Cooling Load Energy Research Articles

Masonry screen walls: a digital framework for design generation and environmental performance optimization

Masonry screen walls are architectural elements made from bricks that create different patterns to provide shade and natural ventilation to buildings. This paper presents a digital framework for the design of masonry screen walls, whose performance as environmental control elements is optimized while complying with vernacular construction rules. The framework employs shape grammars for creating a generative design system based on existing construction rules. This design system is then translated into a parametric model and connected to a simulation engine that calculates daylight metrics and cooling energy loads. A genetic algorithm is then used to find a family of optimized solutions, with visual feedback being provided to facilitate the understanding of trade-offs between such solutions. The proposed framework is tested with a case study, in which design solutions are generated by manipulating selected design variables to find optimal design solutions in terms of environmental performance. .

The application of non-Crassulacean acid metabolism edible plant and lightweight expanded clay aggregate to achieve joint benefits of thermal insulation mitigation and passive cooling strengthening of extensive green roofs in subtropical regions

The advantage of the high passive cooling effect of traditional extensive green roofs during daytime is always offset against their disadvantage of the high thermal insulation effect during nighttime in summer in subtropical regions. The purpose of this study was to develop types of green roofs that can not only improve the passive cooling effect of extensive green roofs during daytime but also mitigate the thermal insulation effect of extensive green roofs during nighttime in summer in humid subtropical regions to reduce the cooling energy load over 24 h compared with that of traditional extensive roofs. The following factors were considered to obtain such an ideal extensive green roof—the depth of growth medium, the proportion and placement of lightweight expanded clay aggregate (LECA), and the presence and absence of a non-CAM edible plant. The results indicated that, compared with the 0% LECA (traditional garden soil) roof without plants in the second stage and under a slightly different air temperature (0.26 °C during daytime and 0.57 °C during nighttime), the introduction of Ipomoea batatas and 10%–40% LECA can significantly increase the passive cooling effect by approximately 1.5 times (5.51–6.21 °C) during daytime and significantly mitigate the thermal insulation effect by approximately half (2.05–3.20 °C) during nighttime. In summary, the introduction of Ipomoea batatas (non-CAM edible plant) and LECA into the traditional extensive roofs can effectively reverse the higher-cooling-and-stronger-warming effects to higher-cooling-and-weaker-warming effects.

Urban road and pavement solar collector system for heat island mitigation: assessing the beneficial impact on outdoor temperature

Road renewable energy system has raised much attention from both industrial and academic research on how abundant solar radiation absorbed by road surfaces can be collected while reducing the impact of high surface temperature towards urban environment. Cities consume about 3% of total global land mass with road and parking lots consuming around 35 to 50% of land use footprint. These urban road networks permit the dynamic movement of human activities and physical development of the cities. Remarkably, researches have given much spaces to explore on how roads can contribute to make cities more sustainable. Therefore, ideas on road renewable energy system have surfaced to its audiences. The heat island effect has been reported to raise temperature up to 12°C in urban areas which affects building cooling energy load and simultaneously the people comfort. High discomfort can lead to high energy and cost utilisation, which further worsens the issue. This study assessed the beneficial impacts of urban road pavement solar collector towards reducing outdoor temperature by carrying out de-coupled numerical modelling of an urban canyon model integrated with the pavement solar collector in ANSYS FLUENT, validated with experimental data. Numerical results showed up to 4.67 °C air temperature reduction and up to 27.0 % surface temperature reduction after the U-RPSC application. When applying to street canyon with different heights, the concern was highlighted on the system performance in reducing potential UHI effect in deeper canyon during less windy condition and during the night-time. The study also presents the experimental work on the performance of a laboratory-scale U-RPSC system.

Investigation of Sun Protection Issues via the Active and Passive Building Integration of Active Solar Energy Systems: A Case Study of the Renovation of an Existing Building in Cyprus

The demand for a continuous and extensive use of buildings in contemporary central business districts without proper maintenance has led to an aging building stock. The need for refurbishment and use of these buildings, based on the Energy Performance of Buildings Directive (EPBD) in Cyprus, is a challenge that all real estate asset managers need to face. This paper aims to examine whether specific building integrated active solar systems (BIPV), along with their basic operation can be used as passive shading devices as part of a double shell, as indicated in the case study for the renovation of an existing mixed-use building in Nicosia, Cyprus. The proposed research starts with an analysis of building and site geometry and an investigation into a philosophy of operation through a literature review, along with the presentation of case studies where these active solar systems are integrated on double building shells. Digital energy simulations are performed where the technologies are examined as a passive shading device, as part of the double shell of the renovated building. These simulations aim to analyse whether the system can cover the energy needs of the aforementioned building, whilst providing adequate sun protection. Consequent to the results of the digital simulation, the heating and cooling energy loads – in order to keep the interior of the simulated building within thermal comfort levels – are examined, thus affording the opportunity to compare and contrast the before and after situation. Moreover, the annual primary energy production of the integrated systems is calculated and compared with the building ‘s annual energy needs. The ultimate aim of this work is to determine the environmental sustainability of these building integration solutions for the refurbishment of existing buildings.

The effect of changing surface emissivity on the natural ventilation rate of a narrow air cavity integrated in a transparent insulation façade

A transparent insulation material (TIM) can be incorporated in a building element in order to improve its thermal performance, including solar heat gain. However, some overheating protection needs to be implemented. The provision of natural ventilation in a façade cavity to avoid overheating, along with other potential techniques, could require a completely different approach to TIM integration in solar façade concepts. This paper concerns an analysis of the effect of different absorber emissivity behind a transparent insulation system. The emissivity changes are primarily studied in order to determine their effects on the overall radiation - natural convection heat transfer through a narrow façade air cavity. A comparative investigation was conducted using experimental full-scale dynamic outdoor tests and the building energy simulation (BES) approach. The thermodynamic response affected by the radiation - natural convection transfer is identified, specifically during the summer peak period, that corresponds to overheating. Depending on the ventilation regime, a low emissivity solar absorber inside a narrow air façade cavity may increase the cooling energy load and temperature response of a façade by 25 and 36%, respectively, in comparison with a high emissivity absorber. When the emissivity of the zone inside the cavity was changed, significant limitations were identified in the BES calculation methods for both vented and unvented cases.

A simplistic and efficient method of estimating air-conditioning load of commercial buildings in the sub-tropical climate

Energy efficiency of buildings is attracting significant attention from the research community, as the world is moving towards sustainable building designs. The average heat gain is the crucial measure for estimating the energy consumption of the buildings. The Envelope Thermal Transfer Value (ETTV) is a simplistic method of determining average heat gain in buildings through its envelopes considering all heat gain components. It also measures the energy efficiency of buildings without inhibiting the design options. The values of ETTV coefficients highly depend on the climatic conditions, geographical locations and the orientation of the buildings. However, no study has been done to investigate the suitability of applying ETTV approach and to develop ETTV formulations for extreme solar radiation with hot and windy climatic conditions like Australian environments. In addition to this, the relevant studies reported in the literature are not comprehensive enough as the coefficient were developed using limited data and the developed formulations were not applied to a variety of real buildings to validate them. Therefore, the main aim of this study is to develop the coefficients of envelope thermal transfer value for commercial buildings, formulate new ETTV equations for buildings with external shadings and estimate the ETTV based annual cooling energy in the sub-tropical climates of Australia. In this study, real life building data relevant to all heat gain parameters of five existing commercial building have been collected and hourly data of wall conduction, window conduction and solar radiation for 11 different types of wall construction and 54 types of window construction have been analysed to determine coefficients of ETTV. Based on these coefficients, the new formulation of ETTV has been proposed to determine total ETTV value of commercial buildings in sub-tropical climate. The developed formulations have been used to estimate the cooling energy loads of 10 real life buildings. A comparative study has been conducted between these estimated cooling energy consumption based on ETTV, actual building load and simulated cooling energy using commercial software. It was demonstrated that developed equations accurately estimate the building cooling load. The computed values of ETTV are within the range 24–42 W/m2, which can be applied in any air-conditioned commercial building in sub-tropical climate like Australia.

Comparative bioclimatic approach for comfort and passive heating and cooling strategies in Algeria

The energy consumption and thermal comfort in buildings are heavily affected by weather conditions. Therefore, the aim of this paper is to analyze the bioclimatic potential of Algerian climate zones. This analysis was made based on eight representative locations using recent weather datasets (2003–2017). The thermal comfort and passive design potential analysis were based on a psychometric chart applying the adaptive comfort model ASHRAE 55–2017. In addition, an evaluation of the bioclimatic potential was conducted using simulations of a monitored and calibrated residential building model in Algeria using EnergyPlus. The building model has been tested in eight previously selected locations. The heating and cooling energy load results were calculated for each climatic zone and compared. The results allow architects and urban planners to better understand the climate and provide practical design guidance.

A transparent insulation façade enhanced with a selective absorber: A cooling energy load and validated building energy performance prediction model

Solar thermal façade concepts for building integration have a relevant contribution in the field of renewable solar energy exploitation. This study is focused on an experimental analysis of a transparent insulation façade (TIF) concept and the options for the prediction of its performance using building energy simulation (BES) modelling. A TIF prototype based on a transparent insulation material (TIM) and a selective absorber is tested and compared with a nonselective type of absorber. An experimental study was conducted involving full-scale climatic chamber and dynamic outdoor tests. The proposed TIF concept with a selective absorber and its solar effective layers provides the same thermal performance as conventional types of thermal insulation. As the TIM integration is potentially limited by overheating phenomena, a maximum cooling energy load obtained by dynamic outdoor conditions provides its real outdoor performance. The results show that a significant difference is measured when compared with the nonselective absorber type. Finally, a detailed comparative investigation of the thermal performance of both TIFs was conducted using the BES method. When applying the low-e functionality of the solar absorber, significant limitations were found specifically concerning the surface radiant heat exchange with the low emissivity surface affecting the air cavity enclosed zone.

The Rasmaska project: Temperature behaviour of three, full scale test cells in hot mediterranean summer: Non-insulated double masonry wall and different insulation locations

There is a global concern to reduce reliance on fossil fuel energy in all sectors, including the built environment. For that reason, global and regional bio-climatic codes and references tend to promote different thickness levels of insulation or low U-value construction, regardless of the climatic zone. Previous studies have already shown that outer wall insulation is the best location for cooler internal summer temperatures, and/or less cooling energy load. However, in face of this global obsession with insulation addition, no research has factually completed any comparative studies with uninsulated structures. This research is about the summer internal temperature performance of different wall and insulation configurations observed simultaneously in three purpose-built test cells under various internal conditions. The monitoring occurred in the coastal climate of Lebanon and spanned an entire summer season. The climate is defined as warm temperate with long hot summers and warm short winters. Each test cell had an internal area of 10 sqm with plastered double masonry walls and a 25 mm insulation placed on the outside, middle, and inside. By mid-summer, the middle insulation was removed to have an uninsulated double masonry wall. Results were consistent with previous studies that outer insulation is better than inner insulation for cooler internal summer temperature. Interestingly, however, once insulation was removed, test cell recorded cooler internal temperatures than the outer insulation counterpart.

A PMV-PPD model based study of thermal comfort in Low-Income Group house in Chhattisgarh

People tend to maintain symmetry between comfort and economy while choosing essential commodities needed in their life. Families buy a house which may offer comfort condition, but at minimum in term expenses of energy throughout a life. Thus, it is most important to erect a house to provide comfortable condition and moderate the lifetime expenditure by saving energy consumption. Sensation of thermal comfort varies from people to people, even in an identical environment. To minimize the consumption of energy of building, cost of consumed energy and to provide a comfortable house, thermal comfort analysis in indoor environments have attracted many researchers. Fanger’s Predicted Mean Vote (PMV) - Predicted Percentage of Dissatisfied (PPD) model is widely accepted theory for assessment of building indoor thermal conditions. In the present work, thermal comfort of an LIG house in Chhattisgarh region of India has been analyzed based on PMV-PPD method for months representing three different seasons in a year i.e. May, September and December representing summer, post monsoon and winter respectively. Cooling, heating and actual energy load of LIG house has been calculated and reported for the above mentioned months. From analysis it is concluded that inhabitants are comfortable only during the winter.

Window-to-Wall-Ratio for Energy Reduction in Early Design Stage of Residential Building

In Korea, it is necessary to improve the performance of buildings with respect to the energy efficiency while improving the quality of occupants’ lives through a sustainable built environment. During the design and development process, building projects must have a comprehensive, integrated perspective that seeks to reduce heating, cooling and lighting loads through climateresponsive designs. The aim of this study is to assess the optimal window-to-wall ratio of multi-rise residential units in the early design phase in Korea. The study analyzed the variation of annual heating and cooling energy load in two apartment prototype units located in Seoul city using different WWRs. The analysis was conducted using Autodesk Ecotect Analysis 2011 tool. The study found for total annual building load reductions WWR on the south and north face should be studied independently based on the room function. It also found reducing the WWR for bedrooms and windows on the northern facade resulted in reduced total annual building load.

A bioclimatic approach to develop spatial zoning maps for comfort, passive heating and cooling strategies within a composite zone of India

Bioclimatic potential studies are important for passive design applications in the conceptual stage of climate responsive building design. Being a land of vast climatic diversity, very few such studies exist in India. This paper aims to develop bio climatic charts for 21 locations within a composite climate zone in India. Spatial zoning maps for natural comfort and passive heating and cooling strategies have been developed for these 21 selected locations based on adaptive comfort criteria. A further evaluation of the bioclimatic potential analysis was carried out through a simple heating and cooling energy load simulation for all locations. Impact of the local climate on building heating and cooling energy load was evaluated using statistical techniques thus establishing a direct relationship between bioclimatic potential and annual energy load. Results show great variation in comfort and passive design potential even within the composite zone. A gradual increase in the number of comfort hours was observed as one moves geographically from the north towards south within the composite zone. The natural comfort potential varies from 23 to 46%, passive cooling potential varies between 26.5 and 53.5% and the passive solar heating potential varies from 3 to 20% of the time of the year based on location. Results of this study can be used for further sub-zoning of the composite region based on thermal comfort and passive design criteria, which will further the development of location specific passive design strategies. Limitations of the present study and scope for future investigation are also delineated.

The impact of the building envelope on the energy efficiency of residential tall buildings in Saudi Arabia

In this paper, the authors explored the hypothesis that the most common approach to improve a building’s energy efficiency in the hot climate of Saudi Arabia, which focuses on engineering parameters, is not sufficient and architectural design parameters should be adopted to reduce cooling loads. In order to investigate this hypothesis, 27 sets of dynamic thermal simulations were compared. The best and worst combinations of glazing ratio, wall and glazing type were identified in order to understand the most influential parameter impacting the cooling energy loads in the building. The findings demonstrated that the reliance on a prescriptive approach for building envelope ‘engineering parameters’ specifications does not achieve the required levels of energy efficiency, and the thoughtful consideration of the ‘design parameters’, such as shading elements, could have a significant impact on cooling energy loads.

Experimental testing of the performance of a solar absorption cooling system assisted with ice-storage for an office space

Energy storage plays a vital role in shifting cooling energy load from period of peak demand to that of low demand. This paper reports performance data of an ice-storage unit in solar absorption cooling system for cooling an office space. The cooling system consists of ammonia-water absorption chiller, evacuated tube solar collectors and ice-storage. Experiments were carried out on two consecutive days in each of the month of March and October in Dhahran, Saudi Arabia. The ice-storage unit was charged on the first day and the cool energy discharged on the other day. The results showed average coefficient of performance (COP) of the chiller during charging as 0.43 and 0.47 for the months of March and October, respectively. The results also indicate that the ice-storage can provide a backup time of about 5–6h, which is sufficient to cool the given space during the early hours of chiller warm-up.

주택에서의 단열성능 강화가 냉난방부하에 미치는 영향

In this study, we chose the rural house as a standard model. In order to review the energy difference of cooling and heating loads, we changed the thermal transmittance standards. By using the thermal transmittance standard in 2011 as the Basic CASE, the thermal transmittance standard in 2013 as well as 2016, and the thermal transmittance standard of passive houses, we compared the results with regard to the cooling and heating energy load. Because of the heat loss, it can be confirmed that with an improved thermal performance of the building structure, the maximum increase of the cooling energy load was 36 kWh from June to September. Because of the heat loss, it was also confirmed that with the improved thermal performance of a building structure, the maximum decrease of the heating energy load is 1,498 kWh from November to April. Even though the heat loss of the building structure could decrease the cooling energy load by improving thermal transmittance standards in Korea, the energy saving performance is worse than the situation of heating energy load in heating period. Compared with CASE 1 and CASE 2, as well as CASE 1 and CASE 3, we CASE 3 was found to have the best energy saving rate when compared to the other cases : CASE 3 increased by 1,452 kWh and CASE 2 by 588 kWh, because the window thermal transmittance standard of 2016 was added.

Influence of Glazing Types on the Indoor Thermal Performance of Tropical High-Rise Residential Buildings

In tropical climates, the solar radiation absorption of glazed windows results in overheated indoor environments and increased cooling energy loads during daytime. Meanwhile, situations differ during nighttime. The present study focuses on the effects of glazing type on the indoor temperature in high-rise residential buildings in the hot and humid climate of Malaysia. The primary objective of this study is to assess the effects of six glazing types on the indoor air temperature of the base case room oriented toward the southwest with a Window Wall Ratio WWR of 45% under both ventilated and unventilated conditions. The effects during daytime and nighttime are investigated separately. A computerized simulation tool (Virtual Environment by Integrated Environmental Solutions) is used to conduct the investigation. Penang is selected as the empirical background location of a hot and humid climate. The study found that reflective double glazing exhibits lower indoor air temperature throughout the day regardless of the ventilation condition, with an optimum improvement of up to 107% and 14% in unventilated and ventilated rooms, respectively, compared with single clear glazing. The study recommends the use of reflective single or double glass in regions with a hot and humid climate similar to that of Malaysia.

Forecasting diurnal cooling energy load for institutional buildings using Artificial Neural Networks

This study presents a methodology to forecast diurnal cooling load energy consumption for institutional buildings using data driven techniques. The cases for three institutional buildings are examined. A detailed analysis on their energy consumption data for two years shows that there is a high variation in diurnal energy consumption. This is largely attributed to the university scheduling and vacation periods. To reduce the degree of variation, the energy consumption data is divided into classes. These class numbers are then taken as inputs for the forecasting model which is developed using Artificial Neural Networks (ANN). The results show that the ANN is able to train and forecast the next day energy use based on five previous days’ data with good accuracy. The model development, along with ANN architecture used in this case is discussed in detail. As a next step, the forecasted output is taken back as an input with a view to forecast the output of the following day. This step is repeated and the model exhibits an R2 of more than 0.94 in forecasting the energy consumption for the next 20 days. It is also noted that such a methodology can be positively extended to other institutional buildings.

Effect of Courtyard Shape Factor on Heating and Cooling Energy Loads in Hot-dry Climatic Zone

In hot and dry climate, the geometry of the courtyard form affects considerably the shadows produced on the building envelope, and consequently the received solar radiation and the cooling and heating loads of the building. Therefore heating and cooling loads for different courtyard shapes should be evaluated. Courtyard shape can be defined by basing on the shape factor (W/L). Shape factor is the ratio of courtyard width (W) to courtyard length (L).This paper aims to introduce a study that has produced a choice of courtyard shape varying the W/L ratios to use in their efforts to reduce heating and cooling loads. The effect of building form surrounding the courtyard is taken into account by its volume (V) and external wall area (A). In the study the V/A ratio is taken 1 for every developed courtyard building form. This study goes further to examine the variation of the obtained heating and cooling loads as a result of changing the building form with the proportion of the courtyard.

Analysis of Cool Roof Coatings for Residential Demand Side Management in Tropical Australia

Cool roof coatings have a beneficial impact on reducing the heat load of a range of building types, resulting in reduced cooling energy loads. This study seeks to understand the extent to which cool roof coatings could be used as a residential demand side management (DSM) strategy for retrofitting existing housing in a constrained network area in tropical Australia where peak electrical demand is heavily influenced by residential cooling loads. In particular this study seeks to determine whether simulation software used for building regulation purposes can provide networks with the ‘impact certainty’ required by their DSM principles. The building simulation method is supported by a field experiment. Both numerical and experimental data confirm reductions in total consumption (kWh) and energy demand (kW). The nature of the regulated simulation software, combined with the diverse nature of residential buildings and their patterns of occupancy, however, mean that simulated results cannot be extrapolated to quantify benefits to a broader distribution network. The study suggests that building data gained from regulatory simulations could be a useful guide for potential impacts of widespread application of cool roof coatings in this region. The practical realization of these positive impacts, however, would require changes to the current business model for the evaluation of DSM strategies. The study provides seven key recommendations that encourage distribution networks to think beyond their infrastructure boundaries, recognising that the broader energy system also includes buildings, appliances and people.

Field Observation of Cooling Energy Savings Due to High-Reflectance Paints

Cooling energy savings in a building with the roof coated with high-reflectance paint are examined. It is difficult to recognize such savings using the data observed hourly. Among the factors assumed to affect cooling energy load are: (1) internal heat generation, (2) set temperature, and (3) weather conditions. By analyzing the relationship between indoor-outdoor air temperature difference (averaged) and electric power consumption (integrated) of the air conditioner in the building over a day, the reduction in electric power consumption due to the use of a high-reflectance paint coating is estimated at approximately 72 Wh·m−2·day−1.