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This paper presents a novel framework for the identification of different consumption patterns of heating loads of buildings. The approach to analyzing the consumption data is carried out by a combination of unsupervised clustering models. Density based clustering is used for outlier detection in the original dataset and K-means for pattern recognition. The proposed framework is then applied to a real building connected to the district heating in Tartu (Estonia). Three main day-types are identified for the building as an outcome of the clustering process, with different patterns throughout these days. More than 60% of the analyzed Cluster Validation Indexes studied in this paper show that classifying the daily demand profiles in three clusters is the optimal classification.

One of the key factors that currently limit the commercial deployment of latent heat thermal energy storage (LHTES) systems is their complex design procedure. The optimization of such kind of systems requires a compromise between the storage capacity and the charging/discharging power, and therefore, there is a need of modeling tools that allow their fast and accurate simulation. In light of this, a novel correlation that allows the straightforward determination of the discharging time of plate-based LHTES systems is developed in the present article. To approach this objective, an experimentally validated CFD model was used. Simulations with 3 commercial phase change materials (PCMs) were first employed to gain knowledge of the melting and solidification behavior of the system. Then, a theoretical formulation of the heat transfer problem involved was performed so as to identify those dimensionless numbers concerned in the process. Afterwards, 15 virtual PCMs were defined and CFD simulations were performed. The obtained discharging time results were adjusted by regression to get the exponents and coefficients of the dimensionless numbers involved in the correlation. Finally, to validate the correlation, simulations with five additional PCMs were carried out and their results were compared with those obtained from the correlation. By means of the obtained expression, the maximum plate thickness capable to provide a desired discharging power can be determined as a function of the properties of the PCM and the operation constraints of the application without the need of simulations. The technique eases the design process of this kind of systems and decreases the amount of time needed to size them from days/hours to minutes.

The use of georeferenced information system and Light Detection and Ranging (LiDAR) data in combination with traditional data analytics tools is very promising in urban scale engineering and especially in energy urban planning. This paper explores the use of new DH networks for industrial waste heat exploitation and for that purpose, a case-study in Vitoria-Gasteiz (Spain) is proposed. The methodology explained in this paper explores the incorporation of data from industrial emplacements, buildings and road network in order to identify optimal areas in the city for the construction of a new district-heating network. An area of influence of a buffer of radius 1.5km from the industry location is defined and the proposed algorithm divides this area into grids of different sizes. The path for the network is calculated by optimizing the economic performance of the network. The results show that the district-heating may be built in the south-west direction from the industry and among the 40 configurations studied, payback periods from 6 to 8.5 years are obtained.

A simple shell and tube heat exchanger provides a straightforward design for near-term integration of latent heat thermal energy storage (LHTES) systems in concentrated solar thermal-tower (CST-tower) plants, but currently there is no literature available for this configuration in the 286–565 °C temperature range. Therefore, the primary objective of this work is to evaluate the potential of this configuration for CST-tower plants. In addition, a proper design method of this storage configuration should simultaneously account for the effects of geometric parameters and the number of modules. The present work optimizes these parameters for market ready phase change materials (PCM) that are suitable in the aforementioned temperature range. This optimization consisted of fixing the PCM volume while varying the other geometric parameters (namely, L, L/d, R/ro) simultaneously over a wide range. The goal was to achieve the highest amount of total stored/delivered energy with a minimum heat transfer surface area. This analysis revealed that there was an optimum area between 36 and 63 m2 GJ−1 (or 0.12–0.22 m2 kWhth−1), depending on the PCM employed. This optimum surface area can be obtained with several combinations of geometric parameters, but only certain combinations were found to achieve the highest total stored/delivered energy. The charging and discharging efficiency for the selected PCMs was found to be ∼99% and 75–85%, respectively. Using the optimized designs, the cost of this shell and tube LHTES system was found to vary between 27 and 170 US$ kWhth−1, which indicates that with further development it may be competitive with conventional sensible storage systems (e.g. two-tank molten salts).

The feasibility of individual natural gas fired boiler-based heating systems in the retrofitting of buildings constructed in the 50–60 s in Bilbao (northern Spain) is evaluated in this paper. A holistic approach through dynamic simulations using TRNSYS is employed for the purpose. An existing dwelling previously monitored and used to validate the model applied is selected as a case study. 54 different scenarios are evaluated, which arise from the combination of 3 different envelope options, 2 types of heat production units, 3 heat production temperatures and 3 comfort temperature set-points. The cases are evaluated in terms of energy results, economic aspects, and the influence of user behaviour. Regarding the latter, the influence of the potential rebound effect is also evaluated. The results show energy savings nearby 10% when condensing boilers are compared with high efficiency boilers. In relation to hot water production temperature, energy savings between 5 and 10% are found when the temperature is lowered from 60 to 50 °C. The greatest impact on energy consumption is related to the occupants’ behaviour: reductions up to 89% are achieved if the indoor temperature set-point is lowered 2 °C. This is reinforced with the results related to the rebound effect, which show significant differences on energy consumption values. These evidences demonstrate that the user behaviour is an essential feature to be considered in studies regarding buildings energy performance. As a consequence, the holistic approach herein employed emerges as a key tool to be applied in further works related with the topic.

Thermal energy storage is a key technology to overcome the structural mismatch between energy supply and demand in thermal energy systems. Its use is essential for a proper integration of renewable or efficient technologies in day-to-day applications, such as heating and domestic hot water. Latent heat thermal energy storage, which is based on the use of phase change materials, has been studied in depth in the literature due to its advantages over conventional storage methods. It can provide a higher compactness and lower thermal losses than traditional sensible heat storage systems. However, to optimize the operation of latent thermal energy storage systems into heating and domestic hot water applications, it is still required to obtain additional information on the effects of the system parameters that can be easily altered and/or controlled. These parameters mainly are: operating temperature range, mass-flow rate and prototype length. This paper aims at evaluating these parameters for an innovative plate-based latent thermal energy storage system previously developed by the authors. The used phase change material is a commercial paraffin wax (RT60) with an approximated phase change temperature of 58 °C. A full-scale experimental setup was developed and forty-two experimental tests were conducted. The tests combined six temperature ranges from 45 to 70 °C, three mass-flow rates from 1.8 to 3 l/min and two module arrangements: a single prototype and two prototypes connected in series. The results showed that, for a specified temperature difference between the charging and discharging inlet temperature, the stored energy depended strongly on the selected temperature range. The thermal power during charging and discharging was strongly affected by the difference between the inlet temperature and the phase change temperature of the PCM. Higher mass-flow rates linearly reduced the required time for completion of charging or discharging. Finally, the addition of a second LHTES prototype in series enhanced the storage capacity of the system, but also increased the required time to complete the process. The obtained results can aid the proper design and operation of the system under specific constraints imposed by a specific application. They are also valuable as a starting point for the design of new plate-based LHTES systems, considering both different geometries and phase change materials.

This article describes the development of a CFD 2D model of a new type of ventilated active facade which includes a PCM (Phase Change Material) in its outer layer. The model was carried out using the software Fluent. The numerical results were compared against experimental data obtained by means of a real-scale PASLINK test facility. Two different approaches were tested to model the PCM. To model the radiation, S2S and DO sub-models were tested. RNG k–e , Standard k–ω and SST k–ω turbulence models were compared to model the air flow inside the ventilated layer. The results showed that for the geometry under consideration it was suitable to consider the PCM to be a solid material with variable C p . The DO model accurately reproduced the radiation phenomena. For an air flow rate that resulted in a turbulent regime inside the air chamber, the RNG k–e model showed good agreement between the experimental data and the simulated results. The developed model can be considered suitable for the simulation and optimization of the facade under turbulent flow conditions. Further research should be conducted to improve the accuracy of the model for low-Reynolds-number turbulence conditions.

This paper presents an innovative finned-plate latent heat thermal energy storage system for its integration in cogeneration systems. For optimization purposes it is very important to maximize the efficiency of the computational calculations. Therefore, three approaches are presented for the simulation of the same storage system: a numerical model, a simplified analytical one and a simplified numerical model. These three models are applied to the simulation of a prototype which has been tested experimentally by means of a test benchmark for storage systems. The simplified analytical and simplified numerical models are implemented by the definition of an effective heat transfer coefficient. From the comparison of the results it was concluded that the three approaches gives rise to a good agreement with the test results. However, the simplified analytical model fails to predict long configurations. On the other hand, the simplified numerical model presents very good results for every configuration, reducing the computational cost of the numerical model from several hours to minutes.

This article describes an evaluation of the thermal performance of a new type of ventilated active facade that includes a phase change material (PCM) in its outer layer. The research was carried out experimentally by means of a real-scale PASLINK test cell facility, located in the city of Vitoria-Gasteiz in Spain. The results of an experiment performed in March 2010 are presented and evaluated. The behavior of the facade was compared with different traditional constructive systems, using the results of computational simulations performed with the Design Builder software. The experimental results showed that the melting–solidification processes that take place in the PCM led to an increase in the heat absorption during the phase-change temperature intervals, which reduced overheating of the facade. The air circulating through the ventilated chamber was overheated up to 12 °C during the daytime. Because of the PCM solidification, 2.5 h after the solar radiation faded out, the air circulating through the chamber was still warmed by 2 °C. The energy efficiency of the facade during the testing period is attributable to the 10–12% incident radiation gains. This efficiency was found to be a function of the circulating air flow rate. The simulations results showed that the thermal inertia of the ventilated facade with a PCM is higher than that of the four traditional solutions evaluated in the study. Further research is required to study the influence of the air flow rate through the ventilated chamber.

In order to evaluate the accuracy and performance of two different heat transfer models for PCM containing systems, a thermal testing has been performed in a conductivimeter. A mixture of PCM and gypsum was submitted to a cyclic surface temperature change inside the conductivimeter, measuring heat fluxes and temperatures. The results of this test were used to validate two different heat transfer models, based on finite differences and on neural networks. Both heat transfer models were compared with the test results, showing good agreement with experimental data in both cases (mean error less than 5%) and a better performance (accuracy and calculation time) for the neural network.

4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC) -- DEC 02-04, 2015 -- Istanbul, TURKEY, WOS: 000387506400026, An overview on the recent results on the engineering and characterization of sorption materials, PCMs and TCMs investigated in the working group WG A1 "Engineering and processing of TES materials" of IEA SHC Task 42 / ECES Annex 29 (Task 4229) entitled "Compact Thermal Energy Storage" is presented. (C) 2016 The Authors. Published by Elsevier Ltd.

The IEA joint Task 42 / Annex 29 is aimed at developing compact thermal energy storage materials and systems. In Working Group B, experts are working on the development of compact thermal energy storage applications, in the areas cooling, domestic heating and hot water and industry. The majority of application projects were in the field of room heating and domestic hot water. In this article, an overview is given of a large number of applications. The storage technologies used in the applications are latent heat storage, open and closed solid sorption, liquid sorption and salt hydrates and composites thereof. On a broad front, a lot of progress was made in the development of components and systems, providing knowledge and experience regarding the design, numerical modeling, building, testing and economical assessing of components and storage systems. Most important findings are that the interaction of storage materials with the materials of components can be deciding for the technical feasibility, that a number of components, like reactor, heat exchangers and evaporators are less understood than initially thought and need more development, that the inclusion of storage materials in systems generate new challenges like the occurrence of non-condensable gases and thermo-mechanical effects and that standardized and simplified system approaches are needed.

In order to reduce the required volume for thermal energy storage, a finned plate latent heat thermal energy storage system for domestic applications is presented in this paper. This innovative design allows the exchanging of energy between water and the RT60, used as the phase change material. The simulation of that system is covered by a validated mathematical model. The model, based on a simplified numerical approach, is used for the optimal design of the final prototype, which is compared with a conventional 500 l hot water tank usually integrated in domestic heating and domestic hot water applications. It is obtained that the resulting design is in the order of one half of the water tank volume, resulting in a more compact configuration which can be easily integrated in the space. This solution will bring a great opportunity for thermal storage especially in those applications where there is a lack of available space, as it is the case of residential flats.

An important prerequisite to select a reliable phase change material (PCM) for thermal energy storage applications is to test it under application conditions. In the case of solid&ndash, liquid PCM, a large amount of thermal energy can be stored and released in a small temperature range around the solid&ndash, liquid phase transition. Therefore, to test the long-term stability of solid&ndash, liquid PCM, they are subjected to melting and solidification processes taking into account the conditions of the intended application. In this work, 18 experimental devices to investigate the long-term stability of PCM are presented. The experiments can be divided into thermal cycling stability tests, tests on PCM with stable supercooling, and tests on the stability of phase change slurries (PCS). In addition to these experiments, appropriate methods to investigate a possible degradation of the PCM are introduced. Considering the diversity of the investigated devices and the wide range of experimental parameters, further work toward a standardization of PCM stability testing is recommended.