## 6 Discussion  
It is known that expanding the allowed ambient temperature corridor reduces the energy consumption of HVAC systems. According to [PERSON] et al. [163], lowering the targeted room temperature during the heating period saves about 10% K\({}^{-1}\). This outcome is supported by [PERSON] et al. [164], who confirm a predicted energy saving that can be attributed to the expansion of the room temperature of about 10% K\({}^{-1}\) for both, the heating and the cooling period. However, the achievable energy savings depend on several factors, one of them being e.g., the outdoor climate conditions. The fundamental intention of the indoor temperature range is to provide a comfortable indoor climate for the occupants inside. Figure 4 shows the correlation between the percentage of dissatisfied individuals related to the indoor air temperature. It is shown that the corresponding dissatisfaction of individuals strongly depends on the used personal climatization system (see Tables A1-A6). The black solid line in Figure 4 represents a PPD that can be regarded as acceptable according to DIN EN ISO 7730 [9], ASHRAE 55 [18] and corresponds to a value of 20%. It is obvious that the implementation of personal HVAC systems allows a considerably high expansion of the acceptable ambient temperature range for both, the warm and cold area. Applying directed airflows towards the face region improves thermal comfort and perceived air quality. A cheap and straightforward approach for the generation of such airflows is the application of table fans. These systems were repeatedly tested for ambient temperatures between 26 \({}^{\circ}\)C and 30 \({}^{\circ}\)C and are able to ensure thermal comfort even at relative humidities of 80% with a dissatisfaction value below 20% (Table A1-1). A small amount of studies applied the table fans at air temperatures of 32.3 \({}^{\circ}\)C (Table A1-4) and 35 \({}^{\circ}\)C (Table A1-13). However, the supply air must be preconditioned to 22 \({}^{\circ}\)C in order to ensure thermal comfort at an ambient air temperature of 35 \({}^{\circ}\)C.  
The application of water cooled table surfaces (Table A1-3, A1-4) ensures thermal comfort up to air temperatures of 32 \({}^{\circ}\)C. Furthermore, a heated table pad guarantees thermal comfort at ambient temperatures down to 18.1 \({}^{\circ}\)C (Table A1-2). Conditioned table surfaces can be applied for both, heating and cooling. However, the energy consumption of the investigated systems is comparably high (>80 W). In contrast, the majority of the available table fans has an energy demand of less than 4 W.  
Personal cooling systems that use ceiling or standing fans (Table A2) affect the indoor climate related to the body as a whole and can provide thermal comfort with a maximum satisfaction  
Figure 3: Schematic of the experimental setup [154]. of 100% at ambient temperatures up to 30 \({}^{\circ}\)C (Table A2-14, A2-16, A2-17, A2-20). In addition, there are systems available that show a very low energy uptake of 10.5 W only, thus being quite energy-efficient. However, further research shows that horizontal ventilation is not capable to compensate air temperatures above 30 \({}^{\circ}\)C (Table A2-17). Conditioned seats have a high efficiency in delivering heating and cooling energy to the human body. Since this personal HVAC system is mobile, its performance is independent of the occupants current position inside a room. According to [PERSON] and [PERSON] [109], [PERSON] et al. [110], conditioned seats in vehicles ensure thermal comfort down to ambient temperatures of 15 \({}^{\circ}\)C (Table A3-31, A3-32). However, this result could not be confirmed by [PERSON] et al. [12], who used heated seats to compensate a global reduction of indoor air temperatures. In their study, the researchers showed that the dissatisfaction of individuals rises above 40% at ambient temperatures of 17.4 \({}^{\circ}\)C due to increasing thermal asymmetries that appear across the human body surface.