# 3. Basics of Solar Radiaiton

57

## Full text

(1)
(2)

 Energy Scenario  Energy demand

 Current energy production status  Solar energy potential

(3)

Solar Radiation availability Photo-voltaic Effect Working of Solar Cell Selection of Battery, Charge controller, Inverter Optimized system design

(4)

18

(5)

### 

~ 0.5% 7.6% 48.4 % 43% ~ 0.5%

(6)
(7)

(8)
(9)

2

sc

### What will be the average intensity falling on earth ?

Assumed to be

Only for calculation of average radiation

(10)

### sc

(11)

Diffused radiations (Diffuse from sky + Reflected from ground) Global (Beam+Diffused)

(12)

### PYRANOMETER

Principle of ‘heating proportional to radiation’

1. The pyronometer is consist of ‘black surface’ which heats up when exposed to solar radiation

2. It’s temperature increases until the rate of heat gain by solar radiation equals the rate of heat loss.

3. The hot junction of a thermopile are attached to the black surface,

while cold junctions are located on side plate so they do not receive the radiation directly.

4. EMF is generated (in range of 0 to 10mV)

5. Integrated over a period of time and is a measure of the global radiation

How does it works !!!

(13)

1. This is done by mounting it at the centre of a semicircular shading ring.

2. Ring is fixed in such a way that it’s plane is parallel to plane of the path of the sun’s daily movement.

3. Hence, the pyranometer measures only the diffused radiation using same principal of thermopile

(14)

### is located at base.

(15)
(16)

Amount of solar radiation on an object will depend on  Location

 Day of year  Time of day

 Inclination of the object

 Orientation of object (w.r.t. North-south direction)

(17)

Latitude Longitude

(18)

### Day of the year is characterized by an angle

Called as Declination angle (δ)

o

o

(19)

### δ

-30 -20 -10 0 10 20 30 0 50 100 150 200 250 300 350 Days of year D e c li n a ti o n (d e g re e ) Dec-21 Sep 21 Mar-21 Dec-21 June 21

### n=1  Jan 1, n=335 Dec 1, for June-21, what would be n?

This is to take care of daily variation of solar radiations

(20)

o

o

### W = 15 (12 - LAT )

Local apparent time In hour Hour angle 15 degree per hour With reference to solar noon

(21)

### 

O Horizontal plane S N Solar collector 90O Normal to collector 

(22)

### Orientation of object (w.r.t. North-south direction)

Surface azimuth angle (γ)

### γ

Normal to the plane

South direction (horizontal plane)

### For inclined object

It can vary from -180O to +180O

Positive if the normal is east of south And Negative if the normal is west of south

(23)

### O

Normal to the plane

(24)

### having any orientation

,

it is necessary to convert the value of the beam flux coming from the

### θ

beam flux Equivalent flux falling normal to surface

b

### I

bn

(25)

Normal to the plane

### θ

θ is affected by five parameters - Latitude of location (φ)

- Day of year (δ) - Time of the day (w) - Inclination of surface (β)

- Orientation in horizontal plane (γ)

θz

Solid lines are reference lines

Vertical

z = Zenith angle)

(26)

o

o

o

o

o

o

o

o

o

o

(27)

(28)

o

z

o

(29)
(30)

(31)

O

O

O

o

o

o

(32)

O

= 14.90o

…..For LAT = 9h

### 

For May 1 , n=121

(33)

O

### Result -

Use all parameters to find cos Θ

(34)

bn

2

2

### Efficiency = 12.5%

From last solution –

cos Θ = 0.65

Power output from array = (Normal incident flux) X Cell area X Efficiency

= (1000Xcos Θ) X 15 X 0.125 = (1000X0.65)X 15X0.125 = 1218.75 W

We will learn this in later section of course

(35)

### Such code is actually used in many simulation software !

(36)

Define variables Call up different parameters

Give input values

Set formulae Display output

(37)

### While developing the code

 Include declarations of the basic standard library  Use the angle values in radiations

#include <iostream> #include <math.h> #include <iomanip> using namespace std; //algorithm in C++ // Output

How will the code look like !

(38)

 Our aim to find out the optimum tilt angle of the panel (β) so that cos ϴ should be maximum

2 tracking modes are usually employed for this.  Single Axis

 Double Axis Tracking

### radiation must be perpendicular to the panel.

A solar tracker is used to orient the panel such that the incident radiation is perpendicular to the panel.

n b b

Recall

(39)

(40)

(41)

(42)

(43)

### horizontal at noon time should be

Under this condition at noon time Sun rays will be perpendicular to the collector

o

At noon,

(44)

### (we need to estimate average value of declination angle over year)

-30 -20 -10 0 10 20 30 0 50 100 150 200 250 300 350 Days of year D e c li n a ti o n (d e g re e )

(45)
(46)

a

### Optimum Inclination over a Month

-30 -20 -10 0 10 20 30 0 50 100 150 200 250 300 350 Days of year D e c li n a ti o n (d e g re e )

(47)

o

(48)

(49)

### (number of hours for which sun is available)

For horizontal collector

From special case 1 β = 0o. Thus, for the horizontal surface

(50)

### 

This equation yields a positive and a negative value for ws Positive corresponds to Sunrise

And negative corresponds to sunset Since 360o corresponds to 24 hours

15o corresponds to 1 hour

Corresponding day length will be

1 max

### S

Smax (day length or maximum number of sunshine hours)

And this will be used in simulation in the form of (Horizon) in later classes Similarly, it can be found out for inclined surface (Home assignment)

(51)

1

s

O

(52)

1 max

max

max

(53)

o

st

st

local

### .

Difference in longitude of location

(54)

### Correction factors

Due to the fact that earth’s orbit and rate of rotation are subject to small

variation

Equation of time correction Difference in longitude of location

Indian Standard Time (IST) is calculated on the basis of 82.5° E longitude, from a clock tower in

(55)

.

(56)

(57)

Updating...

## References

Related subjects :