## 4 Simulations  
In order to verify the system's behaviour, the study authors developed Java software which allows a real-time simulation of the integrated system, featuring custom-developed, physical-based models of the major components (i.e., heating coils, compressors, fans and pumps). In particular, a proprietary semi-empirical model was developed for heating coils, also supported by [14]. The software integrates energy and mass equations numerically, and uses environmental conditions of temperature and relative humidity as input data. The software is a real-time simulation of the integrated system, and works by calculating the circulation of fluids in the pipeline network (mass conservation) and the power exchange (energy conservation) in the different components of the machine. At each time-step the \"actuator\" components (pumps, vents, etc.) force the movement of a fraction of fluids (air, coolant, water, etc.) that enters/exits the \"exchanging\" components (heat exchangers). The amount of power exchanged at such a time-step is calculated and added/removed to/from the fraction of fluids involved. The process is then iterated until the machine reaches a steady-state \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Daily Savings** & **Avoided Costs** & **Daily Savings** \\ \hline Bottled water & 158 dm\({}^{3}\) & 7 pesos/dm\({}^{3}\) & 1106.0 pesos \\ Kitchen water & 1724 dm\({}^{3}\) & 1.4 pesos/dm\({}^{3}\) & 2413.6 pesos \\ LPG & 163.9 dm\({}^{3}\) & 7.47 pesos/dm\({}^{3}\) & 1224.2 pesos \\ Electricity saving & 150 kWh & 0.8243 pesos/kWh & 123.6 pesos \\ \hline Total & & & 4867.4 pesos \\ \hline  & **Daily energy consumption** & **Energy cost** & **Daily cost** \\ \hline Electricity consumption & 832 kWh/day & 0.8243 pesos/kWh & \(-\)686 pesos \\ \hline Results & & & \\ \hline Daily saving & & 4181.4 pesos \\ Monthly saving (November, 30 days) & & 125,442 pesos \\ Exchange rate & & & \\ Monthly saving (November, 30 days) & 17.3735 pesos/USD & 7220.3 USD \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Water, energy, and economic savings. condition (thus replicating the real system), calculating not only the final \"static\" result but also the transient behaviour. The software is thus well suited to correctly predicting the system's behaviour in continuously changing conditions (i.e., in terms of temperature and humidity variations during the day). A detailed description of the simulation will be provided in another paper. In the current work, the model was calibrated and tested based on experimental results, obtaining, for water production estimation, an average error less than 2% and maximum error less than 5% (Figure 12). A testing campaign, using a second integrated system similar to that described above, was carried out for approximately one working month (20 days). For energy consumption, the average error was less than 5% and the maximum error was less than 8%, comparable with the accuracy of measurement instruments (Figure 13). During the campaign, real machine behaviour was monitored by means of on-board and external instruments. An external thermohygrometer, calibrated and certified, measured temperature and humidity of environmental air, with a sampling collection frequency of 1 per s. An external precision scale measured water production, and an external energy meter measured the energy consumption of fans, with a sampling collection frequency of 1 per each 10 min or 15 min. The treated airflow quantity was measured by means of an external anemometer with an average frequency of 15 min. Moreover, by means of internal instruments, temperature and humidity of the airflow were collected in each stage of air treatment (before and after evaporation coils, and after the heat recovery coil), with a frequency of 10 min or 20 min. It also measured compressor behaviour, collecting evaporation and condensation pressures and temperatures. Energy consumption was measured by means of an on-board energy meter. Sampling collection frequency was decided on the basis of an evaluation of steadiness.