Solar panels are installed by people who care about the environment. A side benefit is that while you are doing something positive for the environment you are also saving money. You are no longer dependent on an electricity provider because you generate your own energy!

What are solar panels?
There are 3 main types of solar cells.
Mono-crystalline silicon is the most efficient and produces the smallest solar cells, and therefore the smallest panels.
Mono-crystalline panels produce the smallest solar cells, conserving your rooftop real estate. Tried and tested, some mono-crystalline panel installations commissioned in the 1970′s are still operational today and have even withstood the harsh conditions of space!
Poly-crystalline (or multi-crystalline) silicon produces the next most efficient type of cells and are a popular choice.
Polycrystalline solar panels are one of the most popular choices for grid connect and off grid solar power systems
Amorphous (or thin-film) silicon uses the least amount of silicon and also produces the least efficient solar cells. This means thin film system take up more area than the other two; an important factor to consider in relation to possible future upgrades; i.e. if you’ll have enough space left to do so.
Mono-crystalline and multi-crystalline work very well in bright cool conditions, whereas amorphous (thin-film) silicon will be more efficient at higher temperatures, We generally recommend mono-crystalline or multi-crystalline for large unshaded roofs amorphous panels for roofs with partial shading.
Do not install solar panels on fully shaded roofs as regardless of the technology currently in use, a solar panel in full shade will only generate a small fraction of its rated capacity.
How do solar panels work?
Silicon atoms have room for eight electrons in their outer bands, but only carry four in their natural state. This means there is room for four more electrons. If one silicon atom contacts another silicon atom, each receives the other atom’s four electrons. This creates a strong bond, but there is no positive or negative charge because the eight electrons satisfy the atoms’ needs. Silicon atoms can combine for years to result in a large piece of pure silicon. This material is used to form the plates of solar panels.
Here’s where science enters the picture. Two plates of pure silicon would not generate electricity in solar panels, because they have no positive or negative charge. Solar panels are created by combining silicon with other elements that do have positive or negative charges.
Phosphorus, for example, has five electrons to offer to other atoms. If silicon and phosphorus are combined chemically, the result is a stable eight electrons with an additional free electron along for the ride. It can’t leave, because it is bonded to the other phosphorus atoms, but it isn’t needed by the silicon. Therefore, this new silicon/phosphorus plate is considered to be negatively charged.
In order for electricity to flow, a positive charge must also be created. This is achieved in solar panels by combining silicon with an element such as boron, which only has three electrons to offer. A silicon/boron plate still has one spot left for another electron. This means the plate has a positive charge. The two plates are sandwiched together in solar panels, with conductive wires running between them.
With the two plates in place, it’s now time to bring in the ‘solar’ aspect of solar panels. Natural sunlight sends out many different particles of energy, but the one we’re most interested in is called a photon. A photon essentially acts like a moving hammer. When the negative plates of solar cells are pointed at a proper angle to the sun, photons bombard the silicon/phosphorus atoms.
Eventually, the 9th electron, which wants to be free anyway, is knocked off the outer ring. This electron doesn’t remain free for long, since the positive silicon/boron plate draws it into the open spot on its own outer band. As the sun’s photons break off more electrons, electricity is generated. The electricity generated by one solar cell is not very impressive, but when all of the conductive wires draw the free electrons away from the plates, there is enough electricity to power low amperage motors or other electronics. Whatever electrons are not used or lost to the air are returned to the negative plate and the entire process begins again.

For more information visit www.solarpanels-howtomake.com

With fears of carbon dioxide causing global warming and diminishing supplies of fossil fuels, a looming energy crisis is affecting all countries. As a consequence, a great deal of world-wide effort is going into the development of alternative energy technologies. At present, wind, hydro and geothermal are becoming well established with more niche roles for tidal and solar. The latter technology has two common forms, firstly solar water heating, and secondly photo voltaic (PV) solar electricity generation.

Solar water heating

For domestic hot water needs, solar hot water is starting to make significant inroads in Europe and Turkey but very little impact in the rest of the world, with the exception of China. This country has more than 70% of the worlds solar water heating capacity, assisted greatly by government subsidy and promotion. (REN21 Renewables 2010 Global Status Report)

Photovoltaic Solar electricity

PV Solar from the above mentioned report shows a different picture, with Germany having the dominant usage at 47%, whereas China had less than a few percent at the end of 2009. However, whilst the power from PV in total is no more than about 15% of that of solar water, its use is spread more evenly throughout the world.

There is much research into new and improved photo voltaic technologies as well as rapidly increasing use of existing commercial products. Traditionally the cost per watt of this technology has far exceeded that of conventional power generation and not surprisingly the main development thrusts are increase in efficiency and reductions in cell costs.

The operation of a PV solar cell is based on the photovoltaic effect, when the capture of a light photon photoexcites an electron to a higher energy level. The cell is constructed as a PN junction from semi-conductor material, like the common diode, in which photoexcited electrons preferentially diffuse across the junction barrier and flow around an external circuit providing power.

Silicon single crystal solar cells

Traditional cells are made from single crystal Silicon or c-Si and produce about 0.5Volts per cell, with typical power efficiency of 15-17%. The maximum theoretical efficiency of conversion from light energy to electrical energy is about 30% and recent developments have produced examples exceeding 24%. Clearly, with an output of a mere 0.5V, numerous cells have to be connected together to produce enough voltage to work with. This is done in the solar panel where the cells are arranged in a matrix, encapsulated in transparent EVA, usually behind a glass front cover and sealed into an outer frame. The back of the panel is sealed with a polymer film backsheet, selected for its electrical insulation, toughness, and importantly, lack of water permeation. These devices are expected to last for 25 years or more and corrosion damage to the electrical contacts by water is one of the biggest threats.

Thin film solar cells

At the time of writing, c-Si PV solar cells are the most dominant type in the market by far, occupying over 80% of the market. However this position is likely to change soon with the advances being made with thin film solar cells, which form the remainder of the market. These newer cells are made from other types of semiconductors and are based on an amorphous rather than crystalline material, which is assembled in thin layers allowing it to be flexible.

There are at least three different common types in production, these being, amorphous Si (a-Si), Cadmium Teluride (CdTe), and Copper Indium Gallium deSelenide (CIGS). Mention should also be made at this juncture of dye sensitised solar cells (DSSC), which are also classified as thin film but are not PN junction based. These are referred to as photoelectrochemical cells, and were invented by Michael Grazel. As mentioned for c-Si cells, this type also needs exemplary environmental protection, with emphasis on water ingress through permeation.

While thin film cells are in general less efficient than the c-Si variety, being in the 11-13% region at present, they have some major advantages over their predecessors. Much larger single cells can be made, not being constrained by the size of a single crystal, at markedly lower cost, and their flexibility allows considerable diversity in mounting. It is possible to print the materials, which can be made into a form of inks, in layers onto wide continuous strips a metre or more wide. The resulting rolls can then be deployed in large solar collecting arrays and can even be used as an outer skin on buildings. Not surprisingly, given the volume of research into improving these thin film variants, their market share is expected to soar over the next few years.

Solar panel backsheets

Polymer film backsheets which are used for c-Si panels are often based on polyvinyl fluoride (PVF), which is frequently laminated with other materials for improved properties. The DuPont PVF material known as Tedlar is a favourite and is used to sandwich a layer of polyester film to form TPT or combined with EVA as TPE. Numerous alternative polymers are available offering trade-offs between performance/lifetime and cost. Related materials are available for use on thin film solar products, with perhaps more emphasis on performance because of the need to keep thickness down to maintain flexibility.

Water vapour permeation measurement for PV Solar Cell packaging

Clearly, the future for solar photo voltaic electricity generation looks optimistic and importantly, a major growth area. It is also likely to be a growth market for the solar cell manufacturers, as well as the equipment and instrumentation companies to support the cell production. The ability to provide definitive water vapour transmission rate (WVTR) data for production backsheet materials on a routine QA basis, is key to a reliable PV Solar Cell product. Such WVTR measurement can be provided by the Systech Illinois 7000 water vapour permeation analyser, capable of measuring from as low as 0.002 g/m/day.

Author bio

Bryan Cummings is the Managing Director for Systech Illinois, which specialises in online, portable and laboratory gas analysis equipment. With 25 years as one of the leading experts in gas and moisture measurement, Systech Illinois application and technology knowledge provides efficient gas analysis solutions in many industry sectors worldwide.

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