Energy Demand For Air Conditioning Research Articles

Optimal Design of Tilted Building Envelope Considering Air Conditioning Energy Demand, Daylight Utilization and Glare Protection—Case Study

An important energy-saving method to optimize building envelope design is the integration of local climate characteristics. This study attempts to find sloped facade configurations to balance air conditioning energy demand and daylight utilization for four directions in an area with a hot climate. Tilt angle dependence of the air conditioning energy demand, useful daylight illuminance (UDI) and daylight glare index (DGI) are selected to investigate the acceptance thresholds of the tilt angle. The final facade’s configuration is achieved by employing the graphical optimization method. An acceptable solution that balances better daylight performance and less energy consumption by air conditioning is developed. Due to the considered city being located in a low-latitude area with great daylight availability as well as a fully dimmable light control strategy, unbearable glare reduction can be achieved by benefiting from the sloped facades, without necessarily sacrificing much usable daylight. Meanwhile, there is no obvious increase in the demand for lighting energy consumption, and a good outward view is preserved. The sloped rather than vertical facade provides natural solar shading to the east-, south- and west-oriented windows while allowing low-angle winter solar heat to warm the building space. Tilt angles between 35°and 40° are preferred for the east facade, and smaller tilt angles of between 30°and 35° are recommended for the south facade. Larger tilt angles of between 40°and 45° are preferred for the west facade. However, the north-facing facade’s outward tilt would cause an undesirable increase in air conditioning energy demand. The annual air conditioning energy demand of the east-, south- and west-facing space is found to separately decrease by 7.1%, 7.3% and 9.9%, respectively, benefiting from the sloped facades.

Impact of Passive Design Strategies on Environment, Cooling and Lighting Energy Demand. A Weighted Least Squares-Based Approach

Abstract The energy transition requires optimal knowledge of the thermal behaviour of different passive strategies. This paper explores the impact of 28 variables representing 4 shading devices, 5 external wall compositions (U w), 3 window types (U w), 4 window-to-wall ratios (WWR), 4 types of climates represented by 4 cities, and 8 orientations. Applying the Latin hypercube sampling method, a campaign of 300 dynamic thermal simulations is performed to assess the impact of the variables selected using the weighted generalised linear regression method for the energy demand for air conditioning, the energy demand for lighting, and the environmental impact expressed in kg of CO2. The model of energy demand for cooling (R² = 0.951) shows that the weather data is the variable that most explains energy demand, followed by the glazing ratio, the thermal characteristics of external walls, and shading devices. The model explaining the energy demand for lighting (R² = 0.945) shows that the WWR and shading devices, the weather data, and the orientation, influence the energy demand for lighting. Finally, the model explaining the embodied carbon footprint (kg of CO2) (R² = 0.989) shows that external walls and window type are the main influencing factors. Finally, the best combination for balancing the cooling-lighting-embodied carbon balance equation is discussed.

DETECTION OF DISCOMFORT INDEX WITH REMOTE SENSING TECHNOLOGY: THE CASE OF ANTALYA PROVINCE

Abstract. Thermal adaptation and thermal comfort indices are critical in determining the thermal comfort of the outdoor environment. They also play an essential role in research on heat stress, an environmental threat that can affect individuals' productivity, health and even survival. Urban growth and the resulting expansion of impervious surfaces affect the thermal characteristics of a landscape by raising Land Surface Temperatures (LST). The resulting warming can lead to thermal discomfort, the prevalence of heat-related health problems, air pollution, increased water use and energy demand for air conditioning, among others. Recently, efforts to understand the effects of urbanization and landscape changes on indoor and outdoor temperatures have increased significantly. Together with remote sensing technology, this study aims to understand human heat stress, and geographic information system (GIS) is a tool used in the research. In the estimation of heat stress, besides temperature, physiological status, environmental impact and relative humidity factors are also important. The discomfort index (DI) is a heat stress indicator proposed by Thom (1959), which expresses the contribution of air temperature and relative humidity to human thermal comfort. The discomfort index proposed by Thom (1959) was calculated as DI=0.5Ta+0.5Tw (Ta: dry bulb temperature, Tw: wet bulb temperature) modified by SOHAR, Adar and Laky (1963). In the study, the dry bulb temperature, assumed to be equal to the air temperature, was taken monthly from MODIS LST data at 1km resolution. Relative humidity was produced by interpolating 73 meteorological data in the study area at 1km resolution. Wet bulb temperature is difficult to measure, so it was calculated from dry bulb temperature and relative humidity data so that the discomfort index as a measure of heat stress in the study area was calculated with a resolution of 1 km. The discomfort index was calculated monthly and annually and classified according to Thom's 4 comfort classes. According to the calculation results, Antalya's average discomfort index value for the whole year is 24.9 °C, indicating that Antalya is a moderately comfortable place. This value varies monthly, especially in April and October when the heat stress is the highest.

Reduced CO2 footprint of buildings in agro-industrial communities in Qatar with improved insulation standards and solar cooling

Food production in arid countries like Qatar is strongly linked to water and energy resources to grow plants or rear cattle in a protected and controlled environment. The high energy demand for air conditioning in agro-industrial communities leads to significant CO2 emissions. In a case-study on buildings that are typical in the agro-industrial sector, the reduction potential for these emissions is investigated. Therefore, greenhouses and community buildings with an insulation according to the Passivhaus standard and solar cooling with photovoltaic driven compression chillers are compared to conventional buildings.An innovative solar cooling system is developed: Power is generated in hybrid photovoltaic / thermal collectors to enhance the electric efficiency of the photovoltaic cells and to deliver heat for food processing or other purposes at a high temperature level. A compression chiller model is designed, that is based on the experimentally determined performance of the refrigeration cycle for the harsh operating conditions in Qatar. Different refrigerants are compared regarding their cycle performance and Global Warming Potential.A result of the study at hand is that greenhouses are very well suited for solar cooling since their cooling load is nearly congruent to photovoltaic power generation due to their low thermal inertia and radiative cooling during the night.The case study reveals that an insulation according to the Passivhaus standard combined with the proposed solar cooling system reduces the CO2 emissions caused by the air conditioning of greenhouses by 98% and of residential buildings by 94.7% compared to conventional buildings and air conditioning systems.

Integrating a passive downdraught evaporative cooling tower into a Saudi house - The impact of climatic conditions on PDEC performance

The Kingdom of Saudi Arabia (KSA) generates the most electricity of any country in the Gulf region, and virtually all that electricity is produced by the burning of fossil fuels - natural gas and crude oil. The residential sector accounts for about 50% of the total electricity demand in the Kingdom, and around two-thirds of that electricity consumption is used for air conditioning. As the Kingdom transitions away from its reliance on fossil fuels, reducing air conditioning energy demand in dwellings becomes a key objective. Passive cooling systems can significantly reduce cooling energy loads for buildings while maintaining thermal comfort. This study investigated the potential of integrating a passive downdraught evaporative cooling (PDEC) tower into a typical Saudi Arabian villa. A computational model of a spray PDEC tower was developed in IES-VE software and calibrated against field data. Then, an actual Saudi villa was monitored, modelled, and validated before a PDEC tower was digitally integrated into the villa. Finally, the villa and its PDEC digital twin were used to conduct a series of parametric analyses to determine the PDEC performance in different rooms and cooling energy consumption in the villa as functions of wind speed and direction. The research found that, counterintuitively, higher wind speeds reduced the effectiveness of the PDEC system to cool rooms in the villa and that wind direction also played a role in the degree of cooling experienced in different villa spaces. In the summer season, the results indicated that the total villa energy consumption was approximately 32,415 kWh in the base case, with cooling energy representing 88% of the total energy used (28,337 kWh). The integration of the PDEC tower resulted in a reduction of approximately 22% in cooling energy consumption, from 28,337 kWh to 22,032 kWh, while the PDEC was operational continuously throughout the day.

Cool Cementitious Materials for a More Sustainable Urban Environment

The temperature increase in cities called the “urban heat island” (UHI) depends on the local microclimate (e.g., solar irradiation, population, buildings density, industrial activities, traffic, emissions, heat sources) and results not only in increased electricity consumption for indoor cooling but also in decreased outdoor comfort, especially in summer periods or in warm climate zones. As the world’s urban population continues to grow, there is an urgency to make buildings more ecoefficient and reduce the impact of cities on climate change and global warming. In this framework, the use of cool concretes can mitigate the UHI and improve energy saving and outdoor comfort: cool concrete roofs and facade cement-based tiles can provide valid solutions to decrease the energy demand for air conditioning in building envelops; moreover, cool concrete paving blocks and pervious pavements can improve urban comfort for outdoor wellbeing. The present work shows the improved solar reflective performance of three cool cementitious solutions compared with traditional ones, with both white and colored surfaces, to fulfill both architectural demand and sustainability issues without any additional post-treatments or after placing steps, such as surface coating. Finally, the study is completed with the durability evaluation of the products’ solar reflective performance.

Impact Assessment of Implementing Several Retrofitting Strategies on the Air-Conditioning Energy Demand of an Existing University Office Building in Santiago, Chile

This work analyzed the thermal behavior of an existing building, considering different retrofitting strategies. The methodology starts with an in-situ survey that allowed for obtaining information about occupation, work schedules, envelope materials, lighting, and equipment, which was vital to develop an energy model of the building. Then, the thermal analysis, employing simulations, demonstrates a higher relevance of heat flows through the building’s envelope than internal loads and higher cooling rather than heating demands. Afterward, several retrofit strategies focusing on modifying architectural elements were assessed. Finally, these strategies were compared based on their impact on the air-conditioning energy demand. A systematic review identified a lack of studies relating certification and energy policies to buildings retrofitting. Therefore, we assessed the energy performance of the building, when modified to meet the baseline requirements set on the Chilean certification requirements for sustainable buildings, to verify if the certification is a suitable method to assess the energy efficiency of an office building. Although the study only involves a single building, it aims to illustrate identified limitations using the energy policies for Chilean public buildings. The Chilean certification for sustainable buildings seems not to be suitable for the evaluation of energy consumption for the retrofit of existing buildings. Although this study does not demonstrate general trends, it presents a precedent for subsequent studies to evaluate the relevance of the Chilean certification guidelines.

The Indoor Climate of Hospitals in Tropical Countries: A Systematic Review

An indoor climate impacts human comfort, well-being, and safety. Therefore, it remains an important topic since, nowadays, people spend a significant amount of time indoors. Additionally, as tropical geographical zones become more populated, urbanised, and industrialised, the energy demand for air conditioning will rise significantly. In terms of the indoor climate, hospitals are particularly demanding due to the special needs of their occupants, however there is a paucity of studies about the tropics. Through a systematic analysis of accessible data and peer-reviewed articles, this study performed a quantitative and qualitative review of the scientific studies selected by the defined inclusion and exclusion parameters. A total of 65 tropics-related scientific publications, 28 on indoor thermal comfort and 37 on indoor air quality published between 2000 and 2023, were systematically reviewed. This study’s findings corroborated those from the previous studies, alluding that there is a paucity of scientific studies on the indoor climate conditions of buildings in tropical countries. A total of 42 studies (65%) were conducted in Asia and 15 studies (23%) in Africa. Six studies (9%) were reported in South America and two studies (3%) were obtained from Oceania, Australia. The results indicated that tropical Africa recorded the lowest number of indoor climate studies considering the population indices. Many of the reviewed indoor climate studies employed mixed methods, whereas only very few considered a seasonal approach. Meanwhile, in the developing tropics, only one record was found regarding an indoor climate study of hospitals based on their locations (correlating the outdoor and indoor air quality). Additionally, no record was found regarding the IC studies of hospitals in sub-Saharan Africa, in which, the IC impact on the occupant’s performance, productivity, and behaviour was assessed. Inferably, gaps still exist in the indoor climate of tropical hospitals. The current study highlights the need to improve the indoor climate considerations in the design, siting, awareness, regulations, and policy implementations concerning the hospitals in developing tropical countries. In conclusion, the study emphasises the need for more scientific studies on the indoor climate of tropical hospitals and highlights the relevant areas of the indoor climate studies in future works for considering the climate, environmental, socio-economic, infrastructural, and demographic peculiarities of the tropics for the betterment of hospital indoor climates in developing tropical countries.

Assessment of climate change's impact on energy demand in Mexican buildings: Projection in single-family houses based on Representative Concentration Pathways

In Mexico, buildings' deficient thermal performance is one of the leading causes of the intensive use of energy. This research analyzes the perspective of energy demand required to meet the cooling needs in the country through the Weather-based technical indexes: Cooling Degree Hour (CDH) and Operation Hours (OH). The study considered the 2440 municipalities that make up the 32 states of the Mexican Republic and three chronological progressions throughout the 21st century (2020, 2050, and 2100). Meteorological data was collected through the Meteonorm software considering climate change projections, precisely two Representative Concentration Pathway scenarios (RCP 4.5 - Intermediate) and (RCP 8.5 - High). Based on the calculations, spatial and temporal panoramas of the behavior of air conditioning hours under various target temperatures (20 °C, 23 °C, and 26 °C) were established. Taking the most important type of housing in Mexico (Social Interest Housing) as a case study, a database of air conditioning energy demand was performed and subsequently grouped the states according to cluster similarities. The results show that >50 % of the Mexican Republic requires high air conditioning levels. The maximum CDH for 2100-RCP 8.5 will be 70 % higher than currently needed. Even for the year 2050-RCP8.5, an increase of >40 % of CDH was obtained. Regarding the OH, the results show an increase of >50 % concerning the current behavior of the country. Regardless of the scenario, the range of operating hours with the highest operating requirements is between 11 am and 4 pm, peaking in the summer season. The simulations showed that some Mexican regions exceed 12,000 kWh in air conditioning. An increase of 20 % and 35 % is expected for the years 2050 and 2100. The simulations showed that a considerable percentage of Mexico exceeds 12,000 kWh in air conditioning, while by 2050 and 2100, this consumption will increase by 20 % and 35 %, respectively. Based on these results, the first classification of groups in energy demand was generated, allowing a focus on energy efficiency strategies to obtain net zero Buildings. The data obtained shows that relative humidity is a variable that affects the increase in energy consumption in refrigeration and simplifies the process of classifying regions with similar patterns in air conditioning.

Development of a Portland Cement-Based Material with Agave salmiana Leaves Bioaggregate.

Depending on the morphology of the natural fibers, they can be used as reinforcement to improve flexural strength in cement-based composites or as aggregates to improve thermal conductivity properties. In this last aspect, hemp, coconut, flax, sunflower, and corn fibers have been used extensively, and further study is expected into different bioaggregates that allow diversifying of the raw materials. The objective of the research was to develop plant-based concretes with a matrix based on Portland cement and an aggregate of Agave salmiana (AS) leaves, obtained from the residues of the tequila industry that have no current purpose, as a total replacement for the calcareous aggregates commonly used in the manufacturing of mortars and whose extraction is associated with high levels of pollution, to improve their thermal properties and reduce the energy demand for air conditioning in homes. Characterization tests were carried out on the raw materials and the vegetal aggregate was processed to improve its compatibility with the cement paste through four different treatments: (a) freezing (T/C), (b) hornification (T/H), (c) sodium hydroxide (T/NaOH), and (d) solid paraffin (T/P). The effect of the treatments on the physical properties of the resulting composite was evaluated by studying the vegetal concrete under thermal conductivity, bulk density, and compressive strength tests with a volumetric ratio between the vegetal aggregate and the cement paste of 0.36 and a water/cement ratio of 0.35. The hornification treatment showed a 15.2% decrease in the water absorption capacity of the aggregate, resulting in a composite with a thermal conductivity of 0.49 W/mK and a compressive strength of 8.66 MPa, which allows its utilization as a construction material to produce prefabricated blocks.

Reference weather datasets for building simulation in Vietnam considering thermal and hygrothermal characteristics

This study presents the development and test of reference weather datasets for thermal and hygrothermal building simulations for seven representative locations in Vietnam. Sequences of selected weather datasets from the years 1984–2018 (35 years) are used to represent the weather elements in the periods 2014 to 2018 (5 years) and 2004 to 2018 (15 years). Sequences are monthly, 14-day, 5-day, and daily intervals of the specific year. Selection methods based on simulation results of a thermal building model and a set of weighted weather elements are employed to select sequences from the database. Annual datasets are then constructed from these sequences and tested through thermal simulation and the best-fit of monthly values of hourly weather elements in the target period are determined. The tested characteristics are as follows: monthly average values per hour per day of temperatures, absolute humidity ratio, relative humidity, wind speed, rainfall, solar radiation, and the atmospheric pressure, and annual and monthly simulation results of the energy demand for air conditioning and the components of the energy balance, such as transmission gains/losses, sensible and latent ventilation gains/losses, internal sensible and latent heat gains, and solar heat gains. From the analysis, the most appropriate selection process and length of weather sequences are identified to construct new reference weather datasets in tropical climate zones. Within the presented study, weather datasets for seven locations in Vietnam are constructed and published in formats applicable for thermal building simulation (EPW-format) and hygrothermal simulation studies with the simulation program WUFI (WAC-format).

Direct evaporative cooling from wetted surfaces: Challenges for a clean air conditioning solution

AbstractEvaporative cooling has a major role to play in fighting climate change and in achieving a low‐carbon economy. As it helps to reduce energy demand for air conditioning, it is gaining attention in terms of improving energy efficiency in buildings. Evaporative cooling from wetted media can enhance water–air contact, thereby improving heat and mass transfer further and avoiding aerosols. Wetted media are commonly called evaporative cooling pads and are widely used in greenhouses, intensive livestock farming, and industrial facilities. However, a deep understanding of evaporative cooling pad performance can enhance their application to indoor occupied spaces such as residential or commercial cooling, or in hybrid air conditioning systems. Most studies analyze pad performance mainly in terms of pressure drop and saturation effectiveness. However, some studies propose alternative cooling efficiency parameters and others provide insights into key aspects such as power requirements and the coefficient of performance, water consumption, risk of water entrainment, material decay, and air quality, as well as the effect of water temperature and salinity, solar radiation, or wind speed. Existing results on these less studied performance issues are reviewed, and we identify the gaps in the literature in addition to highlighting the main challenges encountered, in an effort to guide future researchers in the field and enhance the application of direct evaporative cooling.This article is categorized under: Energy Efficiency > Systems and Infrastructure Energy Systems Analysis > Systems and Infrastructure

Impacts of a warmer world on space cooling demand in Brazilian households

Air Conditioning (AC) appliances are a highly effective adaptation strategy to rising temperatures, thus making future climate conditions an important driver of space cooling energy demand. The main goal of this study is to assess the impacts of climate change on Cooling Degree Days computed with wet-bulb temperature (CDDwb) and household space cooling demand in Brazil. We compare the needs under three specific warming levels (SWLs) scenarios (1.5 °C, 2 °C and 4 °C) to a baseline with historically observed meteorological parameters by combining CDDwb projections with an end-use model to evaluate the energy requirements of air conditioning. The effects of the climate change were isolated, and no future expansion in AC ownership considered. Carbon dioxide (CO2) emissions associated with AC energy demand are also calculated. Results show an increase in both average CDDwb and AC electricity consumption for the global warming scenarios in all Brazilian regions. The Northern region shows the highest increase in CDDwb (187% in CDDwb for SWL 4 °C), while the Southeast presents the highest AC energy consumption response (326% in the AC energy consumption for SWL 4 °C) compared to the baseline. At the national level, CDDwb and the AC energy consumption in all SWLs scenarios grow by 70%, 99% and 190%, respectively.

Improving the accuracy of simplified urban canopy models for arid regions using site-specific prior information

An overly complex urban climate/energy model would not be of much practical use in a decision support setting where a large number of year-long simulations are often necessary. While detailed modeling of urban momentum/energy exchanges can be attempted via Computational Fluid Dynamics (CFD) or mesoscale modeling, conducting multiple full year simulations in a design optimization or sensitivity analysis context is practically impossible. Furthermore, CFD models often do not consider climate/building energy exchanges. To address these limitations, standalone Urban Canopy Models (UCMs) have been developed, attempting to replace the full-fledged atmospheric representation with a computationally light equivalent. In this study, we investigate the impact of several modifications to a standalone Single-Layer Urban Canopy Model (SLUCM) for an arid region based on the prior availability of site-specific information. The suggested improvements are portable to SLUCM schemes incorporated within mesoscale models. The SLUCM will undergo several improvements and each variant will be evaluated based on its ability to predict UHI intensity and air-conditioning energy demand. Three original SLUCM improvements are covered in the present study. (1) We use actual radiation parameters instead of those generated for idealized geometries. It is shown that, in the absence of this improvement, standard UCMs can underestimate the average urban heat island intensity by 5% if using the Town Energy Balance (TEB) radiation scheme or overestimate it by 7% if using the Square Prism Urban Canopy (SPUC) radiation scheme. (2) We use the results of a prior steady-state RANS (Reynolds-Averaged Numerical Simulation) simulation to replace some of the default morphological parameters of the UCM by the more accurate values derived from the RANS results. It is shown that, in the absence of this improvement, standard UCMs using default empirical relations can overestimate the average urban heat island intensity by up to 22%. (3) Instead of using the empirically calculated default value of the urban canyon wind speed, we estimate it directly from the concomitant rural value using a regression model trained by historical measurements. It is shown that, in the absence of this improvement, standard UCMs can underestimate the average canyon wind velocity by more than 12%, although the other indicators (UHI, cooling demand) are not significantly affected.

Keep it cool [The energy demand for air conditioning increases in hotter countries

Keep it cool [The energy demand for air conditioning increases in hotter countries

Thermal response of energy foundations installed in unsaturated residual soils

This study focuses on the thermal response of energy foundations with different piping geometries installed in unsaturated soil. Energy foundations are an efficient alternative to traditional space heating and cooling approaches and can reduce energy demand for air conditioning in Brazil, where unsaturated residual soil deposits are abundant. A three-dimensional numerical model for heat transfer and subsurface flow is first validated against field data from a thermal response test at the University of São Paulo. The model is then used to compare the performance of triple and quadruple U-tube piping geometries and helical piping geometries of equivalent length. The helical geometries resulted in initial less uniformly heated foundations and lower heat flux at the foundation boundary compared with the U-tubes, but the differences between the U-tube geometries and their equivalent length helices were less than 1°C. All piping geometries exhibited increased heat output as the length of heat exchanger piping increased. The infinite line source solution was compared with the model results. The infinite line source solution underestimated the thermal response of the system during the first 25-30 days and overestimated it afterwards.

Air infiltrations and energy demand for residential low energy buildings in warm climates

European building legislation is establishing increasingly stricter requirements to reduce the energy demand of buildings as a measure to decrease energy use and associated carbon emissions. In order to comply with the new standards, the most impactful parameters are subject to important revisions.Airtightness is revealed as an impacting parameter on air conditioning energy demand for nearly Zero Energy Buildings (nZEB). Currently the Passivhaus standard, taken as a constructive reference for nZEB in Europe, establishes 0.6 ACH as the maximum infiltration at 50 Pa for all new buildings irrespective of the climate zone. Nevertheless, the influence of infiltrations on the energy demand is lower in warm climates.This study estimates the potential heating and cooling energy demand for different levels of infiltration rates in southern Europe. For this purpose, a dwelling equipped with a mechanical ventilation system with a heat exchanger has been simulated in TRNSYS. The calculations have been performed in different cities with different levels of infiltrations.This research provides the information required to set airtightness parameters in residential buildings in southern Europe to satisfy the new requirements for nZEB.

Influence of trees on the energy consumption of a social housing in mid-western Brazil

In the last decades, many studies have shown ample evidence that the existence of trees and vegetation around buildings can contribute to reduce the demand for energy by cooling and heating. The use of green areas in the urban environment as an effective strategy in reducing the cooling load of buildings has attracted much attention, though there is a lack of quantitative actions to apply the general idea to a specific building or location. Due to the large-scale construction of high buildings, large amounts of solar radiation are reflected and stored in the canyons of the streets. This causes higher air temperature and surface temperature in city areas compared to the rural environment and, consequently, deteriorates the urban heat island effect. The constant high temperatures lead to more air conditioning demand time, which results in a significant increase in building energy consumption. In general, the shade of the trees reduces the building energy demand for air conditioning, reducing solar radiation on the walls and roofs. The increase of urban green spaces has been extensively accepted as effective in mitigating the effects of heat island and reducing energy use in buildings. However, by influencing temperatures, especially extreme, it is likely that trees also affect human health, an important economic variable of interest. Since human behavior has a major influence on maintaining environmental quality, today's urban problems such as air and water pollution, floods, excessive noise, cause serious damage to the physical and mental health of the population. By minimizing these problems, vegetation (especially trees) is generally known to provide a range of ecosystem services such as rainwater reduction, air pollution mitigation, noise reduction, etc. This study focuses on the functions of temperature regulation, improvement of external thermal comfort and cooling energy reduction, so it aims to evaluate the influence of trees on the energy consumption of a house in the mid-western Brazil, located at latitude 15 ° S, in the center of South America. The methodology adopted was computer simulation, analyzing two scenarios that deal with issues such as the influence of vegetation and tree shade on the energy consumption of a building. In this way, the methodological procedures were divided into three stages: climatic contextualization of the study region; definition of a basic dwelling, of the thermophysical properties; computational simulation for quantification of energy consumption for the four facade orientations. The results show that the façades orientated to north, east and south, without the insertion of arboreal shading, obtained higher values of annual energy consumption. With the adoption of shading, the facades obtained a consumption reduction of around 7,4%. It is concluded that shading vegetation can bring significant climatic contribution to the interior of built environments and, consequently, reduction in energy consumption, promoting improvements in the thermal comfort conditions of users.

Influencia de las infiltraciones en la rehabilitación energética de la envolvente. El caso del plan de actuaciones en el parque público residencial de Andalucía

El presente estudio presenta la investigación sobre la rehabilitación energética de la envolvente en una muestra de 615 viviendas sociales, incluidas dentro de los planes de construcción sostenible para el parque público residencial de Andalucía. Se evalúa de forma novedosa la relación entre las tasas de renovación de aire exterior y la demanda de climatización de viviendas en clima cálido. Ambas magnitudes ofrecen un paralelismo en los resultados, con valores promedio de 21,45% de disminución de tasa de renovación y un 21,82% de disminución en la demanda. Para ello, durante la ejecución de las intervenciones se ha desarrollado un muestreo de infiltraciones en viviendas. Las permeabilidades medidas se utilizan como parámetros de entrada en un proceso de modelizaciones energéticas bajo diferentes hipótesis, diferenciando la entrada de aire controlada o necesaria (ventilación) y la incontrolada o innecesaria (infiltraciones). Los resultados permiten visualizar el comportamiento de los edificios rehabilitados, cuantificando el ahorro energético como consecuencia de las infiltraciones para cada caso.

Understanding the relationship between urban outdoor temperatures and indoor air-conditioning energy demand in Zimbabwe

Urbanization causes thermal elevation which increase household energy consumption through air conditioning to reduce human heat stress. The objective of this study was thus to quantify the long term changes in potential energy requirements for indoor space warming and cooling in the built environment of Harare using remotely sensed satellite data. Landsat and in-situ temperature data were used to determine land use and land cover distribution, as well as to estimate trends in air conditioning energy requirements between 1984 and 2015. Daytime Heating Degree Days (HDD) and the Cooling Degree Days (CDD) derived from Landsat thermal data and in situ temperature measurements were used as a measure of indoor heating and cooling energy in the cool and hot season, respectively. Due to surface alterations from urban growth between 1984 and 2015, surface temperature increased on average by 2.26°C and by 4.10°C in the cool and hot season, respectively. This decreased potential indoor heating energy needed in the cool season by 1° day and increased indoor cooling energy during the hot season by 3° days. In-situ observations revealed that energy consumption in residential areas Harare increases with temperature in summer and the opposite in winter. Findings in this are important for implementation of mechanisms to rationalize power supply based on spatial differences in levels of need for air conditioning. The findings are also relevant for authorities to devise measures to capacitate the most vulnerable societies, such as by subsidizing electricity for the urban poor, and ensure that they are protected from stress due to low or high temperature.