Page 62 - JCAU-5-2

Journal of Chinese
Architecture and Urbanism Cooling energy-saving mechanism

rates throughout the year, the conclusion drawn from
the literature (Hoyt et al., 2015; Aryal & Becerik-Gerber,
2018) is that the hotter the climate, the more significant the
energy-saving effect of increasing the set temperature of
air-conditioning, has one-sidedness. In Figure 4, absolute
energy savings in the hottest months of July and August
are lower than that in the cooler months of May, June, and
November. In Figure 5, the relative energy-saving rate in
hot months is significantly lower than that in cool months,
which is contrary to the conclusion of the literature (Hoyt

et al., 2015; Aryal & Becerik-Gerber, 2018). Therefore, the
conclusion is that the hotter the climate, the more significant
Figure 5. Monthly comparison of energy saving rate. Source: Graph by the energy-saving effect of increasing the air conditioner
the authors set-point should be based on the annual energy-saving
effect of different regions with different climatic conditions.
According to the statistics of climate data, only 3 h in However, in the same region, the climate conditions are the
January in Guangzhou have cooling demand before the same all year round, but there are differences in the climate
set-point rises, and the dry bulb temperature of these three characteristics of different seasons and months, which lead
hours is between 26°C and 27°C. In these moments, when to more abundant changes in the absolute energy-saving
the set-point rises by 1°C, there will be no cooling load effect and the relative energy-saving effect. Therefore, an
demand, so the energy-saving rate is 100%. The reason in-depth analysis, instead of a general summary, should be
for the high energy-saving rate in December is similar. conducted.
In February, the dry bulb temperature is lower than 26°C
at all times. Therefore, energy savings in cool months are 4. Energy-saving mechanism
characterized by low cooling load demand, low absolute Ghahramani et al. (2016) applied the measures of adjusting
energy savings, and a high relative energy-saving rate, the air-conditioning temperature set-point to the building
while in hot months, the hourly dry bulb temperature is models in different construction years and obtained the
higher, there is cooling demand almost all the time, and the qualitative results that the newer the building, the lower
cooling consumption base is large, so the relative energy- the energy consumption after the temperature set-point
saving rate is relatively low. (ii) With the improvement of is raised, but the absolute energy-saving potential is
thermal performance of the envelope, the energy-saving lower than the building models in the older construction
rate decreases in hot months and changes little in cool years. Due to the higher building construction level in the
months. However, due to the large cooling load demand newer construction period, the envelope performance of
in hot months, the base of cooling consumption is much the newer building is better. Therefore, according to the
larger than that in cool months, so the weighted average research results in the previous section, the same qualitative
energy saving rate in hot months plays a macro-control conclusion is reached in the paper as in the literature
role, and the common characteristics of the energy-saving (Feng et al., 2010), but there is no in-depth analysis of this
rate in hot months are the characteristics of the annual energy-saving phenomenon in the literature. In this paper,
energy-saving rate. (iii) The characteristic of the energy- to further reveal the mechanism of the above monthly
saving rate in winter is different from that in summer. Even and annual energy-saving effect of air-conditioning under
in December, the characteristic of the energy-saving rate different thermal performance envelope structures, the
is abnormal with the change in envelope performance. internal relationship between hourly load change and
This shows that due to the complexity of building energy outdoor dry bulb temperature, solar radiation, and hourly
conservation issues, no energy-saving measure can have cooling load demand is analyzed at the microscopic level.
the same energy-saving effect at all times of the year. The
monthly energy-saving rate can only reflect the annual 4.1. Microscopic mechanism of absolute energy
energy saving law from the macroscopic perspective, but saving
the deep-seated energy-saving mechanism of the thermal Figure 6A and 6B show the comparison of hourly
characteristics of the envelope coupling setpoint rise still load reduction with the change of outdoor dry bulb
needs to be further discussed at the microscopic level. temperature under the enclosure structure of lower-grade
It is worth noting that by comparing the research and top-grade when the air-conditioning temperature
results of the monthly absolute and relative energy-saving set-point increases by 1°C. We can see from the diagram

Volume 5 Issue 2 (2023) 8 https://doi.org/10.36922/jcau.0877