# Analysis of Climate-Oriented Researches in Building
## 3 Results and Discussion
### Results of Cluster Analysis
#### 3.2.3 Cluster 3--Combined Heating, Cooling and Power Systems  
The third cluster presents 15 investigations, listed in Table S2, dealing with climate-dependent optimisations and an analysis of energy saving potential of combined heating, cooling and power systems (CHCP). Initially, the primary interest of the scientists was to investigate the energy effects of the use of CHCP systems in airport buildings due to a problem related to the high level of energy consumption in these types of buildings, while noting the good potential for energy savings from using these systems in more southerly climatic zones [108]. Thus, in the oldest study of the cluster, the problem of using systems with the right power in the aspect of energy conservation in airport buildings was raised. Systems optimisation measures at Greek airports could result in potential energy savings of 15-20% for the southern climates and 35-40% for the northern climates [109]. Subsequently, studies already focused on office buildings were addressed. Thus, in 2009, in the USA, a method was demonstrated to optimise a combined heating and power system (CHP) in this type of building, and in the context of three objectives: energy saving (ES), operation cost reduction (OCR) and environmental impact minimisation (EIM)--only for carbon emissions; it was shown that electricity and natural gas CHP system optimisation is dependent on climate zones and operational mode [110]. In the case of a building in Beijing, solar CHCP systems were considered, and the OCR optimisation objective was extended in the context of LCA methodology. Moreover, the EIM objective was extended to global warming, the chemical composition of precipitation and the respiratory effect of pollutants, and the results indicate that the energy saving and pollutant emissions reduction potentials of the FTL operation mode are better than that of the FEL mode [111]. The same authors of the previous study used a similar approach for multi-objective optimisation of the electricity and natural gas CHCP system in a commercial office building in Beijing. In this research, the optimal equipment size and operation mode was obtained. The authors found that \"if energy benefits are paid more attention, following the thermal load (FTL) mode is the first choice, while if environment performance is more valuable, following the electricity load (FEL) mode is the good operation strategy\" [112]. In the two papers presented above for Beijing, the authors note that their conclusions were obtained for the specific climatic conditions of this city. In another investigation, the application of CHP systems with Organic Rankine Cycle (ORC) was analysed in small commercial office buildings in six climate zones in the USA. The authors show that the CHP-ORC system helps reduce the primary energy consumption cost and carbon dioxide emissions in comparison with the same building, operating solely with a CHP system in all climatic zones of study [72]. In the case of hotel buildings, optimisation methodologies aimed at three objectives (ES, OCR and EIM) were presented for CHCP systems. The authors concluded that CHCP systems are most relevant in the aspect of primary energy conservation and emission reduction in a cold climate with high heating energy needs [70]. On the other hand, in the USA, it proved effective in the hybrid method for operating a CHP system of a hotel building (which either follows the thermal or the electric demand), by comparing the energy simulation results of this method with FEL and FTL modes of operation strategies in 16 climate zones. It was shown that the choice of the CHP system operation method will depend on the climate zone for this type of building. Therefore, in all climatic zones, the efficiency of the system with the hybrid operational mode was greater than with FEL and FTL. However, the FEL operational mode is more suitable for warm climatic zones of ASHRAE (1A, 2A, 2B, 3A, and 3B) and FTL for cold climatic zones [113].