1:45 PM - 3:15 PM
[O07-P19] Countermeasures against Heat Island Phenomenon: Proposal for a New Building System
Keywords:heat island phenomenon, Wind Path, urea
Introduction
Recently, the heat island phenomenon has become more serious and environmental problem peculiar to cities. The main causes are artificialization due to ground surface cover and high density of urban forms. Therefore, the heat island effect appears mainly in urban areas and needs to be considered separately from global warming. As a countermeasure, the reduction of artificial exhaust heat and the use of wind from the sea to create Wind Path have been mentioned. This time, I focused on the Wind Path and devised an environmentally friendly building structure and system to efficiently cool and utilize the harmful building wind, even in places where no wind reaches from the sea.
Methods and Results
1. Design of a cooling system using endothermic reaction of chemicals: (a) ammonium sulfate, (b) citric acid, (c) baking soda, and (d) urea were selected as relatively safe chemicals that undergo endothermic reaction when dissolved in water, and dissolved in water (100 cc, 35°C) at different concentrations. The time course of temperature decrease was compared. When 5 mol of (a) was dissolved, the water temperature dropped to 24.5°C. When 4 mol of (b) was dissolved, the water temperature dropped rapidly to 19°C. (c) the water temperature dropped only to a maximum of 28°C. The cooling effect of (a), (b), and (d) among the four types was high, and among them, the cooling effect of (d) was the highest. Therefore, two mixtures of (a) + (d) and (b) + (d) were dissolved in water, expecting a synergistic effect. However, all of them dropped to around 13°C and there was no difference, and the expected synergistic effect compared to urea alone could not be obtained.
2. Relationship between walls and wind speed: A model of a cylindrical building was built with side and front walls, and the change in wind speed under the building was measured. The results showed that the buildings with side walls had stable wind speeds overall. In particular, the wind speeds at the 5-25 cm point were all above the average wind speed of 2.0 m/s. In addition, buildings with side and front walls had average wind speeds above 3.0 m/s at the 5 cm point, which were above the average wind speed values for buildings with only side walls at all points.
3. Building Wind-Based Cooling System: A building model with side and front walls was constructed, and wind was applied to the building to measure the ground surface temperature under the following three conditions; (a) building only, (b) radiator filled with water at 23°C, and (c) radiator filled with cooled urea water. The average wind speed through the radiator was 1.2 m/s. The ground surface temperatures at 10, 15, and 20 cm distances from the radiator were (a) 39.7, 37.8, and 35.7°C, (b) 38.0, 37.2, and 36.2°C, and (c) 34.6, 35.1, and 35.2°C, respectively, a decrease of about 5°C at 10 cm and about 3°C at 15 cm. There was not much difference in the surface temperature at 20 cm. When radiators filled with urea water were used, the temperature increase over time was suppressed and the surface temperature under the building was cooled down to the 15 cm point.
Summary and Discussion
As for the structure of the building, it was found that the wind was more concentrated when the side and front walls were attached to the surface of the building. As the cooling water for the wind, several chemicals that cause endothermic reactions when dissolved in water were investigated, and urea, used alone, provides an efficient and strong cooling effect. Urea is safe for the human body and is widely used in skin creams and fertilizers, etc. After cooling the building air, urea can be dissolved and diluted after filtered from the waste water, which is environmentally friendly and can be used as a fertilizer for plants. In devising a building system, it would be even better for the environment if urea could be extracted directly from the urine in the building effluent and sewage. It is said that humans discharge about 30 g of urea per day. There are reports of recovering urea through direct filtration by osmotic urea separation using a dialyzer used for artificial kidneys, and there are proposals to recover urine directly from underground septic tanks in cities. In future, specific methods to extract urea from urine discharged from buildings should be studied. In order to consolidate the complex building wind, the direction and the building structure need to be studied in more detail. In this experiment, a cylindrical building with only one side wall and one front wall in a small area was tested. For realization, experiments should be conducted to expand the area of walls to be attached to the building, or to have multiple buildings densely packed like a city, in order to construct a new Wind Path.
Recently, the heat island phenomenon has become more serious and environmental problem peculiar to cities. The main causes are artificialization due to ground surface cover and high density of urban forms. Therefore, the heat island effect appears mainly in urban areas and needs to be considered separately from global warming. As a countermeasure, the reduction of artificial exhaust heat and the use of wind from the sea to create Wind Path have been mentioned. This time, I focused on the Wind Path and devised an environmentally friendly building structure and system to efficiently cool and utilize the harmful building wind, even in places where no wind reaches from the sea.
Methods and Results
1. Design of a cooling system using endothermic reaction of chemicals: (a) ammonium sulfate, (b) citric acid, (c) baking soda, and (d) urea were selected as relatively safe chemicals that undergo endothermic reaction when dissolved in water, and dissolved in water (100 cc, 35°C) at different concentrations. The time course of temperature decrease was compared. When 5 mol of (a) was dissolved, the water temperature dropped to 24.5°C. When 4 mol of (b) was dissolved, the water temperature dropped rapidly to 19°C. (c) the water temperature dropped only to a maximum of 28°C. The cooling effect of (a), (b), and (d) among the four types was high, and among them, the cooling effect of (d) was the highest. Therefore, two mixtures of (a) + (d) and (b) + (d) were dissolved in water, expecting a synergistic effect. However, all of them dropped to around 13°C and there was no difference, and the expected synergistic effect compared to urea alone could not be obtained.
2. Relationship between walls and wind speed: A model of a cylindrical building was built with side and front walls, and the change in wind speed under the building was measured. The results showed that the buildings with side walls had stable wind speeds overall. In particular, the wind speeds at the 5-25 cm point were all above the average wind speed of 2.0 m/s. In addition, buildings with side and front walls had average wind speeds above 3.0 m/s at the 5 cm point, which were above the average wind speed values for buildings with only side walls at all points.
3. Building Wind-Based Cooling System: A building model with side and front walls was constructed, and wind was applied to the building to measure the ground surface temperature under the following three conditions; (a) building only, (b) radiator filled with water at 23°C, and (c) radiator filled with cooled urea water. The average wind speed through the radiator was 1.2 m/s. The ground surface temperatures at 10, 15, and 20 cm distances from the radiator were (a) 39.7, 37.8, and 35.7°C, (b) 38.0, 37.2, and 36.2°C, and (c) 34.6, 35.1, and 35.2°C, respectively, a decrease of about 5°C at 10 cm and about 3°C at 15 cm. There was not much difference in the surface temperature at 20 cm. When radiators filled with urea water were used, the temperature increase over time was suppressed and the surface temperature under the building was cooled down to the 15 cm point.
Summary and Discussion
As for the structure of the building, it was found that the wind was more concentrated when the side and front walls were attached to the surface of the building. As the cooling water for the wind, several chemicals that cause endothermic reactions when dissolved in water were investigated, and urea, used alone, provides an efficient and strong cooling effect. Urea is safe for the human body and is widely used in skin creams and fertilizers, etc. After cooling the building air, urea can be dissolved and diluted after filtered from the waste water, which is environmentally friendly and can be used as a fertilizer for plants. In devising a building system, it would be even better for the environment if urea could be extracted directly from the urine in the building effluent and sewage. It is said that humans discharge about 30 g of urea per day. There are reports of recovering urea through direct filtration by osmotic urea separation using a dialyzer used for artificial kidneys, and there are proposals to recover urine directly from underground septic tanks in cities. In future, specific methods to extract urea from urine discharged from buildings should be studied. In order to consolidate the complex building wind, the direction and the building structure need to be studied in more detail. In this experiment, a cylindrical building with only one side wall and one front wall in a small area was tested. For realization, experiments should be conducted to expand the area of walls to be attached to the building, or to have multiple buildings densely packed like a city, in order to construct a new Wind Path.