Buildings In Hot Climates Research Articles

Dynamic optimization of multi-retrofit building envelope for enhanced energy performance with a case study in hot Indian climate

When multiple thermal retrofits are to be installed in a building envelope for improving its energy performance, several questions arise such as “what should be the thickness of retrofits and where they should be placed within the wall/roof”, “which retrofit should be installed towards the exterior and which one should be installed towards the interior of the envelope”. Such judgements are made in contemporary studies by comparing limited predefined configurations where either the thickness or the location of retrofit assumes only a few discrete values within the envelope. The novel approach proposed in this study utilizes spatial discretization of structural layers in a composite envelope for two fold benefit. A new version of Genetic Algorithm (GA) is developed for this purpose by modifying its key operational stages. The GA is implemented in a practical scenario to optimally configure a multi-retrofit envelope (carrying phase change material and thermal insulator) of a common residential building in hot climate of India. Analysis of a single housing unit demonstrates that up to 33.5% of heat gain reduction and 9.2 kWh/day of electricity saving are achievable with improved envelope design.

Research and production of prototypes of lightweight concrete panel walls with a screen

Introduction. In industrial housing construction in a dry hot climate, the issues of protecting the premises from overheating have not yet been resolved. The purpose of this study is the theoretical and experimental substantiation of the method of calculating the construction of lightweight concrete panel exterior walls with a screen for large-panel residential buildings in hot climates, with improved performance and providing technical and economic efficiency. Materials and methods. Methods have been developed for ensuring the normative amplitude of temperature fluctuations of the inner surface in the wall due to the targeted formation of material properties and design measures, lightweight concrete wall panels with a screen and suggestions for their production technology have been developed, and recommendations have been made for their operation conditions. The methods of a rational constructive solution to the sun wall consisting of a sunscreen and a supporting structure separated by an air gap have been investigated. Results. It was supposed to carry out theoretical and experimental studies of the operational properties of lightweight concrete panels of external walls with a screen in laboratory and in-situ conditions. The work was performed in stages: At the first stage, the design and production technology of panels with a screen on prototype fragments under laboratory conditions was performed. For this, experimental fragments of 1 × 2 m panels will be made in the laboratory. The parameters of the air gap were determined from the condition of ensuring sufficient natural ventilation. At the second stage, a study was made of the rational structure of lightweight concrete for exterior walls in hot climates. To find the optimal structure of lightweight concrete from a thermal point of view, a 3-factor experiment was conducted. At the third stage, a theoretical study of the temperature regime of shielded and single-layer large-panel exterior walls was performed. At the fourth stage there was a generalization of the above studies, the manufacture and installation of experimental-industrial designs of panels with a screen in the amount of 10 pieces. At the Bukhara house-building combine. Conclusions. The described study by the method of experimental design and the experimental production of sample fragments confirmed the possibility of producing panels with a screen and an air gap in a single technological cycle. Analysis of the results of theoretical calculations shows that walls with vertical screens and a ventilated air gap are quite effective means of reducing the exposure of solar radiation to buildings and reducing the cost of cooling premises.

A photo-/thermo-dual-responsible CsxWO3/PNIPAM composite hydrogel for energy-efficient windows

Cesium tungsten bronze (CsxWO3) is an important functional material for energy efficient windows, showing excellent near infrared (NIR) shielding ability but no optical switching ability. In this paper, we demonstrate a photo-/thermo-dual-responsible CsxWO3/PNIPAM composite by dispersing CsxWO3 nanoparticles into PNIPAM hydrogels. Combination of the photothermic conversion ability of CsxWO3 with the thermochromic property of PNIPAM makes this hydrogel responds to both thermo- and photo-stimuli. In sunlight, the CsxWO3 component converts the absorbed infrared light into heat, triggering the phase transition of PNIPAM and switching the hydrogel into visibly opaque state (for example, transmittance decreased from 58% down to 15% at 590 nm). At the same time, an ambient temperature >32 °C can also initiate the phase transition of PNIPAM. Therefore, a photo- and/or thermo-derived transition between a ‘transparent NIR-shielding’ state and a ‘full-solar-spectrum shielding’ state is achieved, making it highly attractive for the applications as energy efficient windows for buildings in hot climate.

Phase Change Material to Reduce Cooling Load of Buildings in Hot Climate

Due to the hot climate of the United Arab Emirates (UAE), where the external ambient temperature may reach 50°C in the summer season, almost 75% of the total energy is consumed in air-conditioning (AC). A significant improvement in the AC systems performance during hot summer time aligned with energy conservation could be achieved by pre-cooling of the air entering the condensers. Inclusion of Phase Change Material (PCM) as thermal energy storage (TES) have been widely used as one of the environmentally friendly energy saving materials due to its high energy density. The absorption/releasing of heat by PCM during its phase change, provides a latent heating/cooling for the surrounding. Numerous systems have implemented PCM based-TES for cooling purposes, such as thermally activated building systems (TABS), suspended ceilings, external facades or in the ventilation system. This study examines PCM based air pre-cooling concept and evaluates its performance in extremely hot climate of UAE. The drop in the outlet air temperature of the duct system quantifies the cooling effect. A paraffin based PCM with melting range of 30–33°C integrated in containers placed in the test chamber mimic the air conditioning duct system, and its cooling effect is monitored. A Conjugate heat transfer model employing enthalpy-based formulation is developed to predict the optimized PCM container size and optimum airflow rate validated with experimental data. Single and series columns of PCM containers subjected to different levels of supplied air velocity at range of 1 m/s - 4m/s are evaluated. Employing series of PCM enclosures at low air velocity of 1m/s enhanced the pre-cooling performance and reduced the outlet air temperature to 35°C yielding a temperature drop up to 11°C.

Optimizing windows for enhancing daylighting performance and energy saving

Using sustainable architecture design strategies specifically daylighting could reduce lighting energy that have an indirect impact on the HVAC energy requirements especially in cooling-dominated buildings in hot climate. As a result of the interactions between lighting and HVAC, the aims of this paper were to reduce the energy consumption by having the balance between beneficial natural light and excessive solar heat and therefore reducing the energy consumption and to have an easy guideline for the architecture to help in increasing the sustainable building designs in Egypt. This paper utilized simulation techniques for identifying the most efficient glazing with a good WWR and a correct daylight autonomy by dominating the thermal heat gain and reducing cooling load yet as energy consumption.Performance predictions and simulations will facilitate in distinguishing ways for reducing energy consumption and up building performance by rigorous analysis method and that is what's this analysis methodology is about. The implementation of the simulation process is carries out using Rhinoceros 3D modeling which supports DIVA for rhino as a simulation engine to space with southern orientation in Alexandria, Egypt.The outcome of this analysis is needless to say selecting the right glazing kind could be a Brobdingnagian issue of reducing energy.

Energy saving potential for residential buildings in hot climates: The case of Oman

This paper examines the potential of energy saving in electrical consumption if the concept of energy-efficient house is implemented in Oman. Energy consumption in the residential sector in Oman was critically analysed and forecasted based on its growth rate and its historical consumption. Then, a base-case validated simulation model for a typical residential dwelling in different cities was generated using a dynamic building simulation software, covering a wide variation of climate conditions in Oman. A variety of modified design cases that met the minimum requirements for code compliance in residential buildings for four Gulf Cooperation Council countries were developed and subsequently simulated. Then, an economic analysis was performed. The results showed that due to the high annual growth rate of the residential sector (28.5%), a considerable amount of energy (13.2% in warm tropical climate to 48% in hot dry climate) could be saved if proper building codes are put in place. Thus, this paper calls for immediate action to start a large scale programme to promote and subsequently, to enforce the use of the principles of energy-efficient house in Oman.

Energy Modelling and Indoor Air Quality Analysis of Cooling Systems for Buildings in Hot Climates

Energy consumption due to cooling and ventilation of buildings has grown significantly within the last two decades, and therefore advancement in cooling technologies has become imperative to maximise energy savings. This work numerically investigates the performance of vapour-compression unitary and centralised cooling systems for high rise buildings using an office case-study in the United Arab Emirates (UAE). Energy modelling, thermal comfort and indoor air quality analyses have been carried out using the Integrated Environmental Simulation Virtual Environment (IES-VE). Using the benchmark system based on fan-coil units, the findings have indicated that attaching a Variable Speed Drive (VSD) fan can reduce the overall energy consumption of the building by 8%, with 20% reduction in the cooling loads. The unitary cooling system operating on variable refrigerant flow principle achieved an energy reduction of approximately 30%; however, this system is not recommended in high-rise buildings as the CO2 concentration obtained is in excess of 3000 ppm, which is considerably higher than ASHRAE standards. It is essential for buildings running in hot climates to incorporate hybrid cooling techniques to relieve the load on conventional active cooling systems.

Avaliação de desempenho térmico em salas de aula no Alto Sertão da Paraíba – estudo de caso no IFPB, Campus Cajazeiras

<p>The search for greater efficiency in the thermal performance of buildings in hot climate places aims to improve living conditions so as to mitigate extreme climatic conditions and to reduce energy consumption with artificial air conditioning. In this sense, thermal comfort evaluations aim to diagnose the environmental conditions offered to users in order to identify existing problems, and propose solutions for them. These evaluations are even more important in school environments, where this influence becomes more considerable due to the direct contribution of the thermal environment in the delicate teaching-learning relationship. This research is a study carried out in the city of Cajazeiras, located in Paraíba, it evaluated the thermal performance of the Instituto Federal de Educação, Ciência e Tecnologia da Paraíba, Cajazeiras campus classrooms. First of all, it tried to analyze local climatic conditions based on the test reference year - TRY calculated on the Instituto Nacional de Meteorologia meteorological station, located in São Gonçalo city / PB, 30km from Cajazeiras. Then, we described the physical characteristics of the classroom blocks, as well as the monitoring of four classrooms, which represented the two existing typologies, from October 11 to 24, 2016. It was found that the classrooms kept the temperature values within the zone of thermal comfort during class times, with the aid of the air conditioner. However, relative air humidity values were lower than the 60% limit suggested by the World Health Organization. </p>

A field study on thermal comfort and air-conditioning energy use in an office building in Guangzhou

A long term field study was conducted in an office building in Guangzhou, which is located in the Hot Summer and Warm Winter climate zone of China. The study covered three seasons – summer, autumn, and winter. Physical environmental parameters were continuously recorded, while office workers filled in thermal comfort related questionnaires once a week. In summer, cooling was provided to the investigated rooms with relatively high setting temperatures. The neutral temperature of occupants was 26.8 °C, and the upper limit of the acceptable temperature range was 30.4 °C. Unless the indoor temperature was higher than 29 °C, more than 90% of people could accept the thermal conditions, which proved the adaptation to warm environment of local people. At a same outdoor temperature level, higher indoor temperature resulted in less energy consumption through air conditioning system in summer. Thus, the temperature of air-conditioning in office buildings in hot climates could be set to a higher level than it usually was, so that air conditioning energy could be saved while occupants’ comfort won't be sacrificed. In autumn and winter, no heating or cooling was provided to the investigated rooms, and the occupants’ neutral temperatures in the two seasons were 25.8 °C and 23.3 °C respectively. Compared to the PMV/PPD based evaluation method in ASHRAE 55 standard, the adaptive thermal comfort model based method fits better with the occupants’ subjective thermal acceptance.

An integrated energy performance-driven generative design methodology to foster modular lightweight steel framed dwellings in hot climates

This paper presents a study on the application of lightweight steel framed (LSF) construction systems in hot climate. A generative design method created 6010 houses, with random geometry and random roof and exterior wall types with different insulation levels, and EnergyPlus was used to evaluate the energy consumption for air-conditioning of each building. The main goals were to determine which geometric variables correlate with the energy performance, and to provide some guidelines to foster efficient LSF buildings in hot climates. By correlating six geometry-based indexes with the energy consumption for each construction element type group, it was verified that roofs do not show significant correlation, while exterior walls presented weak to moderate positive correlation with the building volume, very weak to weak negative correlation with the relative compactness, no correlation with the shape coefficient, moderate to strong negative correlation with the window-to-floor, window-to-wall, and window-to-exterior surface ratios. The results also show that buildings with larger windows and greater level of insulation have better energy performance. No significant difference of energy performance was found between different LSF construction systems with equivalent thermal resistance.

Hygrothermal behavior for a clay brick wall

In Egypt, the clay brick is the common building materials which are used. By studying clay brick walls behavior for the heat and moisture transfer, the efficient use of the clay brick can be reached. So, this research studies the hygrothermal transfer in this material by measuring the hygrothermal properties and performing experimental tests for a constructed clay brick wall. We present the model for the hygrothermal transfer in the clay brick which takes the temperature and the vapor pressure as driving potentials. In addition, this research compares the presented model with previous models. By constructing the clay brick wall between two climates chambers with different boundary conditions, we can validate the numerical model and analyze the hygrothermal transfer in the wall. The temperature and relative humidity profiles within the material are measured experimentally and determined numerically. The numerical and experimental results have a good convergence with 3.5% difference. The surface boundary conditions, the ground effect, the infiltration from the closed chambers and the material heterogeneity affects the results. Thermal transfer of the clay brick walls reaches the steady state very rapidly than the moisture transfer. That means the effect of using only the external brick wall in the building in hot climate without increase the thermal resistance for the wall, will add more energy losses in the clay brick walls buildings. Also, the behavior of the wall at the heat and mass transfer calls the three-dimensional analysis for the whole building to reach the real behavior.

Energy-Efficient Retrofitting Strategies for Residential Buildings in hot climate of Oman

The aim of this work is to investigate the potential of energy-efficient retrofitting strategies for residential buildings in Oman. An existing residential building located in hot climate with a built-up area of 212 m2 was selected. A building simulation model was created in DesignBuilder software. The model was then calibrated using actual electrical bills and measured weather data for year 2014. The calibrated model was subsequently used to evaluate different energy-efficient retrofitting strategies including the AC efficiencies, using insulations for both walls and roof, upgrading to LED lights, and improving the air tightness of the house. It was concluded that when combing the best strategy from each category, the annual energy consumption of the building can be reduced by as much as 42.5%. This significant reduction in energy consumption can help both the policy makers at governmental institutions and owners to move forward for large retrofitting campaigns to solve the current energy dilemma.

Numerical evaluation on energy saving potential of a solar photovoltaic thermoelectric radiant wall system in cooling dominant climates

Abstract The energy used for mechanical cooling systems in buildings in hot climate is about 70%–80% of the total energy consumption. It is important to curtail this part of energy consumption by exploring new technologies. The proposed system is a building integrated photovoltaic thermoelectric (BIPVTE) wall system which combines the concept of active PV facade and solar cooling. We present a complex model of BIPVTE consisting of a PV system and thermoelectric radiant wall system. The thermal and electrical performance of BIPVTE under cooling dominant climates was numerically investigated using experimentally validated system model. The performance of BIPVTE is embodied by comparative analysis with a conventional concrete wall. A steady state analysis was designed to explain and explore the system working mechanism. A sensitivity analysis was conducted for model parameters optimization. With the optimized results, the energy saving potential of BIPVTE in Hong Kong and other 6 cities in Hot Summer and Warm Winter zone of China was implemented. The results indicated that in Hong Kong, the energy saving ratio of BIPVTE is nearly 480%, and the installation of BIPVTE in other 6 cities can save energy ranging from 29.19 kWh/m2 to 62.94 kWh/m2 annually.

Natural ventilation strategies for indoor thermal comfort in Mediterranean apartments

Natural ventilation strategies as effective low energy refurbishment solutions are identified within this research study, for an existing urban multi-storey apartment building in Athens, representative of over four-million Greek urban residential buildings. Retrofit strategies were evaluated using occupant comfort criteria and the existing ventilation strategy, for a single apartment using dynamic thermal simulations. These strategies included individual day and night ventilation, a wind-catcher and a dynamic facade. Suitable openings operation in response to environmental parameters provided sufficient day and night ventilation and occupant comfort. The inclusion of a wind-catcher yielded very little improvement to the ventilation performance. However, the combined operation of the wind-catcher and the dynamic facade delivered operative temperature reductions of up to 7 °C below the base-case strategy, and acceptable ventilation rates for up to 65% of the cooling period. The successful performance of the proposed strategies highlights their potential for reducing energy consumption and improving thermal comfort in a large number of buildings in hot climates.

SPACE-PLANNING DECISIONS OF LOW-RISE RESIDENTIAL BUILDINGS IN HOT CLIMATES

This article describes the characteristic climatic features of the hot climate. Considered space planning solutions for low-rise residential buildings for areas with hot humid and hot dry climates. Also described ways of dealing with a high temperature of internal air in premises and describes the various options for sun protection devices. Recommendations for improvement of the microclimate according to the area of construction. Reviewed software functional and aesthetic and sanitary-hygienic requirements for space-planning decisions of residential buildings in hot climates.

Simple roofing system suitable for buildings in hot climate and it's effect on energy conservation (Experimental study)

The objective of this paper is reduced the electrical energy which used in air-condition system by replaced the common roofing system by the another which more suitable for hot climate area. The researcher was build (1x1x3)m sample room at 3rd floor in building at Baghdad city (33.2 °N) for 200mm polystiran thermal insulation for other room surfaces and air-conditioner of 0.5 Ton of refrigeration capacity is used to maintain the standard thermal comfort, the roof thermal behavior study for 15 hr/day, at day 21 from five each months (Jan, March, June, July & September). It was found the suggested roofing system reduced the dead load by 300kg/m2 and the electrical energy which used in air-conditioning system reduced by 37% when used open air gap was used, and become 30% when has used closed air gap has used and became 27% relation to ordinary system.

Solar-Powered Air Conditioning for Buildings in Hot Climates: Desiccant Evaporative Cooling vs. Absorption Chiller-based Systems

In many countries, solar cooling systems are one of the best candidates to tackling global warming and summer peak loads of building air conditioning systems. In this work, based on the collaboration with the Saudi research institute “King Abdullah City for Atomic and Renewable Energy”, two types of solar driven cooling systems are investigated and compared: the open-circuit Desiccant Evaporative Cooling technology and the system based on single-stage LiBr absorption chillers. A computer code has been developed in Trnsys® to simulate a well-insulated single-family residential building, starting from a 3D model of the building architecture, and the solar cooling systems. The simulations have been carried out for two different locations: one in a dry desert area (Riyadh, KSA), the other one on the seaside (Abu Dhabi, UAE). The results show that absorption chillers need a very effective heat rejection system to work properly, whilst DEC systems exhibit a dramatic performance reduction in wet climates.

Naturally comfortable and sustainable: Informed design guidance and performance labeling for passive commercial buildings in hot climates

This work develops guidance and tools to understand the performance, improve the design, and simplify the evaluation of naturally ventilated low-rise commercial buildings in warm and hot climates. We conducted ∼50,000 detailed energy and airflow simulations in 427 locations across Brazil, varying 55 parameters representing building morphology, fenestration, construction properties, internal gains, operating times, wind modifiers, flowpaths, window control, and soil traits. Comfort performance was quantified by the average annual fraction of occupied hours that exceeded the upper limit of an adaptive comfort zone, and investigated with sensitivity analysis and machine learning methods. Results indicated that, after climate, building size (both footprint area and number of stories) and internal gains were most influential and were positively associated with discomfort. Adding air movement with ceiling fans and providing for night ventilation both proved highly effective comfort interventions. Except for roof solar absorptance, opaque envelope changes, including increasing insulation or thermal mass, had only marginal impacts. A support vector regression metamodel, requiring 29 easily obtainable inputs plus a weather file, was fit to the simulation results and successfully validated (R2=0.97). The metamodel was developed as a simplified compliance path for naturally ventilated buildings to enhance Brazil’s commercial building performance labeling program, which, because it currently provides such a path only for air conditioned buildings, may discouraging decision-makers from considering even more efficient passive solutions. We use a case study to show how the metamodel, which we will distribute publicly, can also serve as a design tool, and demonstrate that modifying a small set of parameters can drastically improve thermal performance and achieve sustainable comfort in hot and warm climates.

Impact of building forms on thermal performance and thermal comfort conditions in religious buildings in hot climates: a case study in Sharjah city

ABSTRACTThe common system used for thermal regulation in mosques of United Arab Emirates (UAE) is the heating, ventilating and air-conditioning (HVAC) system. This system increases demands on energy consumption and increases CO2 emission. A passive design approach is one of the measures to reduce these problems. This study involved an analytical examination of building forms, followed by testing the impact of these forms on its thermal performance and indoor thermal comfort. The tests were conducted using energy simulations software packages. Passive parameters such as shading devices, thermal insulation and natural ventilation were applied in six cases, including the baseline case within each form. The obtained results showed a significant effect of mosque forms as well as passive design techniques on the thermal comfort within the structures. The findings confirmed that the use of passive design alone would not help achieve thermal comfort, but reduce the annual energy consumption by10%. By integrating a hybrid air-conditioning system as another supporting approach, the annual energy consumption could be reduced by 67.5%, which allows for the designing of a much smaller HVAC system.

Achieving annual and monthly net-zero energy of existing building in hot climate

This paper demonstrates the possibility of converting a public building from inefficient energy consumer into a net-zero energy building (NZEB). This task is achieved through cost effective energy efficient measures (EEMs) and integration of solar energy systems. Three scenarios that utilize the same roof area are proposed to convert the building into NZEB. The first two scenarios use only PV system with the second scenario that incorporates replacing current chillers with more efficient chillers while the third scenario combines both PV and solar cooling systems. The first scenario attains NZEB on annual basis only whereas the other scenarios achieve NZEB on both annual and monthly basis. The second scenario has distinct advantages over other scenarios with respect to energy saving, interaction with energy grids and economic consideration.Both implemented and proposed EEMs result in about 1480MWh saving of the building consumption and about 1021ton avoided CO2 emission annually with payback periods ranging from half to 3years for the considered measures. Annual avoided CO2 emission of about 748ton is achieved for first or second scenario and about 848ton for third scenario with payback periods 14.1, 11.8 and 15years for the 3 considered scenarios, respectively.