## 3 Results and Discussion
### Technical Problem  
As we already know, heating can be provided by the electric heating foils inside the panels or by heating the panels by hot water from the hot water tank--heating by the heat pump or an electric boiler. The technology has been tested and measured in all heating modes. These measurements were successful and the technology was effective without obvious problems. After that, test measurements were performed in cooling mode. As mentioned earlier, cooling can be done by the heat pump or by thermoelectric modules. The cooling mode with the heat pump was made and measured without any problems.  
There were some difficulties in measuring of the thermoelectric cooling. Above all, cooling is ineffective. Instead of decreasing the indoor temperature, it was increasing. Measurement of the original design of the technology and the thermoelectric cooling mode is shown in Figure 5 below. As can be seen, even when the room was cooling by the technology, the temperature was growing. The temperature got to start growing up very fast when the cooling by TEC was turned on. The indoor temperature was about 27.2 \({}^{\circ}\)C at the beginning of the measurement. After active cooling by TEC, it reached up to 30.8 \({}^{\circ}\)C. The result was: the technology transferred more heat to the room than it removed.  
After some time, it has been found out why this problem occurs. A clear indicator was the thermographic diagnostics of the accumulation device and all parts of the thermoelectric modules with coolers. In the thermographic images below, see Figure 6, it can be seen all six thermoelectric assemblies and their temperatures. The image captures the state of the device with active thermoelectric cooling. The lowest temperature on the surface of the hot side is about 20 \({}^{\circ}\)C and the highest temperature is about 45 \({}^{\circ}\)C. This growing up the temperature is caused by connection of the liquid coolers in series. In this place, it can be said, it is also a little mistake of design. Maybe, it could be better to use the parallel connection. On the other hand, it is possible to get lower outtake temperature of chilled water In figures below, see Figure 7, it is possible to see details and temperatures of both sides of the coldest (first in the row) and hottest assembly (last in the row).  
The problem with the overheating came from the waste heat of the TEC modules. The thermoelectric modules are fitted with the liquid heat exchangers on both sides. These are for the extraction of cold and waste heat. The surface of the heat exchanger (cooler) on the warm side is very high. Therefore, the waste heat is radiated to the surroundings from the surface of the cooler. The problem can be solved by additional insulation of TEC modules and hot-water pipelines.  
The problem has been solved by separating the space with thermocouples from the monitored space. Around the thermoelectric system, it was enough to build additional insulation to keep the heat in the enclosed space. However, there is still a freestanding cold water tank for absorbing the waste heat from the thermoelectric modules. On the other hand, the water tank is additionally cooled by the heat pump at a minimum temperature of 10 \({}^{\circ}\)C. Therefore, it was not necessary to separate the  
Figure 5: Technical issue with overheating.  
Figure 6: Technical issue—thermographic diagnostic.  
Figure 7: Technical issue—thermographic diagnostic—details.  
cold water tank from the monitored space. So, the final improvement was additional hot water pipes insulation. All of the following measurements in this article were performed with this adjustment.