# Modeling and Analysis of Contactless Solar Evaporation for Scalable Application
## 3 Result and Discussion
### Comparison between the Laboratory and Scalable SCE  
The size of the laboratory SCE device is limited by the solar simulator, which cannot describe the real operation of SCE with much larger size well. To analyze the difference between laboratory SCE and scalable SCE, a simulation-based analysis SCE for both scenarios was performed, as shown in Figure 6. Since the distribution of vapor escaping holes will be important in scalable application of SCE, the hole area ratio was also adjusted during the analysis. Figure 6 shows the evaporation rates of the two evaporators under hole area ratios of 0.7%, 14.4% and 36.9%, considering hole diameters of 1.1 mm, 5 mm and 8 mm, respectively. Evaporation rates of the laboratory SCE are 0.018 kg\(\cdot\)m\({}^{-2}\cdot\)h\({}^{-1}\), 0.139 kg\(\cdot\)m\({}^{-2}\cdot\)h\({}^{-1}\) and 0.205 kg\(\cdot\)m\({}^{-2}\cdot\)h\({}^{-1}\), respectively, whereas they are 0.067 kg\(\cdot\)m\({}^{-2}\cdot\)h\({}^{-1}\), 0.313 kg\(\cdot\)m\({}^{-2}\cdot\)h\({}^{-1}\) and 0.319 kg\(\cdot\)m\({}^{-2}\cdot\)h\({}^{-1}\) for the scalable SCE. It was found that the evaporation rate increases quickly with the hole area ratio, for both the laboratory and scalable SCE. More notably, the  
Figure 4: Schematic diagram of the test rig for laboratory SCE.  
evaporation rates of the scalable SCE were much higher than that of the laboratory SCE under different hole area ratios.  
To gain deeper insights into the evaporation rate difference between laboratory and scalable SCE, the heat balance of both two SCE processes were analyzed. Figure 6b shows the distribution of energy for both the laboratory and scalable SCE processes, under a hole area ratio of 14.4%. The heat loss of SCE could mainly be classified into the heat loss from water, heat loss from absorber-emitter and other heat loss (the radiation heat loss from the absorber surface to the environment and the convective heat loss between the vapor and the absorber-emitter). The first heat loss mechanism could further be classified into the sidewall loss and bottom loss. According to the analysis, 30.8% of total energy input is dissipated to the ambient through the sidewalls of laboratory SCE, which does not exist in scalable SCE. However, a large percentage of thermal energy is lost to the bottom water in the scalable SCE (31.9%), whereas this is only 8.8% for the laboratory SCE due to the large thermal resistance of bottom wall. Due to the stronger heat loss through sidewalls, the total heat loss from water is more severe for the laboratory SCE. The second heat loss mechanism is affected by both the heat loss area and temperature difference with the ambient. Although  
Figure 5: Temperatures from experiment and simulation results.  
Figure 6: Comparison between laboratory and scalable SCE. (**a**) Evaporation rates of SCE under different hole area ratios (0.7%, 14.4% and 36.9%). (**b**) Heat-balance analysis and key temperatures comparison of two SCE processes under a hole area ratio of 14.4%.  
the scalable SCE has a higher temperature than its counterpart, it also has less heat loss area, since there is no extra sidewall supporting the absorber-emitter. In this case, the scalable SCE has 33.8% heat loss from absorber-emitter, which is slightly lower than the 36.8% for laboratory SCE. Both aspects explain the much lower evaporation rate of the laboratory SCE. The huge difference between laboratory and scalable SCE processes also validates our previous analysis that the experimental test cannot accurately explain the heat and mass transfer mechanisms of SCE in real, large-scale applications.