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ABSTRACT
An Earth Air Tunnel (EAT), constructed recently in the experimental Zero Energy House in the Institute of Engineering of Tribhuvan University utilizes a unique concept of earth Air Tunnel for providing Heating Ventilating and Air Conditioning requirements of spaces. The EAT system draws air, through an air intake at the end of a 75 meter tunnel of diameter 0.5 meter, buried 4 meter below ground, with the help of an Air Handling Unit. The air is then dehumidified and passed on to the spaces requiring HVAC through the conventional system of ducts and diffusers and exhausts through solar chimney, assisted by wind operated exhaust turbine located at the top of the chimney at the terrace level of the building. The profile of temperature as a function of daily input of energy on the ground in the form of radiation and sensible heat is analyzed through rigorous analytical method and compared with actual measurements, which show remarkable closeness to the analytically determined result. The study calculated the cost saving with respect to conventional air conditioning system and found it to have very substantial saving to the tune of 70 percent. The study of the bacterial and fungal pollution of air at the intake and output point of the tunnel and at the room showed considerable decrease of air-borne bacteria and fungi from the air intake to the air delivery point of the tunnel. The microbial count further decreased at the supply grilles. The study clearly shows that while on one hand the EAT system saves electricity thus saving on the emitted particulate, SOX, and NOX at the thermal power house while on the other also has an effect of drastically reducing air borne bacteria and fungi in indoor spaces.
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