## 3 Results and Discussion
### Measurement
From the obtained results, it can be determined that area of the thermal panels, compared to the total area of the measured room, is low. This can be solved by increasing heat flux. Forced convection is one option. The thermoelectric cooling (also heat pump) was powered by the photovoltaic system. This system delivered over 35.5 kWh throughot both cycles of measurement (four days, cooling by TEC). The heat which was removed from accumulation panels was totalled over 8.7 kWh. Consumed of  
Figure 10: Active cooling—thermoelectric cooling. power by the thermoelectric assemblies was over 18.5 kWh. The energy balance that is the production of energy and the consumption of it is shown in Figure 11.  
When comparing and evaluating the results, it is necessary to take into consideration that the operation and efficiency are very dependent on outdoor conditions. The comparison of both measurements is quite difficult because it is not possible to ensure the same conditions for each of them. Moreover, each mode has different conditions, for example, the speed of cooling of liquid and minimum liquid temperature. In the real conditions and operation, the temperature of the liquid from TEC could be lower than from the heat pump. In every case, it must be above the dew point temperature of course. In our both measurements was set the same temperature, about 11 \({}^{\circ}\)C. Measurements are shown in this article were also made when the outdoor conditions were similar, i.e., sunny days and outdoor temperatures between 7 \({}^{\circ}\)C and 25 \({}^{\circ}\)C.  
Table 1 shows the balance of energy produced by the photovoltaic system, energy consumed by the heat pump or by the thermocouples and energy removed from the thermal panels. The table shows values measured during one cooling cycle in the previous year (2016) and values measured during two cycles in this year (2017). In both cases, the one cooling cycle was about two days long. During the first day, the technology was turned on, and the rest of time was turned off. The installed heat pump has average Coefficient of Performance (COP) over 3.5 and Energy Efficiency Rating (EER) over 2.7. The table shows energies removed from the thermal panels (PCM), the energy produced by the photovoltaic system (PV), energy consumed by the heat pump (HP) or by the thermoelectric coolers (TEC), and the last one is the balance of these energies (SUM). Energy balance remains positive in all of these examples. Performance and efficiency of the system are, however, dependent on both weather condition and more importantly on the energy source being applied in proper range of temperature. The biggest disadvantage of the thermoelectric cooling is production of large quantities of waste heat on the thermocouples opposite side. This waste heat caused also our technical issue mentioned earlier in the manuscript. The hot side of TEC is cooled by a \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Year**} & \multirow{2}{*}{**Mode**} & **PCM** & **PV** & **HP** & **TEC** & **SUM** \\  & & **(kWh)** & **(kWh)** & **(kWh)** & **(kWh)** & **(kWh)** \\ \hline
2016 & Cooling & 1.94 & 1.86 & 1.14 & - & 0.72 \\
2016 & TEC & 5.02 & 14.24 & 2.37 & 11.27 & 0.60 \\
2017 & Cooling & 7.84 & 20.03 & 4.51 & - & 15.52 \\
2017 & TEC & 8.74 & 35.65 & 3.91 & 18.51 & 13.23 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Energy balance of the modes used in 2016 and 2017. Figure 11: Balance of the energy consumption and production. liquid cooler connected to the cold water tank. This waste heat can be used to save energy of another system. For example, using the waste heat to pre-heating water for another utilisation. The waste heat from the TEC was up to 35 MJ (9.76 kWh) during both cooling cycles (four days). This energy could be used for preheating domestic hot water (DHW). The amount of heat needed for preparing DHW (\(Q_{\rm DHW}\)) can be calculated by the equation below. \[Q_{\rm DHW}=(1+z)\frac{\rho c_{p}\dot{V}_{\rm DHW}(\theta_{hot}-\theta_{cold})}{ 3600}, \tag{3}\]  
where