Solar Energy

By the end of this century, it is expected that crude oil will be over. Newspaper will miss out of the headlines on petrol price hike. No oil spillage in oceans, no loss of marine bio diversity. Artifact collectors would save a gallon of oil as souvenir of crude oil era. School essays wouldn’t have petro products as reason for global warming. But will life stop if crude oil is over?

Humans have shifted from wood to coal, coal to oil, and oil to gas. This shift was due to better performance, efficiency and feasibility of the new fuel. In simple words new fuel were better than the previous one. And now it’s time for shifting from crude oil to renewable energy source. And one of the most abundant available sources of energy on earth is solar energy. In fact crude oil, coal etc. are in a way forms of solar energy. Solar energy is inexhaustible source of massive energy. According to recent estimates earth receives an average irradiance of 1367W/m²which is also known as solar constant. When this power density is averaged over the surface of the earth’s sphere, it is reduced by a factor of 4. A further reduction by a factor of 2 is due to losses in passing through the earth’s atmosphere. This value varies throughout the year and also from place to place. Now solar energy isn’t just a way of generating power but also for generating money. The world market shares of renewable sources are rising steadily. And today with the development of technology solar energy is a growing market providing ample employment opportunities.

Applications

Solar energy has many applications in our life. It is such a source that can contend all our energy needs. From lighting to heating, from transportation to cooling all the needs can be fulfilled by utilizing solar energy. Solar panels and solar water heaters installed on the rooftops are common applications of solar energy. Solar energy isn’t only used for charging batteries or heating water but can also be used for purifying water. Simple solar desalination and distillation technology has also been known for long time.

Almost all of the satellites from small cubesats to large satellite are powered by solar energy. Nowadays, solar technology is so developed that it can power airplanes; zephyr built by QinetiQ is an example of it. Zephyr is powered by PV cell and has a battery for back up.

Fig. 1: Representational Image of Airbus Zephyr Series of Lightweight Solar-Powered UAV

From past to present

Sun as an ultimate source of energy was well understood by ancient civilizations. The Romans, Egyptians, Greeks, Hindus, Inkas etc. worshipped sun god in various forms. They have developed various means to harness solar energy in various forms. Though, they used solar energy for heating, lighting etc. and not for generating electricity. The use of solar energy for generating electricity was discovered by Edmund Becquerel in 1838. Later, Auguste Mouchout got the first patent for a motor running on solar energy. And today solar energy is used to power houses, cars, charge mobiles, ipods, laptops, satellites, etc. The scope of solar power isn’t limited to just earth. The satellites and space shuttles widely use it for power supply.

Fig. 2: Image Showing Compnents of International Space Station Getting Powered by Solar Panels

Solar Energy Harnessing

Methods to harness solar energy

Solar energy can be harnessed in two ways:

1. Energy from the light of the sun:

This method is based on the phenomenon of photoelectric effect and uses photovoltaic cells. When the sun light strikes the surface of solar panels, the process of photoemission occurs in photovoltaic cell and solar energy is directly converted into electrical energy. Theoretically no heat dissipation is involved in this method. An image showing Solar Panels

Fig. 3: An Image Showing Solar Panels

2. Energy developed from the heat of the sun:

Another method of generating energy using solar energy is by capturing heat. In this method a large number of concave mirrors are used to intensify the heat generated from the sun. This heat is utilized to convert water into steam. Like other methods the pressure of steam moves the turbine in order to produce electrical energy.

Fig. 4: An Image of Solar Power Plant

Photovoltaic Cells

Principle and working of photovoltaic cells

A solar cell converts light energy into electrical energy. This conversion is based on the phenomenon of photovoltaic effect. Sunlight consists of photons with different energy levels depending upon the spectrum from which they belong. When sunlight strikes the surface of the photovoltaic materials it ejects electrons which results in the generation of electricity. This phenomenon is known as photovoltaic effect. This effect was discovered by French physicist Antoine-César Becquerel in 1839.

In theory, solar cells can convert about 30 percent of the incident solar radiation energy into electricity. Commercial cells today, depending on technology, typically have an efficiency of 5 -12 percent for thin films and 13 – 21 percent for crystalline silicon based cells. The first solar cell was built by Charles Fritts in around 1883 using junctions formed by coating selenium (a semiconductor) with an extremely thin layer of gold. The technology was developed long ago and at that time efficiency was below 1 %. New technologies came up, new developments occurred and based on technological development different generation of solar cells have been categorized.

First Generation: Wafer based solar cells

Fig. 5: Image of First Generation Photovoltaic Cell

The first generation photovoltaic cell consists of a large-area, single-crystal, single layer p-n junction diode, capable of generating usable electrical energy from light sources with the wavelengths of sunlight. These cells are typically made using a diffusion process with silicon wafers. These silicon wafers – based Solar cells are the dominant technology in the commercial production of Solar cells, accounting for more than 85% of the terrestrial Solar cell market.

Photovoltaic Cells Contd.

Second Generation: Thin Film

Fig. 6: Second Generation Photovoltaic Cell

These cells are based on the use of thin epitaxial (Epitaxy refers to the method of depositing a monocrystalline film on a monocrystalline substrate) deposits of semiconductors on lattice-matched wafers. (Matching of lattice structures between two different semiconductor materials, allows forming of a region of band gap change in the material without introducing a change in crystal structure.)

There are two classes of epitaxial photovoltaic cells – space and terrestrial. Space cells typically have higher efficiencies (28-30%) in production, but have a higher cost per watt. Though thin-film cells have been developed using lower-cost processes, they have lower efficiencies (7-9%). There are currently a number of technologies and semiconductor materials under investigation or in mass production. Examples include amorphous silicon, polycrystalline silicon, micro-crystalline silicon, cadmium telluride, copper indium selenide/sulfide amongst others.

An advantage of thin-film technology is reduced mass that allows fitting panels on light or flexible materials, even on textiles. Second generation solar cells now comprise a small segment of the terrestrial photovoltaic market, and approximately 90% of the space market.

Third-generation: photovoltaic cell

Improving performance while maintaining low costs the next generation of cells is aimed at enhancing the low electrical performance of the second generation cells while keeping the costs low. They do not rely on a traditional p-n junction to separate photo-generated charge carriers. Few approaches used in this are Multijunction cells, nano – crystal cells, dye – sensitized cells, polymer cells, Modifying incident spectrum (concentration), Sue of excess thermal generation to enhance voltage, For space applications quantum well devices (quantum dots, quantum ropes, etc.) and devices incorporating carbon nanotubes are being studied – with a potential up to 45% production efficiency.

Fourth Generation: Photovoltaic cell
This hypothetical generation of solar cells may consist of composite photovoltaic technology, in which polymers with nano-particles can be mixed together to make a single multi-spectrum layer. The multi-spectrum layers can be stacked to make multi-spectrum solar cells more efficient and cheaper.

Out of the four generations listed above, first two have been commercialized. Bulk of the photovoltaic modules deployed so far consist of crystalline silicon. The efficiency of crystalline silicon modules varies from 17-22%, though theoretical limit is around 29%. Using these modules, large solar farms connected to grid, standalone power stations to electrify villages and small localities have been established.

Solar Energy & World

Today people have realized the importance and benefits of solar energy. Hence, they have started utilizing the solar energy. Now, solar energy has become an emerging market. Based on a study by a survey by Ernst & Young, one of the worlds’ leading professional services organizations, which has made a study on the world leading solar energy producers and given ranks based on market attractiveness.

Solar Energy Top 10

1.   USA
2.   India
3.   China
4.   Spain
5.   Italy
6.   Greece
7.   Japan
8.   Australia
9. France
10. Morocco

Recent news related to Solar Energy

· The UK Government has announced it will invest over £200 million on innovation centers focusing on green and renewable energy, and £20m into two clean technology funds.

· The Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) has developed a roll-to-roll system depositing CIGS solar thin-film on a 25 µm thin polymer film with 10% efficiency.

· Solar World is supplying solar photovoltaic (PV) panels to a 33 MW installation at a 300 acres site in southeast Ontario, Canada.

· The rapid increase in the construction of photovoltaic (PV), grid-tied solar farms has created a surge in the demand for utility-grade inverters. These inverters convert the DC current generated by the PV cells into low voltage AC power. The inverters are coupled to a distribution transformer then stepped up to medium voltage, generally 12 kV or 34.5 kV, for collection in an interconnect substation. The interconnect substation steps the voltage up again to the utility transmission voltage, generally in the 69 kV to 345 kV range.

· According to the analysis conducted by German Advisory Council (WBGU) conclude that a major contribution by solar energy to global energy needs in the long term in future years 2050 to 2100.

Top Ten Solar Energy companies

S. No.	Name of the company	Production in Mw
1	Q-Cell	1.57 GW
2	Sharp Solar	1.00 GW
3	SunTech-Power	2.00 GW
4	First Solar	1.00 GW
5	Kyocera	650 MW
6	Motech Solar	600 MW
7	SolarWorld	780 MW
8	Yingli Solar	600 MW
9	Sanyo	600 MW
10	JA Solar Holdings	550 MW

Conclusion

The day is no far away when fossil fuels will finish up. Hence, it’s the time to switch over to a cleaner and efficient source of energy so that humans need not to suffer from any crisis. The governments of various nation is supporting this industry in the form of tax relaxation, subsidies, financial aids, etc. even individuals shouldn’t hesitate to invest in this because at the end of the day we helped ourselves, we contributed for our children and repaid to our parents.