# Development of Far-UVC-Based Surface Disinfection Prototype for Public Buses
## 3 Results  
To ensure sufficient surface irradiation for disinfection, an evaluation of the distribution of far-UVC light irradiation on the studied surface was first carried out. For this purpose, the area of the tested irradiated surface of 400 \(\times\) 600 mm was divided into 32 sectors (4 \(\times\) 8), and in each sector, the irradiance was measured at different distances between the light source and the surface (20 cm, 30 cm, 40 cm, 50 cm, and 60 cm). The resulting heat maps are shown in Figure 9.  
As we can see, at a small distance (20 cm) between the surface and the lamp, the irradiance on the surface is very unevenly distributed, with very high irradiance in the center and very low irradiance at the edges. These differences decrease as the distance increases, but the average irradiance also decreases. The dependence of the unevenness of the surface irradiance on the distance is also clearly visible after calculating the standard deviations of the sector irradiance in Figure 10.  
Figure 10: The standard deviations of surface sector irradiance according to distance. Figure 9: Heatmaps of far-UVC lamp irradiance measurements at various distances between the light source and the surface. The dependence of the irradiance (measured around the center of the far-UVC lamp) on the distance of the far-UVC source and the measured angle is shown in the polar diagram in Figure 11.  
We can see that the beam angle of the far-UVC lamps used in the prototype is approximately 60\({}^{\circ}\) and can also see how the irradiance decreases with distance. Correspondingly, the dependences of the irradiance on time and the different distances between the lamp and the surface are shown in Figures 12 and 13. Figure 11: The irradiance at the distance of the far-UVC source and the measured angle. Figure 12: The dependences of radiant exposure on time and the different distances between the lamp and the surface. Figure 13: The dependences of radiant exposure on various distances and exposure times. When evaluating the disinfection scenarios described above, the speed of disinfection and the amount of energy used were analyzed. The duration of disinfection for each scenario was determined to achieve 2 mJ/cm\({}^{2}\) radiant exposure at the measurement points. For each scenario, this was done by measuring the radiant exposure using a Gigahertz Optik, X1-5 (Gigahertz Optik GmbH, Tuerkenfeld, Germany) optometer at measurement points 1, 2, and 3. For the disinfection of a bus row with four seats, two cases are considered for each scenario, in which two and four far-UVC lamps are used. When two lamps are used, the disinfection of the row takes more than twice as long, as each lamp has to be moved to the position of the adjacent seat, which takes 30 s. Furthermore, considering the case where the bus has ten rows and experimentally it was found that the transition of the lamp from one row to another takes 54 s, the disinfection times of all the rows of the bus can be calculated. The results are shown in Table 2. For scenarios 1 and 2, the disinfection time for a zone is determined by the longest time at the measured points. Therefore, for scenario 1, the disinfection time of 75 s is determined by measuring point 1 and for scenario 3, the disinfection time of 73 s is determined by measuring point 3. For scenario 2, the disinfection times for each position are summed. The electrical power requirements for the disinfection system are modelled based on the Energy Efficiency Assessment model. The modelling also considers that 2 NEMA34 and 2 NEMA23 stepper motors are used to move the lamps to the next row and to the adjacent seat, and to raise and lower the lamps. The results are shown in Figures 14-16. A summary of the disinfection times and the energy consumption for each scenario is given in Table 2.  
From the results obtained, we can see that disinfection scenario 2 is the least effective, with the longest disinfection time and highest energy consumption.