NAME:-DHRUV

NISHAR

STD/DIV:- SYJC/H

ROLL NO.:- 86

SOLAR ENERGY
 Introduction

Solar energy is radiant light and heat from the Sun that is
harnessed using a range of ever-evolving technologies such
as solar heating, photovoltaics, solar thermal energy, solar
architecture, molten salt power plants and artificial
photosynthesis.[1][2]
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. Active
solar techniques include the use of photovoltaic
systems, concentrated solar power and solar water
heating to harness the energy. Passive solar techniques
include orienting a building to the Sun, selecting materials
with favorable thermal mass or light-dispersing properties,
and designing spaces that naturally circulate air.
The large magnitude of solar energy available makes it a
highly appealing source of electricity. The United Nations
Development Programme in its 2000 World Energy
Assessment found that the annual potential of solar energy
was 1,575–49,837 exajoules (EJ). This is several times
larger than the total world energy consumption, which was
559.8 EJ in 2012.
 Objectives
1. To learn about solar energy.
2. To know about various types of solar energy.
3. To learn about the advantages of solar energy.
4. To study about the disadvantages of solar energy.
5. To analyze the potential of solar energy.
6. To learn about different types of solar apparatus.
7. To understand of solar energy works.
 Importance
Historical Importance of Solar Energy
There are many reasons why solar energy is important to
humankind. It's importance to human survival goes back to
prehistoric times.
Prehistoric cultures used the Sun's energy for crucial
activities such as warming their dwellings, drying their
clothing, and curing their food. Solar energy was so
important for these cultures that many of them actually
worshiped and revered the Sun.
As cultures developed, some even created laws related to
accessing solar energy. For example, the ancient Roman
empire had a law that forbid anyone from constructing a
dwelling that blocked the Sun from their neighbor's home.
In the America's, the Anasazi cliff dwellers also considered
solar energy an important resource. They built their
dwellings along the south-facing side of cliffs in the current
American Southwest in order to use the power of the Sun to
warm their homes.
Modern Importance of Solar Energy
During modern times, we've become reliant on fossil fuels.
This has allowed us to develop our cultures and economies
tremendously, but has come at a steep price.
Due to the side-effects of using fossil fuels, the use of solar
energy has become important to mankind once again. Some
of the reasons solar energy is important are...
  Global energy demand is increasing
 Continued usage of fossil fuels is damaging our
environment
 Solar energy is one of the most promising alternatives
to fossil fuels
For a more thorough discussion about the importance of
solar energy in the modern world
Importance of Solar Energy to Homeowners
Then there are reasons why solar energy is important to
homeowners as well. Some of these reasons are...
 Having a positive impact on our environment
 Solar energy saves homeowners money now and in the
future
 Allows homeowners to have energy independence
For a more thorough discussion on the importance of solar
energy to homeowners, see.
But at an individual level, everyone is motivated by different
things. Some people are interested in solar energy for the
environmental benefits, others see solar energy as a way to
reduce their electricity costs, and yet others are looking to
solar energy as a way to leave a positive legacy for their
children.
 Method of study
Working of solar cooker
1) Concentrating sunlight: A mirrored surface with high
[Specular reflection] is used to concentrate light from the
sun onto a small cooking area. Depending on the geometry
of the surface, sunlight could be concentrated by several
orders of magnitude producing temperatures high enough to
melt salt and metal. For most household solar cooking
applications, such high temperatures are not really required.
Solar cooking products are typically designed to achieve
temperatures of 65 °C (150 °F) (baking temperatures) to
400 °C (750 °F) (grilling/searing temperatures) on a sunny
day.
2) Converting light energy to heat energy: Solar cookers
concentrate sunlight onto a receiver such as a cooking pan.
The interaction between the light energy and the receiver
material converts light to heat and this is called conduction.
This conversion is maximized by using materials that
conduct and retain heat. Pots and pans used on solar
cookers should be matte black in color to maximize the
absorption.
3) Trapping heat energy: It is important to
reduce convection by isolating the air inside the cooker from
the air outside the cooker. Simply using a glass lid on your
pot enhances light absorption from the top of the pan and
provides a greenhouse effect that improves heat retention
and minimizes convection loss. This "glazing" transmits
incoming visible sunlight but is opaque to escaping infrared
thermal radiation. In resource constrained settings, a high-
temperature plastic bag can serve a similar function,
trapping air inside and making it possible to reach
temperatures on cold and windy days similar to those
possible on hot days.
Different kinds of solar cookers (more than 300 models of
solar cooker had been made so far) use somewhat different
methods of cooking, but most follow the same basic
principles.
Food is prepared as if for an oven or stove top. However,
because food cooks faster when it is in smaller pieces, food
placed inside a solar cooker is usually cut into smaller
pieces than it might otherwise be.[4] For example, potatoes
are usually cut into bite-sized pieces rather than roasted
whole.[5] For very simple cooking, such as melting butter or
cheese, a lid may not be needed and the food may be
placed on an uncovered tray or in a bowl. If several foods
are to be cooked separately, then they are placed in
different containers.
The container of food is placed inside the solar cooker,
which may be elevated on a brick, rock, metal trivet, or
other heat sink, and the solar cooker is placed in direct
sunlight.[4] Foods that cook quickly may be added to the
solar cooker later. Rice for a mid-day meal might be started
early in the morning, with vegetables, cheese, or soup
added to the solar cooker in the middle of the morning.
Depending on the size of the solar cooker and the number
and quantity of cooked foods, a family may use one or more
solar cookers.
A solar oven is turned towards the sun and left until the food
is cooked. Unlike cooking on a stove or over a fire, which
may require more than an hour of constant supervision, food
in a solar oven is generally not stirred or turned over, both
because it is unnecessary and because opening the solar
oven allows the trapped heat to escape and thereby slows
the cooking process. If wanted, the solar oven may be
checked every one to two hours, to turn the oven to face the
sun more precisely and to ensure that shadows from nearby
buildings or plants have not blocked the sunlight. If the food
is to be left untended for many hours during the day, then
the solar oven is often turned to face the point where the
sun will be when it is highest in the sky, instead of towards
its current position.[6]
The cooking time depends primarily on the equipment being
used, the amount of sunlight at the time, and the quantity of
food that needs to be cooked. Air temperature, wind, and
latitude also affect performance. Food cooks faster in the
two hours before and after the local solar noon than it does
in either the early morning or the late afternoon. Large
quantities of food, and food in large pieces, take longer to
cook. As a result, only general figures can be given for
cooking time. With a small solar panel cooker, it might be
possible to melt butter in 15 minutes, to bake cookies in 2
hours, and to cook rice for four people in 4 hours. With a
high performing parabolic solar cooker, you may be able to
grill a steak in minutes. However, depending on local
conditions and the solar cooker type, these projects could
take half as long, or twice as long.
It is difficult to burn food in a solar cooker.[5] Food that has
been cooked even an hour longer than necessary is usually
indistinguishable from minimally cooked food. The exception
to this rule is some green vegetables, which quickly change
from a perfectly cooked bright green to olive drab, while still
retaining the desirable texture.
 Observation

The costs of solar photovotiac panels have dropped a hundred-fold

in the last two decades
However, under present conditions, solar power is still expensive.
A single solar panel costs around £250 and has a maximum
generating capacity of 50 Wp (this means that under ideal sunlight
conditions the panel will produce 50 watts of electricity).
Long term investment in the fossil fuel and nuclear industries has
led to their being able to offer electricity to customers at an
affordable rate. Solar power has yet to benefit from the advantages
of such investment, and therefore the cost of solar energy is, at
present, significantly higher than that of "mains" electricity.
In addition to this, the price of electricity does not currently
include the massive environmental costs of fossil fuel and nuclear
generation. Examples of these costs do not include the costs of
acid rain in terms of damaged buildings, depleted fish stocks and
unhealthy forests, the costs of decomissioning nuclear power
stations and the potentially devastating costs of climate change. If
these costs were included in the price of nuclear and fossil
generated energy, the cost of solar power would inevitably be far
more competitive than it is in the present.
With strong and consistent support from governments and
industries, electricity generated by solar photovoltiacs could
become as affordable as fossil-fuel and nuclear power.
Governments and industry in other countries have already started
supporting solar power by investing in the development and
distribution of solar panels. With more of this sort of support the
cost of solar photovoltiacs could be dropped further.
Some time, when the fossil fuels run out and the problems with
nuclear waste cannot be solved, solar power, perhaps, could be
one of the most important energy of the future. With regard to acid
rain, nuclear waste and all the other effects on the environment
(caused by generating conventional electricity) we hope that the
time when solar power will become more important than the
conventional electricity is not too far away. We need a solar future
if our children are to live in an intact environment. They will be
grateful to us.
 Explanation
Effect of solar energy
Land Use
Depending on their location, larger utility-scale solar
facilities can raise concerns about land degradation and
habitat loss. Total land area requirements varies depending
on the technology, the topography of the site, and the
intensity of the solar resource. Estimates for utility-scale PV
systems range from 3.5 to 10 acres per megawatt, while
estimates for CSP facilities are between 4 and 16.5 acres per
megawatt.
Water Use
Solar PV cells do not use water for generating electricity.
However, as in all manufacturing processes, some water is
used to manufacture solar PV components. Concentrating
solar thermal plants (CSP), like all thermal electric plants,
require water for cooling. Water use depends on the plant
design, plant location, and the type of cooling system.
Hazardous Materials
The PV cell manufacturing process includes a number of
hazardous materials, most of which are used to clean and
purify the semiconductor surface. These chemicals, similar
to those used in the general semiconductor industry, include
hydrochloric acid, sulfuric acid, nitric acid, hydrogen
fluoride, 1,1,1-trichloroethane, and acetone. The amount and
type of chemicals used depends on the type of cell, the
amount of cleaning that is needed, and the size of silicon
wafer [4]. Workers also face risks associated with inhaling
silicon dust. Thus, PV manufactures must follow U.S. laws to
ensure that workers are not harmed by exposure to these
chemicals and that manufacturing waste products are
disposed of properly.
Life-Cycle Global Warming Emissions
While there are no global warming emissions associated
with generating electricity from solar energy, there are
emissions associated with other stages of the solar life-cycle,
including manufacturing, materials transportation,
installation, maintenance, and decommissioning and
dismantlement. Most estimates of life-cycle emissions for
photovoltaic systems are between 0.07 and 0.18 pounds of
carbon dioxide equivalent per kilowatt-hour.
Most estimates for concentrating solar power range from
0.08 to 0.2 pounds of carbon dioxide equivalent per
kilowatt-hour. In both cases, this is far less than the lifecycle
emission rates for natural gas (0.6-2 lbs of CO2E/kWh) and
coal (1.4-3.6 lbs of CO2E/kWh)
Disadvantages of Solar Energy
1. Cost
The initial cost of purchasing a solar system is fairly high.
This includes paying for solar panels, inverter, batteries,
wiring, and for the installation. Nevertheless, solar
technologies are constantly developing, so it is safe to
assume that prices will go down in the future.
2. Weather Dependent
Although solar energy can still be collected during cloudy
and rainy days, the efficiency of the solar system drops.
Solar panels are dependent on sunlight to effectively gather
solar energy. Therefore, a few cloudy, rainy days can have a
noticeable effect on the energy system. You should also take
into account that solar energy cannot be collected during the
night. On the other hand, if you also require your water
heating solution to work at night or during wintertime,
thermodynamic panels are an alternative to consider.
3. Solar Energy Storage Is Expensive
Solar energy has to be used right away, or it can be stored in
large batteries. These batteries, used in off-the-grid solar
systems, can be charged during the day so that the energy is
used at night. This is a good solution for using solar energy
all day long but it is also quite expensive. In most cases, it is
smarter to just use solar energy during the day and take
energy from the grid during the night (you can only do this if
your system is connected to the grid). Luckily your energy
demand is usually higher during the day so you can meet
most of it with solar energy.
4. Uses a Lot of Space
The more electricity you want to produce, the more solar
panels you will need, as you want to collect as much sunlight
as possible. Solar PV panels require a lot of space and some
roofs are not big enough to fit the number of solar panels
that you would like to have. An alternative is to install some
of the panels in your yard but they need to have access to
sunlight. If you don’t have the space for all the panels that
you wanted, you can opt for installing fewer to still satisfy
some of your energy needs.
5. Associated with Pollution
Although pollution related to solar energy systems is far less
compared to other sources of energy, solar energy can be
associated with pollution. Transportation and installation of
solar systems have been associated with the emission of
greenhouse gases. There are also some toxic materials and
hazardous products used during the manufacturing process
of solar photovoltaic systems, which can indirectly affect the
environment. Nevertheless, solar energy pollutes far less
than other alternative energy sources.
Conclusion