Page 66 - JCAU-5-2

Journal of Chinese
Architecture and Urbanism Cooling energy-saving mechanism

degree, and the energy saving increment of the envelope transitional season, the absolute energy savings are
with good performance is slightly larger than that of the lower than that in the transitional season. The difference
envelope with poor performance. From the comparison between these rules is that, with the improvement of
and analysis in this section, it can be found that the relative the thermal performance of the envelope, the monthly
energy-saving rate of increasing the temperature set-point absolute energy savings decrease significantly from
by 1°C after adding internal heat source in office buildings May to October, and it decreases more in hot months
has changed little, but the absolute energy-saving rate will than in cool months. This suggests that there is greater
increase significantly, and the value of energy savings will potential for energy savings in the hot months by
be improved. directing the behavior of old office buildings with
poor envelope performance to increase their air-
6. Conclusion conditioning temperature settings.
This work takes the small office buildings in Guangzhou, a (iii) The microscopic mechanism of the monthly and
typical city with hot summer and warm winter, as the study annual difference in absolute energy savings of air-
site. Using the CTM method, four grades of envelope with conditioning with the temperature set-point rise
assumed thermal performance are proposed to represent always lies in the difference of load reduction when
office buildings of different times. Under this condition, the outdoor temperature is between 26°C and 27°C.
the energy-saving effect of air-conditioning when the After increasing the temperature setpoint, there is no
temperature set-point increases by 1°C was studied, and cooling demand at these moments, and the hourly load
the energy saving mechanism was explored from the micro reduction is completely equal to the hourly cooling
perspective. The conclusions are as follows: load at 26°C, with a large value. This kind of energy
(i) The worse the thermal performance of the envelope savings due to temperature-regulating behavior is
of the same office building, the higher the absolute regarded as behavioral energy-saving effect, which
energy savings and the higher the relative energy- is the main contribution of macro air-conditioning
saving rate. This is because the annual cooling energy savings. The annual and monthly absolute
consumption and absolute energy savings decrease energy savings mainly depend on such behavioral
with the improvement of envelope performance, energy savings. The better the thermal performance
but the reduction range is not the same. Compared of the envelope, the smaller the hourly cooling load
with lower-grade envelope, the annual cooling demand of the building when the temperature set-
consumption of top-grade envelope decreases by 30% point is 26°C, thus reducing the behavioral energy
after the set-point rise, but the annual absolute energy savings. Therefore, the annual absolute energy
savings decrease by 50%. The better the thermal savings with a set-point rise of 1°C shows a change
performance of the envelope, the greater the reduction rule that decreases with the improvement of the
degree of absolute energy savings in the whole year thermal performance of the envelope. Although
relative to the cooling consumption; this indicates that better building thermal performance leads to lower
the increase of air-conditioner’s temperature set-point behavioral energy savings and annual energy savings,
by 1°C, after envelope performance has been greatly it can contribute to higher overall energy-saving
improved, does not get the same degree of energy effect, which is also obvious for new buildings. In
saving effect. Therefore, the energy conservation the transitional season, there are many moments
retrofit of existing buildings should not pay too much when the outdoor temperature is between 26°C and
attention to improving the thermal resistance of the 27°C, which greatly reduces energy consumption.
envelope of old buildings, but should pay attention Therefore, measures to increase the temperature set-
to guide the occupants of office buildings in all point during the transitional season have a greater
construction times to conduct behavioral energy potential to behave in an energy-efficient manner.
conservation. (iv) The microcosmic mechanism of the difference between
(ii) Under the condition of the thermal performance the annual and monthly relative energy-saving rates
of the four grades of envelope, the general rule of of air-conditioner with the set-point rise is that: The
monthly energy savings is that: In the cool winter improvement of thermal performance of envelope
months, the relative energy saving rate is high but the reduces the range of cooling load requirements before
absolute energy savings is small; in the transitional temperature rise, and also reduces the microcosmic
season, the absolute energy savings are the highest; load reduction rate under the same solar radiation
in the hot summer months, although the cooling intensity, which changes the distribution rule of load
energy consumption is much higher than that in the reduction rate of envelope with good performance.

Volume 5 Issue 2 (2023) 12 https://doi.org/10.36922/jcau.0877