The document discusses different types of solar technologies, including passive and active systems. It describes passive technologies such as building orientation and materials that circulate air. It then explains two active technologies: photovoltaics which directly convert sunlight to electricity using solar cells, and solar thermal which uses collectors to concentrate sunlight and generate heat or electricity. The document provides details on photovoltaic cell components and types, as well as examples of solar thermal applications like drying, cooking, and distillation.

1. Solar technology
Content
1 introduction
2 classification
3 Active solar technology
3.1 Photovoltaic cell
3.1.1 working
3.1.2 type of solar panel
3.1.3 photovoltaic solar plant work
4 solar thermal technology
4.1 type of solar thermal collector
4.1.1 low thermal collector
4.1.2 medium thermal collector
4.1.3 high thermal collector
5 passive solar technology
6 conclusion

2. 1 Introduction
Sun is an ultimate source of energy, it continuously emits radiant energy know as solar
energy, which supports all form of life on our earth.
The Earth receives 174 pet watts (PW) of incoming solar radiation (insolation) at
the upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed
by clouds, oceans and land masses.
By 1873, concerns of running out of coal prompted experiments with using solar
energy. Development of solar engines continued until the outbreak of World War I. The
importance of solar energy was recognized in a 1911Scientific American article: "in the far distant
future, natural fuels having been exhausted [solar power] will remain as the only means of
existence of the human race".
Solar energy, radiant light and heat from the sun, is harnessed using a range of ever-evolving
technologies such as solar heating, photovoltaics, concentrated solar power, solar
architecture and artificial photosynthesis.
In this entire topic we will discuss different type of technique that we are using to harness
the solar energy, the development in the technology and some of the application of them. We
first start with of classification of the technology that we are using and then we will discuss each
one by one with some of the application of them.
2 Classification of solar technology
Solar technologies are broadly characterized as either passive solar or
active solar depending on the way they capture, convert and distribute solar 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.

3. Active solar technologies encompass solar thermal energy, using solar collectors for heating,
and solar power, converting sunlight into electricity either directly using photovoltaics (PV), or
indirectly using concentrated solar power (CSP)
3 Active solar technology
As we discuss above, in active solar technology we use solar collector, converting solar energy
to electricity by using photovoltaic cell. In an active solar technology we can harness solar energy
by two ways
1 photovoltaic cell
2 Solar thermal technology
We will discuss them one by one
3.1 Photovoltaic cell
Photovoltaic cell can be defined as devices which convert sunlight into electricity. An array of
closely interconnected solar cells makes a solar panel which is use to convert solar energy in to
electrical energy.
3.1.1 Working of photovoltaic cell
To understand how a solar cells works, we must first take the time to understand the properties
of the materials used in the construction of a solar cell. Consider the primary type solar cell that
is constructed from a single crystal of silicon semiconductor.

4. Fig: - Czochralski process
to be useful in electronics and for generating electrical power from solar energy,
silicon must be highly purified. To purify silicon to such a high degree requires special processing.
One purification method is the Czochralski process. In it, a seed crystal is dipped into a crucible of
molten silicon and withdrawn slowly, pulling out a cylindrical single crystal out of the molten
silicon that had crystallized on the seed. The cylindrical crystal is called a Boule. The Boule can be
cut up with a diamond saw into slices (called wafers) and is used to make electrical components.
Fig: - Cell structure
Pure silicon does not conduct electricity; in fact it’s an insulator. Each silicon atom has four
electrons in its outer shell. Each atom fills its outer electron shell to eight electrons by sharing its
four electrons with four other silicon atoms. The atoms form into a tight crystalline structure
where all the electrons are held strongly in place. Without any free electrons to act as charge
carriers pure silicon a good insulator. What makes silicon so useful in electronics is that by adding
a small amount of impurities to the silicon while it is being manufactured alters its electrical
properties in a very useful way. The impurities are called dopants in the industry, and the process

5. of adding the impurities is called doping. By the process of doping we get p-type and n-type.
Silicon is
cut into tiny disks and transformed into silicon wafers. This silicon wafer, not more than a
centimeter thick are then polished carefully.The process of polishing makes the surface of silicon
free from any outside impurities.
Metal conductors that are laid across each disk of silicon crystal help carry electric current within
the solar cell and complete the circuit inside the solar panel as a whole system. Metal connectors
are typically in the form of flat ribbons or thin wires. These kinds of connections between two or
more solar cells are packaged tightly into modules. Solar panels are then covered inside the
sheet of glass (typically tampered glass) on to the front side, so as to be transparent to the light
energy (photons) and hit the solar cells lying within
3.1.2Type of solar panel
Solar panel are classified in to three category
Monocrystalline
this type of solar panel are unique in their use of a single, very pure crystal of silicon.
They are among the oldest, most efficient and most dependable ways to produce electricity from
the sun.

6. Each module is made from a single silicon crystal, and is more efficient, though more expensive,
than the newer and cheaper polycrystalline and thin-film PV panel technologies. You can typically
recognize them by their color which is typically black or iridescent blue.
Polycrystalline
Polycrystalline cells are made from similar silicon material except that instead of being grown into
a single crystal, they are melted and poured into a mold. This forms a square block that can be cut
into square wafers with less waste of space or material than round single-crystal wafers. As the
material cools, it crystallizes in an imperfect manner, forming random crystal boundaries.The
efficiency of energy conversion is slightly lower.marginally less expensive to produce than
monocrystalline
3.1.3 Photovoltaic solar plants work

7. As light hits the solar panels, the solar radiation is converted into direct current electricity (DC).
The direct current flows from the panels and is converted into alternating current (AC) used by
local electric utilities. Finally, the electricity travels through transformers, and the voltage is
boosted for delivery onto the transmission lines so local electric utilities can distribute the
electricity to homes and businesses.
4 Solar thermal technology
. Solar thermal energy (STE) is a form of energy and a technology for harnessing solar energy to
generate thermal energy or electrical energy for use in industry, and in the residential and
commercial sectors We use solar thermal technology to cook food and on a big scale to generate
electricity.
Solar collectors capture and concentrate sunlight to heat a synthetic oil called therminol, which
then heats water to create steam. The steam is piped to an onsite turbine-generator to produce
electricity, which is then transmitted over power lines. On cloudy days, the plant has a
supplementary natural gas boiler. The plant can burn natural gas to heat the water, creating
steam to generate electricity

8. 4.1 Type of solar thermal collector
4.1.1 Low thermal collector
Systems for utilizing low-temperature solar thermal energy include means for heat collection;
usually heat storage, either short-term or interseasonal; and distribution within a structure or a
district heating network. In some cases more than one of these functions is inherent to a single
feature of the system. Some systems are passive, others are active.
MIT's Solar House built in 1939 used seasonal thermal energy storage(STES) for year round
heating.
4.1.2Medium thermal collector
These collectors could be used to produce approximately 50% and more of the hot water needed
for residential and commercial use in the United States. It is commonly used in solar drying,
cooking and distillation.
Solar drying

9. Solar thermal energy can be useful for drying wood for construction and wood fuels such as wood
chips for combustion. Solar is also used for food products such as fruits, grains, and fish. Crop
drying by solar means is environmentally friendly as well as cost effective while improving the
quality. Technologies in solar drying include ultralow cost pumped transpired plate air collectors
based on black fabrics. Solar thermal energy is helpful in the process of drying products such as
wood chips and other forms of biomass by raising the temperature while allowing air to pass
through and get rid of the moisture.
Cooking
Solar cookers use sunlight for cooking, drying and pasteurization. Solar cooking offsets fuel costs,
reduces demand for fuel or firewood, and improves air quality by reducing or removing a source
of smoke. Concentrating solar cookers use reflectors to concentrate solar energy onto a cooking
container. The most common reflector geometries are flat plate, disc and parabolic trough type.
These designs cook faster and at higher temperatures up to 350 °C but require direct light to
function properly.
The Solar Bowl above the Solar Kitchen in Auroville, India concentrates sunlight on a movable
receiver to produce steam for cooking.
Distillation
solar can be used to make drinking water in areas where clean water is not common. Solar
distillation is necessary in these situations to provide people with purified water. Solar energy
heats up the water in the still. The water then evaporates and condenses on the bottom of the
covering glass.
4.1.3 High-temperature collectors
this is mainly use to produce electricity on a big scale. solar radiation is concentrated by mirrors
or lenses to obtain higher temperatures – a technique called Concentrated Solar Power (CSP).

10. Here use of solar tracking system is very necessary so that the reflector can track the solar
position n efficiently concentrate the light on their focal point . we use different type of design to
concentrate the solar light
Parabolic trough designs
Here we use a curved, mirrored trough which reflects the direct solar radiation onto a glass tube
containing a fluid running the length of the trough, positioned at the focal point of the reflectors.
The receiver may be enclosed in a glass vacuum chamber. The vacuum significantly reduces
convective heat loss.
A fluid passes through the receiver and becomes very hot. Common fluids are synthetic oil,
molten salt and pressurized steam. The fluid containing the heat is transported to a heat
engine where about a third of the heat is converted to electricity.
Power tower designs
Power towers capture and focus the sun's thermal energy with thousands of tracking mirrors .

11. A tower resides in the center of the heliostat field. The heliostats focus concentrated sunlight on a
receiver which sits on top of the tower. Within the receiver the concentrated sunlight heats
molten salt to over 538 °C. The heated molten salt then flows into a thermal storage tank where it
is stored, maintaining 98% thermal efficiency, and eventually pumped to a steam generator. The
steam drives a standard turbine to generate electricity.
Dish designs
In this design we use reflective, parabolic dish .It focuses all the sunlight that strikes the dish up
onto a single point above the dish, where a receiver captures the heat and transforms it into a
useful form. Typically the dish is coupled with a Stirling engine in a Dish-Stirling System, but also
sometimes a steam engine is used.These create rotational kinetic energy that can be converted to
electricity using an electric generator.
A parabolic solar dish concentrating the sun's rays on the heating element of a Stirling engine. The entire unit acts as a solar tracke.
Fresnel technologies
In this technology we use a series of long, narrow, shallow-curvature mirrors to focus light onto
one or more linear receivers positioned above the mirrors. On top of the receiver a small
parabolic mirror can be attached for further focusing the light.. This is similar to the trough design
The receiver is stationary and so fluid couplings are not required .The mirrors also do not need to
support the receiver, so they are structurally simpler. When suitable aiming strategies are used
this can allow a denser packing of mirrors on available land area.

12. Fresnel reflector
5 Passive solar technology
Passive solar technologies use sunlight without active mechanical systems . Such technologies
convert sunlight into usable heat, cause air-movement for ventilating, or future use, with little
use of other energy sources. Passive solar technologies include direct and indirect solar gain for
space heating, solar water heating systems.
Passive solar heating techniques generally fall into one of three categories: direct
gain, indirect gain, and isolated gain. Direct gain is solar radiation that directly penetrates, and is
stored in, the living space. Indirect gain technology collects, stores, and distributes solar radiation
using some thermal storage material. Conduction, radiation, or convection then transfers the
energy indoors. Isolated gain systems collect solar radiation in an area that can be selectively
closed off or opened to the rest of the house
a passive solar home work to reduce energy bills and increase comfort in winter
10:00 am to 5:00 pm
Sunlight enters south-facing windows and strikes the thermal mass inside the home. The sunlight
is converted to heat energy, which heats both the air and thermal mass materials. On most sunny
days, solar heat maintains comfort during the mid-morning to late afternoon periods.

13. 5:00 pm to 11:00 pm
As the sun sets, it stops supplying heat to the home. However, a substantial amount of heat has
been stored in the thermal mass. These materials release the heat slowly into the passive solar
rooms, keeping them comfortable on most winter evenings. If temperatures fall below the
comfort level, supplemental heat is needed.
11:00 pm to 6:30 am
The home owner sets the thermostat back at night, so less backup heating is needed. Energy-efficient
features in the home minimize heat losses to the outside.
6:30 am to 10:00 am
Providing a comfortable temperature with passive solar heating systems is toughest in the cool
early morning hours. The thermal mass has usually given up most of its heat, and the sun has not
risen enough to begin heating the home. During this period, the home owner may have to rely on
supplemental heat. Energy-efficient features in the home minimize the need for supplemental
heating.

14. Conclusion
solar energy is renewable source of energy and it does not cause any
environmental pollution like non- renewable source of energy cause. We have many type of
technology to use solar energy for different purposes and we are continuously trying to advance
the technology so that we increase the efficiency of harnessing the solar energy or to maximize
the use of solar energy with lowest price.
We have photovoltaic technology which is used in most of the places like
calculator, watch, to power house hold devices , boiling water etc. it is use almost all satellite to
give them power. We have solar thermal technology which is use to cook food , boil water etc.
most important it is use to generate a electricity on a big scale . we can established a big power
plant based on this technology and give electricity to entire city. We have passive technology
which we can design our home so that we can get maximum benefit from solar energy. Engineers
are constantly trying to improve all these technology so that we can harness solar energy more
efficiently with lower cost.