The Amount of Energy Consumption for Cooling
The examination of the cooling energy consumption performance in peak hot weather conditions in Ilam (32.5 at its peak hot weather on July) was done similar to that of the heating energy consumption. Analysis results showed that Sample H had the highest amount of energy consumption. Evidently, given the specifications listed in Table 2, Sample H with a length, width and total area of 26m, 6m and 156m2, respectively, showed the worst energy consumption performance in terms of both heating and cooling.
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Figure 3.: The amount of cooling energy consumption of samples during the peak hot period (average temperature of 32.5℃)
As previously expressed, following the selection of the eight building samples in the first stage, the amount of energy consumption of the samples during peak hot and cold periods and the wall transparency range of 0-100 were calculated and shown as charts.
As can be seen in Figure 2, increase in wall transparency at the peak cold period reduced the total energy consumption in Samples A, B, D, E, G, and D; in addition, increase in wall transparency compared to dark surfaces led to increased energy consumption. Such reduction and increase in consumption considering wall transparency for Sample E are shown based on Figure 2.
Chart 2 demonstrates that with increased total area of windows as the transparency factor in building walls followed by increase in the received solar energy, the heating energy of the house is somewhat provided by the sun, resulting in lower energy consumption for heating. With the lowest extent of transparency, Sample E had the highest amount of energy consumption.
In contrast, increase in the extent of openings increased the amount of energy waste and subsequently, energy consumption. As shown in Figure 2, increase in the openings by a specific limit in all samples raised the amount of energy consumption significantly.
Figure 3 represents the amount of energy consumption and building performance during the peak hot weather across five selected samples. According to the chart, increase in wall transparency raised energy consumption. The reason behind this is that in hot seasons, increase in the openings would raise the amount of received sunlight and subsequently, more heat is received; in turn, this raises the amount of energy consumption for cooling to lower the building temperature to a desirable degree.
Here, the following question can be posed: What is the cause behind such an increase in energy consumption in Sample E compared to the other samples? To answer this query, Figure 2 should be compared with Figure 3; according to the former, the lower the extent of openings (transparency) in the building, the lower the amount of received solar energy. In this case, considering the difference in temperature between day and night in the examined climate, the amount of received energy during the day is lower than the energy wasted at night; as a result, more energy would be required for heating. By increasing the transparency (total area of openings), the amount of received solar energy is increased by 10-20%; and through the gradual compensation for the lost energy, the chart gained a similar procedure to other samples.
Nonetheless, Chart 3 shows that in the hottest day of the year with 10% transparency accompanied by intense sunshine and insignificant temperature difference between day and night, the temperature of the building interior raised which necessitated a large amount of energy to lower the temperature. Notably, the higher the difference between the interior and exterior of a building, the more the energy exchanged between the two environments; in such cases, more energy would be required to reach the desirable temperature.
However, given the ratios between the building and total areas of openings (transparency) in other samples, there is a proper proportion between received and wasted energy; consequently, the energy consumption of samples has a similar chart. In other words, lower ratio of openings to the building volume in Samples A, C and B had a better performance compared to Sample E in terms of received and wasted energy.
The other samples including D, G, F and H received more solar energy due to larger surfaces of openings and west-east stretch (being in the direction of sunshine).