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  • Interestingly the inverse is also

    2018-11-06

    Interestingly, the inverse is also true. In its intense appearance without a sufficient view, artificial bright light can give a positive effect on human well-being, particularly for healing purpose (e.g., Eastman et al., 1998; Lingjærde et al., 1998; Avery et al., 2001). Many specific lighting products had been manufactured to generate a large amount of light with a particular spectral power distribution for this application. In general, the idea behind this type of VNLS prototypes is to recreate the situation with natural light and its qualities inside a space, and to harvest the benefit it purchase LY 2109761 may offer. In addition, directionality of the light is another important property that distinguishes a real window or skylight from an artificial light source. In fact, directional light is something rarely appears on the existing VNLS prototypes, since most of them only generate light in a nearly diffuse direction. Therefore, a non-diffuse, or directional, light is considered a key feature that should appear in an ideal VNLS prototype. Based on these considerations, any VNLS prototypes (that exist) and models (that do not yet exist) can be classified based on their light and view qualities, as illustrated in Figure 1, into four categories: (1) those providing relatively simplified view and mainly diffuse light, (2) complex view and mainly diffuse light, (3) simplified view and mainly directional light, and (4) complex view and mainly directional light. Examples of the first two types already exist as prototypes or real products in reality, while the last two do not yet exist at the moment and are still under development, of which building performance simulation tools have the role to predict the performance.
    Case description An example of the so-called ‘first generation’ prototype is the one developed by Philips (van Loenen et al., 2007), which is briefly discussed in Section 1.1. Due to the possibility to vary the view display, though very limited, and to add a directional spot lamp for simulating the sun, this prototype was selected as the case study in this article to demonstrate how Radiance can be employed to recreate the scenes and obtain the lighting performance of the space, validated by an actual measurement. The prototype (Figure 2) was installed in a kitchen laboratory setting, located in the ExperienceLab of Philips Research in Eindhoven, the Netherlands. The prototype was constructed of 12 colour tubular fluorescent (TL5) lamps of 54W each, put in an array of 12 rows, and covered with a diffuse panel of 1.20m×1.20m. A halogen, parabolic aluminised reflector (PAR) spot lamp of 70W was installed in the upper right corner to simulate the sunlight. The TL5 lamp array was covered by a white, diffuse panel, installed 0.35m behind the window glass plane. The dimension of the diffuse panel was 1.20m×1.20m, while the window opening was 0.65m×0.65m. The 12 TL5 lamps were divided into four groups; each group consisted of three lamps emitting red, green, and blue light, respectively. Every lamp had its own ballast so that Barr body could be dimmed independently, using the Digital Addressable Lighting Interface (DALI) system. The overcast, clear, and partly cloudy sky scenes were realised by adjusting the intensity of each lamp and were subjectively evaluated to imitate the real sky scenes. Table 1 shows the type of colour emitted by each lamp, the electrical power rating, and the intensity level settings for the three scenes. The actual lighting performance was measured and obtained by collecting the following data at certain lighting conditions: Furthermore, to evaluate the lighting performance, the horizontal illuminance data were post-processed to obtain the average illuminance values (E [lx]), the uniformity (U0), and the space availability (%A [%]). The latter is defined as the percentage of the measuring points satisfying minimum illuminance value of 500lx, which is the typical illuminance criterion for interior areas, including kitchen (CEN, 2002). These three indicators can be expressed as follows:where E [lx] is the horizontal illuminance on each measuring point, E [lx] is the minimum horizontal illuminance, is the number of measuring points satisfying the criterion of minimum illuminance value of 500lx, and N is the total number of measuring points.