An investigation of the potential for natural ventilation and building orientation to achieve thermal comfort in warm and humid climates

The aim of this study was to analyze the most important factor, the climatic conditions with respect to thermal comfort in buildings. The impact of building location and climate and orientation on thermal comfort were investigated.With the help of dynamic computer simulations the different hourly weather data were analyzed. First of all the climate determines the amount of solar radiation and mean outside temperature that a building is exposed to. The climate also influences the amount of energy that is used for heating and cooling but also the amount of energy that is used for lighting. There is solar excess which determines the amount of solar energy that is unwanted in the building. With growing amounts of glass and a glazing system that allows large solar heat gains,the impact of orientation is substantial. A detailed analysis was conducted to evaluate the potentials for improving thermal comfort. Detailed results are given in sample graphics and tables in the study. In a tropical climate the improvement in comfort by NV range between 9% and 41% (Kuala Lumpur in April). For a subtropical climate the improvements vary between 3% and 14%. In a temperate climate the improvements vary between 8% and 56%. The results showed that NV has a good potential in tropical and temperate climates but not in subtropical climates. Especially in Hong Kong it seems to be very difficult to apply NV. The results showed that in particular in the hottest period (summer) the potential for comfort improvements is rather small. The design of climate responsive building envelopes should take this into consideration.     

Effect of solar absorptivity and emissivity of exterior surfaces on the thermal performance of a building

The effects of the solar absorptivity and the thermal emissivity of exterior building surfaces on the indoor air temperature of a one room building are evaluated in terms of the discomfort index. The thermal performance of the building has been investigated for four different climates prevalent in India, namely, composite (New Delhi), hot and dry (Jodhpur), cold and humid (Srinagar), and cold and dry (Leh). The results confirm the common-sense view that the building surface should have low solar absorptivity and high thermal emissivity in hot climates and high solar absorptivity and low thermal emissivity in cold climates for indoor thermal comfort conditions.     

Identification of the building parameters that influence heating and cooling energy loads for apartment buildings in hot-humid climates

Identifying the building parameters that significantly impact energy performance is an important step for enabling the reduction of the heating and cooling energy loads of apartment buildings in the design stage. Implementing passive design techniques for these buildings is not a simple task in most dense cities; their energy performance usually depends on uncertainties in the local climate and many building parameters, such as window size, zone height, and features of materials. For this paper, a sensitivity analysis was performed to determine the most significant parameters for buildings in hot-humid climates by considering the design of an existing apartment building in Izmir, Turkey. The Monte Carlo method is selected for sensitivity and uncertainty analyses with the Latin hypercube sampling (LHC) technique. The results show that the sensitivity of parameters in apartment buildings varies based on the purpose of the energy loads and locations in the building, such as the ground, intermediate, and top floors. In addition, the total window area, the heat transfer coefficient (U) and the solar heat gain coefficient (SHGC) of the glazing based on the orientation have the most considerable influence on the energy performance of apartment buildings in hot-humid climates.     

Energetic contribution potential of building-integrated photovoltaics on airports in warm climates

Especially in warm climates, a considerable fraction of the electricity demand in commercial buildings is due to the intensive use of air-conditioning systems. Airport buildings in sunny and warm regions present a perfect match between energy demand and solar resource availability. Airport buildings are also typically large and horizontal, isolated and free of shading, and have a great potential for the integration of solar photovoltaic (PV) systems. In this work, we assess the potential impact in energy demand reduction at the Florianopolis International Airport in Brazil (27°S, 48°W) with the use of building-integrated photovoltaic (BIPV) systems. We analyse the building’s hourly energy consumption and solar irradiation data, to assess the match between energy demand and potential generation, and we estimate the PV power necessary to supply both the total amount and fractions of the annual energy demand. Our results show that the integration of PV systems on airport buildings in warm climates can supply the entire electric power consumption of an airport complex, in line with the general concept of a zero-energy building (ZEB).     

A generalized methodology for determining the total heat gain through building envelopes

We present a generalized methodology for determining the annual total heat gain through external walls and proofs of large air-conditioned buildings. The methodology is based on the concept of the overall thermal transfer value (OTTV). Respective OTTV equations for building envelopes and roofs are developed through parametric simulations using the DOE-2 computer code. The equations are valid for buildings having different aspect ratios and wall masses. Appropriate coefficients for heat conduction through fenestrations and opaque walls and solar correction factors for wall facades of different orientations are computed from local weather data. The equations allow building designers to make accurate estimates of the total heat gain for the purpose of evaluating energy-efficient building envelope components and air-conditioning systems and plant options. The methodology is validated using DOE-2 computed heat gain results and can be applied to different classes of buildings, construction types and locations.     

夏热冬暖地区办公建筑能耗模拟与分析

夏热冬暖地区是我国经济和建筑产业最发达的地区之一,也是建筑能耗最多的地区之一。分析和研究夏热冬暖地区建筑能耗的特点对建筑节能有重要的意义。本文用eQUEST建筑能耗模拟软件模拟了夏热冬暖气候下不同的建筑围护结构的能耗性能,并与实际调查结果进行了比较。结论表明:办公类建筑中的空调是最大的能耗终端,全年的能耗以办公设备和照明的能耗最稳定。有外保温措施和同时具有内、外保温措施最大区别在于节省空调电力消耗31.3%和39.1%。说明建筑外墙保温系统是建筑节能的重要手段。     

Analysis of the thermal properties of air-conditioning-type building materials

This work develops air-conditioning-type building materials suitable for different climate regions. Results show that using traditional building materials alone is unsuitable for any climate region, and that building materials of various thermal properties are needed to satisfy the requirements specific to each location. Low solar absorptance and high emittance materials are appropriate for hot climates, whereas high solar absorptance and low emittance materials are suitable for cold climates. Materials with variable solar absorptance and emittance properties are applicable to regions characterized by cold winters and hot summers. In addition, cement that is reversibly thermochromic at normal temperature and materials with variable transmittance properties can warm buildings in winter and prevent overheating in summer, thereby satisfying the need to create a thermally comfortable building environment.     

A new variable for climate change study and implications for the built environment

This short technical note presents an attempt to develop a new climatic variable Z for assessing climate change (global warming) with respect to the built environment. Principal component analysis of long-term (30-year) dry-bulb temperature (DBT), wet-bulb temperature and global solar radiation data was conducted in the 5 major climate zones in China. It was found that while the long-term trend was increasing for the DBT in all 5 major climates, hot summer and warm winter climate zone showed a decreasing trend (though slightly) in the annual and seasonal average Z values. This suggests that climate change might not necessarily result in higher cooling loads in buildings.     

Cold Storage Capacity for Solar Air-Conditioning in Office Buildings in Different Climates

The building sector accounts for more than 40% of the global energy consumption. This consumption may be lowered by reducing building energy requirements and using renewable energy in building energy supply systems. Solar air-conditioning systems(SACS) are a promising solution for the reduction of conventional energy in buildings. The storage, especially the cold storage, plays an important role in SACS for unstable solar irradiation. In this paper, we took the absorption refrigerating unit as an example, and the solar air-conditioning system of an office building in Beijing was simulated. The accuracy of this model was verified by comparing with the SACS operation data. Moreover, based on the simulation data, the cold storage capacity of the solar air-conditioning system in different climatic regions was studied. The cold storage capacities of SACS in 20 cities distributed in different climate regions were studied systematically. The results simulated by our proposed model will be beneficial to the SACS design, and will enlarge the application of SACS.     

Evaluation of electrochromic windows impact in the energy performance of buildings in Mediterranean climates

Old buildings refurbishment is essential for the global improvement of building energy indicators. Within this context, the paper focuses on the energy savings that may occur when using electrochromic (EC) windows, an interesting emerging technology alternative to shading devices to control solar gain in buildings located in Mediterranean climates. The EC windows technology is briefly presented and the optical properties adjustments of the glasses are discussed according to the operated range. The EC window dynamic behavior and the different control strategies are modeled and implemented in the ESP-r building simulation program. The EC window impact in the energy needs for heating and cooling is studied, considering different ambient parameters (exterior dry bulb temperature, interior dry bulb temperature and incident radiation) and set points for the EC control. A comparison of several windows solutions (single, double-glazing and EC windows), the type of building, internal gains from occupancy, lighting and equipment and the orientation of windows are considered for discussion through the analysis of the energy needs for heating and cooling. It is concluded that for this climate the best positive results are obtained when the EC are used in the west façade. For the south façade the results show no significant advantages in using EC windows.     

An analysis of future building energy use in subtropical Hong Kong

Principal component analysis of prevailing weather conditions in subtropical Hong Kong was conducted, and a new climatic index Z (as a function of the dry-bulb temperature, wet-bulb temperature and global solar radiation) determined for past (1979–2008, measurements made at local meteorological station) and future (2009–2100, predictions from general circulation models) years. Multi-year (1979–2008) building energy simulations were carried out for a generic office building. It was found that Z exhibited monthly and seasonal variations similar to the simulated cooling/heating loads and building energy use. Regression models were developed to correlate the simulated monthly building cooling loads and total energy use with the corresponding Z. Error analysis indicated that annual building energy use from the regression models were very close to the simulated values; the difference was about 1%. Difference in individual monthly cooling load and energy use, however, could be up to 4%. It was also found that both the DOE-simulated results during 1979–2008 and the regression-predicted data during 2009–2100 indicated an increasing trend in annual cooling load and energy use and a gradual reduction in the already insignificant heating requirement in cooling-dominated office buildings in subtropical climates.     

大型建筑中应用应急柴油发机实现冷热电三联供及其实例分析

介绍了一种新型的高效节能中央空调冷暖系统－自备发电、余热利用及热泵冷暖系统。该系统充分发挥了大型建筑必备设备－自备电源应急柴油发电机的作用,使一次能源在使用中更加符合热力学的原理;该系统不追求某一种机组的高COP,而是利用各种设备的优点,有机匹配,以求一年中最高效的节能。通过与三种常规冷暖系统的一次能源利用率比较,得出该新型冷暖系统的一次能源利用率比三种常规冷暖系统的一次能源利用率高27．88％－104．6％以上。并通过实例计算了采用该系统的某大型广场的全年经济效益。     

Analysis methodology, experimental investigation, and computer optimization of a passive solar commercial building in the Belgian climate

The Fondation Universitaire Luxembourgeoise (FUL) building (completed in 1986) has been selected as a Belgian candidate for participation in the IEA (International Energy Agency) Task XI project devoted to passive solar commercial buildings. Therefore, an evaluation methodology has been set up and a monitoring plan has been defined and performed. Together with this experimental investigation, intensive computer simulation work has defined an optimized design of the building. The main results show that the recorded performance can be improved to an extent of 15% energy savings, which yields a correct performance for a passive solar building in the temperate maritime Belgian climate.     

Review of passive systems and passive strategies for natural heating and cooling of buildings in Libya

By proper passive design concepts which essentially consist of collection, storage, distribution, and control of thermal energy flow, an energy saving of 2.35% of the world energy output is possible. The basic methods of heating and cooling of buildings are solar radiation, outgoing longwave radiation, water evaporation, and nocturnal radiation cooling. A Trombe-Michel wall consists of a large concrete mass, exposed to sunlight through large, south-facing windows; it is used for heating buildings. Solar absorption cooling and solar dehumidification and evaporative cooling are two approaches that utilize solar energy for the generation of the working fluid and the cooling of dwellings. Outgoing longwave radiation is the most practical way of cooling buildings in desert climates and is effective on roof surfaces, emitting the radiations from the surface of earth to the atmosphere and to outer space. Water evaporation in desert coolers is the usual method of cooling in arid regions. Nocturnal radiation both heats in winter and cools in summer, in suitable climates, and does so with no nonrenewable energy other than a negligible amount required to move the insulation twice a day. The study of 24 different locations in Libya divides the country into regions with distinct passive strategies. The northern region and the Mediterranean coast need passive heating. The buildings in this region should restrict conductive heat flow, prevent infiltration and promote solar heat gains. The southern region, a part of the Sahara desert, needs passive cooling. The buildings in this region need high thermal mass and should promote natural ventilation, restrict solar heat gains and encourage evaporative and radiant cooling. The difficulties encountered in passive solar design are the large exposed area required with suitable orientation for the collection of energy and the large space requirement for the storage of thermal energy. This paper reviews these passive systems and discusses suitable strategies to be adopted for Libya.     

Reducing energy use in the buildings sector: measures, costs, and examples

This paper reviews the literature concerning the energy savings that can be achieved through optimized building shape and form, improved building envelopes, improved efficiencies of individual energy-using devices, alternative energy using systems in buildings, and through enlightened occupant behavior and operation of building systems. Cost information is also provided. Both new buildings and retrofits are discussed. Energy-relevant characteristics of the building envelope include window-to-wall ratios, insulation levels of the walls and roof, thermal resistance and solar heat gain coefficient of windows, degree of air tightness to prevent unwanted exchange of air between the inside and outside, and presence or absence of operable windows that connect to pathways for passive ventilation. Provision of a high-performance envelope is the single most important factor in the design of low-energy buildings, not only because it reduces the heating and cooling loads that the mechanical system must satisfy but also because it permits alternative (and low-energy) systems for meeting the reduced loads. In many cases, equipment with significantly greater efficiency than is currently used is available. However, the savings available through better and alternative energy-using systems (such as alternative heating, ventilation, cooling, and lighting systems) are generally much larger than the savings that can be achieved by using more efficient devices (such as boilers, fans, chillers, and lamps). Because improved building envelopes and improved building systems reduce the need for mechanical heating and cooling equipment, buildings with dramatically lower energy use (50–75% savings) often entail no greater construction cost than conventional design while yielding significant annual energy-cost savings.

遮阳型节能玻璃的全年节能评价

提出遮阳型节能玻璃的全年节能评价新方法，即太阳辐射综合节能效率SEC计算公式，将夏季遮阳节能与冬季透光节能同时考虑，不仅包含太阳辐射、建筑体形等常规建筑热工问题，而且还加入供暖空调系统设备的能效问题，该评价方法可用于全国不同地区的建筑玻璃系统选型，对建筑物冬季太阳能的合理利用具有积极意义。     

济南某酒店空调系统节能改造

对济南某星级酒店空调系统改造项目进行节能分析,探讨了对使用年限较长、建筑能耗较大的既有建筑空调系统进行节能改造的必要性。对该酒店空调系统设计的特点、设备配置以及装修配合等方面进行了分析,并就新旧空调方案进行了经济性比较,结果表明改造后空调系统具有较好的经济性和节能性,为同类型酒店的节能改造提供参考。     

Assessment of climate change impact on building energy use and mitigation measures in subtropical climates

Likely increase in energy use in air-conditioned office buildings due to climate change in subtropical Hong Kong was estimated for two emissions scenarios. Towards the end of the 21st century (i.e. 2091-2100), the average annual building energy use would be 6.6% and 8.1% more than that in 1979-2008 for low and medium forcing, respectively. Potential mitigation measures concerning the building envelope, internal condition, lighting load density (LLD) and chiller plant were considered. Thermal insulation to the external wall would not be effective to mitigate the expected increase in building energy use due to climate change. Controlling the amount of solar heat gain through the window would be a better option. Lowering the current LLD of 15 W/m² to about 13 W/m² would result in substantial energy savings because of the reduction in electricity consumption for both electric lighting and air-conditioning. As for the chiller plant, the coefficient of performance (COP) should be improved from the current minimum requirement of 4.7 to at least 5.5 to alleviate the impact of climate change. Raising the summer set point temperature (SST) to 25.5 °C or higher would have high energy saving and hence mitigation potential, which could be readily applied to both new and existing buildings.     

Estimation of Luminous efficacy of daylight and exterior illuminance for composite climate of Indore city in Mid Western India

Daylighting is one of the basic components of passive solar building design and its estimation is essential. In India there are a few available data of measured illuminance as in many regions of the world. The Indian climate is generally clear with overcast conditions prevailing through the months of June to September, which provides good potential to daylighting in buildings. Therefore, an analytical model that would encompass the weather conditions of Indore was selected. Hourly exterior horizontal and slope daylight availability has been estimated for Indore using daylight modeling techniques based on solar radiation data.     

Investigating the feasibility of positive energy residential buildings in tropical climates

Positive energy residential buildings are houses that generate more energy from renewable sources than they consume while maintaining appropriate thermal comfort levels. However, their design, construction and operation present several critical challenges. In particular, the considerable load reductions are not always compatible with the increased level of comfort expected in modern houses. Tropical climates, meanwhile, should be more amenable to the implementation of positive energy houses for two reasons. Firstly, negligible heating is generally required as compared to colder climates, where the heating energy requirements are considerable. Then, renewable energy resources are usually abundant in tropical climates. This paper investigates the feasibility of positive energy residential buildings in the tropical island of Mauritius. A baseline model representing a typical Mauritian house is designed using DesignBuilder software. The energy efficiency of the model is then optimised by investigating a whole range of passive building design strategies, many of them adapted from vernacular architecture. Results reveal that the application of passive strategies such as shading, insulation and natural ventilation have precluded the need for artificial cooling and ventilation in the positive energy (PE) house. The resulting electricity consumption of the house decreases from 24.14 to 14.30 kWh/m²/year. A 1.2 kW photovoltaic system provides the most cost-effective solution to exceed the annual electricity requirements of the house.