| Summary: |
The use of passive cooling techniques in summer is advisable either in the perspective of improving the thermal environment of non-climatised spaces as in the perspective of reducing energy consumption when the spaces are climatised. It can thus be an effective tool for attenuating the growth of energy consumption for air conditioning that has been happening in the latest years in Portugal and other South-European countries.
This project is focused in the evaluation of the potentialities of passive cooling systems using natural heat sinks as the atmosphere and the earth. For this purpose this project includes the development of models that shall allow the prediction of the temperature and relative humidity of the air cooled in the earth-air heat exchanger or in the evaporative cooling tower. The project also includes the construction of a test facility that comprises a test cell, a solar chimney, an evaporative cooling tower and an earth-air heat exchanger and will be used to validate the models. Natural ventilation is assisted through the solar chimney and the incoming air is pre-cooled in the earth-air heat exchanger or, alternatively, by passive downdraught evaporative cooling. 1n the case of earth-air heat exchangers, one of the main drawbacks identified in previous studies is the drying of the soil around the pipe and consequent decreases in the soil conductivity and cooling efficiency. To overcome this problem, a water pipe, commonly used in the drop by drop watering, will keep the soil wetted in the proximity of the buried pipe. As far as the authors knowledge goes, it is an innovative technique to improve the efficiency of the earth-air heat exchanger and consequently to increase its cooling potential. Another passive cooling process that will be tested is the passive downdraught evaporative cooling. The project previews the construction of a tower where a nozzle system injects droplets of water, at the top. The test facility will be monitorized with the  |
Summary
The use of passive cooling techniques in summer is advisable either in the perspective of improving the thermal environment of non-climatised spaces as in the perspective of reducing energy consumption when the spaces are climatised. It can thus be an effective tool for attenuating the growth of energy consumption for air conditioning that has been happening in the latest years in Portugal and other South-European countries.
This project is focused in the evaluation of the potentialities of passive cooling systems using natural heat sinks as the atmosphere and the earth. For this purpose this project includes the development of models that shall allow the prediction of the temperature and relative humidity of the air cooled in the earth-air heat exchanger or in the evaporative cooling tower. The project also includes the construction of a test facility that comprises a test cell, a solar chimney, an evaporative cooling tower and an earth-air heat exchanger and will be used to validate the models. Natural ventilation is assisted through the solar chimney and the incoming air is pre-cooled in the earth-air heat exchanger or, alternatively, by passive downdraught evaporative cooling. 1n the case of earth-air heat exchangers, one of the main drawbacks identified in previous studies is the drying of the soil around the pipe and consequent decreases in the soil conductivity and cooling efficiency. To overcome this problem, a water pipe, commonly used in the drop by drop watering, will keep the soil wetted in the proximity of the buried pipe. As far as the authors knowledge goes, it is an innovative technique to improve the efficiency of the earth-air heat exchanger and consequently to increase its cooling potential. Another passive cooling process that will be tested is the passive downdraught evaporative cooling. The project previews the construction of a tower where a nozzle system injects droplets of water, at the top. The test facility will be monitorized with the installation of temperature and humidity sensors localized inside the test cell, in the earth-air heat exchanger, in the solar chimney and in the evaporative cooling tower.
Tracer gas techniques and anemometry shall be used to evaluate the air flow rates. The theoretical and system simulation models developed will be validated through the test facility. These models shall then be integrated in whole building simulation tools so that the effect of the passive cooling systems when integrated in realistic buildings can be assessed. This assessment shall be performed for a set of three buildings representing the following typologies: a detached of semi-detached dwelling, an office building and a school. The impact of the passive cooling systems in each one of the selected buildings will be evaluated in terms of indoor temperature (when the spaces are not air-conditioned), energy demand (when the spaces are conditioned) and consumption of water. The building simulation will be repeated for locations in each of the three summer climatic zones defined by the Portuguese thermal regulation. |