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    • Efforts in limiting CO emissions from buildings concentrate

    2018-11-12

    Efforts in limiting CO2 emissions from buildings concentrate on energy demand reduction. As fossil fuels still represent the bulk of energy sources used, reducing energy demand reduces carbon emissions. Another approach is to provide energy from renewable sources like sun, wind and biomass. Little consideration is given to how energy demand and supply are linked. We argue that by systems integration and by using the Low Exergy paradigm based on the thermodynamic concept of exergy, there are CO2 reduction potentials that have so far been overlooked (Meggers et al., 2012c, 2011).
    Background
    Methodology
    Results The calculation of the chiller performance based on the anergy sink temperatures in Table 1 resulted in the COP values presented in Figure 6. For each of the 6 types of anergy sinks studied, the COP was calculated using the range of expected evaporation temperatures. Dry air-cooled heat rejection had the lowest performance coefficient, especially when subject to a stack effect of split units. Based on the variations shown in Figure 4, the COP does not vary significantly throughout the day and remains between 3.3 and 3.6 and 4.5 and 5.1 for 8°C and 18°C respectively. The effect of a higher evaporation temperature (see Section 3.6) increases disproportionately with lower condensing temperatures. While the performance gain for dry air heat rejection using 18°C evaporation temperature was small compared to other anergy sinks, it was still 39% better than for the commonly used 8°C evaporation temperature. Table 2 shows the relative performance increase and decrease compared to the estrogen receptor antagonist case of using dry air-cooling with an evaporation temperature of 8°C.
    Discussion There is a large improvement potential if we use other anergy sinks than the standard dry bulb temperature because of the non-linear nature of the COP for chillers and heat pumps. The main points on the different performance increases may be described as follows: Major energy efficiency gains for the overall building design are possible if the dependencies of different system components are taken into account. The effect of these systems considerations will be studied in greater depth using our experimental laboratory BubbleZERO in Singapore (Meggers et al., 2012a).
    Conclusion and outlook
    Acknowledgements
    Introduction Tile exfoliation from external walls gives significant influence on the rain penetration and the durability of the external wall of the building. Sometimes, falling tiles cause serious accidents threatening human lives, even in the case of a low-rise building, and becomes a social problem than before in Japan (Figure 1). Although various measures have been taken to prevent tile exfoliation, this problem has not yet been solved likely because the real reasons for tile exfoliation have not yet been clarified. The following items are regarded as the causes of tile exfoliation: In our previous research (Onmura et al., 2009), the measurement of the hygrothermal properties of the concrete and water absorption experiments using a small-scale concrete wall with tile finishing, were carried out to evaluate the water penetration behavior in a tiled concrete wall. Along with these experiments, a drying experiment at 105°C using a tiled concrete sample (Figure 2) was carried out to examine the influence of the heating. Figures 3 and 4 show the weight change of the sample and the propagation of the tile exfoliation, respectively. Exfoliation occurred starting from the tile at the sample corner, 1 day after drying started. Finally, all of the tiles were exfoliated after 6 days. Tile exfoliation occurred at the boundary between the tile and the concrete body, as shown in Figure 5. From these results, a hypothesis (that tile exfoliation occurs when the moisture content of the mortar on the back side of the tile drops to a certain value because of drying) was proposed, although, it might have occurred because of temperature expansion. Under this hypothesis, the relationship between the change of moisture content due to drying and tile exfoliation was examined in this research. First, drying experiments at 60, 75, and 90°C were carried out to determine whether tile exfoliation occurs at temperatures lower than 105°C. Next, a three-dimensional analysis of simultaneous heat and moisture transport was carried out to estimate the moisture content distribution inside the sample and its time profile under the different conditions of the drying experiments.