Energy Storage In Buildings Research Articles

Experimental investigation of latent thermal energy storage in high-rise residential buildings in Toronto

Recent architectural trends in high-rise apartments are characterized by highly transparent facades. Higher window to wall ratios (WWR) entail larger thermal exchanges, and consequently longer thermal discomfort periods and increased energy consumptions for space conditioning. This study investigates the potential of passive latent heat storage using Phase Change Materials (PCM) as a retrofit measure in high-rise apartments in Toronto. A novel composite PCM system comprised of two commercial PCM products with different melting temperatures of 21.7 °C and 25 °C is proposed. This system is experimentally investigated using small scale test cells exposed to the weather of Toronto from July to October 2016. Five different tests were conducted while different variables were monitored to assess the indoor temperature and heat storage patterns. Results indicate significant extreme temperature reduction and daily temperature fluctuations reduced by 6 °C using the PCM system investigated in this paper. Moreover, incorporating two melting points in one zone proves to be very effective both in summer and fall months.

Design and simulation of gas turbine-based CCHP combined with solar and compressed air energy storage in a hotel building

The popular operation mode of following thermal load often causes power surplus and efficiency decrease in CCHP (combined cooling, heating and power) systems at part load. CAES (compressed air energy storage) is thus one of the appropriate technologies to improve CCHP part-load efficiency through peak load shifting. However，the output power of CAES is possibly not high due to low temperature of the compressed air entering air turbine. In view of these problems, this paper proposed a gas turbine based CCHP combined with solar thermal energy and compressed air energy storage (S-CAES). The off-design models of gas turbine based CCHP and S-CAES were built. The merits and flaws of two different control strategies of S-CAES were analyzed. The characteristics of the proposed system indicate that the energy efficiency and exergy efficiency are both higher than those of the CCHP system without S-CAES. The performances of S-CAES are mainly influenced by the designed parameters, load distribution of demand side and the capacity of gas turbine. A case study of the proposed CCHP with S-CAES system in an 180000m2 hotel building located in South China shows that the optimal power capacity of S-CAES comes to 435kW; and energy efficiency increment gains 1.015% in comparison with a corresponding optimized CCHP system without S-CAES.

Screening alternatives for producing paraffinic phase change materials for thermal energy storage in buildings

Summary Screening alternatives for producing paraffinic phase change materials (PCMs) from natural gas-based products was investigated. Based on the quality and cost of these PCMs, two sources were identified: (i) hydrogenated gas-to-liquid (GTL) products such as heavy detergent feedstocks; and (ii) linear alpha olefins. Fractionation of a typical hydrogenated GTL mixture, containing C14 – C18 alkene and alkane hydrocarbons, has been experimentally conducted to produce five paraffinic PCMs with melting points between 3 and 28 °C. ChemCAD simulation has been proved to be a valid tool for predicting the behaviour of the GTL fractionation, including optimum experimental conditions and compositions of products. Also, hydrogenation of technical 1-octadecene was experimentally carried out in order to evaluate the quality of PCM produced from one of the available technical alpha-olefins. All PCMs produced in this work were analysed by gas chromatography equipped with flame ionization detector to determine their compositions and by differential scanning calorimetry to determine their latent heats. The results showed that the PCM with a melting temperature in the range 22 to 25 °C can be technically produced through hydrogenation of commercial 1-octadecene showing a higher latent heat compared to the PCM produced from fractionation of hydrogenated GTL mixture. Copyright © 2017 John Wiley & Sons, Ltd.

Heat Transfer Performance Enhancement of Paraffin/Expanded Perlite Phase Change Composites with Graphene Nano-platelets

The efficiency of latent heat thermal energy storage systems is often limited by the low thermal conductivity of phase change materials (PCMs), which limits the heat transfer rate and energy storage efficiency. Therefore, this study investigates the performance enhancement of form-stable PCMs with the addition of exfoliated graphene nano-platelets (xGnP) as a heat transfer promoter. Experimental research was carried out on fabrication, characterization and testing the properties of paraffin/EP/xGnP composite PCMs. It was shown that the xGnP particles formed an interconnecting network inside the open pores of EP, which remarkably improved the thermal properties and thermal energy storage/retrieval properties of composite PCMs. For instance, in comparison with paraffin/EP composites, addition of 1% of xGnP increased the thermal conductivity by up to 49%. Thermal energy storage/release test also revealed that the paraffin/EP/xGnP composites reduced the heat storage/ release duration by up to 33%, compared to paraffin/EP composite PCM. The enhancement of thermal properties and thermal energy storage rate of paraffin/EP/xGnP composites is a promising way to achieve high energy storage efficiency in numerous latent heat thermal energy storage applications such as solar energy storage and energy conversation in buildings.

Bi-level Optimization Method of Air-conditioning System Based on Office Building Energy Storage Characteristics

The air-conditioning system of office building is a large power consumption terminal equipment, whose unreasonable operation mode leads to low energy efficiency. Realizing the optimization of the air-conditioning system has become one of the important research contents of the electric power demand response. In this paper, in order to save electricity cost and improve energy efficiency, bi-level optimization method of air-conditioning system based on TOU price is put forward by using the energy storage characteristics of the office building itself. In the upper level, the operation mode of the air-conditioning system is optimized in order to minimize the uses’ electricity cost in the premise of ensuring user’ comfort according to the information of outdoor temperature and TOU price, and the cooling load of the air-conditioning is output to the lower level; In the lower level, the distribution mode of cooling load among the multi chillers is optimized in order to maximize the energy efficiency according to the characteristics of each chiller. Finally, the experimental results under different modes demonstrate that the strategy can improve the energy efficiency of chillers and save the electricity cost for users.

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.

Novel thermosetting phase change materials with polycarbonatediol based curing agent as supporting skeleton for thermal energy storage

PEG based thermosetting phase change materials (PCMs) have been frequently employed for thermal energy storage in building and other fields due to the low cost, no toxic, no corrosive, good thermal properties and no leakage in phase change process. In this article, thermosetting PCMs with polyethylene glycol (PEG) as phase change functional chain and polyaryl polymethylene isocyanate terminated polycarbonatediol (PCD) as curing agent were prepared through a facile and solvent-free bulk polyaddition. This preparation strategy can provide novel mean to design and synthesize PEG based thermosetting PCMs with different structure and performances according to the specific requirement. Moreover, the introduction of PCD will further improve the performance of PCMs. The chemical structure, crystalline properties, phase change properties, thermal reliability and stability of prepared PCMs were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), polarizing optical microscopy (POM), differential scanning calorimetry (DSC), accelerated thermal cycling testing and thermogravimetric analysis (TGA), respectively. FTIR spectra showed that the PEG based thermosetting PCMs were successfully synthesized. XRD and POM results indicated the similar spherulite structure of virgin PEG and prepared PCMs, and the crystallinity and crystal size of PCMs are affected by the introduction of curing agent. Meanwhile, DSC measurements showed that prepared PCMs have good phase change properties. Accelerated thermal cycling and TGA testing proved the excellent thermal reliability and thermal stability of prepared PCMs.

Photovoltaic self-sufficiency of Belgian households using lithium-ion batteries, and its impact on the grid

Countries are pushing for the use of local, renewable energy sources in order to reduce the dependence on fossil fuels for energy supply. One of the main problems with several renewable energy sources is their variability, which can be solved with energy storage. With buildings representing an important share of energy consumption, and given the growing capacity of distributed generation, distributed energy storage in buildings is expected to become increasingly present. In this context, the optimal dimensioning of home installations of photovoltaics and lithium-ion batteries, and the impact of such installations on the grid, is of the utmost importance. While there have been developments on this field, some important handicaps remain, notably the independent treatment of installation optimisation and grid impact and the substantial result differences between studies. In this paper, photovoltaics and lithium-ion storage installations are optimised through the use of real, high-resolution data from several individual households, based on realistic cost figures, and through well-defined metrics that correctly grasp the problem at hand. The impact on the grid as well as possible mitigation measures are also analysed. Results show that up to about 30% of electricity self-sufficiency can be obtained using only PV and close to grid parity. Above 40% self-sufficiency, energy storage must be used, strongly increasing the cost of such installations. Economies of scale play an important role suggesting a preferential implementation for larger users or at a community-scale. Feed-in limits seem to be a good solution to attenuate grid impact. On the other hand, a higher share of a capacity-based component on the grid tariff strongly affects the economic viability of such installations for the average household. These results are important for studies on distributed photovoltaics and energy storage as well as for energy policy. Also, the large range of results made available, calculated on a free market perspective using a simple control mechanism, provide a much-needed benchmark for further comparable studies.

Preparation and properties of fatty acid eutectics/expanded perlite and expanded vermiculite shape-stabilized materials for thermal energy storage in buildings

In this study, the fatty acid eutectics (capric acid (CA) and lauric acid (LA) eutectics) were impregnated into the expanded perlite (EP) and expanded vermiculite (EVM) to form the two kinds of composite phase change material (PCM). The chemical structure, crystalloid phase were determined by the Fourier transformation infrared spectroscope, X-ray diffractometer. The results show that the eutectics with the EP and EVM do not undergo a chemical reaction and only undergo a physical combination. The SEM results proved that eutectics are well adsorbed in the porous structure of the EP and EVM. The thermal properties were determined by the differential scanning calorimeter (DSC). The DSC result shows that the melting temperatures and latent heat values of the PCMs are in the range of about 21–23°C and 81–117J/g. The maximum impregnation ratio of fatty acid eutectics into EP and EVM were 82.93% and 57.48%. The thermal cycling test proves that the composites have good thermal reliability. TG analysis revealed that the composite PCMs had high thermal durability property above their working temperature ranges. Besides, thermal conductivity of the CA-LA/EP and CA-LA/EVM was increased approximately as 89.14% and 87.41% by adding 5wt.% expanded graphite (EG). It is envisioned that the prepared shape-stabilized PCMs have considerable potential for developing their roles in thermal energy storage system.

Characterization of paraffin/ultrasonic-treated diatomite for use as phase change material in thermal energy storage of buildings

In this study, paraffin-/ultrasonic-treated diatomite was characterized for use as phase change material (PCM) for thermal energy storage in buildings. The diatomite was treated with ultrasound at various periods of time. The diatomite treated with ultrasound for 60 min (DA-60) was the optimum condition providing the highest surface area without structural degradation. The melting point and latent heat of the paraffin/DA-60 composite PCM were 59 °C and 45.90 J g−1, respectively. The obtained form-stable PCM had good thermal reliability after 500 cycles of thermal cycling test. The thermal performance of PCM was tested by incorporating the paraffin/DA-60 composite PCM into gypsum board. The results showed that the gypsum board containing the paraffin/DA-60 composite PCM had better thermal energy absorption and release characteristics than those of the control sample. The incorporation of paraffin/DA-60 composite PCM into suitable building materials could thus considerably reduce the energy consumption of cooling system in buildings.

Evaluation of ice thermal energy storage (ITES) for commercial buildings in cities in Brazil

High temperatures and the intensive use of air conditioning are considered the main drivers of the increase in Brazil’s electricity demand in the summer, which has been causing major power cuts due to insufficient supply to meet peak demand. This paper analyses the techno-economic aspects of Ice Thermal Energy Storage (ITES) in Brazil, as a technology that can be used to shift building cooling load to off-peak time. ITES is assessed in five cities and five archetypes of commercial buildings, using two different operation strategies and two types of chillers, for new installations and retrofits. Results have shown that ITES can effectively shape peak demand in commercial buildings, generating economic gains for building owners but also losses in some cases. Although the climate plays an important role, the electricity tariffs vary significantly from city to city and this determined the economic feasibility of ITES. The technology’s potential to shape demand in Brazil’s commercial sector can encourage policy makers, regulators, grid operators and utilities in considering ITES as an option to reduce peak demand, increase security of supply and support the integration of intermittent renewable generation.

Phase diagrams, eutectic mass ratios and thermal energy storage properties of multiple fatty acid eutectics as novel solid-liquid phase change materials for storage and retrieval of thermal energy

A series of binary and multiple fatty acid eutectics such as ternary eutectics, quaternary eutectics and quinary eutectics were successfully prepared and developed as solid-liquid phase change materials (PCMs) by using five kinds of individual fatty acids such as capric acid (CA), lauric acid (LA), myristic acid (MA), palmitic acid (PA), and stearic acid (SA) through melt blending followed by ultrasonication method. The eutectic phase diagrams of binary/multiple fatty acid eutectics were plotted and analyzed on the basis of Schrader equation and MATLAB software, and then their eutectic mass ratios were precisely determined by eutectic phase diagrams and differential scanning calorimetry (DSC) analyses. The deviations between the theoretical calculated eutectic mass ratios and the experimental determined eutectic mass ratios of some fatty acid eutectics could be attributed to the experimental errors of data obtaining from the DSC analyses, impurities of fatty acids and cumulative errors of calculation. The results of DSC indicated that phase change temperatures and enthalpies of the synthesized fatty acid eutectics gradually decreased with the increase of the number of components in the mixtures. The melting peak temperatures of the prepared binary eutectics, ternary eutectics, quaternary eutectics and quinary eutectics were varied from about 22 to 56°C, from about 18 to 49°C, from about 19 to 32°C and about 17°C, respectively. Their minimum and maximum melting enthalpies were about 127.2kJ/kg and 204.7kJ/kg, respectively. The spectra obtained from Fourier transformation infrared spectroscope showed that the binary/multiple fatty acid eutectics exhibited the similar carboxyl group with the single fatty acids and had stable chemical properties. The developed fatty acid eutectic mixtures were suitable for low temperature thermal energy storage applications such as solar water heating systems, building energy storage systems, and thermal regulating textiles.

Adsorbent working pairs for solar thermal energy storage in buildings

In this study, the thermodynamic analysis of several adsorption working pairs for adsorption heat storage applications at domestic level is presented. The selected working pairs employ different working fluids (i.e. water, ethanol, ammonia, methanol) and different adsorbent materials such as classical zeolites, silica gels, alumino-phosphates, composite sorbents and activated carbons. The simulations have been performed taking into account desorption temperatures in the range between 80 °C and 120 °C, compatible with non-concentrating solar thermal collectors, under seasonal heat storage working conditions. The composite sorbent MWCNT-LiCl with both water and methanol as working fluid showed the highest heat storage density under practical working boundary conditions. Among the standard adsorbents, the zeotype AQSOA Z02 showed promising achievable heat storage densities. Classical working pairs, such as zeolite 13X/water, commonly employed for heat storage applications, are not suitable for this working range. Finally, also the influence of the metal to sorbent mass ratio, due to the heat exchanger, was investigated, demonstrating that it can reduce the achievable amount of heat released to the user up to 30%.

Phase Change Material For Solar Thermal Energy Storage In Buildings: Numerical Study

Thermal storage plays a major role in a wide variety of industrial, commercial, and residential applications when there is a mismatch between the offer and the claim of energy. In this paper, we study numerically the contribution of phase change materials (PCMs) for solar thermal energy storage (TES) in buildings. The studied configuration is a plane solar collector incorporating a PCM layer and coupled to a concrete slab (a roof of a building). The study is conducted for Casablanca (Morocco) meteorological conditions. Several simulations were performed to optimize the melting temperature and the PCM layer thickness. The results show that PCM imposes, on the roof, a temperature close to its melting temperature. The choice of a melting temperature Tmelt = 22 °C (the local indoor temperature Tc is fixed as Tc = 22 °C) limits the losses through the concrete slab, considerably. This last seems to be, nearly, adiabatic, in this case. Also, the energy released by PCM solidification, overnight, increases the outlet temperature of the coolant fluid to 35 °C and the useful flux to 80 W/m2, increasing the efficiency of the solar collector by night. The PCM functioned both as an energy storage material for the stabilization of the coolant fluid temperature and as an insulating material for the building.

Pumped hydro energy storage in buildings

The growing use of variable energy sources is pushing the need for energy storage. With Pumped Hydro Energy Storage (PHES) representing most of the world’s energy storage installed capacity and given its maturity and simplicity, the question stands as to whether this technology could be used on a smaller scale, namely in buildings. In this paper, the feasibility of such an installation is analysed by modelling each one of its components and applying it to several installation scenarios. Proposed and existing installations are also reviewed, including a first-time analysis of an installation in France, which is presumably the only existing building with an integrated PHES system. It was found that the economies of scale that render large PHES installations competitive are not present in small installations. This limitation, associated to other important disadvantages, such as the large volume required, seem to point out PHES as an ill-suited solution for energy storage in buildings, an important finding for building design and energy policy. Nevertheless, if synergies with existing reservoirs could be found (for example for a building on a riverside), costs could be significantly lowered. Further research on possible synergies with other building systems as well as a life-cycle assessment analysis are recommended.

Lead–acid batteries coupled with photovoltaics for increased electricity self-sufficiency in households

With distributed generation of electricity growing in importance (especially with photovoltaics) and buildings being one of the main consumers of energy in modern societies, distributed storage of energy in buildings is expected to become increasingly present. This paper analyses the use of residential lead–acid energy storage coupled with photovoltaics and its possible interaction with the grid for different limits of feed-in power without any support policies. In the literature, these subjects are often treated independently and for very specific, non-optimised cases, thus motivating further research. Results show that reaching self-sufficiency values up to 40% is possible, close to grid parity values, and only with photovoltaics. Beyond 40%, energy storage must be used, strongly raising the cost of the electricity consumed and therefore the need for support policies for widespread adoption. Also, peak power consumption from the grid remains constant and load variability rises, suggesting that an increase in self-sufficiency would be accompanied by lower utilisation factors of power plants and, consequently, higher wholesale electricity prices during no sunshine hours. Limiting feed-in power attenuates the increased load variability and only slightly affects the economic viability of such installations. These results present a novel optimisation tool for developers and should be considered in future studies of distributed photovoltaics and energy storage as well as in energy policy.

Thermal regulating performance of gypsum/(C18–C24) composite phase change material (CPCM) for building energy storage applications

A new type of organic/inorganic form-stable composite phase change material (FSCPCM) was prepared via direct impregnation of eutectic mixture of octadecane (C18) and tetracosane (C24) into gypsum. The maximum mass percentage of C18–C24 absorbed in gypsum was determined as 18% without the leakage of C18–C24 in liquid state. The Fourier Transform Infrared (FT-IR) spectroscopy and Differential Scanning Calorimetry (DSC) techniques were used to characterize the FSCPCM. The FT-IR spectra confirmed that any chemical interaction did not occur among the components of the composite during the impregnation. Besides, DSC analysis showed that the FSCPCM had reversible melting and freezing behavior and quite satisfying thermal properties for building applications. The composite maintained its chemical structure and thermal energy storage characteristics after 1000 melting/freezing cycles. In addition, the gypsum plaster with FSCPCM exhibited excellent thermal regulating performance when compared to that of only gypsum plaster under the same conditions. From all results, it can be deduced that the obtained gypsum based composite plaster is a promising material to control room temperature and to conserve energy in buildings.

Building Energy Storage Panel Based on Paraffin/Expanded Perlite: Preparation and Thermal Performance Study.

This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP), which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM) was incorporated into expanded perlite (EP) through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC), scanning electron microscope (SEM), best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1) the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2) the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3) in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency.

Development and thermal performance of pumice/organic PCM/gypsum composite plasters for thermal energy storage in buildings

Organic phase change materials (PCMs) have been mixed with suitable building materials and the resulting form stable-composite PCMs (FS-CPCMs) have been used for low temperature-thermal energy storage (TES) applications for passive solar heating, ventilating and air conditioning (HVAC) purposes in building envelopes. Here, three novel types of FS-CPCMs were prepared as TES materials for building applications by absorption of capric (CA)–palmitic acid (PA) eutectic mixture, heptadecane (HEPD) and dodecanol (DD) as different kinds of organic PCMs into pumice (PUM) via vacuum impregnation. The maximum mass percentages of CA–PA, HEPD and DD into FS-CPCMs were determined as 34wt%, 32wt%, and 31wt%, respectively. The chemical, morphological and thermal characterizations of the developed FS-CPCMs were performed by SEM, FT-IR, DSC, and TG analysis techniques. SEM and FT-IR results showed that the selected organic PCMs were well incorporated into the pores of the PUM particles and have good compatibility among the components of the composites. DSC analysis indicated that the phase change temperatures and TES capacities of the fabricated FS-CPCMs were in the range of 20.98–23.27°C and 55.40–72.38J/g, respectively. TG analysis results revealed that the prepared FS-CPCMs are thermally stable. The thermal cycling test also showed that they have excellent structural stability and good stability for TES characteristics after 3000 cycles. The FS-CPCMs were tested in the form of plasters firstly in this study, which is similar to large-scale building applications. Thermal performance tests showed that the gypsum plasters with the FS-CPCMs can be improved the thermal comfort keeping the indoor temperature at the comfortable range for a long time and reduced the energy consumption. Based on all results, it can be deduced that the newly developed PUM/CA–PA, PUM/HEPD and PUM/DD are potential FS-CPCMs for low temperature-HVAC applications in the construction of energy-efficient buildings.

Optimal operation of energy storage in buildings: Use of the hot water system

We consider the optimal operation of energy storage in buildings with focus on the optimization of an electric water heating system. The optimization objective is to minimize the energy costs of heating the water, with the requirement that we should satisfy the uncertain demand at any time. The main complications in this problem are the time varying nature of the electricity price and the unpredictability of the future water demand. In this paper we use the water heating system as an example for formulating a general framework which could easily be applied to similar problems with energy storage capacity. Feasibility and optimality are discussed and the main points are illustrated in the simulation case studies.