This Presentation talks about low cooling strategies for buildings viz. radiant heating/cooling, geothermal heat exchange, rock beds and ground tunnel with examples and climate consideration.

1. Low Cooling Strategies
Apurwa K
Mitali N
Alefiya B

2. RADIANT COOLING

3. What Is Radiant Cooling? And How It Works?
 A radiant heating/cooling system refers to temperature-controlled surfaces that
exchange heat with their surrounding environment through convection and radiation.
 Radiant cooling cools a floor or ceiling by absorbing the heat from the rest of the room.
 Why water used?
 Because water has 3400 times thermal capacitance as air.

4. IIT Hostel Hyderabad
 Recycled water from the rest
of the campus is used in the
radiant cooling systems.
Here's a view of the hostel rooms back in the construction phase. The
red pipes are meant to contain running cold water.

5. Infosys, Hyderabad
Total BU area=24000 sqm.
Total occupancy=2500
The weather conditions show that there are different
seasons in Hyderabad from hot dry in April-May to warm
humid in July-August.

6. Results
Annual Energy Index of the whole building
including lighting, computers, HVAC and misc. loads
Annual Energy Index of different load components
in the building
Month-wise Energy Index of conventional airconditioning
and radiant cooling systems Energy savings

7. Conclusions
 Cost slightly lower.
 Occupies 1/3rd of space.
 33% better efficiency.
 Provides a better indoor air quality and thermal comfort

8. Applications
 Radiant heating and cooling systems can be used in
 commercial,
 residential,
 education,
 and recreational buildings, museums, hospitals,
 and other type of buildings.

9. Types Of Radiant Systems
 Depending on the position of the pipes in the building
construction, hydronic radiant systems can be sorted into 4
main categories:
 Embedded Surface Systems: pipes embedded within the
surface layer (not within the structure)
 Thermally Active Building Systems (TABS): the pipes
thermally coupled and embedded in the building structure
(slabs, walls)[6]
 Capillary Surface Systems: pipes embedded in a layer at the
inner ceiling/wall surface
 Radiant Panels: metal pipes integrated into panels (not
within the structure); heat carrier close to the surface.
Section diagram of a radiant embedded
surface system
Section diagram of thermally
activated building system
Section diagram of radiant
capillary system
Section diagram of a radiant panel

10. Climate Design Considerations
 Local climate needs to be evaluated and taken into account in the design.
 Radiant cooling is most effective in dry climates
 Problematic in humid climates. But can be regulated by maintain the temp of the
surface and providing secondary air conditioner to reduce the humidity.
 The Radiant cooling system is a part of floor or ceiling can also be a biggest factor.
Ceiling more comfortable than floor.
 Radiant heating is used in cold climates.

11. GROUND SOURCE HEAT PUMP

12. GROUND SOURCE HEAT PUMP
 A geothermal heat pump or ground source heat pump (GSHP) is a central
heating and/or cooling system that transfers heat to or from the ground.
 It uses the earth all the time, as a heat source (in the winter) or a heat
sink (in the summer).
 Through a network of pipes that are installed underground at a depth of 10
to 150m (in the case of a borehole collector), the heat that is being absorbed
by the Earth's crust is transported from the source (underground) to the
designated area (household) and released as high-temperature heat.

14. How it Works

15. Types of GSHP
The ground-coupling is
achieved through a
single loop, circulating
refrigerant, in direct
thermal contact with
the ground
• If the site has an
adequate water
body, this may be
the lowest cost
option.
• A supply line pipe
is run underground
from the building to
the water and
coiled into circles at
least eight feet
under the surface to
prevent freezing.
• Vertical loops
are also used
where the soil is
too shallow for
trenching.
• Vertical loops
also minimize
the disturbance
to existing
landscaping.
• This type of
installation is
generally most
cost-effective for
residential
installations,
particularly for
new construction
where sufficient
land is available.
• It requires
trenches at least
four feet deep.

16. The main environmental impacts are:
 Pollution from using grid electricity generated through
fossil fuel. Measures can be taken to reduce these impacts - for example,
purchasing dual tariff 'green' electricity. However, even if ordinary
grid electricity is used to run the compressor, the system will still produce
less CO2 emissions than the most efficient condensing gas or oil boiler with
the same output.
 Use of refrigerants in the system. Refrigerants are present in ground source
heat pump systems and can pose a threat to the environment as they can be
toxic, flammable or have a high global warming potential. However, new
types and blends of refrigerants with minimal negative impacts are being
developed. A correctly fitted system will also greatly reduce the potential for
leakage, which is why using a professional installer is highly recommended.
Environmental Impact

17.  Used in residential as well as in commercial
building types.
 Used in cold as well as hot climates.
 For cooling, Climates that experience
temperature swing, earth energy is used to
warm room temperature
 In hot arid climates, hot air passes in earth
through system
Applicability and climate

18. EARTH AIR TUNNEL

19. What is Earth air tunnel?
• Earth air tunnel or earth air heat exchanger is a pre-cooling or pre-heating system which
consists of a pipe or network of pipes buried at reasonable depth below the ground
surface.
• It either cools the air by rejecting heat to the ground or heats the air absorbing heat
from the ground.
• It depends upon the ambient temperature of the location.
• Underground heat exchanger Also called: Earth-Air Heat Exchangers
Air-to-soil Heat Exchangers
Earth Canals

20. How does it works?
 EAT may be considered as special types of wind towers connected to an underground tunnel. The
cooling process is based on the temperature a few meters below the ground.
 The wind tower catches the wind which is forced down the tower into the tunnel. The
temperature of the tunnel,being lower than that of the ambient temperature, cools the air
before it is circulated.
 In winter, the temperature of the air tunnel is higher than the ambient temperature and hence
warms the air passing through it.

21. Factors affecting thermal conductivity :
• SOIL:
1. Moisture content: thermal conductivity increases with moisture.
2. Density of soil: as density increases thermal conductivity increases.
3. Mineral Composition: soil with higher mineral content have higher conductivity.
soil with organic content lower conductivity.
4. Soil texture: coarse texture, grained soil has higher thermal conductivity.
5. Vegetation: It acts as an insulating agent moderating the affect of temperature.
• AIR:
1. As the velocity of air increases the exit temp decreases.
• duct length should be 10-90m long &
• 0.2-0.3mdia.

22. Parameters for heat transfer:
• Design parameters that impact the performance of EAT:
• TUBE DEPTH: Ground temperature fluctuates in time, but amplitude of fluctuation
diminishes with depth.
• Burying pipes/tubes as deep as possible would be ideal. A balance between going
deeper and reduction in temperature needs to be drawn. Generally ~4m below the
earth’s surface dampens the oscillations significantly.
• TUBE LENGTH: Heat transfer depends on surface area.
• Surface area of a pipe: Diameter and Length .
• So increased length would mean increased heat transfer and
• hence higher efficiency.
Increased length also results in increased pressure drop and hence increases energy.
• TUBE DIAMETER: Smaller diameter gives better thermal performance. Smaller diameter
results in larger pressure drop increasing fan energy requirement.

23. CALCULATION OF EAT EFFICIENCY

24. TYPES OF EAT:
Classification of EAT system:
• According to layout of pipe
• According to mode of arrangement
•Using earth as a source or sink
•Uses soil thermal inertia
•Depends on the thermal conductivity.
•Condensation occurs because of low air flow & high ambient temp dew point.
•Various factors affect the performance of eat which needs to optimised to
maximum temperature.
•Removal of moisture from cooled air is always an issue.
Conclusion :

25. APPLICABILITY AND CLIMATE :
• EAT can be used in hot and dry , composite climate type and in cold and sunny climate
type.
• In hot and dry temperature where diurnal temperature is seen. where control of sun
radiation & hot summer winds needs to be done.
• In cold and sunny to capture direct solar radiation need to be done.
• Commercial buildings: offices,showrooms.
• University campuses
• hospitals, recreational buildings.

26. Case study:
1.TERI UNIVERSITY CAMPUS,NEW DELHI
LOCATION :Located at Vasant Kunj in South Delhi. Built on around 2 acres
Of land.
Climate: composite
• The Earth Air Tunnel (EAT) is used in the hostel blocks. to maintain
comfortable temperatures inside the building.
• The use of Earth Air Tunnel gives an energy saving of nearly 50% as
compared to the conventional system Thermal mass storage used for
cooling the classrooms and labs

27. ROCK BEDS

28. Concept:
 Rock beds are a means of enlarging the
thermal mass of the building and thereby
increasing its ability to store energy.
 The floor then heats the space by
radiation after a lag time of several hours
required for the heat to move through the
mass.

29. Calculations and graphs
 The size of the rock bed is a function of the input air temperature, heat storage requirements,
rock size, and the flow rate
 Overall flow path through the bed should be limited to 2.4m to keep pressure losses down.
Maximum bed depth should be 1.2m with pebbles of 19-38mm in diameter(ASHRAE, 1988)

30. For low temperature source
 Considering Dharmsala’s Jan month radiation transmitting through
the south facing glass.
 Average daily Radiation on south surface = 2490.77 watts/m2
 =2.49
 Δt = 8.5°C
 From the graph we get = 0.57
 Now multiply solar glass area by storage volume ratio to get the
minimum storage volume required
 Area of the room considered = 20sq.m.
 Area of solar glass area = 12sq.m.
 ∴ 0.57X12 = 6.84m3

31. For high temperature source such as an air collector
 Radiation level incident on collector = 4000 watts/m2
 =4 kwh/m2
 Collector efficiency = 40%
 From the graph we get = 0.12
 Now multiply collector area by storage volume ratio to get the
minimum storage volume required
 Area of collector considered = 25sq.m.
 ∴ 0.12X25 = 3m3

32. To determine the amount of heat that needs to be stored in
rock bed
 Buildings total heat gain - Daily heat stored in the building
 Consider, = 2890 - 2490
 = 400
 Daily minimum Outdoor temp = 10.3°C
 From the graph we get = 0.26
 Now multiply building floor area by storage volume ratio to get the
minimum storage volume required
 Area of the building considered = 250sq.m.
 ∴ 0.26X250 = 65m3 volume of rock bed required

33.  Hot air drawn from the solar heated
atrium into the rock bed
 At night, heat transferred from the
rock bed to the space.
Princeton Professional Park, Princeton, New Jersey

34.  Used mainly in residential building type.
 Rock bed heating used in cold and sunny climates.
 For cooling, Climates that experience a large diurnal temperature swing, cool
outside temperature can be drawn through the bed at night.
 In hot arid climates, the rock bed may be cooled by evaporative cooled air that has
been conditioned with a mechanical evaporative cooler.
Applicability and climate