## 3 Results and Discussion
### Measurement  
In the following paragraphs, there are presented measurements and results of the technology in different cooling modes. The first measurement is focused on common passive mode--the most common use of the PCM. In this mode, the PCM-based panels reduced the temperature fluctuation and also stabilised the indoor temperature during passage of a few days of warm weather. An example of the system's behaviour can be seen in Figure 8. This passive mode managed to stabilise the indoor temperature between 23.2 \({}^{\circ}\)C and 24.0 \({}^{\circ}\)C when the outdoor temperature oscillated between 5.3 \({}^{\circ}\)C and 22.7 \({}^{\circ}\)C.  
Another experiments focus is the active cooling mode. The cooling cycle of the heat pump was used in this measurement. Results are shown in Figure 9.  
Every measurement is made of two cooling cycles. One cycle lasted two days. Active cooling was turned on during the first day. During the next day, the panels were left to just accumulate heat from the room. The cycle was then repeated. During the first cooling cycle, the time it took to cool down of the surface temperatures from 21.4 \({}^{\circ}\)C to 17.9 \({}^{\circ}\)C for the unmodified surface and from 22.6 \({}^{\circ}\)C to 20.0 \({}^{\circ}\)C for the modified surface  
Figure 8: Passive mode. Figure 9: Active cooling—heat pump. was around 7.5 h. The indoor temperature lowered from 24.3 \({}^{\circ}\)C to 23.1 \({}^{\circ}\)C during the day with the active cooling turned on. The indoor temperature continued to decrease until the next morning. The following day the technology was still left unpowered and the indoor temperature was increasing, conforming with the outdoor temperature. In the next cycle, the measurement followed the previous one very closely. The outdoor temperature was a little bit higher in this cycle and the active cooling was in operation longer. The time it took to cool down from 21.8 \({}^{\circ}\)C to 17.6 \({}^{\circ}\)C and from 22.4 \({}^{\circ}\)C to 19.3 \({}^{\circ}\)C amounted to about 8.5 h. The indoor temperature lowered from 23.8 \({}^{\circ}\)C to 22.6 \({}^{\circ}\)C. The second half of this cycle was very similar to the second half of the first cycle. During these two cooling cycles, the sum of energy removed from thermal panels was approximately 7.9 kWh. The following measured mode was focused on thermoelectric coolers. Thermoelectric assemblies were powered by the installed photovoltaic system. As was mentioned earlier, this measurement was also done in two cycles. Both cycles were measured during days with the outdoor temperature reaching up to 25 \({}^{\circ}\)C. In this cooling mode, the reduction in the indoor temperature by the thermal panels was from 24.0 \({}^{\circ}\)C to 22.9 \({}^{\circ}\)C and from 24.1 \({}^{\circ}\)C to 23.2 \({}^{\circ}\)C, respectively. Measured parameters are shown in Figure 10.  
In Figure 10, it is visible that the first cooling cycle was activated before 9 o'clock. Deactivation was at 15 o'clock. At first, the indoor temperature was rising in accordance with the outdoor temperature. Once the technology was activated, the indoor temperature began to fall. The temperature continued to fall all the time when the technology was turned on. After deactivation, the outdoor temperature continued to steadily fall, up to the next morning. Following that, the indoor temperature has risen again in accordance with the outdoor temperature. The subsequent cooling cycle took the similar course and had similar results. The technology was activated after 9 o'clock. Deactivation was before 18 o'clock. The indoor temperature was falling as in the previous cycle, at first. But during the last measured day it started to rise fast. This fast increasing was caused by the higher outdoor temperature and also by the fact that the temperature of the PCM panels has gone over the range of phase change. So, the accumulation device absorbed just sensible heat, and it was not able to store latent heat.