The second experiment was carried out on three typical late-spring days in the beginning of May. In the case of late spring experiments all of the system actuators were active and the set-point temperatures were set in the rage from 15 °C to 25 °C, depending on the time of day. The experiment was designed to test the ability of the fuzzy controller to follow the temperature set-point profile and at the same time to prevent the test cell from overheating. Cooling of the test cell was achieved by combining the movable shading and the ventilation induced by the ventilator imbedded in the wall of the cell. The thermal control algorithm regulated the functioning of the roller blind, heater and ventilator with the aid of PID/V controllers. In the control system the roller blind positioning had a priority. If after a limited time the desired indoor temperature was not achieved, the heater or the ventilator were activated.

Weather conditions during the first two days were constant and almost identical. On the last day a change in weather pattern is evident as the levels of direct solar radiation as well as external air temperatures have dropped. During the first two days solar radiation reached peak levels of 800 W/m2 and the temperatures were in the range from 13 °C in the morning to 30 °C in the early afternoon. On the third day in the beginning of the afternoon the weather changed, which is signified by a drastic drop in solar radiation levels as well as in the external air temperatures. From this point on there was no more need for cooling of the cell, and heater had to be activated to reach the desired internal air temperatures. Thermal fuzzy controller was able to cool the test cell during the first two days as, maximum internal temperatures at any given time did not exceed 27 °C, which were 2 K above the set­point temperature and approximately 3 K below maximum external air temperatures. The experiment also showed that only shading would not be able to achieve satisfactory results, as the ventilator had to be turned on almost throughout the day and most of the night (Fig. 3.). We can speculate that if a ventilator with a lager volume capacity was installed, even beater results could be achieved with the application of natural ventilation during night-time.

3. Conclusion

Experimental test cell with the appropriate controller and measuring equipment was built with the aim to form a fuzzy logic control system for the regulation of internal thermal and optical environmental conditions. The final goal of the control system was the formulation of regulation rules, which would enable harmonious control of thermal and illumination processes in the built environment. The reaction of the test chamber to the illuminance and thermal conditions was regulated by positioning

the externally fixed roller blind and with additional heaters and ventilator. The objective of the system was the optimization of use of the available environmental conditions, especially focusing on the external air temperature and solar radiation. The controller’s algorithm was composed of two separate loops, one for the illuminance and the other for the thermal regulation. In experiments presented in this paper only the thermal loop was used, as the focus of the conducted tests was on the study of cooling load reduction with automated shading. The executed tests confirmed the initial assumption that during mid-seasons properly regulated shading devices can reduce or in some cases eliminate the need for

cooling of internal living and working environments. Because of human adaptation to thermal environments manual regulation can not provide the same precision and efficiency as the automated regulation.

The experiments showed that the fuzzy controller was able to consistently keep internal temperatures in the test cell lower in comparison to the external thermal conditions. Compared to the experiments when the cell was not automatically regulated (e. g. roller blind was left open) the fuzzy system was able to substantially reduce cooling loads in the cell. Additionally, the thermal fuzzy controller was also able to follow the internal set-point profile within the acceptable margin of error. Internal air temperatures in the cell were kept in the acceptable range around the set-point profile even in times of high external air temperatures and clear sunny weather with high solar radiation. Even better results for cooling load reduction during mid-seasons could be attained if the automated shading was used in combination with natural ventilation. Use of natural ventilation is especially effective during night­time when the interior environment can be passively cooled as external air temperatures are lower than internal.

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