in literature, exhibits some convergence issues whose resolution has required longer computation times.

Life cycle assessment of integrated thermal energy storage systems in buildings: A case study in Canada

In this study, a cradle-to-grave life cycle assessment (LCA) of integrated borehole type thermal energy storage (TES) systems in buildings is performed, and the Drake Landing Solar Community (DLSC) in Okotoks, Alberta, Canada is selected for a case study. The results are presented comparatively with a conventional Canadian house. The DLSC is considered a successfully developed community energy system integrated with the solar and TES systems. Consequently, the DLSC meets more than 90% of the space heating needs of each home from solar energy and resulting in less reliance on fossil fuels. The present study, therefore, investigates the environmental impact of the Drake Landing houses. The results of this study are illustrated in 10 different impact categories namely; acidification potential, global warming potential, eutrophication potential, abiotic depletion potential, ozone layer depletion potential, human toxicity potential, freshwater aquatic ecotoxicity potential, terrestrial ecotoxicity potential, ionising radiation, and photochemical oxidation potential. The present analyses show that a Drake Landing house is found to have much lower environmental impacts than a conventional Canadian house in all studied impact categories. While a conventional Canadian house (145.4 m2) produces 6.34 tonnes of CO2 emissions per year, a Drake Landing house produces only 1.91 tonnes of CO2 emissions per year, which is a reduction of nearly 4.5 tonnes of greenhouse gas (GHG) emissions per home per year.

Form-stable phase change material based on fatty acid/wood flour composite and PVC used for thermal energy storage

This work focused on a novel form-stable phase change material (FSPCM) for building energy saving. Capric acid (CA) and palmitic acid (PA) were selected to prepare binary eutectic. The CA-PA/wood flour (WF) composites with different mass ratios were prepared by the vacuum impregnation method. After the shape-stabilized properties were investigated, the results indicated that there were the good encapsulate capacity of WF to CA-PA eutectic and the slight effect of WF on the crystallization. Phase change wood plastic composites (WPCs) using CA-PA /WF composites as the latent heat storage medium and PVC as the matrix were prepared. The relations between mass ratios of CA-PA /WF composites and mechanical properties of WPCs were discussed. The results revealed that the WPCs with appropriate mass fraction of CA-PA eutectic had desired mechanical properties for practical applications. The prepared composites were examined by the scanning electron microscope (SEM), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG) and accelerated thermal cycling test. SEM images showed that the WPC prepared by the CA-PA /WF composite with the mass ratio of 0.4:1(WPC0.4) was more compact and uniform, but as the amount of CA-PA eutectic increased, more gaps and cracks appeared. DSC results showed that the WPC0.8 melted at 22.03 °C with a latent heat of 28.16 J/g and froze at 20.06 °C with a latent heat of 29.77 J/g, which was more applicable to the thermal energy storage systems for buildings. FTIR results demonstrated that there was no chemical reaction between CA-PA eutectic and components in WPC. The prepared FSPCM exhibited excellent thermal stability for the building materials from the TG analysis. Furthermore, the results of accelerated thermal cycling test showed that the composite had a good thermal reliability after 500 thermal cycles.

Optimization of Hybrid Energy Storage Systems at the Building Level with Combined Heat and Power Generation

The average daily benefit to cost ratio of a building energy storage system is mainly constrained by the battery lifetime. This paper aims to minimize the average daily cost of a hybrid energy storage system (HESS) (comprised of a battery and supercapacitor) by optimizing the battery capacity. A novel optimization model is proposed with the objective to find the minimum average daily investment cost of the HESS. The objective function has two parts: (1) the investment cost formula for the battery is derived as a function of the battery capacity, which has an interdependence with the minimum state of charge (SOC) and the maximum discharge current; (2) the investment cost formula for the supercapacitor is also established as a function of battery capacity by matching the maximum battery power with that of the supercapacitor. Case studies demonstrate several ways to increase the average daily benefit to cost ratio: (1) adopting a suitable control strategy to avoid capacity saturation; (2) reducing the battery SOC to increase the threshold for the maximum discharge current (MDC) saturation; and (3) increasing MDC to raise the threshold for the SOC saturation. Results show that the average daily benefit to cost ratio is doubled compared to previous work.

Development and thermal characterization of an innovative gypsum-based composite incorporating phase change material as building energy storage system

This study aims at developing a new integrated component in a passive solar wall to achieve high thermal energy storage potential in building materials. This component was manufactured by conditioning the paraffin inside 24 copper tubes, which were regularly inserted and aligned in a gypsum matrix.Firstly, an investigation by means of a differential scanning calorimeter (DSC) was carried out to obtain the latent heat and the transition temperature of the selected phase change material (paraffin). Secondly, an additional study was conducted to gauge the improvement of energy storage performance in classical construction material (gypsum) when incorporating paraffin by the method of transient guarded hot plates.The results of this experiment revealed a clear improvement in different thermal properties when integrating paraffin in the composite. Besides, the results showed that the composite-PCM prevents the leakage of the molten paraffin during phase transition and proved a good thermal stability.

Thermodynamic analyses and assessments of various thermal energy storage systems for buildings

In this study, energetic, exergetic, environmental and sustainability analyses and their assessments are carried out for latent, thermochemical and sensible thermal energy storage (TES) systems for phase change material (PCM) supported building applications under varying environment (surrounding) temperatures. The present system consists of a floor heating system, System-I, System-II and System-III. The floor heating system stays at the building floor supported with a floor heating unit and pump. The System-I includes a latent TES system and a fan. The latent TES system is comprised of a PCM supported building envelope, in which from outside to inside; glass, transparent insulation material, PCM, air channel and insulation material are placed, respectively. Furthermore, System-II mainly has a solar-thermochemical TES while there are an aquifer TES and a heat pump in System-III. Among the TESs, the hot and cold wells of the aquifer TES have maximum exergetic efficiency values of 88.782% and 69.607% at 8°C dead state temperature, respectively. According to the energy efficiency aspects of TESs, the discharging processes of the latent TES and the hot well of the aquifer TES possess the minimum and maximum values of 5.782% and 94.118% at 8°C dead state temperature, respectively. Also, the fan used with the latent TES is the most environmentally-benign system component among the devices. Furthermore, the most sustainable TES is found for the aquifer TES while the worst sustainable system is the latent TES.

Parameters to take into account when developing a new thermochemical energy storage system

Thermal energy storage by chemical reactions is one of the most suitable energy storage systems for buildings and industrial applications due to the wide range of working temperatures as well as the high energy storage density provided. Developing and characterizing chemical reactions is now one of the most promising areas of research. Chemical heat pumps are one of the systems used when chemical reactions are utilized as thermochemical energy storage technology. Nevertheless, the main problem to implement this technology is found in the material behaviour within the reactors used. Therefore, material and reaction characterization have been identified as key issues to design a proper system. The main goal of this paper is to highlight the parameters to take into account previous to the design.