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Hi everyone.
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Welcome back to be solar energy course.
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today in this block
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We should focus on the central character of the PVsystem which is the PV module.
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Before I start I want to touch upon the difference between the terms the solar modules and solar panel.
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You must have observed that a lot of people use these terms interchangeably but what is the exact difference.
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First the solar module is an interconnection of solar cells as you have seen before in this genetic
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name given to any kind of packaging for any interconnection of solar cell means "the solar module is irrespective
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of technology of any packaging and an interconnection of solar cell will also be called module.
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But the terms of solar panel is a bit more exclusive for the rectangular, rigid packaging.
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with a typical encapsulation for example.
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Most standard crystalline modules are called solar panel 
all solar panel are solar module but the
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converse is not true.
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For a moment the thin film silicon solar cell that is packaged to add flexible lemon is a solar module.
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but it is not entirely accurate to call it "solar panel" 
note that in most cases the commercial
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module being used as panel and the module are called panel in common usage hence forced I might use
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the term solar panel and modules interchangeably as well.
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But I hope you understand the exact difference between the two.
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So let us move on to the module level concept.
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First of all PV module or solar module can be divided in two main category.
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The first category is thin film solar cells.
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The second category is crystalline silicon or C-si  the crystalline silicon forms the basis of mono
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and the poly-crystalline silicon solar cells.
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lets start with crystalline silicone C-si crystalline silicon C-si almost 90 per cent of
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the world photovoltaic today are based on some variation of silicon in 2011 about 95 percent of all shipments
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by US manufacturers to residential sector were crystalline silicon solar panel so set up and use
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the silicon used in PV takes many forms.
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the main difference is the purities of the silicon
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But what does silicon's purities really mean.
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the more perfectly aligns the silicon modules are the better solar cells will be at converting solar
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energy or sunlight into electricity which uses processes called the photoelectric effect
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the efficiency of solar panel goes hand-in-hand with purity but the process used to enhance the puritiy
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of silicon are expensive. efficiency shouldn't be your primary concern as you will later discover that
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as a cost and space efficiency are the determining factors for most people. lets start with
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the mono crystalline silicon solar cell.
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Solar cells made of monocrystalline also called single crystalline silicon 
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are quite easily recognizable by an external event color and uniform look indicating high purity
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silicon.
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As you can see in this picture.
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monocrystalline solar cells are made out of silicon in of ingots which are cylindrical in shape
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to optimize the performance and lower costs of single monocrystaline  Solar cell, four sides are 
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cut out of the cylindrical ingots to made silicon wafer which is what gives the monocrystaline 
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solar cell
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Their characteristic look. A good way to separate mono and poly crystalline solar panel is that
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polycrystalline solar cell.
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looks perfectly rectangular with no rounded edges.
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But what is the main advantage of the monocrystallions silicon solar cell.
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The main advantage is the monocrystalline solar panel has the highest efficiency rates since they are
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made out of high grade silicone.
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The efficiency rate of mono crystalline solar panels are typically between 15 and 20 percent but 
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Sunpower company produces the highest efficiency solar panel on a U.S. market today.
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their E20 series provide panel better conversion efficiencies of up to 20.1 percent
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also they has now released the X series at record breaking efficiency of 21.5 percent
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monocrystallion silicon solar panel are space efficient since these solar panels yield the highest power
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outputs, they also requires at the least amount of space compared to any other types of 
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monocrystalline
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soar panels produces up to four times the amount of electricity as in thin film solar panel 
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Monocrystalline solar panel live the longest. Most solar panel manufacturer put a 25 years.
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warranty on their monocrystalline solar panels
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monocrystalline silicon solar cell tends to perform better than similarly rated other crystalline
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solar panel at low light conditions but what is the main disadvantage of this type.
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First monocrystalline solar panel are the most expensive. From a financial standpoint,
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a solar panels that is made of polycrystalline silicon can be better choice for homeworks and the
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solar panel is partially covered with the shade, dirt or even snow.
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The entire circuit can break down consider getting a micro inverter instead of center a single inverter
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if you think coverage will be a problem.
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The micro inverter will make sure that not the entire solar array is affected by shading issues
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with only one of the solar panels
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the Czochralski process is used to produce monocrystalline silicon.
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Its result in large cylindrical ingots means the four sides are cut out of the ingots to make
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silicon wafers
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this means an amount of the original silicon ends up as waste
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monocrystalline solar panels tend to be more efficient in warm weather
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But performance suffers as temperature goes up but less than polycrystalline  solar panels.
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For most home owners in temperature is not that concern.
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Now we have already finished the main types which it is silicon crystalline solar cell especially 
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monocrystalline type in the next lecture we are going to discuss the polycrystalline silicon
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solar cell of the crystalline of the crystalline silicon solar cell so see you in the next lecture.