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The study presents the experimental and analytical investigation, which was carried out to evaluate the charging/discharging performance of phase change material (PCM) in the thermal energy storage (TES) unit. The experiments performed under different operating modes of the heat storage system, changing the inlet temperature and the mass flow rate of the heat transfer fluid (HTF). The calculated amount of thermal energy based on the partial enthalpy distribution provided by the manufacturer’s datasheet compared to that obtained from the experiments. Based on the experimental results, a three-dimensional response surfaces formed and a regression models obtained, which allow predicting the PCM charging and discharging performance.

Increase in solar fraction has been noted as one of the main goals for wider application of domestic solar thermal systems. To increase solar fraction, higher energy density thermal storage availability is a key point. In this paper phase change materials have been analysed as part of a domestic solar thermal system. Sensitivity analysis of annual simulation in TRNSYS with climate data of Riga, Latvia is used. The paper also explores better methods for evaluating phase change material (PCM) performance based on temperature measurements in PCM. The results showed that the melting point of PCM and temperature set point of an auxiliary heater have the highest sensitivity of aspects analysed in the paper. It also reports that the coefficient of variation of energy in PCM correlates well with solar fraction and can be used as a parameter to evaluate PCM’s suitability for certain applications.

The renovation/modernisation of buildings is one of the most frequently addressed areas in the European Union. It is the basis for the entry into force of Directive 2010/31/EU on the energy performance of buildings. The assessment of renovated buildings has several objectives, characterised by different assessment indicators. To better assess the renovation of buildings and future energy efficiency improvements, natural and computer simulations are used to help make more rational decisions. This work aims to analyse and quantify energy efficiency improvement measures and additional factors based on an existing retrofitted office building using collected, measured, and modelled data. The work is based on measured real building data for the assessment of heat loss of the building and calculating the thermal coefficient of the external envelope. Energy modelling of buildings before and after retrofitting is carried out using simulation, data processing, and analysis software. [ABSTRACT FROM AUTHOR]

National legal and political regulation in the field of energy efficiency is closely connected to minimizing energy consumption in buildings. Within the framework of implementing Directive 2018/844/EU on the energy performance of buildings in Europe, the practice of its application differs from country to country. This study aims to reveal the differences in the energy indicators of an energy-efficient building in European states. To that end, an analysis was made to compare the results of a single-family home model in 11 city locations with different climatic conditions (from the Mediterranean to Nordic) and appropriate national regulations in place for the past three years. The simulation was done using IDA Indoor Climate and Energy software, EQUA Simulation AB, Stockholm, Sweden. The demand for primary energy is based on primary energy factors. A comparison of overall heat transfer coefficients for walls and windows in an energy-efficient building in different locations was made to reveal the differences in applicable national regulations. The results showcase the primary energy demand depending on the different climatic conditions for building heating and cooling purposes, as appropriate, and on CO2 emissions. The study has shown the energy demand for cooling to increase significantly—by 65% in the case of Vilnius, whereas only a slight decrease in the demand for heating. Furthermore, a Lithuanian energy class A+ building is singled out as an individual case, its energy indicators determined for a different location under analysis. [ABSTRACT FROM AUTHOR]

The paper presents an experimental study of the influence of heat transfer fluid (HTF) mass flow rate on phase change materials (PCM) behaviour. The experimental study was performed on a specially designed test bench. Research object - PCM based thermal energy storage unit which consists of a stainless steel tank with dual circuit tube-fin copper heat exchanger. The tank (storage volume) was filled with phase change material RT82. The experiment was carried out using three different mass flow rates of HTF: high - 0.25 kg/s, medium - 0.125 kg/s, low - 0.05 kg/s. The analysis showed that in the case of high and medium mass flow rates the melting/solidification process highly depends on the temperature of inlet HTF. Influence of mass flow rate is higher in the case of low mass flow rate. [ABSTRACT FROM AUTHOR]

This paper presents a thermal analysis of compounds called smart windows in typical building design; such windows are covered with a vanadium dioxide film doped with tungsten and are characterized by their phase transition which makes the transmission coefficient high for low temperatures and low for high temperatures. This leads to the natural optimization of thermal comfort in summer and winter through a decrease in solar radiation transmission in the summer and an increase in it in the winter. A comparative study of four types of glass has been carried out both in summer and winter: simple glass SiO2, dioxide of vanadium un-doped glass, vanadium dioxide glass doped with 3% tungsten and 5% tungsten in order to evaluate their effect on the interior temperature of the building. For these reasons, a thermal model in the dynamic state has been developed to assess the thermal performance in such a building and to evaluate the effect of these windows on thermal comfort in terms of heat flow, density and internal temperature. The analysis was carried out having taken into account the external weather conditions of Fez, such as radiation, natural convection, air exchange, and the outdoor temperature as well as different parameters of the building envelope. [ABSTRACT FROM AUTHOR]

Ecological problems are inherent in the issue of air quality in the buildings. The main goal thus becomes the creation of indoor clime, where concentration of the detrimental impurities, such as carbon dioxide, would not exceed established norms. Thus, it is proposed to develop an alternative system of ventilation, which would ensure necessary indoor climate without outside air use. In order to decrease the levels of it inside the buildings, it is suggested to use a winter garden with much greenery, so that the air would be regenerated since the carbon dioxide would be absorbed and oxygen would be evolved. The current work reveals the study results of thermal, air and gas conditions in a winter garden upon the office building. The proposed methodology based on the ANSYS-CFX software, ensures a successful calculation of heating and aerial regimes within buildings that might differ in accordance with various engineering practices. [ABSTRACT FROM AUTHOR]

The paper analyses the energy and financial possibilities to install renewable energy sources (solar energy) generating systems when renovating multi-flat buildings. The aim is to analyse solar energy system possibilities for modernization of multi-flat buildings (5-storey, 9-storey and 16-storey), providing detailed conclusions about the appropriateness of the energy systems and financial aspects. It is also intended to determine the optimal technological combinations and solutions to reach the maximum energy benefits. For the research computer simulation tools “EnergyPRO” and “PV*SOL Premium” are chosen. Also actual collected heat and electricity consumption data is used for the analysis. [ABSTRACT FROM AUTHOR]

The paper presents experimental study of apartment buildings‘ ventilation parameters which was carried out during the heating season. The results show that the existing apartment buildings often don‘t guarantee the hygienic conditions that are directly related to the indoor air ventilation. Also article contains an analysis of possibilities to upgrade the ventilation systems of apartment buildings. Four ventilation systems‘ upgrade options were examined. The economic analysis showed that according to the economic aspect the best solution for mechanical ventilation in the typical apartment houses is a centralized ventilation system which operates in combination with ground heat pump when supply ducts are mounted on the building facade, and extraction takes place at existing natural ventilation system channels. [ABSTRACT FROM AUTHOR]

To make reasonable solutions concerning integration of PV into the façade, complex assessment must be performed at the design stage of the building, taking into account all benefits and losses. The paper presents multi-criteria analysis of semi-transparent BIPV. It is based on 4 criteria: energy, ecology, economy, comfort - 3e+c. Results show that because of twice lower solar heat gains, PV window enables to save almost half of cooling energy, it also significantly improves thermal comfort. Total primary energy demand of the office after application of PV drops from 171 kWh/m2 to 96 kWh/m2. Multi-criteria analysis shows that office with BIPV is more sustainable than the one with transparent window. [ABSTRACT FROM AUTHOR]

The paper analyses the insulation expediency of the external envelopes of the building with reference to 2E (energy - primary energy consumption and environmental - CO, emissions) criteria and presents an overview of thermal insulation and studies on other structural elements based on life cycle analysis. The object of research is a typical residential building. The article determines different insulation materials of external envelopes, primary energy consumption and CO, emissions by insulating walls from F to B and from B to A ++ class. Graphical interpretation shows primary energy, CO, and the payback period of 60 years. Also, the paper considers primary energy and CO, emissions distributed at various life cycle stages. [ABSTRACT FROM AUTHOR]

The paper explains the results of a detailed energy audit of the buildings of Vilnius Gediminas Technical University. Energy audits were performed with reference to the international scientitle project. The article presents the methodology and results of detailed measurements of energy balance characteristics. [ABSTRACT FROM AUTHOR]

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The paper presents one of the methods of solving unsteady heat transfer problems in buildings, based on the active heat capacity conception. The influence of active heat capacity and the intermittent heating effect on the microclimate in premises and thermal energy consumption were estimated. [ABSTRACT FROM AUTHOR]

All energy processes in buildings are usually unsteady, ie time dependent. But mostly the unsteady factors influence is not taken into consideration for energy demands, microclimate changes estimating. Therefore the practical observations and theoretical investigations show an undesirable behaviour of indoor thermal microclimate and energy use, even with modern enough control systems. As a result, new methods for problem solution and investigations develop. The paper presents some theoretical aspects of unsteady heat transfer analysis based on the energy conservation law. Additionally, an experimental research made at Solar energy investigation centre in Spain -- Plataforma Solar de Almeria -- results and its comparison with theoretical calculations are produced. [ABSTRACT FROM AUTHOR]

Latent heat thermal energy storage systems allow storing large amounts of energy in relatively small volumes. Phase change materials (PCMs) are used as a latent heat storage medium. However, low thermal conductivity of most PCMs results in long melting (charging) and solidification (discharging) processes. This study focuses on the PCM melting process in a fin-and-tube type copper heat exchanger. The aim of this study is to define analytically natural convection heat transfer coefficient and compare the results with experimental data. The study shows how the local heat transfer coefficient changes in different areas of the heat exchanger and how it is affected by the choice of characteristic length and boundary conditions. It has been determined that applying the calculation method of the natural convection occurring in the channel leads to results that are closer to the experiment. Using this method, the average values of the heat transfer coefficient (have) during the entire charging process was obtained 68 W/m2K, compared to the experimental result have = 61 W/m2K. This is beneficial in the predesign stage of PCM-based thermal energy storage units. [ABSTRACT FROM AUTHOR]