1 Introduction
Natural light is a safe, inexhaustible source of clean energy, making full use of natural light, which can save a lot of lighting power and protect the environment. China is located in a temperate zone with a mild climate and abundant natural light resources. Therefore, making full use of natural light has become an important aspect of developing sustainable buildings in China. The biggest problem facing the utilization of natural light is its instability and variability. Light climate research is an important basis for lighting design.
1. 1 Localization trend of architectural design
The current architectural design is moving towards ecological and sustainable development, which raises the need for localization of architectural design. That is to say, the building should adapt to the local geographical environment, climatic conditions, building materials, history and culture, and lifestyle, so as to ensure the building can save energy and protect the environment without sacrificing comfort. In order to create an artificial environment as little as possible, local climatic conditions in localized architectural design are important factors that must be considered. Light climate is an important aspect related to architectural lighting. The study of light climate is to obtain reliable natural light data, so that the architect can carry out accurate lighting calculation and design, which can effectively save energy and obtain a more comfortable indoor light environment.
1. 2 Localized light climate data
China has a vast territory, and there are huge differences in light and climatic conditions in different regions and at different times. Therefore, architects and lighting engineering designers must consider the specific characteristics of different time periods and specific regions when designing architectural lighting. In the past, when lighting design, the lighting calculation was often based on the lighting coefficient under full cloudy conditions. Although regional differences are also considered, the five subareas are clearly insufficient for a vast area of ​​9.6 million square kilometers, and the conservative lighting calculation hypothesis brings waste of electricity.
Localized architectural design and lighting design require localized light climate data. Short-term and long-term regional light climate data including solar radiation, outdoor illumination and sky brightness distribution are for architectural lighting design, architectural design and urban design. necessary. Light and climate change is impermanent, and the natural light and sky conditions available outdoors are constantly changing with time and place. In order to obtain better localized design effects, it is necessary to study the law of natural light changes under local climatic conditions, that is, to obtain regional light climate data.
1. 3 GIS application in data processing
Geographic Information System (GIS) is a specific spatial information system that collects geographically distributed data in all or part of the Earth's surface (including the atmosphere) space, supported by computer hardware and software systems. A technical system that stores, manages, calculates, analyzes, displays, and describes. GIS is used to analyze and process various phenomena and processes distributed within a certain geographical area to solve complex planning, decision-making and management problems. GIS should provide the following basic functions: data acquisition, initial processing of data, storage and retrieval of data, query and analysis of data, display and interaction of graphics. At present, GIS has been applied in urban design. Applying GIS to the storage and analysis of regional light climates can take advantage of GIS's ability to process spatial data.
The task of this project is to first use the scientific method to obtain regional light climate data of various provinces and cities nationwide, and then combine it with geographic information system to establish a reliable database of light climate information, so that architects and lighting designers can make reasonable and accurate. Architectural lighting design.
2 Acquisition of light climate data
The light climate is affected by factors such as solar elevation, cloudiness, cloudiness, and atmospheric transparency. According to the IDMP (International Daylight Measurement Program), solar radiation should be considered when studying the light climate, including horizontal total solar radiation, horizontal direct solar radiation, horizontal solar radiation, etc.; outdoor illumination, including outdoor horizontal illumination and outdoor Vertical illumination; the distribution of sky brightness, including the brightness distribution of the full cloudy day, the full sunny day, and the middle sky. Solar radiation indicates the energy or heat that sunlight emits to the Earth's surface; the distribution of sky brightness affects the indoor illuminance distribution.
The collection of solar radiation data is relatively simple. The solar radiation data in most parts of China is relatively easy to obtain, and its historical data is also relatively abundant. The outdoor illuminance data is relatively small, and the latest data that can be collected is only in the two years of the 1990s in Beijing and Chongqing. Except for a small amount of zenith brightness data in Chongqing, there are very few records about the sky brightness distribution data. In the current situation where large-scale testing is not possible, other methods are needed to obtain light climate data in China.
In addition to the ground observation method advocated by IDMP, methods for obtaining light climate data include sky model method, digital photo method, satellite image method, and data conversion method. Combined with the current situation of abundant solar radiation data and limited funds in China, this paper adopts the model transformation method and uses the conversion model from solar radiant heat to outdoor illuminance and sky brightness distribution to obtain the required light climate data. The conversion process is shown in Figure 1.
At present, the light climate data transformation model is one of the hotspots of foreign research. Several models have been put into use. Based on the existing data of China, based on several mainstream models, this topic selects the Muneer model and the Perez model. Used to obtain outdoor illuminance and sky brightness distribution data, respectively. Due to space limitations, the selection and use of conversion models will be discussed in other articles.
3 Establishment of light climate information system
According to the light climate data calculated by the light climate data conversion model, a regional light climate database is established and combined with GIS to form China's light climate information system. "Light Climate Information Processing System" has obtained the computer software copyright registration certificate issued by the National Copyright Administration of China, registration number: 2010SR000372. The functional modules implemented by the system include a data management module, a view operation module, a query retrieval module, a data maintenance module, a classification and statistics module, and an auxiliary design module, as shown in FIG. 2 .
Using the light climate information system, the total solar radiation, monthly average solar radiation, monthly average scattered radiation, monthly maximum total radiation, monthly maximum scattered radiation, solar elevation, and azimuth can be obtained in 32 major cities across the country. Data such as angle, outdoor illumination, and sky brightness distribution are provided for daylighting design and daylighting calculations. The light climate information system can not only provide historical data, but also input the newly collected solar radiation data into the system. The system will use the stored conversion model to calculate the light climate data such as outdoor illumination and sky brightness, so the system can be real-time. Data processing and calculation, as long as the user inputs real-time solar radiation data, real-time more accurate light climate data can be obtained, so that the indoor light environment can be simulated in real time through the lighting design software.
The light climate information system filters and transforms the initial data of the light and climate in each place, and uses the model to calculate the data needed in the lighting design, and then stores the light climate data as spatial attribute data. At the same time, the basic geographic map is transformed into a vector form, input into the system, and a unified national coordinate grid is established to form spatial coordinate data. The light climate data, that is, the spatial attribute data and the spatial coordinate data are connected to form a complete spatial data of the GIS, and is stored in the form of point data and surface data. The system performs data analysis on the stored spatial data, including statistical analysis. A schematic diagram of the overall framework of the light climate information system, as shown in Figure 3.
