Provision of Earth Air Tunnel.

Another interesting feature of this college is an Earth Air Tunnel to cool down

temperatures during the summer season, in order to reduce energy costs

Earth air tunnel

Earth air tunnelSoil temperature, at a depth of about 12 feet or more, stays fairly constant throughout the year, and isapproximately equal to the average annual ambient air temperature. The ground can, therefore, be used as aheat sink for cooling in the summer and as a heat source for heating in the winter. A simple method of usingthis concept is to pass air through an underground air tunnel. The air thus cooled or heated can be useddirectly for the conditioned space or indirectlywith air conditioners or heat pumps.This system can maintain the temperature at280C inside the room. Earth temperature below12 ft is constant throughout the year and it isequal the yearly average temperature of aparticular geographical location. For Bangalore,the temperature below 12 ft is 24 0C and it isconstant throughout the year.Power consumption: 0.6 kW is required to cool orheat the space of approximately 1500 sqft area

Advantage of the system:

1. Low Energy: 1/3rd of the conventional AC

system’s power requirement.

2. Better indoor air quality.

3.100% fresh air circulation in the premises.

4. Min of 28 0C can be maintained during peak summer.

Technology description/principle

The cooling process is based on the fact that the temperature a few meters below the ground is almost constant throughout the year.

Daily temperature variations hardly affect the earth’s temperature at a depth of more than one meter, while the seasonal variations of the ambient temperature are strongly dampened by the earth. The earth’s temperature up to a depth of 6 to 8 m is influenced by the annual ambient temperature variations with a time delay of several months.

It is seen that in Delhi the earth’s temperature at a depth of about 4 m is nearly constant at around 23°C throughout the year.

A tunnel in the form of pipes or otherwise will acquire the sametemperature at its surface causing the ambient air ventilated through

this tunnel to get cooled.

•Daily and annual temperature fluctuations decrease with the increase in depth below the ground surface.

•At a depth of about 4 m below ground, the temperature inside the earth remains nearly constant round the year and is nearly equal to the annual average temperature of the place.

•A tunnel in the form of a pipe or otherwise embedded at a depth of about 4 m below the ground will acquire the same temperature as the surrounding earth at its surface.

•Therefore, the ambient air ventilated through this tunnel will get cooled in summer and warmed in winter and this air can be used for cooling in summer and heating in winter.

EARTH AIR TUNNELS

•This technique has been used in the composite climate of Gurgaon in RETREAT building.

•The living quarters (the south block of RETREAT) are maintained at comfortable temperatures (approx. 20-30 degree Celsius) round the year by the earth air tunnel system, supplemented, when ever required, with a system of absorption chillers powered by liquefied natural gas during monsoons and with an air washer during dry summer.

•However, the cooler air underground needs to be circulated in the living space. Each room in the south block has a 'solar chimney; warm air rises and escapes through the chimney, which creates an air current for the cooler air from the underground tunnels to replace the warm air.

•Two blowers installed in the tunnels speed up the process.

•The same mechanism supplies warm air from the tunnel during winter. PASSIVE SPACE CONDITIONING USING

EARTH AIR TUNNEL SYSTEM