In order to create a well-designed illumination fuzzy controller, the first set of preliminary experiments was done. The observed variables were inside luminous efficacy and inside illumination resulting from weather conditions during the year. To find out the optical response of the test chamber the experiments were made with fully open roller blind. The figures show the inside illumination and luminous efficacy as response to the global and reflected solar radiation. The first example in Fig. 5 is measurement in April.

Inside luminous efficacy is of about 20 lm/W or less by global solar radiation with maximum by 650 W/m2. Inside illumination is extremely high (up to 12000 lx) when the sky is clear. This is because of the south orientation of the window in the small test chamber with white inside painting. Thus, it is obvious that shading is necessary during the highest solar radiation period. The experiment in Fig. 6 shows the solar radiation in September with optical response of the test chamber.

Luminous efficacy in Fig. 6 is in the range of 2-14 lm/W. On the first day of experiment it is high, up to 14 lm/W, despite of the cloudy sky conditions (solar radiation is of about 100 W/m2). By clear sky conditions solar radiation is more than 700 W/m2, and luminous efficacy is less than 13 lm/W.

Fig. 7 shows the luminous efficacy in wintertime conditions, when the sky is mostly overcast and the sun has the lowest elevation.

Using shading devices in dim wintertime is mostly senseless, while capturing solar radiation in the living space is desired because of energy gain for providing both inside thermal and optical effect. Inside luminous efficacy during the dim winter days is between 20 lm/W and 5 lm/W when solar radiation is between 100 and 350

W/m2. The resulting inside illumination is satisfactory — more than 400 lx. It is interesting to note that in the evenings and in the mornings the luminous efficacy is two times higher than it is at midday. High luminous efficacy on overcast days with low solar radiation derives from high grade of the diffuse component of the daylight.

The observed optical response of the test cell during the year was the basis for the design of the fuzzy controller. Fuzzy controller was progressively optimised. In Fig. 8 the examples for well-designed “winter” and “summer” fuzzy controller are shown. In wintertime regime the direct solar radiation is desired, and this fact was considered in “winter” fuzzy designing. In the summertime regime shading is necessary. Therefore, during the summer period the “summer” fuzzy controller selected higher percentage of shading on window than “winter” fuzzy controller during the winter period for equal amount of solar radiation.

blind movement was relatively moderate and continuous.

Fig. 9 shows the oscillatory movement of the roller blind on the second experiment day as response to changeable solar radiation. Luminous efficacy follows the roller blind movement during the day, it is about 10 lm/W, but in the mornings and evenings it increases extremely.

During the day the inside luminous efficacy is low, less than 8 lm/W (Fig. 10). It is because the window was shaded as response to high global solar radiation with the maximum of 900 W/m2. With the

automatic roller blind movement the desired inside illumination level is maintained.

Fig. 11 shows the inside temperature profile when the inside illumination is controlled during the conditions represented in Fig. 10. It is evident that the inside temperatures are in the tolerable range despite the high solar radiation. Without shading the inside temperature will be at least 20 K higher than the outside air temperature. Therefore,
maintaining the inside illumination on suitable level with proper shading excludes the excessive inside temperatures.

6

Conclusions

The available luminous flux and illuminance in the building are closely related to the available solar radiation. We used the quantitative influence of the available solar radiation for the fuzzy design and the optimization of the

fuzzy control system, which enables optimal dynamic response of the roller blind according to the desired inside illumination and the outside conditions. To design the fuzzy system some preliminary experiments were done, where the observed variables were luminous efficacy and the inside illumination. Luminous efficacy is defined as the ratio of the luminous flux to radiant flux and tells the relationship between the optical and the thermal effect of the available solar energy. Maintaining the desired inside illumination level in the range of 500 — 1500 lx means the inside luminous efficacy between 5 lm/W (summer shaded window) and 14 lm/W (winter unshaded window). The system for the automatically adjustable window geometry is executed in the test chamber with the fuzzy control system, which makes decisions similar to human thinking process. The design of the fuzzy controller is based on setting up a set of linguistic control rules derived from the experimental optical knowledge. The controller was adjusted through experimentation. The two well-modified illumination fuzzy controllers, one for wintertime regime (direct solar radiation inside is the desired priority) and one for summertime regime (the direct solar radiation must be excluded as much as possible), are presented in the paper. The controlling performance is satisfactory and assures the inside daylight illumination with moderate continuous movement of the roller blind in the area, where the desired value oscillates up to ± 50 lx. Such illumination the fuzzy control system enables the optimal use of the available solar energy for improving the optical and thermal inside comfort, and can be applied in any building. The particularity of fuzzy control system is that it must be designed and optimized according to the site and its weather conditions in relation to the desired internal conditions, i. e. experimental designing.