Urban Heat Island Prediction in the Mediterranean Context: An Evaluation of the Urban Weather Generator Model (original) (raw)
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International Journal of Sustainable Development and Planning, 2023
Urban areas can be characterized by higher outdoor air temperatures than rural ones due to the well-known Urban Heat Island (UHI) phenomenon. This significantly affects buildings energy performance, thus influencing energy needs in terms of cooling and heating. Starting from this, the UHI in Rome was here investigated, providing an updated estimation through 2022 climate data. The influence of the UHI on energy efficiency in buildings has been highlighted by applying climatic data logged by different weather stations within a dynamic simulation tool. Thus, actual climate data have been used as thermal boundary conditions to simulate typical building energy needs, for cooling and heating. The findings of this study demonstrate a notable disparity in climatic conditions between the areas outside the city and the urban context. The maximum values of UHI intensities for daytime and night-time were identified as 3.1℃ and 3.5℃, respectively. Moreover, the accurate selection of reference data is a crucial factor for obtaining reliable information regarding the energy demands of buildings within the city. The findings emphasized that utilizing data from airport stations instead of weather stations within urban areas can result in disparities up to approximately-17% for heating and more than 50% for cooling requirements.
Energy & Buildings, 2017
A wide variety of weather-data are readily available for simulating buildings energy performance by using dynamic software. However, climate change and its effects on buildings energy performance represent a critical issue, also considering the implications of climate change on human comfort. Starting from this, the present study aims at analyzing the climatic conditions in Rome and its surroundings, evaluating the occurrence of the Urban Heat Island (UHI) phenomenon. Therefore, meteorological data derived from two airports near the city and climatic data registered for two years in a central, densely-built zone of Rome were analyzed and compared. Furthermore, the differences among weather data were tested by means of a commonly used dynamic software in order to evaluate the effects of different climatic boundary conditions on building energy performance, in terms of heating and cooling energy demands. The results highlight significant differences with regard to temperature, wind velocity and relative humidity, as a result of a prevailing UHI phenomenon in central Rome throughout the year. The simulations show an average increase of cooling energy demand of about 30% and an average reduction of heating energy demand of about 11%. Such differences give the rise for the investigation of the reliability of weather-data files commonly used in building simulations, in order to properly estimate the buildings energy demand under a sustainable city perspective.
Tecnica Italiana-Italian Journal of Engineering Science, 2021
It is well known that the building sector is one of the main responsible for energy consumption in the current global energy scenario. In this context, the concept of efficient buildings passes through newly built and retrofitted constructions. Thus, buildings energy software become essential tools for achieving energy savings, designing the so-called green buildings, and evaluating different energy retrofit solutions for the building stock. However, climate change and its effects on buildings energy performance represent a critical issue. Therefore, the aim of this study is to evaluate the climatic conditions in Rome and its surroundings, estimating the occurrence of the Urban Heat Island (UHI) phenomenon. Consequently, meteorological data obtained from two airports near the city and those recorded for two years in a densely built neighborhood of Rome were examined and compared. In addition, the differences among weather data, also taking into consideration UNI 10349, were highlighted. Then, TRNSYS software was used for creating a simple building, in order to evaluate the effects of different climatic boundary conditions on building energy performance, in terms of heating and cooling energy demands.
The Urban Heat Island (UHI) effect is particularly concerning in Mediterranean zone, as climate change and UHI scenarios foresee a fast growth of energy consumption for next years, due to the widespread of air conditioning systems and the increase of cooling demand. The UHI intensity is thus a key variable for the prediction of energy needs in urban areas. This study investigates the intensity of UHI in Barcelona (Spain), the densest Mediterranean coastal city, and its impact on cooling demand of residential buildings. The experimental analysis is based on temperature data from rural and urban Weather Stations and field measurements at street level. The maximum average UHI intensity is found to be 2.8 ◦C in winter and 1.7 ◦C in summer, reaching 4.3 ◦C at street level. Simulations performed with EnergyPlus indicate that the UHI intensity increases the sensible cooling load of residential buildings by around 18%–28%, depending on UHI intensity, amount of solar gains and cooling set point. In the light of the results, the UHI intensity in Mediterranean context should be properly considered in performing energy evaluations for urban contexts, since standard meteorological data from airport weather stations are not found to be accurate enoug.
Building Simulation Conference Proceedings
The Urban Heat Island (UHI) effect is a welldocumented phenomenon, in which the airtemperature in an urban area is elevated relative to the regional air-temperature. This paper evaluates two recently developed methods for generating urban weather files from a rural station that account for microclimatic impacts on dry-bulb temperature and relative humidity. The two methods examined are computationally inexpensive. The first method is the urban weather generator (UWG) a model developed by Bueno et al. and the second is a temperature alteration scheme developed by Crawley (Bueno et al., 2012; Crawley, 2008). Actual weather data is used to validate the modeled urban data. Actual and modeled weather data is used in simulation of a typical single-family and small office building to quantify model output in terms of combined heating and cooling energy use intensity (EUI). The difference between urban and rural EUI actual is 13% and 17% for the small office and single family building, respectively. The UWG reduces this difference to 8% and 13%. The Crawley scheme reduces this difference to 9 % and 14 % (ΔDB = 1°C) or-9% and-4% (ΔDB = 5 °C).
Energy and Buildings, 2018
Predicting buildings' heating and cooling needs through dynamic simulation methods requires the input of hourly weather data, so as to represent the typical meteorological characteristics of a specific location. Hence, the so called 'typical weather years' (TWY), mainly deduced from multi-year records of meteorological stations outside the urban centres, cannot account of the complex interactions between solar radiation, wind speed and high urban densities which lead to the formation of the urban heat island effect and to higher ambient air temperatures. As the assumption that climatic parameters at a reference location of a meteo station are similar for a densely built up area can lead to miscalculations of the heating and cooling needs, the aim of this study is to present a computational method for assessing the urban climate's effect during the generation of typical weather data for dynamic energy calculations. In this vein, a typical 'urban specific weather dataset' (USWD), reflecting the microclimatic conditions in front of a building unit inside an urban district in the city of Thessaloniki, Greece is created based on microclimate simulations with the Envi-met model; it is then compared with a typical reference weather dataset (RWD), representing climatic conditions at a reference location of a meteo station. The results indicate that the proposed method can capture microclimate characteristics; higher dry bulb temperatures were reported during the year inside the urban canyon, compared to the corresponding values at the reference location, with indicative mean daily deviations up to 1.0 °C and 0.75 °C in February and July respectively. Wind speed, near the building façade is generally found lower than the corresponding values at the reference location, due to wind sheltering by neighbouring constructions. Given that climatic parameters strongly influence the output of energy simulations the proposed computational method provide a contribution for higher accuracy of building energy simulation in the urban context. Future work will involve energy performance simulations of a typical building unit with the generated USWD file so as to evaluate the urban climate's influence on energy needs.
IOP conference series, 2017
Although Urban Heat Island (UHI) is a fundamental effect modifying the urban climate, being widely studied, the relative weight of the parameters involved in its generation is still not clear. This paper investigates the hierarchy of importance of eight parameters responsible for UHI intensity in the Mediterranean context. Sensitivity analyses have been carried out using the Urban Weather Generator model, considering the range of variability of: 1) city radius, 2) urban morphology, 3) tree coverage, 4) anthropogenic heat from vehicles, 5) building's cooling set point, 6) heat released to canyon from HVAC systems, 7) wall construction properties and 8) albedo of vertical and horizontal surfaces. Results show a clear hierarchy of significance among the considered parameters; the urban morphology is the most important variable, causing a relative change up to 120% of the annual average UHI intensity in the Mediterranean context. The impact of anthropogenic sources of heat such as cooling systems and vehicles is also significant. These results suggest that urban morphology parameters can be used as descriptors of the climatic performance of different urban areas, easing the work of urban planners and designers in understanding a complex physical phenomenon, such as the UHI.
Energies, 2020
Building energy simulations are normally run through Typical Weather Years (TWYs) that reflect the average trend of local long-term weather data. This paper presents a research aimed at generating updated typical weather files for the city of Catania (Italy), based on 18 years of records (2002–2019) from a local weather station. The paper reports on the statistical analysis of the main recorded variables, and discusses the difference with the data included in a weather file currently available for the same location based on measurements taken before the 1970s but still used in dynamic energy simulation tools. The discussion also includes a further weather file, made available by the Italian Thermotechnical Committee (CTI) in 2015 and built upon the data registered by the same weather station but covering a much shorter period. Three new TWYs are then developed starting from the recent data, according to well-established procedures reported by ASHRAE and ISO standards. The paper disc...
Urban meteorological forcing data for building energy simulations
Building and Environment, 2021
Despite building energy use being one of the largest global energy consumers, building energy simulations rarely take the actual local neighbourhood scale climate into account. A new globally applicable approach is proposed to support buildings energy design. ERA5 (European Centre Reanalysis version 5) data are used with SUEWS (Surface Urban Energy and Water balance Scheme) to obtain (in this example case) an urban typical meteorological year (uTMY) that is usable in building energy modelling. The predicted annual energy demand (heating and cooling) for a representative four-storey London residential apartment using uTMY is 24.1% less (cf. conventional TMY). New vertical profile coefficients for wind speed and air temperature in EnergyPlus are derived using SUEWS. EneryPlus simulations with these neighbourhood scale coefficients and uTMY data, predict the top two floors have ~40% larger energy demand (cf. the open terrain coefficients with uTMY data). Vertical variations in wind speed have a greater impact on the simulated building energy than equivalent variations in temperature. This globally appliable approach can provide local meteorological data for building energy modelling, improving design for the local context through characterising the surrounding neighbourhood.
Energies
The simulation of the energy consumptions in an hourly regime is necessary in order to perform calculations on residential buildings of particular relevance for volume or for architectural features. In such cases, the simplified methodology provided by the regulations may be inadequate, and the use of software like EnergyPlus is needed. To obtain reliable results, usually, significant time is spent on the meticulous insertion of the geometrical inputs of the building, together with the properties of the envelope materials and systems. Less attention is paid to the climate database. The databases available on the EnergyPlus website refer to airports located in rural areas near major cities. If the building to be simulated is located in a metropolitan area, it may be affected by the local heat island, and the database used as input to the software should take this phenomenon into account. To this end, it is useful to use a meteorological model such as the Weather Research and Forecast...