Oro551 res - unit 1 - instruments for measuring solar radiation and sun shine

ORO551 - RENEWABLE ENERGY SOURCES
M.KARTHIKEYAN
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEERING & TECHNOLOGY, SIVAKASI
karthikeyan@aaacet.ac.in
8825676616M.KARTHIKEYAN AP/MECH AAACET
SIVAKASI

1. Role and potential of new and renewable source.
2. The solar energy option.
3. Environmental impact of solar power.
4. Physics of the sun.
5. The solar constant.
6. Extraterrestrial and terrestrial solar radiation.
7. Solar radiation on titled surface.
8. Instruments for measuring solar radiation and sun shine.
9. Solar radiation data.
UNIT I PRINCIPLES OF SOLAR RADIATION
M.KARTHIKEYAN AP/MECH AAACET
SIVAKASI

To measure global or diffuse radiation:
I. PYRANOMETER
1. Eppley Pyranometer
2. Yellot solarimeter [photovoltaic cell pyranometer]
3. Moll – Goreczynski Pyranometer
4. Bimetallic Pyranograph
5. Yanishevsky Pyranometer
6. Dirmhirn-Sauberer or Star Pyranometer
To measure beam or direct radiation:
II. PYRHELIOMETER
1. Angstrom pyreheliometer
2. Abbot silver disc pyreheliometer
3. Eppley pyreheliometer
SIVAKASI
INSTRUMENTS FOR MEASURING SOLAR RADIATION

 A pyranometer is used to measure global solar radiation falling on a
horizontal surface.
 Pyranometer also measure diffused radiation by using a shading
ring.
 The shading ring will prevent the falling of beam radiation on the
sensor.
 Its sensor has a horizontal radiation-sensing surface that absorbs solar
radiation energy from the whole sky and transforms this energy into
heat.
 Global solar radiation can be calculated by measuring this heat energy.
 Most pyranometers in general use are now the thermopile type,
although bimetallic pyranometers are occasionally found.
SIVAKASI
PYRANOMETER

SIVAKASI
EPPLEY PYRANOMETER

 A thermopile is an electronic device that converts thermal energy
into electrical energy.
 It is composed of several thermocouples connected usually in series.
SIVAKASI
EPPLEY PYRANOMETER

 The sensing element consists of two concentric silver rings.
 The inner ring is coated with black colour.
 The outer ring is coated with white magnesium oxide.
 Thermopile is composed of 50 thermocouples.
 The whole assembly is sealed inside a spherical lamb bulb of
diameter 76 mm & thickness 0.6 mm.
SIVAKASI
CONSTRUCTION DETAILS

 It is based on the principle of change in temperature between
black surface and white surface.
 Due to change in temperature an emf will be produced.
 This emf will be equivalent to the amount of solar radiation
generated.
SIVAKASI
WORKING PRINCIPLE

SIVAKASI

SIVAKASI
BIMETALLIC PYRANOGRAPH

 A bimetallic strip is used to convert a temperature change into
mechanical displacement.
 A bimetal strip is made of two thin metal strips that have different
coefficients of expansion.
 The two metal strips are joined by brazing, so that the relative
movement between them is stopped.
SIVAKASI

 The radiation-sensing element consists of two pairs of bimetals, one
painted black and the other painted white.
 White bimetallic strips are fixed to the frame.
 Black bimetallic strips ones are connected to the recorder section
via a transmission shaft.
 The deflection of the free edge of the black strips is transmitted to
the recording pen through a magnifying system.
 When the air temperature changes, the black and white strips
attached to the common plate at one end both bend by the same
amount but in opposite directions.
 As a result, only the temperature difference attributed to solar
radiation is transmitted to the recording pen.
SIVAKASI

Pyranometers are frequently used in
1. Meteorology
2. Climatology
3. Solar Energy Studies
4. Building Physics
SIVAKASI
APPLICATIONS

SIVAKASI
ANGSTROM PYRHELIOMETER

• It is used to measure beam or direct radiation.
• It can be achieved by locating the sensor disc at the base of a tube
whose axis is aligned with the direction of the sun’s rays.
• Thus diffuse radiation is blocked from the sensor surface.
SIVAKASI
PYRHELIOMETER

• Pyrheliometer is an instrument used to measure the quantity of heat
radiation and solar constant.
• Pyrheliometer designed by Angstrom is the simplest and most
accurate.
• Angstrom pyrheliometer consists of two identical manganin strips
[ 20 x 2 x 0.2 mm] S1 and S2 of area A.
• One junction of a thermocouple is connected to S1 and the other
junction is connected to S2.
• A sensitive galvanometer is connected to the thermo couple.
• Strip S2 is connected to an external electrical circuit.
SIVAKASI

 When both the strips S1 and S2 are shielded from the solar radiation,
galvanometer shows no deflection as both the junctions are at the same
temperature.
 Now strip S1 is exposed to the solar radiation and S2 is shielded with a
cover M.
 As strip S1 receives heat radiations from the sun, its temperature rises
and hence the galvanometer shows deflection.
 Now current is allowed to pass through the strip S2 and it is adjusted so
that galvanometer shows no deflection.
 Now, the strips S1 and S2 are again at the same temperature.
SIVAKASI
WORKING PRINCIPLE

 If the quantity of heat radiation that is incident on unit area in unit
time on strip S1 is Q and a its absorption co-efficient, then the amount
of heat radiations absorbed by the strip S1 in unit time is QAa.
 Also, heat produced in unit time in the strip S2 is given by VI, where V is
the potential difference and I is the current flowing through it.
 As heat absorbed = heat produced
 QAa = VI (or)
 Q=VI/Aa
 Knowing the values of V, I, A and a, Q can be calculated.
SIVAKASI

SIVAKASI
ABBOT SILVER DISC PYREHELIOMETER

 This instrument was designed by Abbot in 1902.
 Here the sensing element is the silver disk.
 Its diameter is 28mm and thickness 7mm.
 The silver disk is painted black on its radiation receiving side.
 The silver disk has a hole to allow the bulb of a thermometer.
 To maintain good thermal contact between the disk and the
bulb, the hole is filled with a small amount of mercury.
SIVAKASI

 It is enclosed outside by a heat-insulating wooden container.
 The stem of the thermometer is bent in a right angle outside the
wooden container and supported in a metallic protective tube.
 A cylinder with diaphragms inside is fitted in the wooden container
to let direct solar radiation fall onto the silver disk.
 There is a metallic-plate shutter at the top end of the cylinder to
block or allow the passage of solar radiation to the disk.
SIVAKASI

 During the measurement phase, the disk is heated by solar radiation
and its temperature rises.
 The intensity of this radiation is ascertained by measuring the
temperature change of the disk between the measurement phase
and the shading phase with the mercury-in-glass thermometer.
SIVAKASI
WORKING PRINCIPLE

 A sunshine recorder is a device that records the amount
of sunshine at a given location.
 The results provide information about the weather and climate as
well as the temperature.
 This information is useful in meteorology, science, agriculture,
tourism, and other fields.
 The popular types of sunshine recorder are :
1. Campbell-stokes Recorder
2. Rotating Mirror Sunshine recorder
3. Blake-larsen Recorder.
SIVAKASI
INSTRUMENTS FOR MEASURING SUN SHINE

SIVAKASI
CAMPBELL-STOKES RECORDER

SIVAKASI
CROSS SECTION OF BOWL AND GROOVES

SIVAKASI
1) For winter
2) For spring and autumn
3) For summer
RECORDING CARDS

INTRODUCTION:
 The Campbell–Stokes recorder was invented by John Francis
Campbell in 1853 and modified in 1879 by Sir George Gabriel
Stokes.
PRINCIPLE:
 A Campbell-Stokes sunshine recorder concentrates sunlight
through a glass sphere onto a recording card placed at its focal
point.
 The length of the burn trace left on the card represents the
sunshine duration.
SIVAKASI
CAMPBELL-STOKES RECORDER

CONSTRUCTION:
 The Campbell-Stokes sunshine recorder consists essentially of a
glass sphere mounted concentrically in a section of a spherical bowl.
 The diameter of which is such that the sun’s rays are focused
sharply on a card held in grooves in the bowl.
 Three overlapping pairs of grooves are provided in the spherical
segment so that the cards can be suitable for different seasons.
 Three different recording cards are used depending on the season
[summer, winter or spring and autumn]
 The hours of bright sunshine are recorded by the rays of the sun
passing through the sphere, which undergo focus and burn a hole
through the card placed behind it.
 The card itself is calibrated so that the hours and minutes of the day
are measured across it.
SIVAKASI

SIVAKASI
ROTATING MIRROR SUNSHINE RECORDER

 A rotating mirror is used to reflect sunlight onto the photosensor.
 The rotating mirror rotates once every 30 seconds.
 A photosensor is an electronic component that detects the presence
of visible light, infrared transmission (IR), and/or ultraviolet (UV)
energy.
SIVAKASI
ROTATING MIRROR SUNSHINE RECORDER

SIVAKASI
BLAKE-LARSEN RECORDER

 The Blake Larsen Sunshine Recorder is a more sophisticated
sunshine recorder that uses sensors to detect solar radiation and
record them.
 The recorder unit and
PC software produce
a fully automated
system to measure the
duration of bright sunlight.
SIVAKASI
BLAKE-LARSEN RECORDER

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