It's a brave location for a university, 120 km from Delhi, across the
Rajasthan border, where temperatures cross 48 Celsius in summer and drop below
five degrees in winter. As I exit the Delhi-Jaipur highway, the modest NH8 gives
way to an eight-lane 'expressway'. I'm in the Japanese industrial zone at
Neemrana, Rajasthan, a short way away from the famous fort and palace in the
Aravali mountain range, driving into the spanking new NIIT University (NU). The
fort spans 25 acres; the university, a 100-acre 'green campus' at the foothills
of the Aravalis. A sculpture of a Möbius strip, that symbol of elegant
seamlessness, illustrates the Anaadi Anant motto--no beginning, no end. The
'seamless' campus will have 54 buildings, and accommodation for 5,000 students
and 500 faculty members, costing over Rs 1,000 crore over 10 years.
NU is new: I was heading for the inauguration. What's
really cool about it is the cooling (or heating, in winter): it's geothermal. A
network of 'earth-air tunnels' over four meters below the surface works as a
heat sink. The tunnels carry air that's pumped through them. The air gets cooled
in summer, and warmed in winter, because several meters below, the temperature
is far more consistent than on the surface. So when it's 45 degrees in the
shade, it's under 30 degrees down there, so the air comes out cooler. The
reverse happens in winter. (See NU's case study at
http://bit.ly/earth-air)
Here's how NU's literature explains it, quoting a research
paper from Tribhuvan University, Kathmandu: “The thermal capacity of the earth
is such that the day-night variations of surface temperature do not penetrate
much deeper than 0.5 m, and seasonal variations up to a depth of about 4 meters.
Beyond this depth, the earth's temperature, therefore, remains constant.”
That is a trifle oversimplified, and also assumes that four
meters down, the earth is an infinite heat sink. Which is (nearly) true of the
aggregate mass, but not for a localized area-which will gradually warm up a bit
as you keep passing hot air from the surface through it (in summer)...and also
warm up a few degrees in summer as surface temperatures stay in the forties.
A more accurate, and plausible, picture is here http://bit.ly/earth-temp.
At soil depths greater than 9 to 10 meters below the surface, temperature is
relatively constant at one location, though this “mean earth temperature” does
vary from place to place.
Even so, the fact remains that in summer afternoons, the
'air from down there' could come up over 15 degrees cooler, and in winter
mornings, perhaps 10 degrees warmer, than the surface air.
This is the air that NU is pumping through its buildings
after de-humidification and dust precipitation. On that warm winter afternoon,
it was certainly cooling effectively. At peak summer, it should help get the
temperature down 10 or 15 degrees, the rest being handled through “booster
chillers”. At a similar (but smaller) setup in TERI's 'green habitat' in
Gurgaon, it reports temperatures of 20 Celsius in winter, and 28 to 30 Celsius
in summer (http://bit.ly/teri-earth). NU claims its HAVC is the largest
earth-air tunnel system in the world.
If this works, this will be a benchmark for large-scale
cooling in campuses and buildings. It's green experiments like this-with major
leaps of faith in investments-that are truly path-breaking, and help push
interest in green tech from the domain of nice-to-do to makes-business-sense.
The author is chief editor at CyberMedia, publisher of 15
specialty titles including PCQuest.
You can reach him at pkr@cybermedia.co.in, twitter.com/prasanto.