Building Thermal Storage Research Articles

A novel building thermal energy storage PCM: lauric acid-palmitic acid- tetradecyl alcohol/vitrified beads

A novel building thermal energy storage PCM: lauric acid-palmitic acid- tetradecyl alcohol/vitrified beads

Energy- efficient cementitious mortar containing clay based shape-stable phase change material: Development, characterization and temperature controlling performance

The need for buildings to ensure a comfortable thermal environment is increasing, leading to a surge in energy consumption. This study proposes an innovative approach to tackle thermal energy storage challenges in buildings by formulating a unique cementitious mortar containing a shape-stable composite of Saudi Arabian natural clay and methyl stearate phase change material (PCM). The inclusion of natural clay, chosen for its cost-effectiveness and eco-friendliness, addresses the issue of methyl stearate leakage—a common concern with PCM usage. Despite PCM incorporation, the mixture maintains desirable fluidity and consistency, albeit with a slightly reduced dry unit weight and compressive strength. Differential scanning calorimetry analysis defines key characteristics of the resulting shape-stable NC/MS composite PCM, including a melting point of 33.81°C and a latent heat storage capacity of 56.15 J/g. Empirical testing demonstrates the efficacy of the natural clay/PCM composite in temperature moderation. During periods of elevated external temperatures, the NC/PCM specimen effectively lowers room-center temperatures by up to 4°C and sustains a cooler environment compared to the control room for almost 8 hours. Additionally, the composite PCM limits the maximum increase in room center temperature post-sunset to only 2.49°C, showcasing its capability in stabilizing indoor temperatures. This innovative PCM composite responds dynamically to ambient temperature variations, transitioning between solid and liquid states to release stored latent heat, consequently reducing building heating and cooling loads, enhancing energy efficiency. The natural clay/PCM composite presents a promising solution for advancing building thermal energy storage systems, aligning with energy efficiency and sustainable design objectives.

Multi-objective sizing and dispatch for building thermal and battery storage towards economic and environmental synergy

The role of building thermal and battery storage is pivotal in advancing smart cities and achieving sustainability goals through effective energy management. Despite their significance, there are several limitations in the sizing approach and value stream analysis with various objectives for their widespread adoption in buildings. This work proposes a flexible and scalable multi-objective optimization framework for optimal sizing and dispatch of building thermal and battery storage, addressing multiple objectives simultaneously using mixed-integer linear programming. The weighted-sum method is adapted, combining multiple objectives into a single function. The two-stage procedure iterates over different weights, generates optimal solutions, and forms the Pareto front. Case studies are performed to assess the energy, economic, and environmental benefits of building energy storage systems for a large office building in three climate locations. The results demonstrate that the proposed framework efficiently determines optimal sizing and dispatch strategies, addressing the balance between economic viability and emission reduction. The dynamic relationship between time-of-use energy charges and emission factors leads to diverse strategies based on whether economic or environmental concerns are prioritized. This research enhances our understanding of the benefits of thermal and battery storage systems in buildings, providing valuable guidance to stakeholders.

Experimental investigation of heat transfer rate for building roof with corrugated sheets using phase change material (PCM)

Research on cost-effective and efficient technology that can hold enormous amounts of heat or cold in a specific volume has been ongoing for a while. Due to its isothermal behaviour throughout the phase change process and high energy storage density, latent heat storage in phase change materials (PCM) is highly appealing. The incorporation of latent heat of storage in building materials considerably aids in the energy conservation of structures, which is a major role of thermal storage. By reducing the frequency of internal air temperature swings and keeping the indoor air temperature closer to the ideal temperature for longer periods of time, increasing the building's thermal storage capacity can improve human comfort. Nonetheless, a phase change material can be chosen to accommodate every type of weather in a certain area.

Potential for Electricity Reduction in Demand Response Using Building Thermal Storage

Demand response (DR) contributes to filling the gap between electricity supply and demand by controlling energy resources on the consumer side and promoting the installation and use of renewable energy. This study is performed to identify the potential of building thermal storage for power reduction in DR. In addition, the optimal conditions are identified, in particular the on/off status of air-conditioning and changes in room temperature setpoints. A simulation model for an office building equipped with packaged air-conditioners is developed, and dynamic programming is applied to calculate the on/off and load ratios to minimize the cumulative electricity during the DR period. Based on the results, two types of operations are suggested: one is to maintain the temperature at the upper allowable limit (in cooling) during the DR period, and the other is to repeatedly turn the air-conditioner on and off. In addition, the following factors affect power reduction: the allowable room temperature range, the time between the request for reduction and the start of the DR period, and the partial load characteristics of the air-conditioning equipment.

A real time peer-to-peer energy trading for prosumers utilizing time-varying building virtual energy storage

With the increasing penetration of distributed energy resources (DER) in the electric power system, Peer-to-Peer (P2P) energy trading has become a promising paradigm for future electric power systems. Building thermal load, which is an important demand side resource, should be considered carefully in the design of a P2P trading method. In this paper, we investigate the application of building thermal energy storage capability in P2P energy trading. We aggregate and model building thermal loads as a virtual energy storage and derive a time-varying virtual energy storage system (T-VESS) model to quantify the flexibility of a building. Key parameters of T-VESS, including charging/discharging rate, energy capacity, and state of charge (SOC), are analyzed so that T-VESS can be embedded in the building prosumer model to participate effectively in electricity-oriented P2P energy trading. We propose a real time P2P energy trading method of prosumers based on model predictive control (MPC). This method consists of an energy supply and demand quantification stage and a transaction price optimization stage, which can effectively capture the time-varying nature of T-VESS. To preserve the trading preference for prosumers, we propose a distributed P2P energy trading actions implementation method based on the continuous double auction (CDA) considering multiple trading preference grades. Numerical results demonstrate that the proposed P2P energy trading method considering T-VESS can reduce the operational cost of prosumers by 3.7%, while also promoting the local integration of renewable energy by 3.1%. Furthermore, compared to existing P2P trading methods considering single preference grade, the proposed method greatly enhances the utilities of both individual prosumers and the overall community.

Corn straw supported high-performance phase change composites: Strategy to turn agricultural residues into high efficient and stable thermal energy storage materials

Using polypyrrole (PPy)-coated agricultural corn straw (CS) as support frameworks, polyethylene glycol (PEG) as phase change components, a shape-stable phase change thermal storage composite (CS@PPy-PEGx) was obtained by simple crosslinking, melt-blending, and freeze-drying processes. With the help of potential non-covalent interactions among each component (e.g., hydrogen bonding), the encapsulation of PEG in these composites reached as high as 90 wt%, and displayed-enhanced thermal conductivities (a maximum of ∼0.22 W/(m·K)), thermal reliabilities and stabilities (with no obvious shape deformation after 100 heating and cooling cycles), promising thermal storage capacities (with max latent melting heat of ∼145.80 J/g and crystallization heat of ∼141.50 J/g), as well as conducive leakage resistance. Thus, this study paved a green and feasible strategy to convert agricultural straw residues into shape-stable and high-performance phase change composites that demonstrated great potential in the field of building thermal energy storage.

Tradeoffs in optimization of Active Insulation Systems and HVAC: A case study in residential buildings

Active insulation systems (AIS) have been conceptualized to make buildings more responsive to changing environmental conditions, creating energy efficiency and flexibility gains. Building flexibility and efficiency can be further improved if the building is also equipped with optimized HVAC system controls. Optimal control of AIS and HVAC systems can be used to activate thermal mass, and past work has quantified the potential benefits of jointly optimizing both systems. In this work, we more fully elucidate and evaluate the potential tradeoffs between optimal control of these technologies with respect to building energy use and peak demand–including different configurations of heat pump systems and integrated building thermal energy storage. Tradeoffs are revealed by applying a multi-objective optimal control framework and comparing the Pareto optimal sets across various system configurations. Discussion of the results provides insights into how buildings can be best designed and controlled to achieve both energy efficiency and flexibility.

Analyzing Harmony and Discord Among Optimal Building Controllers Responding to Energy, Cost, and Carbon Reduction Objectives

AbstractOptimization and control of building thermal energy storage holds great potential for unlocking demand-side flexibility, an asset that is being given much attention in current grid reforms responding to the climate crisis. As greater information regarding grid operations is becoming available, grid-interactive building controls inherently have become a multi-objective problem. Typical multi-objective optimization frameworks often introduce greater complexity and computational burden and are less favorable for achieving widespread adoption. With the overall goal of easing deployment of advanced building controls and aiding the building-to-grid integration, this work aims to evaluate the trade-offs and degrees of sub-optimality introduced by implementing single-objective controllers only. We formulate and apply a detailed single-objective, model predictive control (MPC) framework to individually optimize building thermal storage assets of two types of commercial buildings, informed by future grid scenarios, around energy, economic, environmental, and peak demand objectives. For each day, we compare the building’s performance in every category as if it had been controlled by four separate single-objective model predictive controllers. By comparing the individual controllers for each day, we reveal the level of harmony or discord that exists between these simple single-objective problems. In essence, we quantify the potential loss that would occur in three of the objectives if the optimal control problem were to optimally respond to only one of the grid signals. Results show that on most days, the carbon and energy controllers retained most of the savings in energy, cost, and carbon. Trade-offs were observed between the peak demand controller and the other objectives, and during extreme energy pricing events. These observations are further discussed in terms of their implications for the design of grid-interactive building incentive signals and utility tariffs.

Integrated energy system operation considering building thermal inertia and hydrogen storage systems

(1) An IES operation optimization system considering building thermal inertia and hydrogen energy storage systems is formed. (2) A hybrid particle swarm optimization-cuckoo search based on the beetle antennae search strategy (BPSO-CS) is proposed.

Worst CVaR based energy management for generalized energy storage enabled building-integrated energy systems

Generalized energy storage (GES) can reduce the renewable energy curtailment, carbon emission and operational cost risk in the building-integrated energy system (BIES) energy management when faced with uncertainties of multi-energy loads and PV. In this context, GES integrated with the differentiated building thermal load-based virtual energy storage (VES) is proposed in the energy management model of BIES. Specifically, the differentiated building thermal load VES is introduced by differentiated personal factors (e.g., metabolic rate and clothing insulation) based on the predicted mean vote. Furthermore, a worst conditional value at risk (WCVaR) energy management method is developed to evaluate the operational cost risk of BIES. Meanwhile, possible probability distribution uncertainties of PV, electric and thermal loads are all fully considered by a boxlike uncertainty set. Then, the proposed WCVaR model is transformed into a linearized model by the Lagrange duality theory. Finally, the whole energy management model is solved by the CPLEX solver. Case studies and comparative analysis are performed based on a representative BIES. Numerical results show that the proposed model can reduce 33.55% of operational cost, 74.25% of carbon trading cost, and 16.96% of PV curtailment cost for BIES compared with that without GES. In addition, the conditional value at risk (CVaR) with the proposed WCVaR method ($5700.22) is between that with the traditional CVaR method considering multiple operational scenarios ($5684.68) and that with the traditional CVaR method only including the worst operational scenario ($6043.48), which indicates that the proposed WCVaR method can avoid overly-high and overly-low operational cost risks.

Development of a new composite material for building energy storage based on lauric acid-palmitic acid-paraffin ternary eutectic and expanded perlite

Building thermal energy storage is critical to global sustainability as building energy consumption rises. In this study, a lauric-palmitic acid-paraffin ternary eutectic (LPP) was prepared from lauric acid, palmitic acid, and paraffin, and this LPP eutectic was adsorbed into expanded perlite (EP) via vacuum adsorption method to form a composite phase change material (LPP/EP). Leakage tests show that the maximum loading rate of EP on LPP is 75 %. Then, the chemical structure, crystal structure, crystalline morphology, micromorphology, and thermal property of LPP/EP were evaluated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Polarizing Optical Microscope (POM), scanning electronic microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TG). The results show that LPP/EP has superior crystal and chemical compatibility, LPP/EP melts at 31.78 °C and absorbs 117.34 J/g of latent heat, and LPP/EP has good thermal stability. Meanwhile, LPP/EP exhibits better thermal storage performance than EP. In addition, the 1000 melting-solidifying cycling experiment indicates that the LPP/EP has excellent durability. Therefore, the LPP/EP composite phase change materials will have an amazing performance in the field of building thermal energy storage.

Glass fiber reinforced gypsum composites with microencapsulated PCM as novel building thermal energy storage material

A comprehensive study involving the fabrication and characterization of gypsum plasterboards combined with microencapsulated phase change material (mPCM) is introduced to evaluate their benefits regarding thermoregulation management and energy saving performance in buildings. For this purpose, the produced new type of gypsum plasterboard was subjected to the detailed chemical, morphological, mechanical, physical and thermal tests. The gypsum plasterboard incorporated with mPCM (7.5 wt%) and reinforced by glass fiber has latent heat capacities as high as 16.7 and 16.6 J/g at onset melting and solidification temperature of 11.90 °C and 12.09 °C, respectively. TGA analyzes revealed high thermal stability of gypsum plasterboard up to about 140 °C. Outcomes exhibited that mPCM-gypsum plasterboard can substantially diminish cooling load of a building during the daytime even at the high room temperature and offer decline in heat necessity of a house during night-time. During peak room temperature hours, the mPCM-gypsum plasterboard achieved 3 °C lower temperatures than the reference room, and it provided a cooler room temperature for about 7 h during the daytime while a warmer temperature of 0.3 °C was achieved at the cold weather. As a result, the produced gypsum-based composites can be considered as an energy-saving and indoor temperature regulating material in buildings.

Uncertainty-aware optimal dispatch of building thermal storage portfolios via smoothed variance-reduced accelerated gradient methods

The rapid penetration of uncertain renewable energy resources into the power grid has made generation planning and real-time power balancing a challenge, prompting the need for advanced control on the demand-side. Although a grid-integrated building portfolio has been studied by coordinating building-level flexible energy resources, to reap further benefits, the need to develop a scalable supervisory control framework with computational efficiency is paramount. In this work, we introduce an uncertainty-aware transactive control framework for a large-scale building portfolio with thermal energy storage (TES) using a decomposition-based approach. We propose a day-ahead decision making framework for the power procurement problem, which is cast as a two-stage stochastic optimization problem. To solve this problem, we propose a smoothed variance-reduced accelerated gradient method. Notably this framework allows for parallelization in computing the sampled gradient. Preliminary numerics demonstrate the scalability and computational efficiency of the proposed algorithm to apply to the control framework with respect to the existing algorithm. Substantial energy cost savings were observed for the stochastic control framework over all the validation scenarios. This study provides further insights into the supervisory controller development for building portfolio-based grid services that can help advance electrification goals through coordination of energy storage assets.

Investigation of the effect of the envelope on building thermal storage performance under model predictive control by dynamic pricing

Dynamic pricing is designed for the load shaping to help match the amount of the energy demand to the energy supply capacity. Since the buildings’ characteristics influence the performance of the energy shifting, renovation of the building towards a higher energy flexibility is worth investigating. This study evaluated the effect of the envelope on building thermal storage performance. A model predictive control (MPC) was developed to achieve a multi-objective control i.e., indoor comfort temperature and minimise the total energy cost. MPC automatically triggered the energy storage during the low price periods and used the stored energy during the high price periods. The results confirmed the ability of MPC on peak demand reduction up to 45% electricity cost. Besides, the results also demonstrated the ability of heavyweight thermal mass in terms of reducing energy consumption and shifting a greater high price energy to the low price times. Therefore, adding insulation layers into the lightweight thermal mass is highly recommended, especially for the places experiencing the significant mismatch between the demand and supply during daily peaks or the areas scheduling a large amount of intermittent renewable energy source in the energy production.

Sludge-incinerated ash based shape-stable phase change composites for heavy metal fixation and building thermal energy storage

Incineration is a harmless way to treat municipal sludge. However, it is difficult to fix heavy metals in the sludge-incinerated ash (SIA). To fix the heavy metals and recycle the SIA effectively, this work innovatively proposed the SIA as skeleton material, and five shape-stable phase change composites (SSPCCs) with different mass ratios of SIA to NaNO3 (phase change material, PCM) were fabricated via the cold-compression & hot-sintering (CCHS) method. Then, key thermal performance, mechanical strength, and micromorphology were investigated while the chemical compatibility between the SIA components and NaNO3 was analyzed. Results showed that the SSPCCs could fix the heavy metals properly, and the SIA was suitable for skeleton material; The SSPCC with the mass ratio 5:5 of SIA to NaNO3 reached a maximal thermal energy storage (TES) density of 409.25 kJ/kg in the range of 100–400 °C, which had high mechanical strength of 139.65 MPa and good thermal stability; The SIA components demonstrated excellent chemical compatibility with NaNO3.

Thermal storage performance of eutectic sugar alcohols applied to buildings and enhancement of crystallization

Sugar alcohols are suitable for compact and high-density building thermal energy storage systems because of the high enthalpy, low price, and non-toxicity. But most sugar alcohol materials have severe supercooling characteristic, which limits their application as phase change materials (PCMs) in thermal energy storage systems. In this study, xylitol, sorbitol, erythritol, mannitol and dulcitol were selected as PCMs. Based on the five single sugar alcohols, ten multicomponent eutectic sugar alcohols were obtained which melting temperatures is between 60 °C and 90 °C applied to buildings. The thermal parameters of sugar alcohols were tested by differential scanning calorimetry (DSC), the supercooled eutectic sugar alcohols were stimulated by means of mechanical agitation to accelerate crystallization. The crystallization after excitation was monitored by microscope, and the supercooled crystallization phenomenon of eutectic sugar alcohols was investigated by isothermal phase change tests. The results showed that only three eutectic sugar alcohols could crystallize by stirring, and the melting temperatures of three eutectic sugar alcohols are about 80 °C. After multiple repetitive experiments, three eutectic sugar alcohols still have good crystallization characteristics. The results of the research provide a reference value in practical aspects for the design and selection of phase change materials in buildings.

Feasibility analysis and feature comparison of cold thermal energy storage for off-grid PV air-conditioned buildings in the tropics

Cold thermal energy storage (CTES) is a cost-efficient storage approach for PV powered air-conditioning systems in tropical buildings. However, the feasibility and performance of different CTESs, including chilled water storage, ice storage, PCM cooling storage, and building thermal storage, are still unclear for off-grid PV air-conditioned buildings.In this study, an off-grid PV system with battery and CTES is proposed, including the operation strategy to manage the energy-storage process. To implement all CTES-types, a co-simulation model, which integrates the system model with the ARX (autoregressive with exogenous input) cooling-load model, is constructed to enable the interaction between supply- and demand-side. Based on the minimization of net present cost and the constraint of a certain required solar fraction, an optimization method is developed to find the optimal system-configuration. Moreover, an office, a hotel, and a residence are selected for a case study.The results indicate that CTES is feasible for higher solar fraction. The feasibility ranking of building type is (from high to low): residence, hotel, and office. In the most suitable case (residence), the maximum reduction of system costs (compared to battery-only system) is 49.76%, 41.77%, 44.31%, and 22.78%, respectively, for chilled-water storage, ice storage, PCM cooling storage, and building thermal storage. These values are 22.48%, 12.00%, 17.42%, 2.60% for the hotel, and 19.26%, 11.57%, 13.64%, 4.06% for the office. In addition, the sensitivity analysis shows that the increasing cost of both PV-array and CTES-device affects the feasibility of CTES negatively, while the increasing battery cost is a positive factor. Compared to the cost of the PV-array and the CTES-device, the battery cost represents the most significant effect-factor for feasibility.

Load shifting potential assessment of building thermal storage performance for building design

As major energy consumers, buildings have great potential to alleviate the imbalance between renewable energy generation and consumer demand. A building thermal mass is a free energy storage object, and can provide a load shifting capacity. In this study, a parameter denoted the ‘effective thermal capacitance’ was proposed to characterise the building thermal mass, and a reduced-order RC model was established to predict the building cooling and heating loads. By using the particle swarm optimisation algorithm to identify the effective thermal capacitance values, the linear relationships between the effective thermal capacitance and building areas were summarised. The results show that, with an increase in the effective thermal capacitance, the hourly load and energy losses caused by load shifting strategies decrease. According to comparison results from applying the preheating and precooling strategies in four climatic zones of China, it is found that although the total load throughout the day is increased, the peak electricity consumption can be shifted without noticeable changes in the daily electric bill. During office hours, the preheating strategy reduces the heating load by approximately 12% in the severe cold and cold zones, whereas precooling reduced the cooling load by 20%–45% in all four climatic zones.

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.