Thermal and energy performance of a nearly zero-energy building in Mediterranean climate: the gap between designed and monitored loads of space heating and cooling systems

ABSTRACT

The mismatching between the predicted and the operational performance of buildings designed to be nearly zero-energy underlines the importance to study the post-occupancy behavior, to understand if the building-HVAC system is capable to meet the variable conditions even due to the progressive climate change. The paper proposes a discussion about the operational performance of an existing nearly zero-energy building in the Mediterranean climate, during the heating and cooling seasons. The monitoring shows that the required electrical power is always lower than the nominal one, also because the external conditions are not extreme as the design ones. In the colder days, the difference in the required power is −21%. In summer, there is a delay of two hours between the external maximum temperature and the maximum required power. However, the monitored power is usually higher than the nominal one, with a maximum value of +11%. Considering all proposed combinations for the design calculation, it is demonstrated that the real performance cannot be predicted during the design, because indoor and external conditions influence the dynamic behavior of the building-HVAC system.

KEYWORDS:

• Nearly zero-energy building
• heating load
• cooling load
• direct expansion system
• Mediterranean climate

Abbreviation

TH, Temperature and relative humidity sensors; TE, External air temperature sensor; EM, Energy meter; T_out_ave, Hourly average outdoor temperature [°C]; T_out, Outdoor temperature [°C]; T_in, Indoor temperature [°C]; Text, p, Monitored outdoor temperature when the power peak occurs [°C]; PEAK_H I, First most significant power peak in the heating period [°C]; PEAK_H II, Second most significant power peak in the heating period [°C]; PEAK_C I, First most significant power peak in the cooling period [°C]; PEAK_C II, Second most significant power peak in the cooling period [°C]’; T_min, Minimum dry-bulb temperature over the day [°C]; T_max, Maximum dry-bulb temperature over the day [°C]; T_wb,coinc, Wet-bulb temperature at the time of the maximum dry-bulb temperature [°C]; COP, Coefficient of Performance; EER, Energy efficiency ratio; HC_tot, Nominal heating load [kW]; CC_tot, Nominal cooling load [kW]

; P_input, Theoretical power peak [kW]; T_in (T_max), Average indoor temperature at the maximum dry-bulb temperature [°C]; BNZEB, Nearly zero-energy building of Benevento.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the MIUR [PON PON03PE_00093_1].