A report on

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• A report on
• SOLAR DEVICES

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INTRODUCTION

• Solar energy is the most readily available source
  of energy.
• It is also the most important of the
  non-conventional sources of energy because it is
  non-polluting and, therefore, helps in lessening
  the greenhouse effect.
• Solar energy can be put to great use in our day
  to day life vis-à-vis the use of solar devices.
• This energy is used for Cooking/Heating,
  Drying/Timber seasoning, Distillation,
  Electricity/Power generation, Cooling,
  Refrigeration, Cold storage

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Various Types of Solar Devices

• The various types of solar devices are
• Solar collectors
• Solar cookers
• Solar cells
• Apart from the above stated there exist solar
  heaters, solar dryers, solar timber kilns, solar
  air conditioners, solar invertors etc.

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SOLAR COOKERS

• As the supply of fossil fuels like coal, kerosene
  or cooking gas is deteriorating, more and more
  solar energy is harnessed for cooking purposes.
• THREE BASIC DESIGNS OF SOLAR COOKER-
• FLAT PLATE BOX TYPE SOLAR COOKER
• MULTI REFLECTOR TYPE SOLAR OVEN
• PARABOLIC DISC CONCENTRATOR TYPE SOLAR COOKER

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FLAT PLATE BOX TYPE SOLAR COOKER

• It consists of a solar box of size usually 60 cm
  x 60 cm x 20 cm.
• It is made up of inner and outer metal or wooden
  box with double glass sheet on it.
• Absorber tray is painted black with dull color
  so that it can withstand maximum temperature
  attained inside the cooker as well as water
  vapour coming out of cooking utensils.
• Top cover contains 2 plain glasses 3mm each,
  fixed in wooden frame with 20 mm distance between
  them.
• Neoprene rubber sealing provided around contact
  surface of glass cover and cooker box. small vent
  is provided in sealing for vapour escape.
• On one side of glass frame, plane reflecting
  mirror is hinged equal to size of box.

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MULTI REFLECTOR TYPE SOLAR OVEN

• The solar oven consists of a well insulated
  semi-cylindrical box made of aluminum sheet and
  wood.
• Two shells are made and the space between them,
  7.5 cms, is filled with fibre glass insulation.
• The interior sheet is painted black.
• A door of the same insulating material is also
  made for keeping and taking out food.
• The window (40 X 40 cm) of the oven consists of
  two transparent glass sheet (3 mm thk) with a
  spacing of 2 cms.
• Eight reflectors made of silvered glass mirrors,
  four of square shape and four of triangular shape
  have been used.
• The oven can be manually tilted and oriented
  towards the sun.
• With single reflector, temp attained reaches upto
  160 deg and in multi- reflector temp reaches
  around 200 deg/c to 250 deg/c.

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PARABOLIC DISC CONCENTRATOR TYPE SOLAR COOKER

• Parabolic disc is used in this type of solar
  cooker.
• Solar radiations are concentrated at a point,
  focus.
• Cooking pot is placed at this point where a very
  high temperature is maintained, about 450 deg
  celcius.
• 
  Wall Reflector
• Solar Cooker

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Pictures

• Reflective Cooker
  
  Inclined box type cooker
• Box type solar cooker
  Inclined
  Solar Cooker

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ADVANTAGES

• No attention is needed in cooking as in other
  devices.
• No fuel is required.
• Negligible maintenance cost.
• No pollution.
• Vitamins of food are not destroyed and food
  cooked is nutritive and delicious with natural
  taste.
• No problem of charring of food and no over
  flowing.
• DISADVANTAGES
• One has to cook according to the sun shine.
• One can not cook at short notice and food can
  not be cooked in the night or during cloudy days.
• It takes comparatively more time.
• Chapattis are not cooked because high
  temperature for baking is required and also needs
  manipulation at the time of baking.

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Solar collector

• FLAT PLATE COLLECTORS
• The flat plate collector forms the heart of any
  solar energy collection system
• Designed for operation in low temperature range
  from,ambient to 600 C, or the medium temperature
  range, from ambient to 1000 C.
• PRINCIPLE
• The principle behind a flat plate collector is
  that if a metal sheet is exposed to solar
  radiation, the temperature will rise , until the
  rate at which energy is received is equal to the
  rate at which heat is lost from the plate ( this
  temperature is termed as the equilibrium
  temperature.)
• If the back of the plate is protected by a heat
  insulating material, and the exposed surface is
  painted black and is covered by one or two glass
  sheets, then the equilibrium temperature will be
  much higher than that for the simple exposed
  sheet.

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Pictures

• Closed loop solar water heater
  Batch solar water heater
• Flat plate solar heater
  Flat plate over
  roof

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ADVANTAGES

• absorb direct ,diffused and reflected components
  of solar radiation
• are fixed in tilt and orientation and, thus,
  there is no need of tracking the sun
• are easy to make and are low in cost
• have comparatively low maintenance cost and long
  life
• operate at comparatively high efficiency.
• MATERIALS FOR FLAT PLATE COLLECTORS
• Absorber plate
• It should have
• high thermal conductivity
• adequate tensile and compressive strength
• good corrosion resistance.
• Copper is generally preferred.
• Other materials are aluminium, steel
• and various thermoplastics

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• Insulation
• Several insulating materials which can be used to
  reduce the heat loses are available .
• Desired characteristics of these insulating
  material are -
• Low thermal conductivity
• Stability at high temperature ( upto 200degree
  Celsius)
• No degassing upto around 200 degrees Celsius
• Self supporting feature without any tendency to
  settle, ease of application
• No contribution in corrosion.
• Cover plate
• Characteristics of cover plates through which
  solar energy is transmitted are extremely
  important in the functioning of a collector.
• Functions of the cover plate are -
• To transmit maximum solar energy to absorber
  plate .
• Minimize upward heat loss from the absorber plate
  to the environment .
• To shield absorber plate from direct exposure to
  weathering .
• Other factors such as strength , durability , non
  degradability are important .

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• THE LIQUID FLAT PLATE COLLECTOR
• It consists of several basic elements
• flat absorbing plate, normally
• metallic upon which the short wave
• solar radiation falls and is absorbed
• tubes, channels or passages
• attached to the absorber plate to
  FLAT PLATE COLLECTOR
• circulate the liquid required to remove the
  thermal energy from the plate
• thermal insulation provided at the back and sides
  of the absorber plate to minimize the heat losses
• a transparent cover of glass or transparent
  plastic to reduce the upward heat loss from the
  absorber plate
• a weather-tight container to enclose the above
  components.

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Flat plate collectors are classified into three
groups depending on the applications

• simple and low cost collectors with no cover and
  insulation.
• e.g. for heating swimming pools where less heat
  is required.
• Collectors with low cost insulation and one
  transparent cover e.g. in areas requiring
  domestic water heating.
• Well engineered and sophisticated flat plate
  collectors for process heating or small-power
  production.

• The absorber plates can broadly be divided into
  three basic types
• Pipe and fin type, in which the liquid flows only
  in the pipe, and hence has comparatively low
  wetted area and liquid capacity.
• Rectangular or cylindrical full sandwich type in
  which both the wetted area and the water capacity
  are high.
• Roll bond type or semi-sandwich type,
  intermediate between type I
• and II.

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Pictures

• Basic collector absorber plate types
  Flat plate solar heater for swimming pools

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• Solar panels
• The fundamental power unit of a pv system is a
  solar cell.
• It is a semi conductor generally made of silicon.
• A solar cell is a thin wafer , which is
  chemically treated and processed at high
  temperature .
• Many such wafers are joined together to create a
  p-n junction , across which voltage develops when
  sunlight falls on these cells .
• There are four common types of silicon photo
  voltaic cell -
• Single crystalline silicon
• Poly crystalline silicon
• Ribbon silicon
• Amorphous silicon

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• Solar photovoltaic panel - when many cells are
  connected in series to increase the voltage .
• Several series of cells cen be interconnected in
  parallels to increase the power output .
• Solar cells are extremely fragile , so to protect
  them from damage , they are sealed on the top by
  a layer of glass and bottom with a layer of
  plastic or a metal or a combination of the two .
• The spv panels are rated in terms of peak watt
  units which means minimum no. of hours of
  sunlight required to produce a desirable amount
  of electricity daily .

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• Solar lantern
• Solar lantern is a single light point portable
  system .
• Apart from the pv panel , it consists of
• Lamp
• Battery
• Electronic components
• All placed in a casing , either made of metal
  plasticor fibre glass .
• Because of the portability , it is found in both
  indoors and outdoors applications .

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• Battery
• A sealed maintenance free , lead acid battery or
  a tubular plate lead acid battery with spill
  proof feature is used .
• PV panel
• This PV panel has a power rating of 12 volts .
• Electronic component
• Invertors with atleast 80 percent efficiency is
  provided with system .
• Solar lantern are also provided with two led
  indicators to indicate charging and deep
  discharge state .

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THE END

• THANKS