The document explains the relationship between the Earth and the Sun, detailing how solar radiation affects life on Earth, the seasons, and climate variations. It covers key concepts such as solar angles, energy cycles, and atmospheric interactions that influence weather patterns and climate controls. Additionally, it introduces heliodons as tools for simulating solar angles to aid in energy-efficient building design.

1. EARTH SUN
RELATIONSHIP

2. WHAT IS EARTH
The third planet from the Sun and the
only astronomical object known to
harbour life

3. WHAT IS SUN?
The Sun is the star at the centre of
the Solar System.
It is a nearly perfect sphere of
hot plasma, with internal convective
motion that generates a magnetic field via
a dynamo process.
It is by far the most important source
of energy for life on Earth.

4. EARTH’S ROTATION
Turning eastward direction at uniform rate every 24 hours.
The most intense incoming sola radiation occurs where the sun’s
rays strike the earth at highest angle.
As the sun angle decreases the beam of light is spread over a larger
area and the intensity decreases due to thickness of atmosphere,
increase in reflection and scattering of light.
The tilt of axis is responsible for opposite
seasons in northern and southern
hemisphere.

5. EARTH’S
REVOLUTION
Equinox – Wednesday, 20 March 2019
Sun lies directly above the equator
Summer solstice – Friday, 21 June 2019
Sun lies directly above the tropic of
Cancer
Equinox - Monday, 23 September 2019
Axis of rotation parallel to sun rays.
Winter – Sunday, 22 December 2019
Sun rays are direct at tropic of
Capricorn

6. SOLSTICES
6 months of night at the north pole.
Marks the shortest day in the northern
hemisphere.
6 months of night at the south pole.

7. EQUINOXES
The axis of earth’s rotation is still tilted
but it is inclined sideways with respect
to the sun. At these times, the tangent
rays strike the poles so that the days
& nights are equal over the entire
earth.
The autumnal equinox on September 22
indicates the beginning of autumn season in
the northern hemisphere.
March 22 is the first day of spring season &
hence this date is known as the spring
equinox. Equinoxes mark the transition
between the two extreme seasons, summer
& winter.

8. WEATHER
Monsoon when most of the region’s
average annual rainfall occurs.
Winter is when the hemisphere is tipped
away from the sun.
Summer is when the hemisphere is tipped
towards the sun.
Monsoon is followed by Autumn
Spring is time between winter and summer
where the rise in temperature is pleasant

9. SOLAR RADIATION
• The energy received by all the earth’s
surface is in three forms of radiation
• Ultra-violet 290 nm to 280 nm, produces
photo-chemical effects, bleaching,
sunburn etc.
• Visible light 380 nm (violet) to 700 nm
(red)
• Infra-red radiation 700 nm to 2300 nm,
radiant head and some photo chemical
effect.
• Solar radiation provides heat, light, and energy necessary for all living organisms.
Infrared radiation supplies heat to all habitats, on land and in the water. Without
solar radiation, Earth’s surface would be about 32°C colder.

10. RADIATION AT EARTH SURFACE
• The sun’s radiation must make it
through multiple barriers before it
reaches Earth’s surface.
• The first barrier is the atmosphere.
About 26% of the sun’s energy is
reflected or scattered back into space
by clouds and particulates in the
atmosphere.
• Another 18% of solar energy is
absorbed by the Ozone.
• Ozone absorbs ultraviolet radiation,
while carbon dioxide and water vapor
can absorb infrared radiation.
• The remaining 56% of solar radiation is
able to reach the surface.

11. ALBEDO
The ratio of reflected radiation to the total intercepted radiation, in terms of percentage of
reflected radiation.
The albedo of earth’s atmosphere is 0.30
The moon’s is only 0.07, that means it absorbs most of the solar radiation striking its surface
Fresh snow 0.75 –
0.90
Cloud tops 0.60 –
0.90
Old snow 0.50 –
0.70
Sand 0.15 –
0.35
Seas (high sun angle) 0.05 –
0.10

13. HEAT LOSS BY THE
EARTH SURFACE
The total amount of heat absorbed by the
earth each year is balanced by a
corresponding heat loss.
Without the cooling the thermal balance of
earth would not be maintained.
By long-wave radiation to cold outer space, around 16%
escapes to space.
By evaporation as the surface liquid changes into vapour
and mixes with the air.
By convection air coming in contact with the warm earth
surface becomes lighter and rises to the upper atmosphere
and dissipates its heat to space.

14. CONVECTION CURRENTS
Unequal heating
of the earth’s
surface
Temperature differences &
atmospheric pressure
differences
winds & ocean
currents
(in order to restore
the energy
balance)
Winds are convection currents in the atmosphere.
Trying to even out the differential heating of various zones.
The movement pattern is modified by the earth’s rotation.

15. REGIONS
Polar regions
Tropic regions
Desert

16. GLOBAL WIND PATTERN
At the maximum heating zones, air is
heated by the hot surface.
It expands, pressure decreased, it
becomes lighter and rises vertically and
flows off at a high level towards colder
regions.
Part of this air, cools down and
descends at the surface in subtropics
region.
From here the cooler, heavier air is
drawn in towards the equator from
north and south.

17. The area where the air rises, where
northern and southern winds meet, the
tropical front is formed and is called
Intertropical Convergence Zone (ITCZ)
The polar easterlies are winds
that are found between 60 and
90 degrees north and south
latitude that blow from the
poles and are deflected towards
the west.
Tropical easterlies or trade
winds blow from the
northeast in the Northern
Hemisphere and from the
southeast in the Southern
Hemisphere and are
located between 0 and 30
degrees north and south
latitude.
Prevailing Westerlies are
winds located 30 to 60
degrees north and south of
the equator that blow
eastward towards the
GLOBAL WIND PATTERN

18. WIND SHIFTS
When these winds are averaged
over many years a well-defined
pattern of large-scale 'cells' of
circulation appears.
Engineer Cameron Beccario of NullSchool has created
the EarthWindMap, a truly mesmerizing animated
interactive view of global weather patterns using
forecasted information from a variety of reliable sources.

19. ANNUAL WIND SHIFTS
The global wind pattern shift from
north to south and back again.
Remaining broadly symmetrical about
the inter-tropical convergence zone.

20. INFLUENCE OF TOPOGRAPHY
The force, direction and moisture content of air flows are
strongly influences by the topography.
• Air can be funneled by
mountain ranges.
• Air flow deflected
upwards, as it cools,
releases moisture
content.
• Rainfall characteristics
vary between locations
on windward and
leeward slopes od
mountain ranges.

21. ENERGY CYCLE
Gases in Earth’s atmosphere absorb
some of the outgoing energy and
return part of it to the Earth's
surface.
These gases (water vapour, carbon
dioxide, methane, nitrous oxide,
ozone and some others) act like a
blanket by trapping some of the
heat.

22. CONTROLS OF
CLIMATE
The most fundamental control of
both weather & climate is the
unequal heating & cooling of the
atmosphere in different parts of
the earth.
Unequal heating occurs due to
differential between high & low
latitudes, between continents &
oceans, between snow-covered &
snow-free areas, between forested
& cultivated land.
These heating & cooling
differences & the air movements
they induce represent the overall
general background control of
climate.

23. 1. Latitudinal variations in solar
radiation
• Most basic climate control factor.
• In low latitudes the sun is high in the
sky, the solar radiation intense & the
climate is warm & tropical; in high
latitudes the sun is lower in the sky,
solar radiation is weaker and the
climate is cooler.
2. Altitudes
• Temperature normally decreases with
increasing altitude.
• When a high mountain chain lies in the
path of prevailing winds, it acts to block
the movement of air & hence the transfer
of warm or cold air masses.

24. 3. Distribution of continents & oceans
• Continents heat & cool rapidly than oceans.
• Consequently non-coastal continental areas
experience more intense summer heat &
winter than oceanic areas.
4. Pressure & wind systems
• Differences in heating & cooling
between high and low latitudes, land &
water etc. lead not only to regional
temperature contrasts but also to
differences in atmospheric pressure
which in turn induce air movements.
• Air in motion serves as a transporter of
heat from regions of net heat gain to
region of heat loss thus operating as a
major climate control.

25. 5. Ocean currents
• Ocean currents both warm & cold, which
are induced by the major wind systems
also an important climatic control.
• They are responsible in transporting
warmth & chill in a north-south direction.
6. Local features
• The climate of a place is affected by a variety
of local features such as the slope of the land,
characteristics of vegetation & soil.
• In the northern hemisphere, south-facing
slopes receive more direct sunlight & have a
warmer climate than those with a northern
exposure.
• Urban areas are usually warmer than the

26. CORIOLIS FORCE
• The tendency of the atmosphere to lag behind
the earth’s rotation where the rotation is the
fastest i.e. at the Equator.
• There is slippage at the boundary layer,
between earth’s and the atmosphere called
Coriolis force.
• The effect is experienced as a wind blowing in
opposite direction to the earth’s rotation.

27. SOLAR GEOMETRY
• "Solar Azimuth” is the bearing of the sun
from true south. At solar noon, the sun is
at true south and the solar azimuth angle
is defined as 0. Morning angles are
measured as negative.
• "Solar Altitude” is the bearing of the sun
above the horizon. At sunrise and sunset,
the solar altitude angle is 0. At solar noon,
the sun reaches its highest point (greatest
altitude).

28. SUN PATH
• While viewing the sun from different
locations on the earth, the sun will rise
and set from a different point on the
horizon and move along different paths
across the sky. To understand where you
stand on the earth, it is specified by the
latitude and longitude coordinates.
• The latitude and longitude will have
significant effects on the sun path and
hence affect the behavior of the sun’s
lighting and heating characteristics.

29. • Altitude is the angular distance above
the horizon measured perpendicularly
to the horizon. It has a maximum
of 900 at the zenith, which is the point
overhead.
• Azimuth is the angular distance
measured along the horizon in a
clockwise direction.

30. Azimuth Lines - Azimuth angles
run around the edge of the
diagram.
Altitude Lines - Altitude angles
are represented as concentric
circular dotted lines that run from
the center of the diagram out.
Date Lines - Date lines start on
the eastern side of the graph and
run to the western side and
represent the path of the sun on
one particular day of the year.
Hour Lines - Hour lines are
shown as figure-eight-type lines
that intersect the date lines and
represent the position of the sun
at a specific hour of the day. The
intersection points between date
and hour lines give the position of
the sun.
T h e S u n p a t h D i a g r a m - Few terminologies

33. W h a t i s a H e l i o d o n ?
A heliodon is a device
that simulates the angle
at which sunbeams
strike a physical model
of a building or
landscape.
All heliodons consist of
one or more light
sources and a
mechanism to support
the model and to rotate it
through one to three
axes. Since the three
variables of
-latitude,
-time of year, &
-time of day determine
sun angles, a heliodon
must be adjustable for
all three factors.
Many different types of heliodons exist but
most utilize one light to simulate the sun.
Most heliodons simulate sunbeams by a
combination of moving the light source
and rotating the model.
Only a few heliodons exist where our
everyday experience is replicated by the
model being fixed in a horizontal position
and the light moves along three axes to
adjust for all 3 variables.

34. Energy consumption is the primary cause
of climate change, and buildings use about
50% of the energy consumed. Buildings
use energy primarily for heating, cooling,
and lighting all of which are all greatly
impacted by the sun.
Solar responsive design can significantly
reduce this energy demand by harvesting
the winter sun for heating, by rejecting the
summer sun to reduce the cooling load.
Successful solar responsive design requires
a thorough understanding of solar
geometry and its impact on design.
Heliodons can teach developers, builders,
and architects the basic concepts that will
allow them to design low-energy solar-
responsive buildings.
W h y s h o u l d w e u s e H e l i o d o n s ?

35. The Sun Simulator heliodon is conceptually clear
because it imitates our everyday experience of the
sun passing across the sky-dome, and the model
being fixed on a horizontal ground plane.
It is a large device usually greater than 10 ft (3 m) in
diameter that cannot be easily moved. Although it is
built for a particular latitude, the model support
table can be tilted plus or minus 5 degrees
a 10 degree latitude range without loss of clarity.
Because of annual symmetry, only seven arches are
needed to simulate the 21st day of all 12 months. For
example, only one arch is needed to define the
sunpaths for both November 21 and January 21.
The Sun Simulator has a light for each hour of
daylight for each month. The switches that control
these lights can be located on a control panel, in a
wired remote control, or a wireless remote control.
Since its lights are fairly far from the
model, its accuracy is quite good.
The further the lights are from the model
the more parallel are the light rays when
they reach the model on the support
table.
The large size also allows the use of fairly
large architectural models, and it allows
many people to simultaneously observe
the simulation.
Sun Simulator heliodon

36. The Sun Emulator heliodon is an intuitive
and conceptually clear heliodon. It is
completely manufactured in a factory and
only needs to be plugged in when it is
unpacked. Its footprint is about 6 x 6 ft (2
x 2 m), and it can be rolled around on its
own casters.
The seven rings that represent the
sunpaths for the 21st day of each of
months can be rotated to simulate the
time of day. The cradle that supports the
rings can be rotated 90 degrees to
simulate all latitudes from the equator to
the poles.
The time of year is selected by a rotary
switch with 12 positions for the 12
months.
The three main advantages of the Sun Emulator
are:
-shipped completely assembled,
-can simulate all latitudes, and
-is small enough to fit through a standard door.
When folded up, the heliodon requires little
storage space of about 3 x 6 ft (1 x 2 m)..
Sun Simulator heliodon

37. SOLAR RADIATION –
The Source of never Ending Energy
The complete concept of harnessing solar
energy to generate electricity is based upon
the phenomenon of solar radiation
Direct Normal Irradiance (DNI) is the
amount of solar radiation received per
unit area by a given surface that is always
held perpendicular to the incoming rays.
Components of Solar Radiation
• Direct Radiation (the radiation which comes
directly from the sun)
• Diffused Radiation (the radiation which is
diffused by the sky, layers of atmosphere and
other surroundings)
• Reflected Radiation (the radiation which is
reflected back by the lake, seas and other water
bodies)

38. The total ground reflection is a sum of all
the above three components.
Although the sun’s energy output is fairly
constant, the total solar radiation falling
on the earth’s surface varies and
depends on a lot of factors
• Atmospheric Conditions (Cloud
Ozone layer condition, etc.)
• Earth’s Rotation (time of the day,
activity, etc.)
• Earth’s Revolution (distance between
earth and sun, seasons, angle of
inclination of earth’s surface, etc.)

39. GLOBAL INSOLATION
• Solar insolation is affected by factors
such as atmosphere, angle of the
sun and distance.
• The thinner the atmosphere in which the
sun is passing through, the more the
insolation.
• Insolation is also at its highest when
the sun is directly overhead in an area.
This is also the shortest distance
between the sun and an area.
• World insolation maps show the
amount of solar insolation in a given
area at a given time.

40. COSINE LAW
The intensity on a tilted surface equals
the normal intensity times the cosine of
the angle of incidence.
ATMOSPHERIC
DEPLETION
The absorption of radiation by ozone,
vapors and dust particles.
The lower the solar altitude angle, the
longer path of radiation through the
atmosphere

41. Both weather and climate are
characterized by the certain variables
known as climatic factors.
•Solar radiation
•Ambient temperature
•Air humidity
•Precipitation
•Wind
•Sky condition
FACTORS AFFECTING CLIMATE

42. Solar radiation is the radiant energy
received from the sun.
It is the intensity of sunrays
per unit time per unit area and is
usually expressed in Watts per
meter (W/m2).
The radiation incident on a surface
varies and it depends on
• Geographical location (latitude
and longitude)
• Orientation
• Seasons
• Time of day
• Atmospheric conditions
1. SOLAR RADIATION
EXAMPLE:
BUILDING ON A SOUTH FACING
SLOPE IN SHIMLA WILL RECEIVE
MORE RADIATION COMPARED TO
OTHER ORIENTATIONS
Solar radiation on surfaces normal to suns' rays
is higher than on horizontal surfaces
EFFECT OF ORIENTATION

43. 1. SOLAR RADIATION

44. 1. SOLAR RADIATION

45. Solar radiation is the
most important weather
variable that determines
whether a place
experiences high
temperatures or is
predominantly cold.
The instruments used
for measuring of solar
radiation are the
pyranometer and the
pyrheliometer.
1. SOLAR RADIATION

46. HOW TO MEASURE SUNSHINE
DURATION?
Sunshine recorder essentially consists of a
glass sphere mounted in a spherical bowl
and a metallic groove which holds a
record card.
Sun's rays are refracted and focused
sharply on the record card beneath the
glass sphere, leaving burnt marks on the
card.
As the sun traverses, continuous
burnt marks will appear on the card.
Observers can measure the sunshine
duration based on the length of the
burnt marks.
SUNSHINE RECORDER

47. The sunshine meter consists of three
sensors. When sunlight is detected by the
sensor, it will be transformed into
electricity. Solar radiation can be
calculated based on the generated
voltage.
The front sensor measures global solar
radiation and is not shaded and receives
sunlight from all around.
The middle sensors and the rear
sensors are partly shaded to avoid direct
sunshine for measurement of diffuse
solar radiation
SUNSHINE METER

48. The temperature of air in a shaded
(but well ventilated) enclosure is known as
the ambient temperature; it is generally
expressed in degree Celsius (ºC).
Temperature at a given site depends
on wind as well as local factors such as
shading, presence of water body, sunny
condition, etc.
Stevenson’s screen can measure
ambient temperature.
2. AMBIENT TEMPERATURE

49. STEVENSON’S SCREEN
The Stevenson Screen or thermometer screen is
a standard shelter (from rain, snow and high
winds, but also leaves and animals) for
meteorological instruments, particularly wet
and dry bulb thermometers used to
record humidity and air temperature
It is kept 1.25m above the ground by legs to
avoid strong temperature gradients at ground
level, has louvered sides to encourage the free
passage of air, and is painted white to reflect
heat radiation, since what is measured is the
temperature of the air in the shade, not of the
sunshine.

50. Air humidity, which represents the amount of
moisture present in the air, is usually expressed in
terms of ‘relative humidity’.
Relative humidity is defined as the ratio of
the mass of water vapour in a certain volume
moist air at a given temperature, to the mass
water vapour in the same volume of saturated
at the same temperature; it is normally
as a percentage.
It varies considerably, tending to be the
highest close to dawn when the air temperature is
at its lowest, and decreasing as the air
temperature rises.
3. AIR HUMIDITY

51. Precipitation includes water in all its
forms rain, snow, hail or dew. It is usually
measured in millimeters (mm) by using a
rain gauge.
4.PRECIPITATION

52. The standard rain gauge instrument generally consists
of a funnel connecting to a graduated cylinder which is
marked in millimeters. It has an outer cylinder which is
20 cm in diameter and 50 cm tall. When the rainwater
overflows the inner cylinder, the large outer cylinder
holds it. The amount of water in the outer cylinder and
the inner cylinder are taken for rainfall measurement.
Rain gauges should be placed in an open area where
there are no obstacles like buildings or trees to block
the rain. This is also to prevent the water collected on
the roofs of buildings or the leaves of trees from
dripping into the rain gauge after a rain, resulting in
inaccurate readings.
RAIN GAUGE

53. Wind is the movement of air due to a difference in atmospheric pressure,
caused by differential heating of land and water mass on the earth’s surface by
solar radiation and rotation of earth.
WIND

54. Wind speed can be measured by
an anemometer and is usually
expressed in meters per second
(m/s).
It is a major design consideration
because it affects indoor comfort
conditions by influencing the
convective heat exchanges of a
building envelope, as well as causing
air infiltration into the building
WIND

55. An anemometer is an instrument that
measures wind speed and wind pressure.
The most common type of anemometer has three
or four cups attached to horizontal arms. The arms
are attached to a vertical rod. As the wind blows,
the cups rotate, making the rod spin. The stronger
the wind blows, the faster the rod spins. The
anemometer counts the number of rotations, or
turns, which is used to calculate wind speed.
Because wind speeds are not consistent, wind
speed is usually averaged over a short period of
time.
Wind speed helps indicate a change in weather
patterns, such as an approaching storm, which is
important for pilots, engineers, and climatologists.
ANEMOMETER

56. Sky condition generally refers to the extent of cloud cover in the sky
or the duration of sunshine.
Under clear sky conditions, the intensity of solar radiation increases;
whereas it reduces in monsoon due to cloud cover.
SKY CONDITION

57. The re-radiation losses from the external surfaces of buildings increase
when facing clear skies than covered skies.
The measurement of sky cover is expressed in oktas.
For example, 3 oktas means that 3/8th of the visible sky is covered by
clouds.
SKY CONDITION