• Energy Research

AbstractThe goal of this study is to characterize the thermal performance of the opaque ventilated facade from sample-scale to building scale. To begin with, a representative sample has been built in order to test it in outdoor conditions using a traceable and precise methodology. The testing equipment used is a PASLINK test cell developed by DYNASTEE network at the Basque Government Laboratory of Quality Control in Buildings.The experimental results provide information to define a mathematical model of the ventilated gap's convective behavior for the application of building scale simulation. In this way, a building dynamic simulation has been carried out by TRNSYS. Results not only show the benefits of this solution in warm climate areas and drawbacks in cold climate areas, but also provide guides for the optimization and improvement of the opaque ventilated facade.

This paper explores the effects of multi-zone heating systems in residential buildings in different Mediterranean climates. The aim is to evaluate their potential in residential sectors to provide a general basis from the results (from the energy and economic point of view). In addition, if feasible, a further detailed evaluation of this management strategy for optimising the energy use in residential buildings would also be carried out. To do so, the effects of two different zoning controls in different types of apartment, occupancy patterns, building characteristics and locations in Spain, have been assessed. Different combinations of these parameters have resulted in 336 different scenarios that have been dynamically simulated using Design Builder software. The obtained energy results have been analysed in detail. Moreover, an economic analysis of these results has also been carried out to evaluate the economic feasibility of these systems in residential buildings located in temperate climates. This has been calculated by evaluating the maximum investment that can be assumed in each scenario to achieve different payback periods (namely 10 and 20 years). The results obtained show that these systems could be a cost-effective strategy aimed at reducing the energy consumption in residential buildings, not only in cold climates, such as is shown in the literature (the majority of the studies found are located in the UK and northern countries), but also in more temperate climates, such as that of Spain. Savings of around 20% were obtained in the most usual scenarios in Spain (coherent with results obtained in previous studies in the UK found in the literature), showing that in several cases, the initial investment in zone-controlled systems could be paid off in less than ten years, especially in large apartments and the coldest weather conditions This work was supported by the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund through the MONITHERM project ‘Investigation of monitoring techniques of occupied buildings for their thermal characterization and methodology to identify their key performance indicators’, project reference: RTI2018-096296-B-C22 (MCIU/AEI/FEDER, UE)

Abstract Nowadays, several regulations exist covering different general guidelines that must be considered in order to decrease the energy demand in residential buildings. One of the main ones consists in increasing the insulation of the building envelope with the aim of minimizing heat losses or gains. As a result, a proper treatment of thermal bridges and their in situ construction becomes more relevant because their relative effect on the overall thermal demand of the building increases. Nevertheless, there is still a great uncertainty about the dynamic behavior of thermal bridges and few energy simulation programs allow implementing them considering their thermal inertia. To obtain more information about the thermal response of thermal bridges, a series of tests have been carried out in a guarded hot box testing facility. The characteristics of a pillar thermal bridge have been studied in both steady and dynamic regime, being one of the main objectives of this study the determination of the area of influence of a thermal bridge. For this purpose, test results are compared with simulation ones.

Micro-cogeneration has been recognized as an efficient technology that can contribute to European Union's energy and climate objectives with respect to delivering low-carbon heat and power to citizens and small businesses. For improving the performance of this technology and so take as much advantage as possible of its potential, thermal energy storage plays a key role. This paper presents a techno-economic evaluation and optimization procedure focused on properly sizing and designing a micro-cogeneration residential installation, emphasizing how thermal energy storage is arranged and the different thermal loads prioritized within the plant. Therefore, the proposed methodology can be easily applied to buildings with different conditions and constraints. The methodology is then applied to a representative case study that consists of a detached house with a 1 kWe micro-cogeneration plant. Results of the case study show that in small installations DHW accumulation does not provide any significant improvement but a worsening of efficiency. Additionally, it is also proved that the layout of the distribution loop has an importance on the final performance of the plant that must be kept in mind. Moreover, results show that TES systems coupled with micro-cogeneration engines are traditionally highly oversized, thus worsening economic viability of these facilities This work was supported by the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund through the MONITHERM project ‘Investigation of monitoring techniques of occupied buildings for their thermal characterization and methodology to identify their key performance indicators’, project reference: RTI2018-096296-B-C22 (MCIU/AEI/FEDER, UE)

AbstractOne of the key factors that currently limits the commercial deployment of thermal energy storage (TES) systems is their complex design procedure, especially in the case of latent heat TES systems. Design procedures should address both the specificities of the TES system under consideration and those of the application to be integrated within. This article presents a fast and easy to apply methodology for the selection of the design of TES systems suitable for both direct and indirect contact sensible and latent TES. The methodology is divided into four steps covering: (a) description of the thermal process or application, (b) definition of the specifications to be met by the TES system, (c) characterization of the specific TES system under consideration and (d) the determination of the TES design. This methodology needs as major inputs the operation conditions of the energy system where the TES system will be integrated, that is, temperatures and mass‐flow; as well as the charging and discharging time performed by the TES system under different conditions. The latter can be generally deduced from the Fourier number, which can be obtained both theoretically (ie, by simulation) or empirically from the analysis of the TES technology under consideration. The methodology is then applied to a 10 kW residential cogeneration application considering two TES technologies. One consists of a direct‐contact hot water storage tank and the other, of an indirect‐contact plate‐based latent heat TES system developed by the authors. The resulting volume needs for the hot water storage tank is approximately twice the volume of the latent heat TES system, respectively, 5.97 and 2.96 m3. The presented methodology eases the design process of TES systems and decreases the amount of time needed to size them from days/hours to minutes.

One of the factors that limit the commercial deployment of LHTES systems is their complex design procedure; accordingly, there is a need of tools that allow their fast and accurate simulation. In the present work, a correlation that allows the determination of the discharging time of plate-based LHTES systems is first presented. Based on that correlation and other parameters constrained by the application, a simplified methodology for the design of plate-based LHTES systems is presented. It consists of 3 simple steps and allows a complete sizing of the system without the need of simulations. This reduces the design procedure time from days/hours to minutes.

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.

Abstract To spread the nearly Zero Energy Building (NZEB) concept, there is a need for the combined integration of energy saving measures and energy supply systems that minimize the non-renewable primary energy consumption. This paper aims to analyse the capabilities of a novel system composed of a photovoltaic (PV) double skin facade (PV-DSF) coupled to an air source heat pump system (ASHP). The main goal of this system is to provide heating and domestic hot water (DHW) using renewable energy. A quasi-steady mathematical model has been developed to assess the energy capabilities of the proposed system. The thermal and electric generation of the system can be estimated with the hourly outdoor temperature and solar radiation as input data. Calculations have been carried out on an existing block of flats in Bilbao (Spain) to estimate the energy viability of the proposed system. It has been proved that almost all the thermal energy demand can be supplied with the ASHP system, which improves its Seasonal Performance Factor (SPF) in 14.8%. Regarding electric energy, the PV-DSF panels can supply approximately 70% of the electricity consumed by the ASHP system and the fans of the PV-DSF. In addition, if more PV modules are installed on the roof, the demand can be covered with a surplus for other uses. Economically, comparing it with a conventional natural gas boiler facility, the investment cost is amortized in 6.4 years.