Solar technology

Solar energy

Solar energy is radiant light and heat from the sun harnessed using a range of ever-evolving technologies

such as solar heating, solar photovoltaics, solar thermal electricity, solar architecture and artificial

photosynthesis.

Type of solar technology

Active solar technology

1)Photovoltaic cell

2) solar thermal technology

Photovoltaic cell

Phot

photovoltaic cell is a device which convert solar energy in to electrical energy

Solar panel

Several photovoltaic cell are interconnected together to form solar panel

This solar panel can fix on roof top , in calculator or even on a big land area to generate electricity to entire city

working of solar cell

The main component of solar cell is a semiconductor know as silicon (si)

Si share all it four valance electron to their nearest atom and leave no free electron.

boronWe add some impurities to make its conductivity increase , called doping , here boron is added in si which give a hole denoted by + sign also know as proton

PhosphorousWhen phaphorous is added it give an extra electron know as free electron

This is a different layer of solar panel

If we look at the boundary of the p –n layer , there is more concentration of _ve charge at n- side and +ve at p-side . Both –ve and +ve try to recombine , due to this a electric field is generated which stop further recombination

When sunlight fall on this layer , it produce more electron and hole pairs , which increase the electric field and increase the potential difference

Due to increased electric field , electron and hole pair cant recombine , so if we connect the both layer from outside by a conducting wire like its shown in the above piq , then electron will flow through the wire to the p layer and recombine . This movement will produce a electric current , which we can use for different purposes ..

take a look of a solar pannel on the roof top

When the sunlight fall on it this solar panel will generet a DC current

Photovoltaic solar plants work

Type of solar panel

3 type:-

1) Monocrystalline

2) Polycrystalline

3) Amorphous Thin Film

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.

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.

• Polycrystalline panels are made up from the silicon offcuts, moulded to form blocks and create a cell made up of several bits of pure crystal. Because the individual crystals are not necessarily all perfectly aligned together and there are losses at the joints between them, they are not quite as efficient. However, this mis-alignment can help in some circumstances, because the cells work better from light at all angles, in low light, etc. For this reason, I would argue that polycrystalline is slightly better suited to the UK’s duller conditions, but the difference is marginal.

• The appearance is also different – you can see the random crystal arrangement and the panels look a little bluer as they reflect some of the light.

• Since they are cut into rectangular blocks, there is very little wasted space on the panel and you do not see the little diamonds that are typical of mono or hybrid panels. Some people prefer this more uniform appearance, others like the diamonds. The choice is yours because the overall size and cost is very similar to monocrystalline.

Amorphous Thin Film

A thin-film solar cell (TFSC), also called a thin-film photovoltaic cell (TFPV), is a second generation solar cell that is made by depositing one or more thin layers, or thin film (TF) of photovoltaic material on a substrate, such as glass, plastic or metal

Film thickness varies from a few nanometers (nm) to tens of micrometers (µm),

Thin-film has always been cheaper but less efficient than conventional c-Si technology

three thin-film technologies

• 1) Cadmium telluride

• 2) Copper indium gallium selenide

• 3) Amorphous silicon

Cadmium telluride

Cadmium telluride (CdTe) photovoltaics describes a photovoltaic (PV) technology that is based on the use of cadmium telluride, a thin semiconductor layer designed to absorb and convert sunlight into electricity.Cadmium telluride PV is the only thin film technology with lower costs than

conventional solar cells made of crystalline silicon

Copper indium gallium selenide

• CIGS is a I-III-VI2 compound semiconductor material composed of copper, indium, gallium, and selenium. The material is a solid solution of copper indium selenide (often abbreviated "CIS") and copper gallium selenide

• A copper indium gallium selenide solar cell (or CIGS cell, sometimes CI(G)S or CIS cell) is a thin film solar cell used to convert sunlight into electric power

• They are manufactured by depositing a thin layer of copper, indium, gallium and selenide on glass or plastic backing, along with electrodes on the front and back to collect current

• Because the material has a high absorption coefficient and strongly absorbs sunlight, a much thinner film is required than of other semiconductor materials.

structure• Soda lime glass is commonly used as a substrate• A molybdenum layer is deposited (commonly by sputtering) which serves

as the back contact and reflects most unabsorbed light back into the absorber.

• Following molybdenum deposition a p-type CIGS absorber layer is grown by one of several unique methods.

• A thin n-type buffer layer is added on top of the absorber. • The buffer is typically cadmium sulfide (CdS) deposited via chemical bath

deposition• The buffer is overlaid with a thin, intrinsic zinc oxide layer (i-ZnO) which is

capped by a thicker, aluminum (Al) doped ZnO layer• The i-ZnO layer is used to protect the CdS and the absorber layer from

sputtering damage while depositing the ZnO:Al window laye• The Al doped ZnO serves as a transparent conducting oxide to collect and

move electrons out of the cell while absorbing as little light as possible.

Conversion efficiency• CIGS is mainly used in the form of

polycrystalline thin films. The best efficiency achieved as of October 2013 was 20.8%

Amorphous silicon

• Amorphous silicon (a-Si) is the non-crystalline form of silicon.

• It is widely used in pocket calculators, but it also powers some private homes, buildings, and remote facilities.

• Amorphous silicon panels are formed by vapor-depositing a thin layer of silicon material – about 1 micrometer thick – on a substrate material such as glass or metal

Efficiency

• While crystalline silicon achieves a yield of about 18 percent, amorphous solar cells’ yield remains at around 7 percent.

Solar thermal technology

• Solar thermal technology is 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.

Type of solar collector

• Low temperature collector

• Medium temperature collector

• High temperature collector

High temperature collector

• Parabolic trough designs

• Power tower designs

• Dish designs

Parabolic trough

A parabolic trough is a type of solar thermal collector that is straight in one dimension and curved as a parabola in the other two, lined with a polished metal mirror. The energy of sunlight which enters the mirror parallel to its plane of symmetry is focused along the focal line, where objects are positioned that are intended to be heated.

Power tower design

Power tower designs

Here the sunlight is directed by the heliostats to fall on the receiver , inside the receiver there is a pipe charring molten salt or water are circulating , which absorbed the heat .

Steam power tower

This pipe is connected to the power generator

In steam tank it will generate steam which turn the turbine , generate electricity, then through transmission line it go to to the consumer . The steam is the recirculated and used again and again

Molten salt power tower

In the case the pipe is carrying molten salt then it has two tank hot and cold , the hot molten salt is store in the the hot tank , from which it go to the power block

Then the same things happen as in the case of steam

Dish designs

A dish system uses a large, 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 Stirlingengine 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

Collected thermal energy is converted to mechanical energy with the use of different types of engines and then this mechanical energy is converted to electrical energy with the used of generators or alternators

• known to have the highest efficiency of all solar technologies around 30% compared to solar PV approximately 15%, and is predicted to be able to produce the cheapest energy among all renewable energy sources in high scale production and hot areas, semi deserts etc

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 :-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. 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.

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.

5:00 pm to 11:00 pm

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.

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.