Slides containing -ORO 551 Renewable Energy Sources -UNIT 1

1. SOLAR ENERGY
•Solar energy is radiant light and heat from the Sun that is harnessed using a
range of ever-evolving technologies(electro magnetic radiation).
• It is an important source of renewable energy and its technologies are
broadly characterized as either passive solar or active solar depending on
how they capture and distribute solar energy or convert it into solar power.
• Energy used for cooling/heating/drying/distillation/power generation ,etc.,
• The Earth receives 174,000 terawatts (TW) of incoming solar radiation
(insolation) at the upper atmosphere.
• Most of the world's population live in areas with insolation levels of 150-
300 watts/m², or 3.5-7.0 kWh/m² per day.

2. The energy radiated from the sun is electromagnetic waves reaching the planet
earth in three spectral regions;
(i) Ultra violet 6.4 % ( ≤ 0.38 μm),ƛ
(ii) Visible 48.0 % (0.38 μm < < 0.78 μm), andƛ
(iii) Infrared 45.6 % ( ≥ 0.78 μm) of total energy.ƛ
Due to the large distance between the sun and the earth (1.495 × 108 km) the
beam radiation received from the sun on the earth is almost parallel.
Direct Radiation: Solar radiation that reaches to the surface of earth without
being diffused is called direct beam radiation.
Diffused Radiation: As sunlight passes through the atmosphere, some of it is
absorbed, scattered and reflected by air molecules, water vapour, cloud, dust,
and pollutants from power plants, forest fires, and volcanoes. This is called
diffused radiation.
Global Solar Radiation: The sum of diffuse and direct solar radiation is
called global solar radiation.

3. ENVIRONMENTAL IMPACT OF SOLAR POWER
Every type of energy utilization for electricity generation has
environmental consequences, including renewable energies. Such as
follows:
• manufacture processes
• aesthetic impact
• use of large areas of land
• impact on the eco-system
BY MANUFACTURE PROCESSES
• Due to the large size of the systems involved, manufacture,
installation,maintenance and ultimately disposition of all the system
components are to be optimized and subjected to an LCA (life cycle
assessment) analysis[Cradle to Grave].
• Should photovoltaic cells be considered, the hazardous materials
contained in them (arsenic and cadmium) can pose a serious problem in
areas subject to dust abrasion, such as deserts. Even silicon dust might pose
a health problem.

4. ACTIONS REQUIRED:
1.Rigorous and quantitative LCA analysis.
2. Study of the rates of removal of hazardous materials from atmospheric agents
.
BY AESTHETIC IMPACT
• The construction of overhead transmission lines and other facilities of a
HVDC grid (pylons and transmission towers) in scenic areas.
ACTIONS REQUIRED:
1.Contingent analysis to identify the locations suitable for the construction
of wind turbine towers.
2.Consider tunneling and micro tunneling, using the technology borrowed
from oil field exploration

5. BY USE OF LAND
• While wind power does not pose any significant problem, solar energy does,
unless on worthless soil (deserts).
• The use of energy crops sent prices soaring and created the 3F-conflict
(Food - Feed - Fuel).
ACTIONS REQUIRED:
1. Use wastes, refuses and lingo-cellulosic products or energy crops harvested
in off-years
2. Optimize the production of electricity, fuels and chemicals in integrated
Bio refineries
BY IMPACT OF ECO-SYSTEMS
• The major impact reported for solar is bird deaths from electrocution or
collisions with spinning rotors.
• Large extensions of concentrating solar systems might disturb migratory
birds.
ACTIONS REQUIRED:
1. Identify areas which are not included in migratory paths
LIFE-CYCLE GLOBAL WARMING EMISSIONS

6. PHYSICS OF THE SUN
•The phenomena of the sun is determined by solar magnetic field it was done
by the astronomical methods.
• It intersects with many disciplines of pure physics, astrophysics, and
computer science, including fluid dynamics, plasma physics including
magneto hydrodynamics(MHD), seismology, particle physics, atomic physics,
nuclear physics, stellar evolution, space physics, spectroscopy, radiative
transfer, applied optics, signal processing, computer vision, computational
physics, stellar physics and solar astronomy.

7. CHARACTERISTICS OF SUN

8. DISTANCE OF PLANETS FROM EARTH IN MILES

9. SOLAR CONSTANT
The rate at which energy reaches the earth's surface from the sun, usually
taken to be 1,388 watts per square metre. The formula for calculating the
solar constant is written as
So = E(Sun) x (R(Sun) / r)2,
• So-solar constant,
• E- irradiance of the sun
• R-Radius of the sun
• r-distance between the Earth and the sun

10. ASTRONOMICAL UNIT-A unit of length used for distances within the solar
system; equal to the mean distance between the Earth and the Sun
(approximately 93 million miles or 150 million kilometers)

11. EXTRA TERRESTRIAL SOLAR RADIATION
Solar radiation incident outside the earth's atmosphere is called extra
terrestrial radiation. On average the extra terrestrial irradiance is 1367
Watts/meter2 (W/m2).

12. TERRESTRIAL SOLAR RADIATION
Terrestrial radiation is the energy released by the Earth itself as opposed to
solar radiation that it receives from the Sun.
• Apart from the energy generated by the decay of radioactive minerals in
rock, the energy that drives terrestrial radiation ultimately comes from the
Sun, and it is a major factor in the study of global warming
TERRESTRIAL REGION OF EARTH

13. SOLAR RADIATION ON TITLED SURFACE
IRRADIANCE VARIABLES:
1. Latitude at the point of observation
2. Orientation of the surface in relation to the sun
3. Day of the year
4. Hour of the day
5. Atmospheric conditions
INSTRUMENTS FOR MEASURING SOLAR
RADIATION
• The global solar radiation has two components namely direct and diffuse
radiation.
• The global radiation is measured with the pyranometers, and the direct
radiation with pyrheliometer.
• The devices use two types of sensors:thermal and photovoltaic.

15. A pyranometer shaded from direct solar radiation can be used to measure
diffuse radiation. One implementation uses a band stretching from the
eastern to the western horizon that is oriented according to the solar
declination to shade the pyranometer with the plane of the band parallel to
the celestial equator. Since the solar declination changes, this band must be
adjusted with a frequency that depends on accuracy requirements and time
of year.
Pyranometer

16. PYRHELIOMETER
It measure the direct component of solar irradiance which is important
when installing concentrating collectors.

17. WORKING PRINCIPLE OF PYRHELIOMETER

18. SUN SHINE (SUN SET)

19. SUN SHINE RECORDERS

20. SUN SHINE METHOD
•Calibrated pyrheliometer and solar tracker
•Clear sky periods
•Alternate shade and unshade of pyranometer
Advantages
•Can automated
•Provides unbiased estimate of cosine response
•No zero irradiance bias
Disadvantages
•Which value of K?
•Transitions of bright sun to sky
Most ideal for daily exposure calibrations

21. SUN SHINE
• The duration and the intensity of sunlight is measured using a Campbell-
Stokes sunshine recorder.
• These focus light from the sun onto a piece of card where it leaves a burnt
trace. The more sunshine there is, the longer the line.

22. SOLAR RADIATION DATA
• Solar radiation is the electromagnetic energy emitted by the sun, can be
captured and converted into useful forms of energy.(nasa)[National Solar
Radiation Database]

23. SOLAR ENERGY COLLECTION
• A solar thermal collector collects heat by absorbing sunlight.
• It is possible to harness the energy from the sun and convert it into either
electricity or heat using PV (photo-voltaic) or ST (solar thermal)
technologies respectively.
• An evacuated solar system is the most efficient and a common means
of solar thermal energy generation with a rate of efficiency of 70 per cent.
• Solar Thermal Energy Collector: Solar thermal energy collector is an
equipment in which solar energy is collected by absorbing the radiation in
an absorber and then transferring to a fluid. There are two type of
collectors

24. TYPES OF SOLAR COLLECTORS
Back-pass solar collectors
• Used to heat air
• Glazed surface
• May be integrated with thermal mass
Concentrating solar collectors
• Best suited for clear skies
• Steam production
• Concentrates light at absorber which can increase efficiency at high
temperature
• Four forms: parabolic trough, parabolic dish, power tower, stationary
solar collectors
Trombe Wall
• Thermal mass designed to radiate heat during the night
• Glass to allow sunlight through
• With added salt fillers stored energy changes from 200 cal/day to 80,000
cal/day
Batch Solar Collectors
• Water heating
• Glazed water collectors

25. FLAT PLATE COLLECTORS
• It has no optical concentrator. Here the collector area and the absorber area
are numerically same. The efficiency of flat plate collector is low and
temperature of working fluid can be raised only up to 100 0C.
SCHEMATIC CROSS SECTION OF A FLAT PLATE
COLLECTOR

26. The flat plate collector consists of five major parts as given below:
1: A metallic flat absorber plate: It is made of copper, steel or aluminium
(having high thermal conductivity) and having black surface. The thickness
of the metal sheet ranges from 0.5 to 1.0 mm.
2: Tubes or channels: they are soldered to the absorber plate. Water
flowing through these tubes takes away the heat from the absorber plate.
The diameter of tubes is around 1.25 cm, while that of the header pipe
which leads water in and out of the collector and distributes it to absorber
tubes is 2.5 cm.
3: A transparent toughened glass sheet: of 5 mm thickness is provided as
the cover plate. It reduces convection heat losses through a stagnant air layer
between the absorber plate and the glass. Radiation loss are also reduced as
the spectral transmissivity of glass is such that it transparent to short wave
radiation and nearly opaque to long wave thermal radiation emitted by
interior collector walls and absorbing plate.
4: Fibre glass insulation: of 2.5 to 8.0 cm thickness is provided at the
bottom and on the sides in order to minimize the heat loss.

27. 5: A container encloses the whole assembly in a box made of
metallic sheet or fibre glass.
The commercially available collector have a face area of 2 m2. The
whole assembly is fixed on a supporting structure that is installed on a
tilted position at a suitable angle facing south in northern hemisphere.
For the whole year, the optimum tilt angle of collector is equal to the
latitude of its location. During winter the tilt angle is kept 10-150 more
than the latitude of the location, while in summer it should be 10-150
less than the latitude

28. CONCENTRATING TYPE SOLAR COLLECTOR
Here the receiving area of solar radiation is several times
greater than the absorber area and the efficiency is high. Mirrors and
lenses are used to concentrate sun rays on the absorber. The temperature
of working fluid can be raised only up to 500 0C.
For better performance, the collector is mounted on a tracking
equipment to always face the sun with its changing position
Types of concentrating collectors
• Parabolic trough system
• Parabolic dish
• Power tower
• Stationary concentrating collectors

29. PARABOLİC TROUGH SYSTEM
Parabolic troughs are devices that are shaped like the letter “u”. The
troughs concentrate sunlight onto a receiver tube that is positioned along
the focal line of the trough. Sometimes a transparent glass tube envelops
the receiver tube to reduce heat loss .

30. PARABOLİC DİSH SYSTEMS
A parabolic dish collector is similar in appearance to a large satellite dish, but
has mirror-like reflectors and an absorber at the focal point. It uses a dual axis
sun tracker .
The below figure 3.2.1 shows
Cross Section of parabolic dish.
The Parabolic dish collector is shown
in the below figure 3.2.2.

31. POWER TOWER SYSTEM
A heliostat uses a field of dual axis sun trackers that direct solar energy
to a large absorber located on a tower. To date the only application for
the heliostat collector is power generation in a system called the power
tower .
Heliostats are shown in the figure 3.3.2 below.

32. STATİONARY CONCENTRATİNG SOLAR COLLECTORS
Stationary concentrating collectors use compound parabolic reflectors
and flat reflectors for directing solar energy to an accompanying absorber or
aperture through a wide acceptance angle. The wide acceptance angle for these
reflectors eliminates the need for a sun tracker.
This class of collector includes parabolic trough flat plate collectors, flat
plate collectors with parabolic boosting reflectors, and solar cooker. Development
of the first two collectors has been done in Sweden. Solar cookers are used
throughout the world, especially in the developing countries .