## 7 Conclusions  
According to DIN EN ISO 7730 [9], the operative indoor temperature range of HVAC systems in office buildings must be kept between 22 \({}^{\circ}\)C and 24.5 \({}^{\circ}\)C to provide a comfortable indoor climate for the occupants inside. By applying personal HVAC systems, this temperature range can be expanded to values between 18 \({}^{\circ}\)C and 30 \({}^{\circ}\)C while causing thermal dissatisfaction below 20% (see Figure 4). Only a few studies investigate thermal comfort outside this temperature range (see Tables 11-16). Some of them [109; 110; 116] prove that even higher or lower ambient temperatures can be regarded as comfortable, when using personal HVAC systems. According to these researchers, a wider indoor air temperature range between 16 \({}^{\circ}\)C and 35 \({}^{\circ}\)C is still comfortable. However, there is a need for further research since the data base for these temperature levels is quite small. [PERSON] et al. [117] confirmed that an indoor air temperature range between 18 \({}^{\circ}\)C to 30 \({}^{\circ}\)C can be regarded as comfortable. Furthermore, the researchers estimated the predicted energy savings for this temperature range to be 40%, when personal climatization systems are used that consist of a heated and ventilated keyboard, foot warmer and an air supply system that directs local air flows towards the face region of a person. The calculated energy savings of the researchers is valid for a comparison of their system to mixing ventilation systems that are designed for a temperature range between 21.5 \({}^{\circ}\)C and 24 \({}^{\circ}\)C. However, a systems' energy demand strongly varies with respect to the applied hardware components, applied control algorithms and system design. For example, the energy demand for cooling systems varies between 2 W to 46 W as shown in Figures 11 and 12. Furthermore, [PERSON] et al. [67; 165] showed that the achievable energy saving is strongly dependent on the outdoor climate. Results of a field study performed by [PERSON] et al. [29] confirm the advantages of personal HVAC systems in comparison to central air-conditioning systems regarding thermal comfort and perceived air quality. In their study, the researchers implemented a personal HVAC system and included a user control approach, which was designed for office buildings in San Francisco. According to [PERSON] et al. [17], [PERSON] et al. [29], thermal comfort, IAQ and room acoustics are commonly weak points in existing buildings. Consequently, there is a high optimization potential. Most of the existing personal HVAC systems in the literature [93; 95; 171] are user-controlled systems that do not consider automated control of local thermal actuators. The so-called HCCLC-concept described in [15; 15; 15; 156; 172] uses a human being/numerical human thermoregulation model as a core component of a personalized HVAC system. The system itself can be expanded by a variable amount of local climate actuators and allows to consider user feedback systems to establish self learning control algorithms with the goal to automate the entire climatization of individuals in a much more energy-efficient way than it is currently done in buildings and vehicles. Finally, this paper contains an extensive comparison of existing and investigated personal thermal actuators from the current literature and enables the choice of thermal actuators and their combination depending on environmental conditions, energy demand, expected thermal comfort and thermal comfort improvements. The corresponding selection process is enabled by the use of Figures 11 and 12, Tables 11-16. Additionally, the paper showed the necessity and potential of local thermal comfort models in connection with the design and application of energy-efficient personal climatization systems and highlighted the potential of further areas of system application such as for the improvement of health, productivity or the reduction of mortality rates due to energy poverty.