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PRESENTATION ON

MEASUREMENT OF SOLAR RADIATION

PRESENTED BY:-VIVEK KUMAR SINGH 2013BTECHEE014 JK Lakshmipat University

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SOLAR ENERGY TERMS

• Solar Radiation-energy radiated by the sun.Or,

Solar radiation is a term used to describe visible and near-visible (ultraviolet and near-infrared) radiation emitted from the sun.• Ultraviolet: 0.20 - 0.39 µm• Visible: 0.39 - 0.78 µm• Near-Infrared: 0.78 - 4.00 µm• Infrared: 4.00 - 100.00 µm

• Solar irradiation-the radiated energy received on the earth surface.• Solar insolation-solar radiation received on a flat horizontal surface

on earth 2

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Why we need solar radiation?

It is important to measure solar radiation:-

• Owing to increasing the number of solar heating and Colling

application.

• For accurate solar radiation data to predict performance.

• To know the availability of the solar energy.

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DEVICES USED FOR MEASURING THE SOLAR ENERGY

PYRANOMETER

4PYRHELIOMETER

SUNSHINE RECORDER

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1.PYRANOMETER• It measure the total hemispherical solar radiation.• Solar constant-The average amount of solar radiation

received by the Earth's atmosphere, per unit area, when the Earth is at its mean distance from the Sun.

• The value of the solar constant is found experimentally to be 1368 W/m2.

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CONSTRUCTION

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• When it placed in sun rays then it receive the radiation, due to which the temperature of the surface(absorbing surface) start rising .

• The rise in temperature of the absorbing surface is detected by thermopile.

• Now the thermopile generate thermo emf proportional to radiation absorbed.

• This thermo emf is calibrated in terms of received radiation

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working

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placed in sun raystemperature of the surface(absorbing

surface) start rising

rise in temperature detected by thermopile

thermopile generate thermo emf proportional to radiation absorbed

This thermo emf is calibrated in terms of received radiation

• Principle-working principle is that sensitive surface is exposed to total radiation.

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WORKING

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• Used to measure beam of direct radiation.• It collimate the radiation to determine the beam intensity as

a function of incident angle.• Also known as normal incidence pyranometer.

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PYRHELIOMETER

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Principle of working

Sunlight enters the instrument through collimator tube and is

directed onto a thermopile (sensing element) which converts

heat to an electrical signal that can be recorded.

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CONSTRUCTION & WORKING

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• Uses a long collimator tube to collect beam

radiation whose field of view is limited to a

solid angle of 5.5° by appropriate

diaphragms inside the tube.

• Inner surface is blackened to absorb any

radiation.

• At the base of tube a wire wound thermopile

having a sensitivity of approximately 8 micro

volt/W/M^2

• Tube sealed with dry air to eliminate

absorption of beam of radiation within the

tube by water vapour.

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• Measures the duration in hours of bright sunshine during the course of the day.

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Sunshine recorder

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• Consist of a glass sphere installed in a section of “spherical metal bowl” having groves for holding a recorder card strip and the glass sphere.

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CONSTRUCTION

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WORKING

• Glass-sphere which act as a convex lens, focusses the sun’s rays to a

point on the card strip.

• Whenever there is bright sunshine the image formed is intense

enough to burn a spot on the card strip.

• The image moves along the strip due to the sun movement.

• Thus a burnt space whose length is proportional to the duration of

sunshine is obtained on the strip.

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Solar radiation data

Solar radiation data includes following information:- Whether they are instantaneous measurements or

value integrated over some period of time.• Time period of the measurement.• Whether the measurement are of beam or of total

radiation .When data are not available ‘maps’ can be used as a

source of average radiation. 17

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Solar radiation data is collected on the basis of :-1. Solar power calculation with reference to the movement of

the sun2. Hourly measurement of solar radiation at the location and

calculation of :-o “daily average” at the location for a month (kj/m^2*day)o “Monthly average” at the location for various month

(kj/m^2*year)

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Estimation of average solar radiation

• Angstrom equation for average daily global radiation:= a+{b (La/Lm)}Where, Hg=monthly average of the daily global radiation on a horizontal surface at the location(kj/m^2 day).Hc=monthly_ _ _ _ __ _ _ _ _ _ on the same horizontal surface at the same location but on clear sky day (kj/m^2 day).a,b=Constant determined from various cities in the world by measurementsLa= avg. length of solar day for a particular month calculatedLm=length of longest solar day in the month 19

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Modified angstrom’s equation

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Non conventional energy sources and utilization by Er. R K Rajput

Non conventional energy resources by B H Khan www.globalspec.com www.directindustry.com http://www.campbellsci.com/solar-radiation

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BIBLIOGRAPHY

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