## 3 Results  
By compiling real operating data of the mobile energy generation unit for one year, it turns out that about 60% of the heat supplied in the winter, spring and autumn seasons (for case of Riga) from the exhaust air is recovered from the air-to-air heat recovery unit [16]. The maximum diesel consumption for supplying the recreated temporary shelter with energy occurred in winter (see Table 4). In most cases in spring, summer and autumn, the electricity produced by the PV was higher than the consumed electricity per day. For data validation several simulations were performed in TRNSYS. Digital models developed for a series of cities (Riga, Latvia; Stockholm, Sweden; London, United Kingdom--with similar climate conditions) for demonstration of the PV impact in off-grid case temporary shelter operations. The high energy consumption for heating depends on country-specific climatic conditions, mainly from October to April [31]. The efficiency of solar panels depends on the following factors:  
* climatic conditions;
* current lighting (presence or absence of shading);
* possible contamination (soiling, dust cover, etc. );
* the angle of inclination of the elements. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**Year Seasons**} \\ \cline{2-5}  & **Spring (2020)** & **Summer (2020)** & **Autumnn (2020)** & **Winter (2021)** \\ \hline Electricity consumed (kWh) & 4.22 & 5.20 & 354 & 1.001 \\ \hline Diesel generator produced electricity (kWh) & 210 & 60 & 370 & 1.173 \\ \hline Diesel consumed (l) & 70 & 20 & 119 & 378 \\ \hline Diesel generator work time (h) & 193 & 55 & 298 & 955 \\ \hline Recovered heat (kWh) & 1.347 & - & 1.080 & 3.114 \\ \hline Heat from heat pump (kWh) & 804 & - & 687 & 2.104 \\ \hline Waste heat from diesel generator (kWh) & 480 & - & 803 & 2.554 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: One-year operational data for Riga, Latvia climate conditions. Figure 6: TRNSYS model validation ((**a**) real electricity consumption; (**b**) measured solar radiation; (**c**) comparison of measured and calculated data; (**d**) battery capacity). In our case the most important factor is climate conditions, because the energy generation unit is mobile, therefore the factors, such as the current lighting of the PV and angle of inclination of the PV, can be easily adjusted, and the unit can be easily cleaned of dirt and dust. The average solar radiation in Northern Europe is 1.1 kWh/m\({}^{2}\). For the simulated cases see Table 5 (data obtained from the \"Global Solar Atlas 2.0\"--a free, web-based application is developed and operated by the company Solargis s.r.o. on behalf of the World Bank Group, utilizing Solargis data, with funding provided by the Energy Sector Management Assistance Program (ESMAP). For additional information: [[https://globalsolaratlas.info](https://globalsolaratlas.info)]([https://globalsolaratlas.info](https://globalsolaratlas.info)) (accessed on 26 November 2021) [32]). In the case of Riga (see Table 6) for the electricity supply and HVAC systems operation, the PV system-produced electricity would reduce the diesel fuel consumption for diesel generator operation by 71-93% in spring and summer seasons and in winter by 9%. Analyzing the simulation results, the electricity required for the equipment load and HVAC system operation of the temporary shelter mobile energy generation unit can provide off-grid work by approximately 54% without diesel generator. In summer, this increases to approximately 93%. Table 7 presents simulation data for four cities with similar climate conditions, where more heating is needed than cooling. The electricity output (kWh) generated by the PV is higher than the consumed electricity (kWh). However, it is highly dependent on the optimal HVAC system operation algorithms--different types of camps/shelters, number of occupants, equipment loads, etc.