Francisco José Sánchez de la Flor

Flow Pattern Effects on Night Cooling Ventilation

Abstract Passive cooling techniques such as night time cross ventilation can potentially provide substantialcooling energy savings in warm climates. The efficiency of night cooling ventilation is determined by three main factors: the external airflow rate in the room, the flow pattern and the thermal mass distribution. The aim of this paper is to analyse the effect of the enclosure shape and the situation of inlet/outlet openings on the total cooling energy stored in the structure. This analysis presents a comprehensive sample of typologies to generate guidelines which can help the designer with the distribution of the thermal mass and inlet/outlet openings in the enclosure. The approach combines a theoretical analysis which characterizes the enclosure charge/discharge time constants and storage efficiencies with simulation studies based on computational fluid dynamics software (CFD).

Simulation Model for Some Types of Double Envelope Elements

Abstract It has been found that, among the tools and methods available for the energy calculation of double envelope elements, there are some debatable aspects such as: the selection of correlations for calculating the convective heat transfer coefficient and the procedure for calculating the temperature of the air layer. In addition, the validation of some models only refers to specific cases or no information is available whether or not a validation has been performed. This paper presents a transient model for the energy calculation of double envelope elements, using correlations for the calculations of the convective heat transfer coefficients specifically developed for this type of element. For validation, information reported by other authors has been used. This model can be applied to those elements with an opaque or semitransparent exterior envelope (usually glazing) of negligible thermal inertia, an air layer thickness less than 0.1 m, and an opaque interior envelope (usually a massive wall) with or without thermal inertia. This model is suitable for short time step calculations.

ME3A: Software tool for the identification of energy saving measures in existing buildings: Automated identification of saving measures for buildings using measured energy consumptions

At present, actions for the rehabilitation of cities, districts and buildings are being promoted for tertiary as well as for residential buildings. However, the difficulty of assessing the energy savings achieved after energy efficiency improvement measures (or even worse, a combination of them which have cross effects) with enough certainty is well known. The tendency in order to solve this issue is the use of buildings energy performance simulation tools, either detailed or simplified. Nevertheless, the estimation of the energy consumption made by these tools differs from the measured values, due to either the case definition or the assumptions taken into account. This publication aims to present a solution for both of the above mentioned problems, by using a simulation tool which has been corrected with climatic and consumption measured data. This tool has been developed within the framework of the project ME3A-Energy Efficiency Improvement of Buildings in Andalusia (2014–2016), funded by the Regional Government of Andalusia. The main development work is the correction of the simulation tool using consumption data counters monitored in the building, so this development is tested in three building and this paper shows the results of one of them. The benefits presented by this tool are the result of the previously carried out research, which was focused on the automated generation of baselines through which the estimated energy situation made by the official tool and the real measurement can be corrected. These baselines are stated in terms of the main energetic parameters that define a building. In this way, they are converted into a diagnostic protocol with which energetic indicators and the expected reference values can be compared. This methodology shows as a result the optimal rehabilitation project in economic and energetic terms. It is worth mentioning that the developed tool is integrated as a complement within the existing methodology of energy certification (CE3). Therefore, apart from drawing data from the building definition and its systems (performed by the official tool), it allows to obtain the modified official certificate once the optimal rehabilitation project has been chosen.

Ventilation and Architectural Design Strategies for Cooling Office Buildings in Different Climates of Chile

In Office buildings in Chile, cooling energy demand is higher than heating demand. The climate of the country show important differences between cities by the ocean and those of interior regions. Main cities of Central Chile are Santiago and Valparaiso, both located at around 33°S. Santiago presents a Mediterranean climate, with a high temperature oscillation between day and night during cooling period. Valparaiso, by the coast, shows lower temperature fluctuation compared with Santiago during identical period. In order to define design strategies for energy efficiency of office buildings in mentioned cities, a sensitivity study has been made, considering variables like window to wall ratio, type of windows (clear and selective glazing, including low e, single and double glazing), use and type of external solar protection (ESP) and use of nocturnal or diurnal ventilation. In opaque facades, thermal insulation is considered. In case of walls, in order to increase thermal inertia external insulation is assumed. The sensitivity analysis is developed considering a square building containing office rooms on all four orientations. This 10 story building has been specially proposed and designed for this analysis. Methodology considers an evaluation of heating and cooling demand of the building in both cities. For this purpose, simulation software under dynamic conditions has been used (TAS). The lowest cooling energy demand is reached when using the lowest window to wall ratio (20 %), with ESP in east, west and north oriented glazed areas. In fact, fully glazed facades in both cities are not recommended. Nocturnal ventilation was highly effective for decreasing cooling demand in both cities. In the case of Valparaiso, due to relatively low temperature during cooling period (maximum lower than 26 °C), diurnal ventilation for cooling purposes is also effective.