DESIGN OF

EARTH AIR TUNNELS

TO CONSERVE ENERGY

Presented by:

APURVA ANAND

10-MARC-01

M.ARCH.(BUILDING SERVICES)

Direct

Industrial & Domestic heating HVAC

Greenhouses

Indirect

Electricity generation

GEOTHERMAL ENERGY

DEFINITION

•Geothermal Energy is heat

(thermal) derived from the earth

(geo).

•It is the thermal energy from

the earth's core, which is stored

in the rock in the earth's crust.

APPLICATIONS

ADVANTAGES

• Renewable

• Environment friendly

• Sustainable

• Cost effective

LIMITATIONS:

• Not every area has

accessible geothermal

sources.

• Green house gases

emission.

• Localized Depletion

Hot water spring

Geothermal Power Plant

GEOTHERMAL ENERGY SYSTEMS Systems that utilizes the thermal energy

stored in earth.

PRINCIPLE

• Earth behaves as a huge collector-

cum-storage .

• Beyond 4m depth earth

temperature remains constant

(equal to mean air temperature at

surface), since it absorbs only 50%

of all solar energy

WAYS OF TAPPING

Geothermal energy

indirect coupling

Earth air tunnel

Geothermal exchange systems

direct coupling

earth envelope

Geothermal Gradient

Earth sheltering

In-hill construction

Earth berming

underground/fully recessed

DEFINITION

• Architectural practice of

using earth against building

walls.

• Passive solar & sustainable

architecture.

TYPOLOGY

• Earth Berming

• In-hill construction

• Underground/fully recessed construction

ADVANTAGES

• Taking advantage of the earth as a

thermal mass.

• Offering extra protection from the

natural elements

• Energy savings

• Efficient use of land in urban settings

• Shelters have low maintenance

requirements

LIMITATIONS

• Water seepage

• Internal condensation

• Bad acoustics

• Poor indoor air quality.

• Requires heavier

construction than

conventional building

techniques

DIRECT COUPLING- EARTH ENVELOPES

OVERVIEW

An active technique that applies geothermal energy in required purposes using ground source

exchange. It is the refrigerant that circulates throughout the loop.

Ground Loop system

Heat Transfer fluid Heat Pump Air distribution

system

COMPONENTS

WORKING

Circulation of fluid through pipes buried in ground

Exchange of heat either-way ( from fluid to earth or

vice-versa)

Electrically driven concentrates this energy

& release it at desired temperature

Distribution through various distribution

systems

INDIRECT COUPLING – GEOTHERMAL

EXCHANGE SYSTEMS

OVERVIEW

• A passive technique consisting of a tunnel for

passage of calculated amount of air for the

purpose of HVAC of a space using natural

heat of the earth, 4 m below the earth surface.

• Also known as ground- coupled heat

exchanger or earth- tube heat exchanger.

• Used for either partial or full cooling and/or

heating of facility ventilation air.

INDIRECT COUPLING – EARTH

AIR TUNNEL

Earth Air Tunnel

Open loop

System

Closed Loop

System

Combination system

PRINCIPLE

• Uses constant air

temperature below 4

m of earth’ surface.

• Air blown through long

tubes buried in earth.

• Heat Dissipated

through surface

contact.

• Conditioned air

supplied to space

Space to be

conditioned Surface

Earth Air Tunnel

Open System

Space to be

conditioned

Surface

Closed

System

Space to be conditioned

Surface

Earth Air Tunnel

Combination System

Inlet

Inline fan

(optional)

Filter

concrete/plastic coated metal/ plastic coated

with antimicrobial layer tubes,hume

pipes and tunnels with ceramic tile

Outlet

Blower

Air Handling

Unit (optional)

Air distribution system

Air exhau

st syste

m

COMPONENTS

WORKING

Fresh Air sucked in through inlet.

Inlet air filtered

(mechanically/ natural filters)

Air passed through the length of tunnel. Heat gained/ lost

through surface contact

Conditioned air supplied to AHU

AHU contains evaporative coolers(summers)/dehumidifi

ers (monsoons)/ chillers/cooling pads.

Air Distribution, circulation and re-circulation of return air

Air Exhaust through solar chimneys/ exhausts

Schematics Earth Air Tunnel

INDIRECT COUPLING – EARTH

AIR TUNNEL

Efficiency

Surface Area available for

contact

Length of tube(80 M)

Diameter of tube(4-24

inch)

Soil Type Clayey Soil is most

effective. Sandy soil is least

Season Works best in dry

summer and winters

Soil Conditions

Depth of water table

Depth of tunnel

Surface conditions Shady, sunlit, wet, dry,

combination

INDIRECT COUPLING – EARTH

AIR TUNNEL

ADVANTAGES

Cost saving(operational phase-upto 70%)

Reduces air pollution

Energy saver

Reduces green house gases

100% fresh air without recirculation

Retrofit

Durable

Low Noise

High installation costs

Cumbersome Installation

Subject to climate

Need add-ons to achieve effective conditioning

Large space required

Not every area has accessible geothermal sources.

Long payback period

LIMITATIONS

INDIRECT COUPLING – EARTH

AIR TUNNEL

STUDY I- RETREAT, GUAL PAHARI

•EAT used for south block living

quarters.

•Tunnels cool outside air and maintains a comfortable temperature of 22-26

oC inside.

•4 tunnels to handle 6,000CFM

•Each Tunnel 70 m with 70 cm dia.

•4 fans 2 HP each force air in.

•Solar chimney force air out.

•Supplemented by 10 TR dehumidifier and chillers.

PRACTICAL APPLICATION IN INDIA

ENERGY CONSERVATION

STUDY II-CINEMA HALL IN JODHPUR,

CHOPASANI ROAD, JODHPUR

PRACTICAL APPLICATION IN INDIA

Exit Verandah, 1.8 M Wide &35.36 M Long

East wall, there are no windows or ventilators. The east side has extended foyers and A

recessed entrance with an overhang of 1.75 M which reduces the solar load on this wall

The projector room projects out

at a height of 3 M X 2 M.

The north, south

and east walls

contribute very

little to the heat

load of the

conditioned

space. The

overhang

provided for

these walls

reduces the solar

load.

STUDY II-CINEMA HALL IN JODHPUR,

CHOPASANI ROAD, JODHPUR

PRACTICAL APPLICATION IN INDIA

Roof is made of asbestos sheet,

supported on beams. Acts as an air

cavity to circulate the cooled air

available through a wind tower.

Total heat gain - 218 KW

= 218 x 3412 BTU

= 7,43,816 BTU

Therefore 61 TR is the HVAC load.

After introducing the passive

techniques and earth air tunnel the

HVAC load was reduced to 23 TR.

Almost 70% reduction in energy

consumption

Area Volume Temperature U value Thermal

gain/loss

Item (m2) (m3) (°C) (W/m2 °C) (W)

Roof (without treatment) 1800 — 53.48

-

27 = 26.48

3.53 168 253.9

Roof (with treatment) 1800 — 33.9- 27 = 6.9

3.53 43 842.6

West wall 344.3 — 43.75 - 27 = 16.75 3.5 20 184.6

North wall 11 743.34 — 41.75-27 = 14.75 1.86 20 385.3

East wall 344.3 — 41.75 -27= 14.75 3.5 17 774.5

South wall 11 743.04 — 41.75-27= 14.75 1.86 20 385.3

Doors 45 — 41.75-27 = 14.75 0.5 331.9

Floor 1537.92 — 33.75 -27 = 6.75 4.42 45 883.8

Ventilation — — 6.75 0.28 227.3

Infiltration — 19 839.16 — — 57 220

Occupancy (a) 806 (No.) — — — 75 60 450

Occupancy (b) 806 (No.) — — — 55 ( - )44330

Light (a) 1500W — — — 1.25 1875

Light (b) 1000 W — — — — 1250

Appliances 15 770W — — — — 15880

Length of EAT- 40 m

Dia of hume pipes- .7 m

Humidity is added by the

fresh air inlets covered with

wet gunny bags at the wind

tower.

STUDY III- ONGC- RAJIV GANDHI URJA

BHAWAN VASANT KUNJ, NEW DELHI

PRACTICAL APPLICATION IN INDIA

OVERVIEW

Client ONGC.

Architect Hafeez Contractor.

Site Area- 36,340 Sqm.

G+5 Structure with two basements

Built Up Area- 46,900 Sqm

HVAC Load- 3100 TR.

GREEN AND ENERGY EFFICIENT FEATURES

Use renewable energy such as geothermal energy, solar energy to reduce power

consumption

Ensure roof / wall insulation to reduce load on HVAC.

Use high efficiency and HFC based chillers for reducing environmental degradation due to

carbon & NOX emissions

Use energy modeling before construction so that complete building performance is known and

can be optimized at the design stage itself

Use CO2 sensors monitoring air quality to enhance benefits to occupants

Use building material with high recycled content.

Use certified wood & high-performance glass.

Use double skin external wall.

STUDY III- ONGC- RAJIV GANDHI URJA

BHAWAN, VASANT KUNJ, NEW DELHI

PRACTICAL APPLICATION IN INDIA

To cater the requirement of the building HVAC load a Hume

pipe is being laid at the depth of 8 m from the natural ground

level covering a running length of about 1000 m.

This pipe is having a diameter of 880 mm and at the

corners where the 90o turn is required, is being connected

to each other using the 3mm thick mild steel plates.

As the Hume pipe is running all along the basement

retaining wall so to avoid the infiltration into the walls

through the condensation part of the pipe a gap of 1350

mm has been maintained between the walls and the

pipes.

STUDY III- ONGC- RAJIV GANDHI URJA

BHAWAN, VASANT KUNJ, NEW DELHI

PRACTICAL APPLICATION IN INDIA

From the primary pipe secondary pipes are connected which

consequently connects the earth air tunnels to the seven

AHUs planned at the various points of the basement layout.

The Hume pipes are resting over the 1:2:4 R.C.C. bases so as to

avoid deflection from the pressure exerted by the soil

To cater the humidity requirement in hot and dry summer days two fan

towers are incorporated with the mist sprays have been assimilated

into the designing parameters which in later stage will act as a

landscape feature to the site.

STUDY III- ONGC- RAJIV GANDHI URJA

BHAWAN, VASANT KUNJ, NEW DELHI

PRACTICAL APPLICATION IN INDIA

As the Hume pipes

territory ends on the

outward portion of the

basement retaining walls

the rest of the distance

covered by the cool air to

the AHUs is undertaken

with the help of ducts

placed at the ceiling

level.

At the intersection the air

filters and the dampers

are also proposed to

enhance the indoor air

quality and to minimize

the noise created by the

change in the cross

sectional area from the

Hume pipe to the duct

The tunnel can be constructed using any type of pipe ,concrete ,masonry etc, thickness of

tunnel wall should be as less as possible for faster heat exchange

The pipe diameter should preferably be between 3-6” Pipes of lower diameter would require a

larger flow velocity and more pressure to ensure same volumetric supply of cool air.

Adjacent pipes shall have minimum gap of 2 times of the diameter of each pipe.

The pipe overlay ground should preferably be left loose or covered with lawn/foliage. Shade

on the ground would be even better.

CONCLUSIONS

The blower should be used with Variable

Frequency Drive(VFD)

In case of space constraints the vertical air shaft

can also be used. In dry ambient conditions, use of

water mist/spray in the tower before supplying air to

rooms/AHU is suggested.

The depth should be 4 meters below the ground level for nearly

constant ground temperature characteristics..

The length of the tunnel should be limited between 60-

70meters for optimum results.

BIBLIOGRAPHY

No. Title Author Publisher

1) RENEWABLE ENERGY:

SOURCES FOR FUELS

AND ELECTRICITY

LAURIE BURNHAM (EXECUTIVE

EDITOR)

ISLAND PRESS

2) GEOTHERMAL

RESOURCES: AN

ENERGY ALTERNATIVE

HARSH K. GUPTA ELSEVIER

SCIENTIFIC

PUBLISHING

COMPANY

3) ENERGY

CONSERVATION IN A

CINEMA HALL UNDER

HOT AND DRY

CONDITION

A. K. SINGH, G. N. TIWARI, N.

LUGANI AND H. P. GARG

‘DEVELOPMENT

ALTERNATIVES, B-

32, TARA

CRESCENT, QUTAB

INSTITUTIONAL

AREA, NEW

MEHRAULI ROAD

SECONDARY SEARCH

TERTIARY SEARCH

http://www.worldbank.org/html/fpd/energy/geothermal/index.htm

http://www.geothermie.de/egec-geothernet/ci_prof/europe/italy/italy_data.pdf

http://gibsonhomebuilders.com/masterbuildershow/2008/07/08/earth-sheltered-homes

http://en.wikipedia.org/wiki/Geothermal_energy

http://www.eai.in/ref/ae/geo/geo.html

http://www.thefullwiki.org/Earth_warming_tubes

http://www.geos.iitb.ac.in/geothermalindia/pubs/geoweb.htm