What is Solar?

Solar energy is the cleanest and most inexhaustible of all known energy sources. Solar radiation is the heat, light and other radiation that is emitted form the sun. Solar radiation contains huge amounts of energy and is responsible for almost all the natural processes on earth. The suns energy, although plentiful, has been hard to directly harness until recently.
Solar Energy can be classified into two categories, Thermal and Light. Photo –voltaic cells (PV) use semiconductor-based technology to convert light energy directly into an electric current that can either be used immediately, or stored in a battery, for later use.

PV panels are now becoming widely used, as they are very versatile, and can be easily mounted on buildings and other structures. They can provide a clean, renewable energy source, which can supplement and thus minimize the use of mains electricity supply. In regions without main electricity supply such as remote communities, emergency phones etc, PV energy can provide a reliable supply of electricity. The disadvantage of PV panels is their high cost and relatively low energy conversion rate (only 13-15%). Thermal solar on the other hand has average efficiency levels 4-5 times that of PV, and is therefore much cheaper per unit of energy produced. 

Thermal energy can be used to passively heat buildings through the use of certain building materials and architectural design, or used directly to heat water for household use. In many regions, solar water heaters are now a viable supplement or alternative to electric or gas hot water production.

Thermal energy obtained form the sun can be used for a number of applications including producing hot water, space heating and even cooling via use of absorption chilling technology.

Using solar and other forms of renewable energy reduces reliance on fossil fuels for energy production, thus directly reducing CO₂ emissions. CO₂ emissions contribute to global warming, an environmental issue which is now of great concern. The average household can reduce CO₂ emissions by as much as 20% by installing solar collector.

Flat plate thermal solar collectors have been in use for several decades, but only in relatively small numbers, particularly in Western countries. Evacuated tubes have also been in use for more than 20 years, but have been much more expensive than flat plate, and therefore only hosen for high temperature applications or by those with money.

In recent years the production volume of evacuated tubes has exploded, resulting in greatly lower manufacturing and material costs. The result is that evacuated tubes are now similar in price to flat plate, but with the insulating benefits of the evacuated tube, they are set to become the default choice for thermal solar applications worldwide.

The meaning of Solar Cell or PV

Solar Cell, PV and photovoltaic cell are different terms that are used to describe the same word, photovoltaic. The term photovoltaic comes from two words photo (light) and voltaic (voltage). The photovoltaic effect is the transformation of the sun's rays into electricity. The scientific investigation of the photovoltaic effect started in 1839, but the efficient solar cell could not be made. Until 1954, a silicon solar cell was developed and this kind of solar cell was used in specialized applications as satellites from 1959.

Conclusion
 

Solar cell is a device that is made up of semiconductor materials such as silicon, gallium arsenide, indium phosphide, cadmium telluride and copper indium diselenide, etc. that absorbs sunlight and converts them into electrical carrier, then separate to electrons and holes to produce energy at positive/negative junctions. If the positive and negative junctions of solar cell are connected to DC electrical equipment, it is workable.

Types of solar cell

• Two types of crystalline silicon solar cell are single crystalline silicon solar cell, which is known as monocrystalline silicon solar cell, made by slicing wafers and polycrystalline silicon solar cell, made by sawing a block of silicon first into bars and then wafers. The crystalline silicon solar cell is very hard and thin.
• Amorphous silicon solar cell is the best developed of the thin film technology, which its thickness is 0.5 micron (0.0005 millimeter) and lightweight with its efficiency of 5-10%.
• Other semiconductors such as gallium arsenide, cadmium telluride and copper indium diselenide, etc. have both of single crystalline and of polycrystalline. The solar cell, which made by gallium arsenide is high efficiency about 20-25%.

The solar cell structure

The most type of semiconductor currently in use is silicon crystal, which is the inexpensive and most available semiconductor. Because silicon crystals are laminated into p-type and n-type region, it is used to make the solar cell. The silicon has been smelt and purified until it becomes crystals. Then doping atoms are to create a p-type and n-type region. P-type doping, the creation of excess holes, is achieved by incorporating and atoms with the boron and n-type doping, the creation of excess electrons, is achieved by incorporating an atom with the phosphorus. Once a p-n junction is created, electrical contacts are made to the front and the back of the cell by evaporation or screen-printing metal onto the wafer. The rear of the wafer can be completely covered by metal, the front has a grid pattern or thin lines of metal and the back has the metal, which block out the sun from the silicon.  
 

How solar cell works

When the sunlight strikes the solar cell surface, which consists of two types of materials, p-type and n-type semiconductor, and the cell creates charge carrier as electrons and holes. The internal field produced by junction separates some of the positive charges (holes) from the negative charges (electrons). The holes are swept into the positive or p-layer and the electrons are swept into the negative or n-layer. When a circuit is made, the free electrons have to pass through the load to recombine with the positive holes, current can be produced from the cells under illumination.  
 

For example, -a silicon solar cell, which its diameter is 4 inch typically, produces from 2 to 3 amperes and approximately 0.6 volts. Because the output current of each cell is very low, a number of cells are wired together to make a module to reach the required current. And these modules are wired into large arrays. The solar arrays wiring depend on current and voltage requirement.  

• If the solar arrays are wired in parallel, the output current increases.

• If the solar arrays are wired in series, the output voltage increases.  

Manufacture solar cells

The single crystal or monocrystalline solar cell has the process as below:  

The melt silicon has been grown at 1400 °C then drawn the crystal from the melted silicon by slowly decreasing the temperature until become a large single crystal ingot. The large single crystal ingots are sliced into the single crystal wafers.

The single crystal wafers were doping atoms to create a p-type and n-type region and thereby producing a p-n junction. This doping can be done by high temperature diffusion (900-1000 °C), where the wafers are placed in a furnace with the dopant to introduced as a vapour.

The polycrystalline solar cell has the process as below:  

The molten silicon is poured into a mould and allowed to set. Then it is sliced into   the wafers.  

The polycrystalline wafers were doping to create a p-type, n-type region and p-n junction same as the single  crystal solar cell process.  

The amorphous solar cell has the process as below:
 

The silane gas (SiH₄) is reacted by Plasma Chemical Vapor Deposition device. The amorphous silicon is made by depositing silicon onto glass or another substrate material from a reactive gas. The layer thickness amounts to less than 1 micron (0.001 millimeter).  

When the silane gas reaction the dopants as phosphine and diborane are included to create a p-type,n-type region and p-n junction.

The p-n junction is made up of translucent junction as indium tin oxide.

The gallium arsenide solar cell has the process as below: 

The gallium arsenide crystal has been grown by a Liquid Phase Epitaxy furnace.

The p-type and n-type region are created by Molecular Beam Epitaxy device.  

Main features of solar cell

• Use the natural power, sunlight, which is clean and non-polluting 
• Efficiently use a renewable power source and no limiting
• Able to be installed anywhere to produce and take direct current
• Use no fuel other than sunlight
• No burning and therefore no air and water pollution

• Give off no waste and therefore harmless environment  

• No moving parts so there is no mechanical noise being operation
• Minimal maintenance requirement
• Long lifespan and stable efficiency
• Light weight, easy to install and transportable
• With the modular characteristic, it can be constructed any sizes as required
• Reduce collection of gases such as carbon monoxide, sulfur dioxide, hydrocarbon   and nitrogen, etc., which generated from fuel, coal and fossil fuel burning power plants. All decrease the impacts of energy on the environment like greenhouse effect, global warming, acid rain and air pollution, etc.  

The multifarious advantages of Solar Power

Nowadays, most of us use equipments, machines and tools to reduce our loads and make us more convenient. They are used in the office, industry or at home. The more varieties of electronic and electrical products, the more demand of electricity.

There are many power sources to generate electricity such as water turbine generator, wind turbines, steam turbines generator, coal, oil, fossil fuel, natural gas and nuclear power. As mentioned above, more and more electricity is demanded whilst the power sources will be a lack of power in the near future. During the process of electricity production, wastes, toxic gases (Carbon dioxide, Carbon monoxide, Sulfur dioxide) or smokes may be generated. These are one of factors that cause air pollution, acid rain and global warming. Besides, the nuclear power is not safe for uses. As long as the power demand remains consistent, the renewable energy source must be replaced. Especially, it is clean and environmental friendly. The solar power is one of the solution and being studied by several researchers and research groups.

The major component for producing the solar energy is solar cell or the other term is PV. PV is an abbreviation for Photovoltaic that means voltage generated from light or sunlight. Solar cell is made up of two crystalline silicon wafers. The rear of the wafer is doping with the phosphorous to create the electrical charges, electrons. When sunlight strikes the exposed surface, electrons move toward the inner wafer, which is doping with the boron to create the electrical charges and holes. There are different in potential between two layers. To produce sufficient electricity, a number of cells are wired together to becomes a module and these modules are wired into large arrays. The principle work of solar power is the sunlight is converted into the electricity and be charges the batteries for any applications or other purposes.

There are multifarious advantages of solar power; example include it is the natural power, free, unlimited, clean and non-polluting, no moving parts being operation, minimal maintenance need and easy to use. Moreover, it can be applied to everywhere that sunlight is visible, the hill, the island, the sea or even in outer space.

At this time, solar cell can be used in various applications including calculators, watches, microwave repeater stations, lighthouses, traffic lights, street lightings, motor boats, airplanes, water pumping for irrigations and satellites, etc. In several countries, the solar power stations are widely used to provide electrical power. In Thailand, the solar power stations are constructed for rural electrifications. Additionally, several groups involved with the solar power join the cooperation and extensively publicize about the solar power. Also, research and develop the solar cell.

Although, today we can produce electricity from the sun, unlimited power resource, the power research and development team still continuously progress to optimize the resources.  
 

Solar Home Systems

Bright Sunshine in your home

Solar home system is power sources for home appliances and suitable for household purposes. The stand-alone Solar Home lighting system is meant for illuminating homes using solar energy. The custom designed system has 9 watts CFL/FTL lamps and has been designed to operate for 4 hours daily with autonomy of 3 days.

This system has been engineered to light up places where grid power is not available. Solar home lighting system is autonomous and maintenance free. There is no operating cost in terms of electricity consumption and is environment friendly.

Features:

• High reliability and durability  
• Overcharge and deep discharge protection
• Protected against short circuit  
• Low maintenance lead acid tubular battery

Typical Applications:

• Offices   
• Schools/Collages
• Residential Houses
• Hospitals
• Industries/Factories  

There are several sets as follows:

Stand-alone Solar Systems

Stand-alone solar system is suitable for any areas where utility power line is not available. This system requires a charge controller to charge storage batteries for discharge to run electrical appliances.

Street Lighting Systems

Lighting up the dark alleys

Solar lighting system is suitable for outdoor lighting such as street lighting. The stand alone
Solar Street Lighting System is used to illuminate dark streets using solar energy. The solar PV Module functions as a dusk sensor for automatically switching OFF at sunrise. The system has been designed to operate form dusk to dawn with autonomy of 5 days and ease of installation and maintenance.  
 

Features:  
 

	High reliability and durability
	Overcharge and deep discharge protection
	Protected against short circuit
	Automatic switch in and off
	Temperature compensated battery charging

Typical Applications:
 

	Rural areas and villages
	Farms and Resorts
	Parks and Playgrounds
	Gardens
	Forest Area

Solar Water Pump System

The green way to grow green

Solar pump system is designed to substitute power from generator or utility power line. Its application is to pump water from reservoir and convey the water to point of use. Solar Pump system has been designed for pumping water where conventional grid supply is not available. Depending upon the depth of the water level and volume of water to be pumped, it can be designed and integrate both, submersible and non-submersible pumps of different capacities. Once installed, it does not require skilled personnel to maintain and operate the system. There is no running cost in terms of electricity consumption and is environment friendly. 

Features:

• High reliability and durability  
•  Maintenance free  
• One time investment  
• Stand-alone system  
• No fuel needed  
• No use of battery  
• Unattached operation

Typical Applications:

• Homes
• Schools
• Rural areas  
• Small-scale micro-irrigation  
• Gardens

Solar Water Pumping

Pum