Lecture - 3 Solar

8/13/2019 Lecture - 3 Solar

1/87

Pradip Majumdar, Ph.D

Professor

Mechanical Engineering

Northern Illinois University

UEET 603

Introduction to Energy Engineering

Spring 2010


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1/9/2014

Solar Energy

Pradip Majumdar

Department of Mechanical

Engineering


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1/9/2014

Solar RadiationSolar Components

Applications

Flat Plate

Collector

Photovoltaic

Cell

Solar Thermal

Power

Generation

Extraterrestrial

Solar Radiation

Solar Radiation

at Earth SurfaceOptical

Properties for

Materials for

Solar Radiation

Direct, Diffuse,

Reflected

Radiation

Focusing

Collector

Solar

Heating and

Cooling

Direct Electric

Power

Generation

Geographical

Location andWeather

Conditions

ELEMENTS OF SOLAR

ENERGY MODULE

Energy

Storage

Solar

Energy

Principles


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Topics

Solar energy and Application

Major Characteristics of Sun and Earth

Solar RadiationSolar and wall angles

Estimation solar irradiation of a surface

Optical properties of surfaceSolar collectors

Solar thermal systems


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Solar Energy and Applications

Solar radiation is potential energy source

for power generation through use of solar

collector and photovoltaic cells.

Solar energy can be used as thermal

energy source for so lar heat ing,

Aircondi t ion ingand coo l ing sys tems.

Solar radiation has important effects on

both the heat gain and heat loss of a

building.


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Solar Radiation

Intensity of solar radiation incident on a surface isimportant in the design of solar collectors, photovoltaic

cells, solar heating and cooling systems, and thermal

management of building.

This effect depends on both the location of the sun in the

sky and the clearness of the atmosphere as well as on

the nature and orientation of the building.

We need to know

- Characteristics of suns energy outside the earths

atmosphere, its intensity and its spectral distribution

- Variation with suns location in the sky during the day

and with seasons for various locations on the earth's

surface.


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Solar Radiation

The suns structure and characteristicsdetermine the nature of the energy it radiatesinto space.

Energy is released due to continuous fusionreaction with interior at a temperature of theorder of million degrees.

Radiation is based on suns outer surfacetemperature of 5777 K.


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Solar Geometry

I

II

III

Photosphere

Chromosphere

Corona


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Solar Geometry

The Sun: Major Characteristics- A sphere of hot gaseous matter

- Diameter, D = (865400 miles) (Sharp circular boundary)

- Rotates about its axes (not as a rigid body)

- Takes 27 earth days at its equator and 30 days at polar

regions.

- The sun has an effective black body temperature of 5777 K

i.e. It is the temperature of a blackbody radiating the sameamount of energy as does the sun.

Mean earth-sun distance: D = (865400 miles) (Sharp

circular boundary)


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The Structure of SunCentral Region: (RegionI)

Energy is generated due to fusion

Reaction of gasestransforms

hydrogen into helium.

- 90% of energy is generated within

the core range of 00.23 R- The temperature in the central

region is in million degrees.

- The temperature drops to 130,000 K

with in a range of 0.7R

Convection Region ( RegionIII)

- 0.7R to R where convection process

involves

- The temperature drops to 5,000 K

Photosphere:

Upper layer of the convective zone- Composed of strongly ionized gas

- Essentially opaque

- Able to absorb and emit continuous

spectrum of radiation

- Source of the most solar radiation

Chromosphere (10,000km)Further outer gaseous layer with

temperature somewhat higher tan the

Photosphere.

CoronaStill further outer layer

- extremity of sun.

- Consists of Rarified gases.- Temperature as high as 1000,000 K


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Thermal Radiation

Thermal radiation is the intermediate portion (0.1~ 100m) of the electromagnetic radiation

emitted by a substance as a result of its

temperature.

Thermal radiation heat transfer involvestransmission and exchange of electromagnetic

waves or photon particles as a result oftemperature difference.


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Plancks Spectral Distribution of

Black Body Emissive Power

The thermal radiation emitted by a black

substance covers a range of wavelength

(), referred as spectral distribution and

given as

1e

C

E T/2C51

b, 2482

01 m/m.W103.7422hC K.m101.439k/hcC

402

s.J10626.6ttanconss'Planckh

24

K/J10381.1ttanconsBoltzmannk23


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Solar Intensity Distribution

Spectral distribution show the variation of

solar radiation over the a bandwidth

m3.0to0.25


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Black Body Emissive Power

The total black body emissive power is

obtained by integrating the spectral emissive

power over the entire range of wavelengths

and derived as

4TE

b

Where = Stefan-Boltzman constant

=428

./106697.5 KmW

d1e

CEE

0T/2C5

1b,b


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Real Body Emissive Power

bEE factorEmissivityEEb

bEE Spectral Emissive Power

emissivitycalhemispheriSpectralE

E

b

Total Emissive Power

4

TE


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Extraterrestrial Radiation

Solar radiation that would be received in the

absence of earth atmosphere.

Extraterrestrial solar radiation exhibit a spectral distributionover a

ranger of wavelength: 0.1- 2.5

- Includes ultraviolet, visible and infrared

m


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Solar Constant

Solar Constant = Solar radiation intensity upon asurface normal to sun ray and at outeratmosphere (when the earth is at its meandistance from the sun).

hr

mWGSC2

2

Btu/ft433

/1367

scG


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Variation of Extraterrestrial Radiation

Solar radiation varies with the day of the year as

the sun-earth distance varies.

An empirical fit of the measured radiation

data

365

360ncos033.01scGDG

2Bsin0.0000772Bs0.000719co

Bsin0.001280Bcos0.0342211.000110

scGDG

n = day of the year

365

3601nB


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The Earth

Diameter: 7900 miles

Rotates about its axis-one in 24

hours

Revolve around sun in a period of

365+1/4 days.Density=5.52 times that of H2O.

I: Central Core:1600 miles diameter,more rigid than steel.

II: Mantel: Form 70% of earth mass.

III: Outer Crust: Forms 1% of total

mass.

I

II

III


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Direct Radiation on Earths Surface

dG

DifuseDirect

Reflected

DG

rG

DNG

Normal to surface

DNG

cosDND GG rdDt GGGG

Total radiation on a surface

Orientation of a surface on earth with respect sun or

normal to suns ray can be determined in terms basic

Earth-Sun angles.


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Basic Earth-Sun Angles

Suns Ray TimeThe earth is divided into 360oofcircular arc by longitudinal lines

passing through poles.

The zero longitudinal line passesthrough Greenwich, England.

Since the earth takes 24 hours to

complete rotation, 1 hour = 15oof

longitude

What it means?

A point on earth surface exactly

15owest of another point will

see the sun in exactly the same

position after one hour.

The position of a point P on earth'ssurface with respect to sun's ray Is

known at any instant if following

angles are known:

Latitude (l), Hour angle (h)

and Suns declination angle (d).


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Local Civil Time (LCT)Universal Time or Greenwich Civil Time (GCT)

Greenwich Civil Time: GCT time or universal time

Time along zero longitude line passing through Greenwich,

England. Time starts from midnight at the Greenwich

Local Civil Time (LCT)

Determined by longitude of the observer. Difference being 4

minutes of time for each degree or 1-hr for 15

Example: What is the LCT at 75 degree west longitude

corresponding to 12:00 noon at GCT

75 degree corresponds to 75 / 15 = 5 hours

LCT at 75 degree west longitude = 12:00 PM5 hrs= 7

AM


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Standard TimeLocal civil time for a selected meridan near the center of

the zone. Clocks are usually set for the same time

throughout a time zone, covering approximately 15 of

longitude.

ExampleFor U.S.A different standard time is set over different time

zone based on the meridian of the zone. Following is a list

of meridian line.

EST: 75 CST: 90MST: 105 PST: 120

Also, there is Day Light Savings Time


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Solar Time

Time measured by apparent daily motion of the sun

Local Solar Time, LST = LCT + Equation of time (E)

Equation-of- t imetakes into account of non-symmetry of

the earthly orbit, irregularity of earthly rotational speed and

other factors.

Bsin0.032077-Bcos001868.0000075.0(2.220 E

2B)sin0.04089-2Bcos0014615.0

365

3601nB

2B)sin0.04089-2Bcos0014615.0


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Equation of Time and Suns

Declination Angle


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Example: Local Standard Time

Determine local solar time (LST) corresponding to 11:00 a.m. CDST on

February 8 in USA at 95 west longitude.

CST (Central Standard Time) = CDST - 1 hour = 11:00-1 = 10:00 a.m.

This time is for 90 west longitudinal line, the meridian of the central

time zone.

Local Civil Time (LCT) at 95 west longitude is 5 X 4 = 20 minutes

less advanced

LCT = CST - 20 minutes = 10:00 am20 min= 9:40 am

LST = LCT + Equation of Time (E)

From Table: For February 8 the Equation of time = -14:14

LST = 9:40-14:14 = 9:26 a.m.


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Solar and Wall Angles

Following solar and wall angles are neededfor solar radiation calculation:

Latitude angle, l

Sun's Zenith angle ,

Altitude angle, Azimuth angle, or Suns incidence angle

Wall-solar azimuth angle,/

Wall azimuth angle,

Latitude (l) is defined as the angulardistance of the point P north (or south) ofthe equator.

l = angle between line opand projection o


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Declination (d)

Angle between a line extending from

the center of the sun to the center ofthe earth and the projection of this

line upon the earth equatorial plane.

It is the angular distance of the sun's

rays north (or south) of the equator.

Figure shows the sun's angle of

declination.

d = - 23.5o C at winter solstice, i.e.

sun's rays would be 23.5osouth of

the earth's equator

d = +23.5o at summer solstice, i.e.

sun's rays would be 23.5onorth of

the earth's equator.

d = 0 at the equinoxes

d = 23.45 sin [360(284+n)/365]


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Hour Angle: 'h'

Hour Angle is defined as the angle measured inthe earth's equatorial plane between the projection

of opand the projection of a line from center of the

sun to the center of earth.

- At the solar room, the hour angle (h) is zero,

Morning: negative and Afternoon: positive

The hour angle expresses the time of the day

with respect to solar noon.

One hour time is represented by 360/24 or 15

degrees of hour angle

-


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SOLAR ANGLES

= Zenith Angle = Angle

between sun's ray and a lineperpendicular to the horizontal

plane at P.

= Altitude Angle = Angle in

vertical plane between the sun'srays and projection of the sun's

ray on a horizontal plane.

It follows + =/2

= Azimuth angle = Angle measured from north

to the horizontal projection of the sun's ray.

= Azimuth Angle = angle measured from

southto the horizontal projection of the Suns ray.

180

Sun


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Solar Angles

From analyt ical geometry

Suns zenith angle

cos () = cos (l) cos(h)cos(d)+ sin (l) sin (d)

Also = /2 -

Suns altitude angle:sin () = cos (l) cos (h) cos (d )

+ sin (l) sin (d)

Sun's azimuth( ) is given by

cos( ) = sec (){cos (l) sin (d)

-cos (d) sin (l) cos (h)}

Or

Cos = (sin sin lsin d )/(cos cos l)


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Tilted Surface=

= wall-solar azimuth angle= For a vertical surface the

angel measured in horizontal

plane between the projection of

the sun's ray on that plane and a

normal to that vertical surface

= angle of tilt= normal to surface and

normal to horizontal surface

= Wall azimuth angle

= Angle between normal to

vertical surface and south

'

/

Where

= Solar Azimuth Angle

'


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Angle of Incidence ()

Ang le of inc idenceis the angle between

the sun's rays and normal to the surface

cos= coscos sin+ sincos

For vert ical su rface

cos= cos cos , = 90For ho r izon tal surface

cos = sin, = 0

'

'


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Solar Radiation Intensity at Earth Surface

Solar radiation incident on a surface at earth has three different

components:

1. Direct radiation:

The solar radiation received from the sun without having

been scattered by the atmosphere.

2. Diffuse radiation:

Radiation received and remitted in all directions by earth

atmosphere:

3. Reflected radiation:

Radiation reflected by surrounding surfaces.


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Total Incident Radiation

dG

DifuseDirect

Reflected

DNG

rG

Normal to surface

DI

rdNDt GGcosGG


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ASHRAE Clear Sky Model

Normal Direct Radiat ion: GND

The value of solar irradiation at the surface of the earth on

a clear day is given by the empirical formula:

GND= A/[exp(B/sin )] = Normal direct radiationA = apparent solar irradiation at air mass equal to

zero, w/m2

B = Atmosphere extinction co-efficient

= Solar altitudeAbove equation do not give maximum value of GNDthat can

occur in any given month, but arerepresentation of

condition on average cloudiness days.


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Constants A, B and C for Estimation of Normal

direct and diffuse radiation


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Modif ied equat ion:

GND= A/[exp(B/sin )] x CN

CN = Clearness factor

=multiplying factor for nonindustrial location in USA

GD= GNDcos

= Direct radiation on the surface of

arbitrary Orientation.

= Angle of incident of sun's ray to the surface


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Clearness factor (CN)


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Diffuse Radiat ion :Gd

Diffuse radiation on a ho r izon tal surfaceis

Gd = C GNDWhere

C = ratio of diffuse to normal radiation on a

horizontal surface = Assumed to be constant for an

average clear day for a particular month.

Diffuse Radiat ion onNon Horizontal Surface:

Gd= C GND FWS

FWS = Configurat ion factor

between the wall and the sky .

FWS = (1+ cos )/2

Where = Tilt angle of

the wall from horizontal

= (90-).


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Reflec ted Rad iat ion (GR)

Reflection of solar radiation from ground to a tilted surfaceor vertical wall.

GR = GtH g FWg

Where,

GtH = Ratio of total radiation (direct + diffuse) onhorizontal or ground in front of the wall.

g = Reflectance of ground or horizontal surface

FWg = Angles or Configuration factor from wall to

groundFWg = (1- cos )/2.

= Wall at a tilt angle tothe horizontal.

E l E i i f S l R di i


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Example: Estimation of Solar Radiation

Calculate the clear day direct, diffuse and total solar radiation

on horizontal surface at 36 degrees north latitude and 84degrees west longitude on June 1 at 12:00 noon CST

Local Solar Time: LST = LCT + Equ of time

LCT = LCT + (90-84)/15 * 60 = 12:00 + (90-84)/15 * 60

At Mid 90 degree

LST = 12:00 + (90-84)/15 *60+ 0:02:25 = 12:26

Hour angle: h = (12:00 - 12:26) * 15/60 = 65 degrees

Declination angle: d = 21 degrees 57 minutes


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Suns altitude angle:

Sin= Cos (l) Cos (d) Cos (h) + Sin (l) Sin (d)

= Cos (36) X Cos (2157 min) + Sin (36) Sin (2157)=(0.994)

(0.928) (0.809)+ 0.588 XS 0.376, Sin = 0.965

Incidence angle for a horizontal surface: Cos = Sin = 0.965

Direct Normal Radiation: GND = A/ [exp (B/sin )]

= 345/ [exp (0.205/0.965)]GND= 279 Btu/hr-ft

2

The direct radiat ion

GD=GNDCos = 279 X 0.965 = 269 Btu/hr-ft2,The dif fuse radiat ion

Gd= C GND= 0.136 X 279 = 37.4Btu/hr-ft2

Total IrradiationG = GD+ G

d= 269 + 37.6 = 300 Btu/hr-ft2


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Material Optical Properties

G

GflectivityRe re

GGvityTransmissi tr

G

G

tyAbsorptivi tr

bodyblackabyemittedEnergybodyrealabyEmittedEnergy

EEEmissivityb

The Khirchoffs law

In equilibrium: In general , ,

, ,

Wavelength incidentofAngle

S l R di i M i l


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Solar RadiationMaterial

Interaction

Opaque Surface:

Transparent Surface:

0 1

1GG,absorbedEnergy ab

GG,absorbedEnergy ab GG,dtransmitteEnergy tr


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Solar Heart Gain

Solar Heat gain through atransparent Glass Cover:

fwN

tftsg GNGAq

Solar Heat gain Through aGlass Window:

ScGNGAq tftsg

Where

A = Surface area of glass

= Total solar irradiation

= Fraction of absorbed solarradiation that enters Inward

=

Sc = Shading coefficient

tG

fN

oh

U

tfwwsg GNAq ,

Solar Heat gain opaque

wall: = Fraction of absorbed solarradiation that enters Inward

= oh

U


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Use of Solar Energy

1. Solar Thermal Energy:

Converts solar radiation in thermal heat energy

- Active Solar Heating

- Passive Solar Heating

- Solar Thermal Engine

2. Solar PhotovoltaicsConverts solar radiation directly into electricity

S l Th l E S t


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Solar Thermal Energy System

The basic purpose of a solar thermalenergy system is to collect solar radiation

and convert into useful thermal energy.

The system performance depends on

several factors, including availability of

solar energy, the ambient air temperature,

the characteristic of the energy

requirement, and especially the thermal

characteristics of solar system itself.

Cl ifi ti S l S t


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Classification Solar System

The solar collection system for heating and

cooling are classified as passive or active.

Active System

Active systems consist of components whichare to a large extent independent of the building

design

Often require an auxiliary energy source (Pump

or Fan) for transporting the solar energy

collected to its point of use.

Active system are more easily applied to existing

buildings


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Passive System

Passive systems collect and distribute solarenergy without the use of an auxiliary energy

source.

Dependent on building design and the thermalcharacteristics of the material used.

Solar Water Heating System


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Solar Water Heating System

Uses solar collector

mounted on roof top togather solar radiation

Low temperaturerange: 100 C

Applications involves

domestic hot water or

swimming pool heating

Hot Water

Pump

Collector

Cold Water

Supply


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Solar Space Heating System

Solar Collector

Space

Auxiliary Heater

Pump

Thermal

Storage

A collector intercepts the suns energy.

A part of this energy is lost as it is absorbed by the cover glass orreflected back to the sky.

Of the remainder absorbed by the collector, a smal l por t ion is lost b y

convect io n and re-radiat ion, but most is useful thermal energy, which

is then transferred via pipes or ducts to a storage mass or directly to the

load as required


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An energy storage is usually necessary since

the need for energy may not coincide with the

time when the solar energy is available.

Thermal energy is distributed either directly after

collection or from storage to the point of use.

The sequence of operation is managed by

automatic and/or manual system controls.


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Solar Cooling System

C200 0

Air inletEvaporator

TurbineCompressor

Solar

Collector

Condenser

10 kpa

Condenser

Cooling Capacity

Qe = 5 kW

HR


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A Solar-driven Irrigation Pump

Turbine

SolarCollector

CondenserPump

IrrigationPump

ph

pm

A solar-energy driven irrigation pump operating on a

solar driven heat engine is to be analyzed and designed.

C150T0

H

kPa10Pc


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Solar Collector

Several types are available

Flat Plate Collector- Glazed and unglazed

- Liquid-based- Air-based Evacuated Tube Concentrating

- Parabolic trough


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Fixed Vs Tracking

A tracking collectors are controlled to follow the sunthroughout the day.

A tacking system is rather complicated and general ly

only used for special h igh-temperature

appl icat ions.

Fixed col lectors are much simpler - their position

or orientation, however, may be adjusted on a

seasonal basis. They remain fixed over a days time

Fixed co l lecto r are less eff ic ient than tracking

col lectors; nevertheless they are generally preferred

as they are less costly to buy and maintain.


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Flat-plate and Concentrating

Concentrating collectors uses mirrored surfaces

or lenses to focus the collected solar energy on

smaller areas to obtain higher working

temperatures.Flat-plate collectors may be used for water

heating and most space-heating applications.

High-performance flat-plate or concentrating

collectors are generally required for coolingapplications since higher temperatures are

needed to drive chiller or absorption-type cooling

units.

Flat Plate Solar Collector


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Used for moderate

temperature up to 100 C

Uses both direct anddiffuse radiation

Normally do not needtracking of sun

Use: water heating,building heating and air-conditioning, industrialprocess heating.

Advantage: Mechanicallysimple

Outer GlassCover

Insulation Fluid FlowTubes

AbsorberPlate

Inner GlassCover

Flat Plate Collector

Incident Solar Radiation ( tG )

Consists of an absorber

plate, cover g lass,

insulat ionand hous ing.

Characteristics of Flat Plate


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Characteristics of Flat Plate

Collector

Used for moderate temperature up to 100 C

Uses both direct and diffuse radiation

Normally do not need tracking of sun

Use: water heating, building heating and air-conditioning, industrial process heating.

Advantage: Mechanically simple



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Flat Plate Solar Collector The absorb er plateis usually made

of copper and coated to increase theabsorption of solar radiation.

The cover glass o r glassesareused to reduce convection and re-

radiation losses from the absorber.

Insulationis used on the back edges

of the absorber plate to reduceconduction heat losses.

Thehousing holds the absorber withinsulation on the back and edges,

and cover plates.

The working fluid (water, ethyleneglycol, air etc.) is circulated in aserpentine fashion through the

absorber plate o carry the solar

energy to its point of use.

Outer GlassCover


AbsorberPlate

Inner GlassCover



Consists of an absorber

plate, cover g lass,

insulat ionand hous ing.


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Collector Performance

x

y

x

T

)T(x

Temperature Distribution

in the Absorber Plate

The temperature of the working fluid in aflat-plate collector may range from 30 to90C, depending on the type of collector

and the application.

The amount of solar irrradiation reachingthe top of the outside glazing will dependon the location, orientation, and the tilt of

the collector.

Temperature of the absorber plate varies

along the plate with peak at the midsection

Absorbed heat diffuses along the lengthtowards the tube with and transferred to

the circulating fluid.


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Collector PerformanceThe collector efficiency of flat-plate

collectors varies with design orientation,time of day, and the temperature of the

working fluid.

The amount of useful energy collected

will also depend on- the optical properties (transmissivity

and reflectivity) of cover glasses,

- the properties of the absorber plate

(absorptivity and emissivity) and

- losses by conduction, convection and

radiation.

Outer GlassCover


AbsorberPlate

Inner GlassCover



Collector PerformancefiT


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An energy balance for the absorber plate is

cond

a

conv

ca

rad

caaccsolca

R

TT

R

TT

R

TTIAq 2

4

2

4

21

A simplification leads to

TTUIAq f iaccsolca 21

Where

= temperature of the fluid at inlet to

collector

U = over all heat transfer coefficient

empirically determined heat collection factor

fiT

fiT

Collector PerformanceplateCollectorAc


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Useful energy output of a collector

apctpcu TTUGAQ Where= Total absorbed incident

radiation at the absorber plate

Overall heat transfer

coefficient (Represents total heat

loss from the collector.

Temperature of the absorber

plate

Temperature of ambient air

tpG

cU

pT

aT

One of the major problem inusing this equation is the

estimation and determination of

the collector plate temperature

.


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A more useful form is given in terms of fluid inlet

temperature, and a parameter called collector heat

removal factor ( ), which can be evaluated analytically

from basic principles or measured experimentallyRF

The heat removal factor in defined as

TaTUGA QF pctpc uR Where the heat removed bythe circulating fluids throughthe tubes is given as

fofipu TTCmQ TaTUGA TTCmF pctpc fofipR

Heat Removal Factor

Effective Transmittance n1i 1iiae a1


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Effective Transmittance-

Absortance Product

In order to take into account of the mult ip le abso rpt ion,

t ransm iss ion b y the mult ip le layer of g lass coversand

reduced loss of by the overall heat transfer coefficient, an

effect ive transm ittanceabso rptance productis

Introduces and expressed as

n

1i

1iiae a1

An effective transmittance-

absorptance product can be

approximatedfor collectors

with ordinary glass

01.1e


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Collector Efficiency

Typical collector efficiencycurves:

As absorber temperature increases,

the losses increases and the efficiencydrops.

At lower ambient temperatures theefficiency is low because of higher loss.

As the solar irradiation on the coverplate increases, the efficiency

increases because the loss from the

collector is fairly constant for given

absorber and ambient temperature and

becomes a smaller fraction.

c

t

afic

G

)TT(U

A collector is characterized

by the intercept, and

the slope

nRF

eRF cRUF

t aficeRc G TTUF

Example: Flat Plate Solar Collector


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Example: Flat Plate Solar Collector

Efficiency

A 1 by 3 flat-plate double-glazed collector is availablefor a solar-heating applications. The transmittance of

each of the two cover-plates is 0.87 and the aluminum

absorber plate has an absorptivity of =0.9. Determine

the collector efficiency when ,and . Use and

2

/800 mWISol

CTfi0

55 CT 010

sol

fi

accrcolI

TTUF

21

800

10555.39.087.087.09.0col

9.0FRKmWU ./5.3 2

%5.43435.0 col


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Concentrating Solar Collector

Parabolic Trough- Line focus type

Focuses the sun on to a pipe running

down the center of trough.

- Can produce temperature upto 150200 C

- Used to produce steam for producing

electricity- Trough can be pivoted to track the sun


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Parabolic Trough- Line focus type

Focuses the sun on to a pipe running

down the center of trough.

- Can produce temperature upto 150200 C

- Used to produce steam for producing

electricity- Trough can be pivoted to track the sun


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Parabolic Dish Concentrator- Point focus type

Focuses the sun on to the heat engine

located at the center of the dish.- Can produce very high temperature

700-1000C

- Used to produce vapor for producing

electricity

- Dish can be pivoted to track the sun

f O


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1/9/2014

Description of a Project Oriented

Learning Module

A typical solar projects are

discussed in the following section.

The objective is to understand some

of the basic steps to be followed.


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Solar Heated Swimming Pool

Option-2:With a Auxiliary Heater and without a Thermal Storage

Solar Collector

Swimming Pool

Auxiliary Heater

Pump


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Option-3:With a Auxiliary Heater and a Thermal Storage

Solar Collector

Swimming Pool

Auxiliary Heater

Pump

Thermal

Storage


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Option-3:With a Auxiliary Heater and a Thermal Storage

Solar Collector

Swimming Pool

Auxiliary Heater

Pump

Thermal

Storage


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Known Data

1. Geographical Location:

Santa Barbara, CA

2. The Pool Dimension

12m long x 8m wide with water

depth that varies in the lengthwisedirection from 0.8m to 3.0m

To be Designed Selected or


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To be Designed , Selected or

Determined

1. Design Conditions

- A comfortable water temperature for theindoor pool and indoor air condition

- Design outdoor conditions

2. A solar water heating system with or without

thermal storage

3. A system with or without a auxiliary gas orelectric heater

4 Determine size and type of solar collector


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4. Determine size and type of solar collector

5. Decide placement of these collectors,

their location, and orientation

7. Estimate the total cost of the system

including initial, operating andmaintenance

8. Compare these costs to those associatedwith the use of a natural gas waterheating system

A S l d i I i ti P


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A Solar-driven Irrigation Pump

Turbine

SolarCollector

CondenserPump

IrrigationPump

ph

pm

A solar-energy driven irrigation pump operating on a

solar driven heat engine is to be analyzed and designed.

C150T0

H

kPa10Pc

B i Th


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Basic Theory

The solar collector collects a fraction of incident

radiation and transfer to the circulating working

fluid, producing saturated vapor and heating the

working fluid.

i,f0,ffu hhmQ

tccu GAQ

pppumpirr HgmW

CHfturbine hhmW



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Determined

Select:Location, time and month of the year

Determine:Incident solar radiation based on the

selected location, day and month of the year.

For Example: Over 0< t < 10

Watt,10

tSinAGtG ct

Selection and Design of Solar


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Selection and Design of Solar

Collector

Type: Flat Plate

TransmittanceAbsorptance Product:

Collector removal factor: = 0.024

Overall loss coefficient:Collector efficiency:

Where

= Fluid temperature at inlet to the collector

= Ambient air temperature

= Incident solar radiation

ain

t

LRc TT

G

UF

84.0RF

C.m/W0.8U 02L

inT

aT

tG

Perform the analysis for the base case and assuminga pumping rate of 10 GPM at the mid noon.


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p p g

Determine the collector area needed to meet this

demand.

Plot the irrigation pump flow rate during the daylighthours.

Estimate the total water pumped in a day

10

0dtpmpm

If the pumping rate is kept constant at 10 GPM


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p p g p

by using an auxiliary after-heater and

maintaining the (saturated vapor) temperature

constant at inlet to the turbine, determine theauxiliary energy needed at the after-heater.

Repeat steps 1-2 with varying range of Turbineinlet temperature and condenser pressure and .Summarize your results for (a) solar collector

area needed, (b) total pumping rate and (c) total

auxiliary energy needed.

Documents

Lecture - 3 Solar