节能促进了建筑采光技术的发展

太阳是一个巨大的洁净能源，在建筑中如何有效地利用太阳光资源，节约人工照明用电，有着重要技 术经济和现实意义。本文简要地介绍了节能促进建筑采光技术的发展概况。对照明节能的潜力，我国天然 光资源的分布，太阳光在建筑中的利用方法和利用太阳光的采光设计等问题作了较系统的论述。     

Measurements of solar radiation and illuminance on vertical surfaces and daylighting implications

There is a growing concern about the rapid development of infrastructure and building projects and their likely impacts on the environment. Particular concerns have been raised about office building developments and energy consumption issues. In recent years, there has been increasing interest in using daylight to save energy in buildings. Lighting control integrated with daylighting is recognised as an important and useful strategy in terms of energy-efficient building design. It is believed that proper daylighting schemes can help reduce the electrical demand and contribute to achieving environmentally sustainable building developments. This paper presents a simple method for estimating the likely energy savings in electric lighting due to daylighting and the possible cooling penalty. Vertical solar radiation and illuminance data measurements are described. Cumulative frequency distributions of daylight availability are reported. The likely energy savings in office buildings are determined based on on–off and top-up controls, and the energy and environmental implications are discussed.     

Luminous effectiveness of tubular light-guides in tropics

Novel tubular light-guides with a transparent hemispherical cupola placed on an unobstructed flat roof collect all sunlight and skylight available at ground level year round. This advantage is heightened in the dry and sunny tropical regions where the sun rises to very high altitudes and often the hours of sunshine last throughout the whole day. Hollow light-guides with very high inner specular reflectances can transport sunbeams downward into the windowless building core very effectively. Due to the tube’s diameter and length and multiple reflections, complex illuminance patterns are produced on the underside of the tube, i.e. on top of the glazed ceiling aperture that illuminates the interior space or its working plane. This paper discusses several daylight conditions in tropical interiors illuminated by tubular light-guides. The recently published HOLIGILM calculation program and the user-friendly tool HOLIGILM 4.2 have facilitated the production of this paper.     

Artificial neural networks for energy analysis of office buildings with daylighting

An artificial neural network (ANN) model was developed for office buildings with daylighting for subtropical climates. A total of nine variables were used as the input parameters – four variables were related to the external weather conditions (daily average dry-bulb temperature, daily average wet-bulb temperature, daily global solar radiation and daily average clearness index), four for the building envelope designs (solar aperture, daylight aperture, overhang and side-fins projections), and the last variable was day type (i.e. weekdays, Saturdays and Sundays). There were four nodes at the output layer with the estimated daily electricity use for cooling, heating, electric lighting and total building as the output. Building energy simulation using EnergyPlus was conducted to generate daily building energy use database for the training and testing of ANNs. The Nash–Sutcliffe efficiency coefficient for the ANN modelled cooling, heating, electric lighting and total building electricity use was 0.994, 0.940, 0.993, and 0.996, respectively, indicating excellent predictive power. Error analysis showed that lighting electricity use had the smallest errors, from 0.2% under-estimation to 3.6% over-estimation, with the coefficient of variation of the root mean square error ranging from 3% to 5.6%.     

New component for daylighting: first italian application of a sun duct

The use of daylighting in a room is certainly better than the use of lamplight alone, due to its undubitable chromatic properties and correlated psychological effects. In many cases, especially for pre-existing buildings, the income of daylighting appears an unsolvable problem forcing people to use intensively electric lighting. In this paper the use of a component for natural lighting of a space with no direct openings to the exterior is presented. The project was carried out in a building situated in the old town centre of S. Colombano al Lambro near Milan.     

Towards green buildings: Glass as a building element—the use and misuse in the gulf region

The recent economic growth in the Gulf region notably in Dubai, United Arab Emirates (UAE) has led to a colossal number of buildings that has been constructed in the past 5 years. In the last decade, a total glazed building's façades became the icon of Dubai. This large area of glazing in each façade needs protection against overheating and sun glare in summer. According to leader in energy and environmental design (LEED) glass selection becomes a main element in this equation to contribute towards achieving a green building. The aim of this paper is to investigate the problems associated with misuse of glass, as a building element in UAE particularly in Dubai. Inadequate design with ill-selected glass/glazing type may lead not only to poor daylighting in building interiors but also contribute significantly to fatigue, insomnia, seasonal affective disorder (SAD) and above all increase CO₂ emission.The purpose of the study is to specify the required improvements to permit natural, ‘free’ daylight to filter through the building façade into interior space, especially with the right type of glass. This paper examines the status of buildings in Dubai in terms of glass type, visible light transmittance, reflection (out/in) and relative heat gain. A quantitative analysis is conducted to assess the impact of glass on the building users' performance in terms of daylight environment. A recent built high-rise office building was selected in the investigation to asses whether selected glass provide the recommended daylight factor (DF) and daylight level (DL) according to IES standards. The results revealed that most the glass/glazing was misused in 70% of buildings in intermediate and low performance groups. The DF and DD in the selected office building were unexpectedly tremendous and found far beyond the recommended level due to the use of spectrally selective glazing (clear on both sides).     

Daylighting performance of optical rods

A novel tubular daylighting device, the light rod, is shown to have high transmittance throughout the day in Singapore. Constructed of an optical quality polymer and clad by air, the light rod is intended for use in buildings where fabric constraints prevent the use of larger daylighting devices. Maximum measured output is around 360 lm per rod and peak output is expected to be around 400 lm. Bending of light rods by up to 90° to accommodate corners is found to reduce output by less than 20% and modification of light emission is straightforward and aesthetically pleasing. An equation is used to describe light rod transmittance and used to predict performance at high aspect ratios, which is found to far exceed transmittance by light pipes of similar aspect ratio. Light rods of small diameter are expected to transmit light effectively at lengths greater than 4 m. The compact size of the light rods is expected to allow installation in locations previously without access to natural light.     

An analysis of energy-efficient light fittings and lighting controls

Electric lighting is one of the major energy consuming items in many non-domestic buildings. Using appropriate energy-efficient light fittings with dimming controls and proper daylighting schemes can help reduce the electrical demand and contribute to visual comfort and green building development. This paper presents a study on the energy and lighting performances for energy-efficient fluorescent lamps associated with electronic ballasts and high frequency photoelectric dimming controls installed in a school building. Electricity expenditures and indoor illuminance levels for a workshop and a classroom employing high frequency dimming controls were analyzed. Simple prediction methods were used to illustrate the lighting savings. The findings provide the operational and performance information, which would be applicable to other spaces with similar building layouts and lighting schemes.     

Efficient venetian blind control strategies considering daylight utilization and glare protection

This paper presents the development of new venetian blind control strategies considering daylight provision, lighting energy use and visual comfort. A hybrid ray-tracing and radiosity method is used to calculate transmission through the window-blind system and interior illuminance distributions taking into account specular and diffuse material properties. Work plane illuminances are used to extract daylighting metrics, while directional light distribution and respective luminance values are used to calculate glare potential. Four types of control strategies were evaluated – a cut-off angle control, a daylight-redirecting control, and two glare protection control modes. Using the common “cut-off” angle may result in a strong second reflection that might significantly affect visual discomfort depending on view direction and profile angle. Proper rotation of the tilt angle and consideration of specular characteristics can minimize this effect and redistribute daylight deeper into the space, although glare problems cannot be eliminated in some cases. Moreover, two additional control strategies were developed based on glare probability and sky conditions: the first is a model-based control derived from real time glare simulation results. The second is a “simplified” control that uses pre-calculated correlations between glare probability and transmitted illuminance to establish binary set points that can be used in model-predictive control algorithms.A detailed daylighting analysis was performed in order to evaluate set points for blind control actions, annual daylighting metrics, lighting energy use and daylight glare probability and duration. Different room sizes, glazing properties, blind material characteristics and orientations were studied. The results showed that diffuse blinds do not reduce the risk of glare when light redirection is desired; double-sided slats with a diffuse top and a specular bottom surface are better in this regard. Fixed angles at 60° or higher provide satisfactory results for most cases, although there is a penalty in daylighting efficiency. The two glare protection control algorithms proved to be efficient in providing high daylight autonomy values without the risk of glare for all studied cases.