A New Energy Model for Madrid: Urban Nanoclimates

Transcription

1 A New Energy Model for Madrid: Urban Nanoclimates Speakers: Carmona Casado; Juan Carlos Camilo José Cela University, Madrid, Spain. Abstract: This research work is aimed at making evident the significant gradient of temperature (up to 6 ºC) at street level within the same urban environment (not larger of 2 Km in length) and with measurements taken at the same hour, day and month of the year. Energy savings will be quantified by producing a more reliable climate database at the level of an urban block, thus introducing the new concept of Urban Nanoclimate to produce more accurate environmental simulations. These temperature gradients on building external conditions, for the same urban environment, make possible to propose a new alternative by describing in detail the regulation in force. This may lead to a saving model not considered so far, but very useful from an energy viewpoint. Keywords: Urban Nanoclimate, saving, energy model, efficiency State of the Art If we are aware of the existence of microclimates inside microclimates in an urban environment at the scale of a neighborhood or block, we generate a much more effective description of the climate reality than the one established in the regulation in force of the Building Technical Code. We will change then the prefix and rename the new situation as Urban Nanoclimates. Just think about the meaning of this (...) (1) This discourse awakened inside me an arduous interest in first-hand knowning and showing the existence of these Nanoclimates, and more specifically in quantifying the Energy Saving that the assumption of its existence would provide to our architecture. The theoretical framework was indisputable: Heat Island effect (2), very general climate databases based on measurements from weather stations fixed in places far away from the city and one another, very general Technical Regulations based on previous data, range of analysis constrained to a city scale A first approach, thermometer in hand, took us to analyze the physical and architectonic environment of Alcalá Street, Madrid. More specifically, a stretch of this street going from Cibeles Square (around number 20) to its intersection with Arturo Soria Street (around number 414). This first touchdown was highly revealing, to the point of being able to see firsthand, differences amounting up to 4 ºC among different measurement points. This first

2 evidence opened a precise path towards a new conception of energy consumption in buildings: we could quantify reliable differences among the thermal charges of buildings in terms of the demand according to the current and general regulation and weather data and those that can be postulated from a new existent physical situation. We are well aware that this is a first step towards a new conception of energy saving. The climate data used in the current regulation address clino periods, weighted mean of the data obtained within the last 30 years, while our study is based on measurements obtained in a single year. Because of this, we shall specify that it is not a matter of generating a new database, but of stressing and quantifying in percentage and economic terms the new discovered architectonic reality. The new temperature values are not so important as the differences or increments among them. Once the matters of study within a given urban environment are determined, we shall extract from the databases generated the corresponding values of temperature, relative humidity, wind speed and atmospheric pressure (3). Among these values, the first ones are those truly meaningful regarding a quantification of the real temperature increase, unconsidered by the Measurement Integral System (SIM) that the Honourable Ayuntamiento de Madrid has established in the city, but in our opinion at a larger scale than that suggested in our hypothesis. Additional data of relative humidity, wind speed and barometric pressure will be used as reliable signatures justifying temperature increments in our chosen physical environment. Antecedents The existing studies on urban climate have mainly focused on confirming the existence of a temperature gradient in favor of the downtown, between the latter and the city suburbs. The first study is relatively early and was verified in London (Howard, 1818). Ulterior studies in Paris and Vienna corroborated the same phenomenon, which was called a heat urban island by Manley in It was readily noticed that a temperature difference is associated with a humidity difference, in inverse order. The discovery of this double climate phenomenon, together with the publication of the former general works on urban climate, as well as the international symposium on urban climates in 1968, sponsored by the WMO (WMO, 1970), motivated the research on local basis urban climatology, mainly focused on the acknowledgement of the heat island in different cities, these studies being of a relatively easy methodology.

3 Nowadays it can be said that most of world metropolis count on climatic studies at two level analysis. One of them, preliminary, with an essentially approximate and descriptive nature; in the other, more recent and deeper, urban climate is analyzed in its complexity, with climatic and urban implications, and where the concept of microclimate is developed. With respect to the methodology, we know that in order to clearly determine the existence of microclimate differences within the city it is not enough dealing with observations coming from usual weather stations, since their main scope is very different regarding the spatial scale and, therefore, their data cannot be taken as a reference. Hence it is necessary to carry out a direct observation of the climate elements by means of systematically making meteorological measures on the ground. This procedure, very usual at present, constituted a decisive advance in the study of the city climate, apparently first used by Schmidt in 1930 in Vienna, introducing a new technique that has been revealed along these years to be a very useful and efficient tool to study the temperature differences observed within the cities. In Spain all these studies have been rather scarce. Researchers from the CSIC, in Madrid, have tried to cover the gap with a preliminary pioneering publication (López Gómez, 1988). Later on, some analogous investigations have also been carried out in other Spanish cities, such as Barcelona (C. Carreras, M. Marin, J. Martin Vide, M. Moreno, J. Sabí, 1990), Logroño (Ortigosa Izquierdo, Sobrón García, Gomez Villar, 1998), Madrid (ESA, Universidad de Valencia, Universidades Autónoma and Complutense de Madrid, Universidad de Vigo, CIEMAT, AEMET, CECAF, 2008), Bilbao (Tecnalia, Universidad de Kassel (Alemania), 2011). The work here presented is inserted into the same effort, but it also intends to give a stroke of rigor so that from the results obtained it will begin a reflection on the implications of including nanoclimate conditions in Town Planning Regulations and/or Energy Efficiency. As already discussed, London was the first one in attracting attention of this type of research since the beginning of the XIXth century (Howard, 1818), becoming a paradigm of the heat island phenomenon (Chandler, 1961) and the studies on urban microclimate (Chandler, 1965). Nonetheless, in recent years pioneering studies funded by European funds have been carried out in some North-Western cities, such as the cities of Rotterdam and Arnhem (Netherlands) and Athens (Greece) (Future Cities Programme; University of Wageningen (Netherlands), with the objective that their results will be taken into account to improve the town planning, and to develop standards and urban design tools. New York City has a preliminary study about the heat island (Bornstein, 1968). Obviously, Tokyo is among the more studied Japanese cities, with many works on urban microclimate (Kayane, 1964; Sasakura, 1965; Nishizawa,

4 1979). In Latin America, Mexico City (Jáuregui, 1973), Rio de Janeiro (Gallego, 1972) and especially Sao Paulo with a thesis constructed from information taken from satellite pictures (Lombardo, 1985) are worth mentioning. Regarding the inclusion of the results obtained from the various existing investigations carried out worldwide, as mentioned above, into the Town Planning and/or Temperature Regulations or of Energy Efficiency, it follows that issues on climatic zoning within a city or a province have not been taken into account, but the existing classifications are much wider, usually covering regions, cities, or even boroughs in the most rigorous ones. In the United States of America, the ASHRAE Standards; in Latin America, we highlight the Normativa Térmica de Argentina (IRAM); in Europe, it is worth mentioning, for example, the French Réglementation Thermique (TR) and, of course, our Código Técnico de la Edificación Environment of study Figure 1: Google Earth study environment Within the urban fabric of Madrid we choose one of its most representative streets as working area, in particular, a stretch of 5, m, East-West oriented, between its intersections with Recoletos promenade, at Cibeles Square (Point 1), and Arturo Soria Street, more East. Figure 2: Google Earth study environment

5 It seems reasonable to establish a grid of measurement points along a rectilinear path with a maximum distance of 250 m between consecutive points. In this way a table is generated, which will be able to verify variations of up to half a Celsius degree in relatively short distances within the urban scale that we are considering. It is also intended to establish a clear difference between sidewalks in the shade and under the action of solar radiation. Because of this, two simultaneous measurements for each sidewalk are carried out in order to remove the possibility of needing a weighted mean of the results by taking a single daily measure. In the case of two measurements, a single sidewalk could have been considered to generate the daily mean values necessary to work and to carry out the corresponding energy calculations. Similarly all those aspects of the urban morphology that may affect the recorded temperature differences will be analyzed, to take them into account when generating any kind of respective conclusion: vegetation or its absence, pavement class, degree of traffic at the street, width, users, finish colors of the façade materials and street furniture (incidents in the albedo) We therefore have a solid basis to support our investigation regarding the proposal of a new concept to understand Energy Savings, such as it is suggested by the European guidelines in this matter. The supervised field work, regarding physical measures, corresponds to an anual planning, with a minimum of two weekly measurements, on alternate days, and at the same solar time. To make the students work easier concerning availability, no measurement will be taken over the weekend (less user traffic than usual in the street), nor in consecutive days in order to establish feasible differences in the performed measurements. Calculation method Once the climate database to be used is set, we shall establish a standard virtual model to compute the different heating and refrigerating (in the wintertime and summertime, respectively), and ventilation (in both seasons) demands according to different positions of such a model within the chosen urban environment. The difference between the results obtained will allow us to quantify the saving percentage that we can suggest, following this new methodology, and with respect to the reference values currently accepted. Figure 3: data-collection card model

6 Therefore, any energy difference will be understood as a saving, since the design to be considered in the architecture that addresses the needs of that plot of the urban grid will be affected by these new computed values, much closer to the existing physical reality. TRABAJO DE CAMPO A01 MES SEPTIEMBRE ⁰ N 3⁰ O DIA TEMPERATURA ( C) HUMEDAD RELATIVA (%) VELOCIDAD VIENTO (m/s) PRESIÓN ATMOSF. (kpa) MED TEMP Hª 3 23,80 48,20 0,80 93,98 20, ,10 49,70 0,70 93,96 20, ,90 44,10 0,40 94,40 20, ,80 48,70 0,50 94,39 20, ,60 46,00 0,00 93,52 20, ,50 38,10 0,00 93,87 20, ,10 39,60 0,30 93,61 20, ,30 39,80 0,00 93,56 20,50 MEDIA 23,26 44,28 0,34 93,91 20,50 COTA 687,77 TOMA DE DATOS CLIMATOLOGICOS C/ ALCALÁ - MADRID Field measurement model Measurement tables will be thus generated for each month of the year at each point of study, with the purpose of establishing weighted monthly means during the most unfavorable simulation periods (winter and summer). 100,00 80,00 60,00 40,00 20,00 0,00 35,00 30,00 25,00 Presión Atmosférica (kpa) 20,00 Humedad Relativa (%) Velocidad Viento (m/s) 15,00 Temperatura (ºC) 10,00 Temperatura Media Hª 5,00 0, Figure 3: data-collection card model Choice of the architectonic model to be simulated Within the study environment, we have a wide range of typologies, building systems and singular buildings that can properly define Madrid s architectonic environment in a given period. It is precisely because of this that the choice of one model or another is not that important, but keeping the particular choice and choose, apart from the real position, other virtual locations of plots with the purpose of being able to simulate the weather conditions measured in the field work. In this way, we will be able to make evident the different thermal charges (and, consequently, different energy demands) that are generated from new external conditions. We will try to make evident that within the same urban environment, even at the scale of a neighborhood or a block, there are (positive and negative) increments of temperature with respect to the temperature mean value out of the city, the latter being used in any energy calculation (this reference mean value comes from the closest weather station, namely Retiro, in our case). We shall thus focus in increments and not in given values of temperature to reproduce the virtual conditions for the same model in different environments. In this way, the measurement scale will always be the same and we will be able to conclude why we can detect such differences.

7 After the previous assumptions, we decided to consider a characteristic model for living block, in principle framed in time around half the urban life of the axis of Alcalá Street, corresponding to an architectonic typology of closed block, dwelling row house, with main façade and a service inner yard with two side bays housing dwellings. The year of construction of the chosen dwelling block is 1955, a decisive year for Madrid s urban history, which coincides with the construction of social housing neighborhoods and supervised villages in the city (Hortaleza, Canillas, ). Our study model will then be a reference building with the same typology to the one located in 308 Alcalá Street. Conclusions Figure 4: Planimetry and views of the reference building in 308 Alcalá Street

8 COMPARACIÓN ENERGÉTICA DE PUNTOS DE SIMULACIÓN A1 A2 B1 B2 C1 C2 P % CARGAS (W) REFRIG. CALEF. REFRIG. CALEF. REFRIG. CALEF. REFRIG. CALEF. REFRIG. CALEF. REFRIG. CALEF. REFRIG. CALEF. REFRIG. CALEF. PLANTA SÓTANO 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 PLANTA BAJA 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 PLANTA , , , , , , , , , , , , , ,35 1,92 1,76 PLANTA , , , , , , , , , , , , , ,33 1,76 1,19 PLANTA , , , , , , , , , , , , , ,65 1,76 1,19 PLANTA , , , , , , , , , , , , , ,31 2,22 1,20 PLANTA ATICO 8.197, , , , , , , , , , , , , ,06 1,67 1,22 TOTAL EDIFICIO 34636, , , , , , , , , , , , , ,00 9,32 6,56 COMPARACIÓN ENERGÉTICA DE PUNTOS DE SIMULACIÓN P % CARGAS (W) REFRIG. CALEF. REFRIG. CALEF. PLANTA SÓTANO 0,00 0,00 0,00 0,00 PLANTA BAJA 0,00 0,00 0,00 0,00 PLANTA , ,35 1,92 1,76 PLANTA , ,33 1,76 1,19 PLANTA , ,65 1,76 1,19 PLANTA , ,31 2,22 1,20 PLANTA ATICO 3.290, ,06 1,67 1,22 TOTAL EDIFICIO , ,00 9,32 6,56 From the results obtained, we corroborate that according to the position of the building within the same urban environment, due to the influence of a series of factors here analyzed (new climate database, orientation, sun exposure, shades, ) we may obtain a difference of up to 9.32% concerning refrigeration charges and up to 6.56% for the heating ones. Other factors such as traffic, materials, vegetation, use, will be decisive to climatology classify each part of the city. A difference of up to 10% in energy demand per dwelling implies a remarkable economical saving when going up in the urban scale (building-block-borough-city). Because of this, we shall always advocate for an institutional and political turn towards this path by only redefining the existing legal framework: we may become efficient in Architecture without making Architecture. References: (1) Excerpt from master class given by D. José Miguel de Prada Poole in his course on Análisis de Proyectos Paradigmáticos, within the Master in Energy Efficiency and Bioclimatic Architecture, at Universidad Camilo José Cela. July 2011 (2) Antonio López Gómez, Julia López Gómez, Felipe Fernández García, Antonio Moreno Jiménez. El clima urbano. Teledetección de la isla de calor en Madrid. Ministerio de Obras Públicas y Transportes