DESIGN OF EARTH AIR TUNNELS TO CONSERVE ENERGY

Presented by: APURVA ANAND

10-MARC-01M.ARCH.(BUILDING

SERVICES)

Direct

Industrial & Domestic heatingHVAC

GreenhousesIndire

ctElectricity 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 SYSTEMSSystems 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

OVERVIEWAn 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 TunnelOpen 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 distributi

on system

Air exhaust

system

COMPONENTS

WORKINGFresh 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 AHUAHU contains evaporative coolers(summers)/dehumi

difiers (monsoons)/ chillers/cooling pads.

Air Distribution, circulation and re-

circulation of return airAir 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 TypeClayey Soil is most

effective. Sandy soil is least

Season Works best in dry summer and winters

Soil ConditionsDepth of

water table

Depth of tunnel

Surface conditions Shady, sunlit, wet,

dry, combination

INDIRECT COUPLING – EARTH AIR TUNNEL

ADVANTAGESCost 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 22-26oC 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 BTUTherefore 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   20 184.6North wall 11 743.34 — 41.75-27 = 14.75 1.86   20 385.3East wall 344.3 — 41.75 -27= 14.75 3.5   17 774.5South wall 11 743.04 — 41.75-27= 14.75 1.86   20 385.3Doors 45 — 41.75-27 = 14.75 0.5   331.9Floor 1537.92 — 33.75 -27 = 6.75 4.42   45 883.8Ventilation — — 6.75 0.28   227.3Infiltration — 19 839.16 — —   57 220Occupancy (a) 806 (No.) — — — 75   60 450

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

Light (a) 1500W — — — 1.25   1875Light (b) 1000 W — — — —   1250Appliances 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