The project will be done under the Supervision of Prof. Maurizio Sasso and his team in the Engineering Department.

Maurizio Sasso was born in Naples, Italy, in 1960. He graduated cum laude in Mechanical Engineering at the University Federico II of Naples in 1986. Since 2001 he is Full Professor of Engineering Thermodynamics at the Engineering Department of the University of Sannio, Benevento, Italy.

In 2018, the energy demand of the civil sector amounted to about 41% of the total final energy consumption worldwide and it corresponded to 40% of the total greenhouse emissions. Over 70% of residential energy requests are due to air-conditioning. In particular, in the last decade, the increase of the electric energy demands for cooling purpose in buildings caused the summer peak loads instead of winter ones in industrialized countries.

In this context, with increasing concerns about the energy savings and the greenhouse gas emissions reduction, more efforts are being put into the analysis of the environmental performance of the air conditioning systems.

To this aim, the Total Equivalent Warming Impact (TEWI) index is commonly used in the evaluation of vapour compression plant environmental performance, as they provide both direct and indirect contributions to global warming. The former depends on the GWP (Global Warming Potential) of refrigerant fluids and on the amount of refrigerant charge wasted in the surrounding environment during operation and maintenance and at the end of the technical life of the unit. GWP is a relative measure of the greenhouse effect of a certain gas in the atmosphere. It compares the effect of that gas to that of an equal mass of carbon dioxide, whose GWP is set to 1. GWP is calculated over a specific integration time, commonly 20, 100 or 500 years. The indirect contribution is related to the energy consumption of the system, either electricity or fossil fuels. This contribution is more complex to be evaluated, as it depends on several factors, such as the performance factor of the system (e.g. the COP), the efficiency of the electricity production mix, the fuel used, the CO2 emissions per kWh of electricity (depending upon the electricity production mix of each Country). For example, Figure 1 reports TEWI, split in direct and indirect contribution, for alternative refrigerant fluids used in electrically-driven air conditioning systems. The direct and indirect air conditioning systems environmental impact contemplated by TEWI, represents the contribution of these systems to the global warming. Besides the air conditioning systems are also responsible for a local environmental impact, arising in the urban air temperature increase. Indeed, air temperature of urban or metropolitan areas is higher than the air temperature of the neighbouring rural areas.

This is the well-known Urban Heat Island (UHI) phenomenon observed in many large urban centres in the last decade (Figure 2).

The Urban Heat Island Intensity (UHII) quantifies the UHI effects. It expresses the average air temperature difference between urban area and the rural one in a certain reference period. During summer 2011 the maximum value of UHII registered in Rome (Italy), was equal to 4.5 °C. Data from climatic stations in Manchester (UK), showed a summer maximum UHII of 8 °C in recent period. In summer maximum UHII of 2.8 °C and 3.7 °C was measured in Osaka and Tokyo (Japan) respectively.

The UHI phenomenon depends by anthropogenic activities, such as the rise of comfort expectations in buildings and the energy consumption (in particular cooling demands supplying by the air conditioners), and the related greenhouse gas emissions.

Thus, air conditioning is one of the serious causes of the UHI. The heat rejected by the condensers of air conditioning systems, increases the air temperature next to the buildings in which they are installed causing a local environmental impact. The thermographic image reported in Figure 3 shows this phenomenon, evidencing the increase of the air temperature next to a building due to heat rejected by the installed air conditioners systems.

In this context, the stage at University of Sannio is aimed to evaluate the environmental performance of an electric air-condensed chiller with a cooling capacity of 8.50 kW located at the experimental test facility of Engineering Department. The environmental analysis will be performed under different conditions (varying the external air temperature, the CO2 emission factors for electricity, etc.) by means of collected data and numerical investigations.

Figure 3. Increase of the air temperature due to heat rejected by air conditioners system