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Abstract: This paper presents a thermal analysis of a building concrete roof with vertical cylindrical holes filled with phase change material (PCM). The objective of incorporating the PCM into the concrete roof is to increase the value of thermal mass of the roof. The PCM absorbs the heat through the melting process before it reaches the indoor space, and thus reducing the heat gain. Numerical method is extensively utilized in this research and it is validated with experimental work. The thermal effectiveness of the proposed concrete roof with PCM is assessed by comparing the heat flux at the indoor surface with that of solid concrete roof during the day. A parametric study is conducted to evaluate the effects of the cylindrical holes dimension, PCM melting temperature, and operating month on the heat gain. The results indicate that heat gain can be reduced significantly with larger PCM holes diameter. The PCM melting temperature of PCM should be selected based on the operating month and working hours for the best performance. For the examine cases in this research, the heat flux at the indoor surface of the roof is reduced between 9% and 17.26%, depending on the selected PCM, working hours, and operating month. [Copyright &y& Elsevier]

Abstract: Iran is a country with five different climates and 50°C temperature difference between its warmest and coldest regions. In the present paper, the prime-mover capacity of a CCHP system for the same building in five different climates is determined. For this purpose, five cities from these climates are chosen and their weather information for the last five years is gathered from the Iran Metrological Organization. The hourly load of the five cities for the whole year is calculated and the maximum rectangle method is used to determine the size of the prime mover and the recommended full load operation time. The results show that the CCHP system saves energy during the whole year for all the climates. The yearly average fuel energy saving ratio of 37.85%, 33.16%, 30.75%, 29.60% and 25.30% are achieved for Chabahar, Ahwaz, Kamyaran, Tehran and Bandar Anzali, respectively. Furthermore, the analyses show that no heating system is needed for the cities of Chabahar and Ahwaz, but an auxiliary boiler is needed for all the climates to compensate the lack of heating or to support the absorption chiller. The sensitivity analysis shows that the hourly load of building is least sensitive to the minimum wet bulb temperature. [Copyright &y& Elsevier]

Abstract: Energy use in the built environment represents a large part of total energy use in Sweden and is one important sector where energy conservation needs to be significantly improved in order to meet the national implementation of the European goals. One key question that needs to be investigated in relation to these goals is the performance and implementation of passive or low-energy houses. This paper presents results and an evaluation of a newly built house in an area with passive houses in Linköping, Sweden. Nine passive houses were built with the aim to be energy efficient, with an annual space heating demand of 21kWh/m2, and at the same time to have the same visual appearance as any other building in the surrounding area. This study evaluates the energy performance of a residential area with low-energy buildings based on Building Energy Simulation (BES) (IDA ICE 4), and measurements from the real object. Both annual and hourly validation is performed using room by room modeling and internal heat gains. A novel approach to internal heat gain modeling is presented using time-use data (TUD). The results show possible improvements in the design, the building envelope and in the heating control. [Copyright &y& Elsevier]

Abstract: This paper presents a detailed meta-analysis of end and primary energy use for heating, cooling and ventilation of 11 low-energy non-residential buildings and one residential building in Germany that belong to the EnOB research program launched by the German Federal Ministry for Economy. In particular, the analysis emphasizes the substantial impact of auxiliary energy use on the efficiency of heating and cooling performance. The investigated buildings employ environmental energy sources and sinks – such as the ground, ground water, rainwater and the ambient air – in combination with thermo-active building systems. These concepts are promising approaches for slashing the primary energy use of buildings without violating occupant thermal comfort. A limited primary energy use of about 100kWhprim/(m2 neta) as a target for the complete building service technology (HVAC and lighting) was postulated for all buildings presented. With respect to this premise, a comprehensive long-term monitoring in high time resolution was carried out over the course of two to five years, with an accompanying commissioning of the building performance. Measurements include the energy use for heating, cooling, and ventilation, as well as the auxiliary equipment, the performance of the environmental heat source and sink, and local climatic site conditions. [Copyright &y& Elsevier]

Abstract: The large thermal time constant of thermally activated building systems (TABS) hampers communication between the system''s production and emission. Therefore, conventional building control strategies, typically using room temperature feedback, are unadapted to control thermal comfort efficiently. In this paper, measurement data and simulation results reveal that unadapted TABS control has a dramatic impact on overall energy performance. Measurements in a TABS building with room temperature feedback show the HVAC system switching between heating and cooling in a very short time frame. A simplified, generic room model is used to simulate, understand and evaluate this behaviour. For room temperature feedback control, only 45% of the cold and 15% of the heat produced actually controls room temperature. The remainder is stored in the TABS and exchanged between the heating and cooling system. Enlarging the heating-to-cooling set point band improves this ratio, while maintaining thermal comfort. On the other hand, night time operation control of the circulation pump, adapted to the TABS thermal time constant, eliminates this ‘unused’ energy completely. In this case, however, even with perfect heat gain forecasts, it is difficult to avoid room temperatures dropping below thermal comfort limits during initial office hours. Hence, a supplementary air-conditioning system seems inevitable. [Copyright &y& Elsevier]