DESIGN OF
EARTH AIR TUNNELS TO CONSERVE ENERGY
Presented by:
APURVA ANAND 10-MARC-01 M.ARCH.(BUILDING SERVICES)
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 Industrial & Domestic heating HVAC Direct
Hot water spring
Geothermal Power Plant
Greenhouses Indirec t
Electricity generation
ADVANTAGES •
Renewable
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Environment friendly
LIMITATIONS:
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Sustainable
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Cost effective
Not every area has accessible geothermal sources.
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Green house gases emission.
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Localized Depletion
GEOTHERMAL ENERGY SYSTEMS Systems that utilizes the thermal energy stored in earth. PRINCIPLE •
Earth behaves as a huge collectorcum-storage .
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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
direct coupling
earth envelope
indirect coupling
Earth air tunnel
Geothermal exchange systems Geothermal Gradient
DIRECT COUPLING- EARTH ENVELOPES DEFINITION •
Architectural practice of using earth against building walls.
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Passive solar & sustainable architecture. Earth berming
TYPOLOGY •
Earth Berming
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In-hill construction
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Underground/fully recessed construction
Earth sheltering
ADVANTAGES
LIMITATIONS
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Taking advantage of the earth as a thermal mass.
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Water seepage
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Internal condensation
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Offering extra protection from the natural elements
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Bad acoustics
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Energy savings
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Poor indoor air quality.
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Efficient use of land in urban settings
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Shelters have low maintenance requirements
Requires heavier construction than conventional building techniques
In-hill construction
underground/fully recessed
INDIRECT COUPLING – GEOTHERMAL EXCHANGE SYSTEMS
OVERVIEW An active technique that applies geothermal energy in required purposes using ground source exchange. It is the refrigerant that circulates throughout the loop.
COMPONENTS Ground Loop system
Heat Transfer fluid
WORKING Circulation of fluid through pipes buried in ground Exchange of heat eitherway ( from fluid to earth or vice-versa) Electrically driven concentrates this energy & release it at desired temperature Distribution through various distribution systems
Heat Pump
Air distribution system
INDIRECT COUPLING – EARTH AIR TUNNEL
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.
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Also known as ground- coupled heat exchanger or earth- tube heat exchanger.
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Used for either partial or full cooling and/or heating of facility ventilation air.
Earth Air Tunnel
Open loop System Closed Loop System
PRINCIPLE •
Uses constant air temperature below 4 m of earth’ surface.
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Air blown through long tubes buried in earth.
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Heat Dissipated through surface contact.
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Conditioned air supplied to space
Combination system
Space to be conditioned Space to be conditioned Space to be conditioned
Open System Closed Combination System System
SurfaceSurface Surface
Earth Air Tunnel Earth Air Tunnel
concrete/plastic coated metal/ Inline plastic coated with antimicrobial Inle fan Filter layer tubes,hume t (optiona l) pipes and tunnels with WORKING ceramic tile Fresh Air sucked in through inlet.
COMPONENTS
INDIRECT COUPLING – EARTH AIR TUNNEL Outle t
Blower
Air Handling Unit (optional)
Air distributio n system
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 Schematics Earth Air Tunnel
Air Exhaust through solar chimneys/ exhausts
Air exhau st syste m
INDIRECT COUPLING – EARTH AIR TUNNEL
Surface Area available for contact
Soil Type
Season Efficiency
Length of tube(80 M) Diameter of tube(4-24 inch) Clayey Soil is most effective. Sandy soil is least
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
LIMITATIONS
ADVANTAGES Cost saving(operational phase-upto 70%)
High installation costs
Reduces air pollution
Cumbersome Installation
Energy saver Reduces green house gases
Subject to climate
Need add-ons to achieve effective conditioning
100% fresh air without recirculation Large space required Retrofit
Durable
Not every area has accessible geothermal sources.
Low Noise
Long payback period
PRACTICAL APPLICATION IN INDIA STUDY I- RETREAT, GUAL PAHARI •EAT used for south block living quarters. •Tunnels cool outside air and maintains a comfortable o temperature of 22-26 C 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.
ENERGY CONSERVATION
PRACTICAL APPLICATION IN INDIA STUDY II-CINEMA HALL IN JODHPUR, CHOPASANI ROAD, JODHPUR Exit Verandah, 1.8 M Wide &35.36 M Long
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.
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
PRACTICAL APPLICATION IN INDIA STUDY II-CINEMA HALL IN JODHPUR, CHOPASANI ROAD, JODHPUR Roof is made of asbestos sheet, supported on beams. Acts as an air cavity to circulate the cooled air available through a wind tower. 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.
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
Item Roof (without treatment) 3.53 Roof (with treatment) 3.53 West wall North wall East wall South wall Doors Floor Ventilation Infiltration Occupancy (a) 806 (No.) Occupancy Light Light Appliances
(b) 806 (No.) (a) 1500W (b) 1000 W 15 770W
Area
Volume
Temperature
(m2)
(m3) 1800
(°C) —
344.3 11 743.34 344.3 11 743.04 45 1537.92 — — —
— — — — — — — 19 839.16 —
168 253.9 — 43 842.6 43.75 - 27 = 16.75 41.75-27 = 14.75 41.75 -27= 14.75 41.75-27= 14.75 41.75-27 = 14.75 33.75 -27 = 6.75 6.75 — —
—
—
—
— — —
— — —
— — —
1800
U value (W/m2 °C) 53.48 -
Thermal gain/loss (W) 27 = 26.48
33.9- 27 = 6.9 3.5 1.86 3.5 1.86 0.5 4.42 0.28 — 75 55 1.25 — —
20 184.6 20 385.3 17 774.5 20 385.3 331.9 45 883.8 227.3 57 220 60 450 ( - )44330 1875 1250 15880
PRACTICAL APPLICATION IN INDIA STUDY III- ONGC- RAJIV GANDHI URJA BHAWAN VASANT KUNJ, NEW DELHI 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.
PRACTICAL APPLICATION IN INDIA STUDY III- ONGC- RAJIV GANDHI URJA BHAWAN, VASANT KUNJ, NEW DELHI 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.
PRACTICAL APPLICATION IN INDIA STUDY III- ONGC- RAJIV GANDHI URJA BHAWAN, VASANT KUNJ, NEW DELHI 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.
PRACTICAL APPLICATION IN INDIA STUDY III- ONGC- RAJIV GANDHI URJA BHAWAN, VASANT KUNJ, NEW DELHI 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
CONCLUSIONS
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 6070meters for optimum results. 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.
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.
BIBLIOGRAPHY SECONDARY SEARCH No.
Title
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RENEWABLE ENERGY: LAURIE BURNHAM (EXECUTIVE ISLAND PRESS SOURCES FOR FUELS EDITOR) AND ELECTRICITY GEOTHERMAL HARSH K. GUPTA ELSEVIER RESOURCES: AN SCIENTIFIC ENERGY ALTERNATIVE PUBLISHING COMPANY ENERGY A. K. SINGH, G. N. TIWARI, N. ‘DEVELOPMENT CONSERVATION IN A LUGANI AND H. P. GARG ALTERNATIVES, BCINEMA HALL UNDER 32, TARA HOT AND DRY CRESCENT, QUTAB CONDITION INSTITUTIONAL AREA, NEW MEHRAULI ROAD
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Author
Publisher
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
