Natural resources such as daylight and sunlight are highly appreciated in countries with prevailing overcast skies. Taking advantage of this scarce resource contributes to saving energy on arti¿cial lighting. In contrast to northern, southern European cities are distinguished by a large number of days with direct sunlight caused by a propitious climate condition. While it is a positive issue in terms of energy availability, the abundance of it can be counterproductive if management measures are not taken. Apart from the thermal consequences, lighting penetration into buildings causes a great contrast between inside and outside. This is especially critical when the visual system does not have enough time to adapt, as happens at entrance areas. The aim of this study is to analyze the light contrast between these areas and the urban outside in sunny conditions. To attain this objective, light data from ¿ve entrance spaces and their contiguous streets were analyzed and measured. The results were divided into three zones in the visual scene, showing an increasing contrast from top to bottom of the visual ¿eld. It may be concluded that interventions applied to urban areas and building pavements can improve visual adaptation in the transition zone.
Energy is considered as a main influence on urban configurations. However, there is a difficulty on translating the city models based on theoretical renewable energy concepts into practical applications. This study considers the possibility of understanding this future model as a transformation of the existing urban centres. With this objective, a methodology to intervene in existing cities based on the study of solar access is developed. Therefore, an analysis of solar potential in relation with urban morphology is carried on through a simulation software in l’Eixample, a neighbourhood of Barcelona. The distribution of the sun factor in the different areas of the building blocks envelope displays possible morphological modifications that would facilitate solar energy collection. Consequently, the analytical method presented could be applied to regulate urban interventions with the aim of obtaining more solar energy based cities.
Rodríguez , J. A.; Coch, H.; de la Paz, G.; Chaos, M.; Matzarakis, A. International journal of biometeorology Vol. 60, num. 8, p. 1151-1164 DOI: 10.1007/s00484-015-1109-4 Data de publicació: 2015-12 Article en revista
Climate regional characteristics, urban environmental conditions, and outdoors thermal comfort requirements of residents are important for urban planning. Basic studies of urban microclimate can provide information and useful resources to predict and improve thermal conditions in hot-humid climatic regions. The paper analyzes the thermal bioclimate and its influence as urban design factor in Cuba, using Physiologically Equivalent Temperature (PET). Simulations of wind speed variations and shade conditions were performed to quantify changes in thermal bioclimate due to possible modifications in urban morphology. Climate data from Havana, Camagüey, and Santiago of Cuba for the period 2001 to 2012 were used to calculate PET with the RayMan model. The results show that changes in meteorological parameters influence the urban microclimate, and consequently modify the thermal conditions in outdoors spaces. Shade is the predominant strategy to improve urban microclimate with more significant benefits in terms of PET higher than 30 °C. For climatic regions such as the analyzed ones, human thermal comfort can be improved by a wind speed modification for thresholds of PET above 30 °C, and by a wind speed decreases in conditions below 26 °C. The improvement of human thermal conditions is crucial for urban sustainability. On this regards, our study is a contribution for urban designers, due to the possibility of taking advantage of results for improving microclimatic conditions based on urban forms. The results may enable urban planners to create spaces that people prefer to visit, and also are usable in the reconfiguration of cities.
The combined effects of urban heat island (UHI), urban population growth and energy overexploitation are undermining the safety of urban areas. Urban morphology plays a prominent role in this context, because it affects building's energy demand and local climate at urban scale. However, this contribution is recurrently neglected. The present contribution seeks to investigate the direct and indirect effect of urban morphology on buildings energy performance in the Mediterranean
climate. Urban morphology affects energy demand by modifying two relevant variables: outdoor air temperatures and incident radiation. The relevance of these effects were studied on a sample of urban textures of Rome and Barcelona. The study is parametric in approach. The textures were modelled and parameterized and their performances were compared. The UHI in different urban textures was calculated, by Urban Weather Generator tool. Then a sensitivity analysis of the building energy demand to the outdoor air emperatures and the incoming solar radiation was carried out, by EnergyPlus engine. Results confirm the relevance of urban morphology to the UHI intensity. Warmer temperatures lead to an average increase of energy demand from 10% to 35%, according to different urban densities. At the same time, the incident radiation reduction due to urban obstruction is desirable in Mediterranean climate; it allows a reduction of annual energy demand up to the 19% compared to an unobstructed environment. Therefore, relevant errors may occur if urban morphology’s contribution to energy demand is neglected, approximately 89% for space heating and 131% for space cooling calculations, depending on the texture density and the building orientation.
The link between city morphology and urban energy consumption, although proved, requires further research. In that sense, the analysis of parameters describing the urban texture may be a useful approach for energy assessment at a city scale. Some geometrical parameters have been used to study urban energy aspects related to the radiative phenomena, such as heat island or even a rough indicator of solar energy availability in locations where direct radiation is not determining. This paper aims to explore the correlation between one of these parameters -the Sky Factor (SF)- and direct solar radiation over facades, as a characterization tool of solar access within an urban context. Barcelona, a Mediterranean city where direct sunlight and the built environment density are deciding factors, has been chosen as case study. At different points of the facade for several urban canyons, SF value and direct solar radiation for different orientations and times of the year have been computed using Heliodon software. Both results have been related one to another and it has been found that, for a specific latitude, it is possible to define a smooth dependence between these parameters, if the orientation is taken into account. This paper shows that, beyond the SF threshold of 0.42, direct solar radiation on the facade reaches an almost asymptotic value for all orientations and times of the year.
The present study deals with the potential reduction of energy consumption for lighting of shop window displays in the Mediterranean countries. Urban commerce has a very high impact on economics and it is a highly energy-consuming sector. Light has the power of attracting people’s attention, which is one of the goals of the trading and selling activity and very high illuminance levels are usually recommended. In the Mediterranean areas, where daytime lasts for many hours, commercial activity takes place mainly under sunshine conditions and shop windows frequently fail to fulfil their main corporative goal, namely the unobstructed observation of the products exhibited. The necessary increase of artificial lighting illuminance levels to accent interior light conditions, due to extremely high-luminance urban surroundings, leads to an important increase of energy consumption. Nevertheless, the results are generally very poor, due to reflections and other kinds of visual problems. The present study evaluates the visual and energetic benefits of an innovative passive design that obstructs solar rays and redirects them into the interior of the shop window scene. A scale model of this new design confirms the visual benefits produced by its use, via the different luminance maps tested.
As a result of the current economic and energy crisis, it has become necessary to rethink
urban planning, starting from a global concept of efficiency and considering buildings not as
isolated entities, but as part of an urban system, which consumes energy on a much larger
The connection between urban morphology and microclimate is a widely discussed question,
including issues like the urban heat island phenomenon or outdoor comfort in open spaces.
However, there is still a lot of work to be done regarding the influence of these microclimatic
variations on building energy consumption. In that sense, would it be possible to apply
efficient measures of microclimate modification on an urban scale to increase comfort levels
in public spaces while at the same time, reducing building consumption?
This paper focuses on urban canopy shading. Its effectiveness as a shading device and its
capability to improve outdoor climate in areas with an excess of solar radiation is widely
demonstrated. In this case, its effect on indoor climate of is evaluated.
The case study is located in Cordoba (Spain), as an example of a climate with a hot and dry
summer (according to CTE, level 4). A complete street canyon model has been created. Two
buildings, one on each side of the street canyon, have been tested using an energy
simulation software (Design Builder). Model features and simulation settings correspond to
real values. Urban canopy shading effectiveness has been analyzed according to cooling
demand decrease, taking into account both buildings. Spatial factors (street orientation,
width-height ratio, windows-opaque ratio) and material factors (U-values and skin mass, %
obstruction) have been considered.
Results show 18% to 45% cooling demand decrease due to the canopy shading. Spatial
factors are much more relevant than material factors: windows-opaque ratio is a determining
factor, in contrast to mass and U-values. This study shows the importance of evaluating both
urban facades, which means working from an urban perspective beyond the local scale of a
The present study deals with the potential reduction of energy consumption for the lighting of shop window displays, which is a highly energy-consuming sector. Light has the power of attracting people´s attention, which is one of the goals of the trading and selling activity and very high illuminance levels are usually recommended. In the Mediterranean areas, where daytime lasts for many hours, commercial activity takes place mainly under sunshine conditions and shop windows frequently fail to fulfil their main corporative goal, namely the unobstructed observation of the products exhibited. The necessary increase of artificial lighting illuminance levels to accent interior light conditions, due to extremely high-luminance urban surroundings, leads to an important increase of energy consumption, as a common solution. Nevertheless, the results are generally very poor, because reflections and other kinds of visual problems still defy solution and the final result is an economic and energy waste during daytime, especially in low latitude countries. The present study evaluates the visual and energetic benefits of an innovative passive design that obstructs solar rays and redirects them into the interior of the shop window scene. A scale model of this new design confirms the visual benefits produced by its use, via the different luminance maps tested. This new lighting passive system results in a very simple, effective and low cost solution. The most important fact is that high illuminance levels are achieved and, simultaneously, there is important energy reduction, taking advantage of natural light instead of competing with sun power.
The absence of solar radiation at night gives good opportunities for passive cooling of buildings in hot climates with frequently clear sky. However the possibility of also taking advantage of a clear sky cooling potential during the day is seldom considered.
Thermal radiation to sky can be used to cool. A body surface emits thermal radiation (far IR) and if direct solar radiation (visible and near IR) and thermal radiation coming from other surfaces do not reach it, there would be a net heat flux out.
A previous prototype was done with a simple element. That experiment confirmed that was possible to reduce around two degrees the interior temperature of the test unit exposed to sun light in July.
In this work a new design based on the first one is developed to adapt it to architectonical needs in order to reduce interior spaces temperature in hot climates.
The aim of this design is focused to so an architectonical adaptation is needed. Modular and replicable units could be a solution that permits to fulfill large flat surfaces as roofs or other architectonic elements. In this occasion, measurements were taken from a modular model with a geometrical design that avoided de direct solar incidence. These measurements were taken by a pyrgeometer during two weeks of August and results were similar to the previous experiment.
Coch, H.; Pardal, C.; Pages-Ramon, A.; Isalgue, A.; Crespo, I. World Renewable Energy Congress / Network p. 569-579 DOI: 10.1007/s00484-015-1109-4 Data de presentació: 2014-08 Presentació treball a congrés