120729 Solar Research

7/31/2019 120729 Solar Research

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[group solar]

JEFFREY JIANG

YOUNG HUN KIMLILY PAN

FUTURE CHRISTCHURCH / CAMIA YOUNG / JORDON SAUNDERSCOURSE TUTOR ASSISTANT TUTOR


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PT 1: RESEARCH


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2 Group Solar Research

Global Average Annual Total no. of Hours of Bright Sunshine

Average Annual Total no. of Hours of Bright Sunshine

Mean Annual Sunshine Hours Mean Annual Temperature Mean Annual Rainfall

2600

2500

2400

2300

>3000

3000-2000

2000-1000

1000-500


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3Jeffrey / Young / Lily

Factors effecting sunlight interception

June 2012

June

May 2012

May

April 2012

April

March 2012

March

Febraury 2012

Febraury

January 2012

January

December 2011

December

November 2011

November

9

8

7

6

5

4

3

2

1

125

115

105

100

95

85

%

9

8

7

6

5

4

3

2

1

Hours

Hours

Mean Daily Bright Sunshine (basedon historic average)

Bright Sunshine Anomaly

Observed Daily Average BrightSunshine


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Micro ClimateMean Anual Solar Radiation Mean Anual Temperature

Mean Min. Temperature of the coldest month Winter Solar Radiation


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Solar radiation

Mean Anual Solar Radiation- MJ/m2/day

13.5

13.6

13.7

13.8

13.9

14

14.1


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P() = exp[-K() ()Lt /cos()]

()Lt = Le()

() =e()

e

1.7

0.0

2.4

5.2

The probability P(q) of a directbeam penetrating a plantcanopy at a zenith angle of q,assuming azimuthal symmetry

K(q) is the fraction offoliage projected indirection q

W(q) is the Total nonrandomnesscorrection factor including needlesclumped on individual conifer shootsand the clumping of branches andshoots on tree crowns

Lt is Total hemi-surface area ofall foliage per unit ground surfacearea in canopy

Indirect measure of hemi-surfacearea index of all foliage (leaves,

shoots, ranches, stems) in acanopy; half the total surface areaof all foliage per unit ground surfacearea. Referred to as the effectiveLAI

We(q)is the element clumping indexquantifying the effect of foliageclumping at scales larger thanindividual leaves or shoots.

ge is the within-shoot clumpingfactor accounting for the clumpingof needles on shoots; dened as1/2 total needle surface area to1/2 total shoot envelope surfacearea

Calculating Sunlight through Canopies


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e() = a0 + a1 fc + a2 + a3 fc + a4 fc2 + a52 + a62 ( fc) + a7( fc)2 + a8 fc3 + a93.

= fgap,c(0) / fc

1. Crown diameter

3. Stem density

2. Crown depthCrown depth, dened as the vertical distance between

the top of the crown and the lowest living foliage

4. Foliage densityZenith gap fraction partitioned into between-crown

and within-crown components

F is crown porosity,the within-crown gapfaction

fgap,c(0) is the Canopy gap fractioncontribution from within-crown gapsestimated with a zenith view angle

fc is the Fractional area coverage ofcrowns; m2 crown silhouette areaper m2 ground area obtained withprojection of a crown from nadir

linear oblong rhombic lanceolate

ovate elliptic obovate cuneate

spatulate oblanceolate orbicular reniform

cordate deltoid hastate sagittate

Factors effecting sunlight interception

round

ra

d

1/2c

1/2f

1/2f

e**

** e a* c 2a

d is max. width

f

1/2ec

b

b

invertedtriangle

square

ellipsis

triangle

lobe

Leaf Shapes Catalogue

Breakdown into simplied shapes


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diaheliotropism: (n) A tendency of leaves or other organs

of plants to have their dorsal surface faced towards the

rays of light.

heliotropism: (n) The directional growth of a plant in

response to sunlight.

Heliotropism


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Cellular StructureMovement Abstraction / Section

Apparent movement of theleaf detected during the daywhen the sun moves from

east to west.

[Records at randomintervals]

Mechanism that allows movement is calledPulvinus and is plants equivalent to mus-cle. The structure Consists of Epidermis,

Cortex, and Vein.

Cortex is broken down to two sides.Flexor and Extensor, each at left to rightrespectively.

[Logintudinal Section]

Leaves that fold upwards when closing atnight has the extensor cells in the upper-most part of the pulvinus.

Leaves that fold downwards when clos-ing has the extensor cells in the lowerpart of the pulvinus.

[Transverse Section]

K+

- Turgid Cell (High Pressure)

- Flaccid Cell (Low Pressure)

- Potassium ions

Pulvinus Explained

Pre-stimulus Stimulus Post-stimulus

Heliotropism - the mechanism

Denition:

Botany . a cushionlike swelling at the base of a leaf or leaet, at the point of junc-tion with the axis.

This swelling or shrinkage is caused by movement of water from exor cells toextensor cells, and vice versa. This process is called osmosis, where the wateralways travel from an area of high pressure to area of low pressure.

But because of potential difference, one can guess that pressure of water wouldwould come to a halt if both sides reached 50/50. Another factor that inuenceswater movement are potassium ions. From stimulus, potassium is pumped outfrom exor and by osmosis, extensors water potential becomes lower. Becausewater travels from high to low, exor becomes accid and extensor turgid causingforce to be exerted.

Once nished, the potassium diffuses into the stems to activate other pulvinus torelease their potassium.

Epidermis

Cortex

Vein

Dumping of potassium& Movement of water

Potassium diffusion &Uptake of water


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Christchurch Sunrise and Sunset times

January

May June July August

February March April


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SUNRISE

SUNSET

WEEKS

HOURS

Sunrise and Sunset hours throughout one year in Christchurch

September October November December


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Waldram principle : Flat projection onplan of the complete hemisphere. Thismethod of projection is particularlysuited to estimate the heat radiationon vertical surfaces.

Christchurch Sun path diagram

Equator

Christchurch

ChristchurchJan - June

ChristchurchJuly - Dec

JUNE22

MAY22

APRIL22

MARCH 22

FEB22

JAN22

DEC22

8

7

6

5

4

3

21 12 11

10

9

8

7

6

5

JUNE22

JULY22

AUG 22

SEP 22

OCT 22

NOV 22

DEC22

8

7

6

5

4

3

21 12

11

10

9

8

7

6

5

60

40

20

0

-20

-40

-60

Sun path diagrams


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angle of incidence

E illuminance on surface

direction of beams

Light on a surfaceIlluminance is proportional to the cosine of the angle between the direction of the incident

angle and a line at 90 degrees to the surface.

E cos

Illuminance is inversely proportional to the square of the distance from source to surface

E 1 / ww^2

Specular reection

Surfaces and the nature of reections

Lambertian reection (diffuse)

The amount of inter reected light in any enclosure depends on three factors:1. The amount of light entering the enclosure2. The surface area of the enclosing surfaces3. Their reectance

Parabolic mirror

Light reectancy on surfaces

Specular

Lamberan

Compound:

transparent layer

over pigmented

surface

Polished metal;

surface-silvered mirror

Blong paper;

woollen cloth;

earth

Picture under glass;

gloss paint; water

The luminance and

colour of what is

seen in reflecon;

this varies with

direcon of view

The illuminance and

colour of the surface;

equally bright in

every direcon of

view

A combinaon of the

two above; depend-

ent on angle of view

Increased reflectance

Decreased illumi-

nance; enhanced

visibility of texture as

angle between light

and beam and view

angle increases

Increased shininess,

diluon of pigment

colour

Ideal surface Approximates to Luminance andcolour depend on

Effect of increasing angleof incidence of light


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14 Group Solar Research 14

The surface characteristics of the transparent and reecting materials determine the type of reection or transmittance.Reected light can either be directed or scattered. Similarly, the transmitted light is directed or scattered. The result is oftena combination of reection and transmittance since both types of reection and transmittance occur in conjunction.

Retro- reecting elements and their properties play an important r ole in day lighting technology. These elements are retro-reecting materials or reectors that reect the incident light; preferably back in the direction of incidence. In day lightingtechnology, reectors are generally preferred, mirrors with specic geometries or prisms that utilize the principle of totalreection in the medium with greater optimal density.

Material reectancy

Mirror

Window glass Opal or ground glass Opaque or obscured glass Retro prisms

Surface scattering (reector matt) Volume scattering (e.g. white) Retro reection


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Louvres

Daylight decays exponentially with roomdepth, so the building form should be reason-ably shallow.

Maximum depth of a room for benecial day-light with windows on one side only is twicethe height of the room.

Maximum depth of a room with windows on opposite sides is ve times the height of the room.

2h

h h

5h

Daylight in a room

externalhorizontallouvres

externaloverhang

internal blinds

externalverticallouvres

Horizontal louvres are used in the north facing windows. Exterior louvres are usuallymade of galvanised steel, anodised or painted aluminium or plastic for high durabilityand low maintenance. Louvres may obstruct, absorb, reect and or transmit solar ra-diation. Horizontal blinds in a horizontal position can receive light from the sun sky andground. Upward tilted slats transmit light primarily from the ground surface.

Fixed systems are usually designed for solar shading, but could reduce day lighting.Operable systems can be used to control thermal gains and protect against glare andredirect daylight, operable systems need to be fully or partially retracted to operateoptimally and according to outdoor conditions.A constantly moving louvre system that changes as the sun angle changes throughoutthe day.

Internal blinds are generally movable, but creates more overheating in the r oom com-pared to external blinds. They are easily maintained and reduce glare.

Vertical louvres are usually used in the east and west facing windows, because theydo not protect well from high angle sun. They can be motorized for optimum shading.


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Light shelves should be designed specically for each window orientation, room conguration, and latitude. They canbe applied in climates with signicant direct sunlight and are applicable in deep spaces on a north orientation in thesouthern hemisphere. Light shelves do not perform as well on the east and the west orientation and in climates domi-nated by overcast sky conditions.

For north facing facades, it is recommended that the depth of an internal light shelf be roughly equal to the height ofthe celestory window above the shelf.An exterior light shelf creates a parallel movement of shaded area towards the window facade, which reduces thedaylight levels near the window and improves daylight uniformity. The recommended depth of an external light shelf isroughly equal to its own height above the work plane. Glazing height and light shelf depth should be selected based onthe specics of latitude and climate.

At low latitudes, the depth of the internal light shelves can be extended to block direct sunlight coming through theclerestory.At higher latitudes and with west and east f acing rooms, a light shelf may let some direct sunlight (low solar elevations)penetrate the interior. Tilting the shelf downwards will reduce the amount of light reected to the ceiling. Upward tiltwill improve penetration of reected daylight and reduce shading effects.

The ceiling reects the light by having a smooth surface nish, and perhaps slope. The penetration of light from a lightshelf system depends on the ceiling slope. A gable typed ceiling that slopes upwards from the window towards thecentre of the building will dramatically increase the depth to which light is reected into the space.

Light Shelf

Projecting light-shelves guide daylight throughthe upper facade into the interior, protecting thelower window area from the high summer sun.

Interior light-shelves offer better protectionagainst low sunlight entering through fanlightareas. However, in summer, incident heat istrapped in the room interior

Low- angled winter sun is able to penetrate eas-ily through fanlight areas. An additional shad-ing device is necessary for lower window areaswhen the sun is low.

In both winter and summer, the lower windowarea should be protected by additional shading.

Winter - low angle

Summer - high angle sun


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The Anidolic Zenithal is used to collect diffuse daylight from a large portion of the sky vault without allowingsun penetration. This form of sky lighting system is best utilized to prov ide daylight to single storey buildings,atrium spaces or the upper oor of multi- storey buildings.The optical design of the device offers efcient protection against direct solar radiation transmission through-out the year without use of movable parts. Also overheating from the sun penetration is prevented. It is goodfor glare control and improved visual comfort than conventional skylights.

This system transmits more low elevation light andless high elevation light. Normally, a diffusing panelis used at the ceiling aperture. Useful tilt anglesrange between 45 and 55 for the tropics and sub

tropics. Tilt angles of 25 and 35 are used for lowelevation light.Function of an angular selective skylight is to pro-vide relatively constant irradiance to the interiorduring the day and to reduce the tendency to over-heat the building on summer days.This type of skylight enhances low elevation inputand rejects high elevation input.

Sky lights

Angular selective transmission


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COOL

TEMPERATE

ARID

TROPICAL

1:1

1:1.6

1:2

1:3

x :y

x

y

When x > 6m,mechanical ventilation is necessary

YE

The roof should be adapted to the low angles of

solar incidence in winter.Arcades should ideally be north- south orientated.Arcades running east - west are to be avoided sincethe sunlight cannot penetrate the arcade space.,Whereas the upper level of the northern facade isquickly overheated. With a north south orientation,even the low lying winter sun has the chance tofully illuminate the arcade space.

Light coloured and reectivefacade surfaces in courtyardsare espcially recommended,when-ever possible, parapetsections are mirrored so thatthe courtyard can act as alight conductor

Y = Solar Altitude angle= Azimuth differenceE = Vertical shadow angle

tan E = tan Y x Sec

Altitude and Azimuth of

Sun

Altitude - angle the sunsrays make with the hori-zontal. The suns altitude iszero during sunset.

Azimuth- compass direction

East west orientation North south orientation

Courtyard as light con-ductor

Sun angles effects on Orientation and Form

Documents

120729 Solar Research