when the p-type & n-type semiconductors are brought into contact, the magic begins. the crazy electrons at the n-side see the positive holes (p-side) and are fully attracted, they rush towards the holes without a word. however, at the junction between the 2 materials, the electrons and holes attract each other and form a barrier. this barrier make it hard for the electrons to penetrate to the other side. once equilibrium has reached, the barrier acts like a forward diode, making the electrons to move from p-side to n-side but not the other way round.
when a photon from sunlight strike on the surface & move towards the junction, they break apart and the electron is send to the n-side and the hole to p-side, making it more imbalance. now when an external circuit is connected between the n-side and p-side, the resistance is relative low and electrons will tend to flow from n-side to p-side. since current is generated at the opposite direction to electron flow and voltage is produced by the cell electric field (due to p and n-side semiconductor producing an electric field) , power is obtained. (P=I*V)
Thursday 11 July 2013
Thursday 27 June 2013
Solar cell
Solar energy seems to be one of the most promising green energy in the future. We know that the sun is a powerful and huge resource, easily overpower the oil reserves in the current state. Solar energy usually is related to solar cell. This cell allows the conversion of light (usually sunlight in the context to be 'green' apposed the artificial or lamp light generated by fossil fuels) directly to electrical energy without an external voltage source. You may possibly seen the cells in different forms, such as modules from which the cells are framed together to form a larger pieces and arrays which are the combination of modules, usually used in power plants etc. Also worth to mention solar energy is applicable to almost everything as long as there is light, from the cells in a calculator to those installed on the roof top of a high rise building.
Now let's have a look at the mechanism of a solar cell. Silicon is widely used in solar cell due to its property, it has 14 electrons in 3 different shells with a electrical configuration of 1s2 2s2 2p6 3s2 3p2. To become stable, it will require another 4 electrons in the outer shell. A pure Si is not what we want because when it is in stable state, the conductivity is very low due to the absence of free electrons. As contrast to most cases in which impurities are to be avoided, to make things work like a charm, we add impurities into the Si, with a ratio of 1 in a million, this process is also known as doping. To get a P-type semiconductor, Boron is usually added. Boron has 3 outer electrons, hence an additional hole ( a positive charge) is created. In the contrary, Phosphorous is added to obtain an N-type semiconductor. Phosphorous has 5 valance electrons, but only 4 will bond with Si atoms, the other 1 will have no one to bond with and is left alone. When there is more electrons, an N-type material is produced as in the latter case.
to be continued...
Now let's have a look at the mechanism of a solar cell. Silicon is widely used in solar cell due to its property, it has 14 electrons in 3 different shells with a electrical configuration of 1s2 2s2 2p6 3s2 3p2. To become stable, it will require another 4 electrons in the outer shell. A pure Si is not what we want because when it is in stable state, the conductivity is very low due to the absence of free electrons. As contrast to most cases in which impurities are to be avoided, to make things work like a charm, we add impurities into the Si, with a ratio of 1 in a million, this process is also known as doping. To get a P-type semiconductor, Boron is usually added. Boron has 3 outer electrons, hence an additional hole ( a positive charge) is created. In the contrary, Phosphorous is added to obtain an N-type semiconductor. Phosphorous has 5 valance electrons, but only 4 will bond with Si atoms, the other 1 will have no one to bond with and is left alone. When there is more electrons, an N-type material is produced as in the latter case.
to be continued...
Friday 14 June 2013
Kite energy cont
It is a two edged sword, previously we have talked about the good side of this energy system, today lets have a look on the other side of it.
Kite energy as we know, need to be launch and pull back every time. You have to launch it so it could fly up high in the sky, and after finish using or when the weather is really bad (eg thunderstorm) , you have to keep it back otherwise it might be struck by thunder and damaged.
Imagine when the rope suddenly snap off and the kite drop into someone inventory or hurt a passenger, who is gonna held responsibility for the accident? How would the insurance company handle the case? Cases like this need to be considered and the potential hazard it will cause must be minimized if not eliminated.
Since the kite can reach up to few hundred meters, we couldn't really drive its direction. This means that it might be floating here and there depending on the wind direction. So it usually requires some lightening like what we usually see in a lighthouse or high-rise cable station. This is to make sure it is visible to aircraft. Besides, it must be operated away from the airport to prevent any accident, collision and signal interruption.
Kite energy as we know, need to be launch and pull back every time. You have to launch it so it could fly up high in the sky, and after finish using or when the weather is really bad (eg thunderstorm) , you have to keep it back otherwise it might be struck by thunder and damaged.
Imagine when the rope suddenly snap off and the kite drop into someone inventory or hurt a passenger, who is gonna held responsibility for the accident? How would the insurance company handle the case? Cases like this need to be considered and the potential hazard it will cause must be minimized if not eliminated.
Since the kite can reach up to few hundred meters, we couldn't really drive its direction. This means that it might be floating here and there depending on the wind direction. So it usually requires some lightening like what we usually see in a lighthouse or high-rise cable station. This is to make sure it is visible to aircraft. Besides, it must be operated away from the airport to prevent any accident, collision and signal interruption.
Wednesday 12 June 2013
Kite energy
ok so there are many different kind of green energy available, some are 'rare' but interesting, like using kite to produce energy but i believe the concept is near to that of wind turbine, and it is commonly called kite energy system. From the name itself, the concept is launching a kite into high altitudes to enable it to generate power from wind. So the question is why do we need this kite system instead of utilising the well developed wind turbine? Well there must be some reasons why engineers and companies are looking into this new system.
A kite is basically supports by a string or rope. It is cheap to manufacture compared to a concrete wind tower. In order to produce more energy, a wind turbine has large turbines (up to few meters) to increase the surface area. Similar to wind turbine, a kite can be build to have huge surface area to perceive more wind. As long as the string is strong enough to support the tension, weight, etc, then it can be produced. Next, a wind turbine is stationary, it couldn't be elevated or lowered, thus it must be build in a strategic location. In contrast, a kite poses high flexibility, it can be raised or lowered and able to be launched at different locations as long as you feel appropriate, hence it should be more versatile and flying higher means it could receive more consistent wind.
to be continued
A kite is basically supports by a string or rope. It is cheap to manufacture compared to a concrete wind tower. In order to produce more energy, a wind turbine has large turbines (up to few meters) to increase the surface area. Similar to wind turbine, a kite can be build to have huge surface area to perceive more wind. As long as the string is strong enough to support the tension, weight, etc, then it can be produced. Next, a wind turbine is stationary, it couldn't be elevated or lowered, thus it must be build in a strategic location. In contrast, a kite poses high flexibility, it can be raised or lowered and able to be launched at different locations as long as you feel appropriate, hence it should be more versatile and flying higher means it could receive more consistent wind.
to be continued
Wednesday 5 June 2013
Green Energy
today the world is moving towards green, from building to lifestyle to energy, everything is pushing towards a greener tomorrow for our own benefits as well as the future generations.
The term green energy should be familiar to most of you out there, you can easily see articles or advertisement in the newspaper everyday. But one might question why is it so important to turn green? Well the most generic answer will be to protect the environment from pollution etc.. However from my point of view, the main reason is very much due to the depletion of fossil fuels which are generally non-recyclable, meaning once they are consumed, they decrease in the volume. So as the world reserves are decreasing, that means the price will be increasing in the near future if not now, and that will be a thunder that strikes most of the consumers, especially to businessmen at a means of decreasing their profits. Remember this is just a game of number, and the results might be a huge one. In view of this, organisations and entrepreneurs started to fund for development or R&D for something that could overcome their worries. So After years of determination, engineers & scientists finally came out with green energy which are also known as renewable energy.
For sure, this is a great news to the funders because from the terms itself, the energy is basically free of charge since the main sources are usually the Sun, wind, wave, etc and you don't really have to pay to get them. For them, free means no expenditure and this will directly impact on the total income. The environmentalists were excited initially because this renewable energy is 'clean', however later they discovered that the energy used to process the devices are not actually pleasing. Imagine at the current state, most countries are still heavily depending on fossil fuel generated electricity, and every single energy comes from fossil fuel again.
To be continue...
The term green energy should be familiar to most of you out there, you can easily see articles or advertisement in the newspaper everyday. But one might question why is it so important to turn green? Well the most generic answer will be to protect the environment from pollution etc.. However from my point of view, the main reason is very much due to the depletion of fossil fuels which are generally non-recyclable, meaning once they are consumed, they decrease in the volume. So as the world reserves are decreasing, that means the price will be increasing in the near future if not now, and that will be a thunder that strikes most of the consumers, especially to businessmen at a means of decreasing their profits. Remember this is just a game of number, and the results might be a huge one. In view of this, organisations and entrepreneurs started to fund for development or R&D for something that could overcome their worries. So After years of determination, engineers & scientists finally came out with green energy which are also known as renewable energy.
For sure, this is a great news to the funders because from the terms itself, the energy is basically free of charge since the main sources are usually the Sun, wind, wave, etc and you don't really have to pay to get them. For them, free means no expenditure and this will directly impact on the total income. The environmentalists were excited initially because this renewable energy is 'clean', however later they discovered that the energy used to process the devices are not actually pleasing. Imagine at the current state, most countries are still heavily depending on fossil fuel generated electricity, and every single energy comes from fossil fuel again.
To be continue...
Sunday 26 May 2013
Adhesive Types
Adhesive bonding is one of the most common joining technology available. you can easily purchase a cyanoarylate (commonly known as super glue) from a stationery shop to glue your broken mug with a couple of dollars. It is easy to used, and it serves well in most condition. There are still many types of adhesive if this isn't suitable for you, such as epoxy, anaerobic, etc...
Lets first have a look at epoxy, which usually consists of epoxy resin + hardener. It is easy to use, simply mix the resin with the hardener together so that the end parts of the adhesive (diepoxy and diaming) are joined, and apply them on adherents. It wouldn't take long to polymerise, so you have to act fast before they cure, or simply make everything ready before you mix them togethher. However you may find that it is very hard to remove the adhesive from the substrates once it cured, so always act wisely and carefully.
The next one, anaerobic, which means 'no oxygen or lack of oxygen'. So the polymerisation basically happens when there is little or no oxygen at the surrounding. Apply the adhesive on the adherent, but the adhesive will remain as it is when there is oxygen around. But once there is a lack of oxygen, the process initiates and it happens just within a flash of seconds. So this process is usually used for thin closed gaps.
Super glue is a type of adhesive which cure very fast as well. The water vapours in the surround atmosphere act as initiator to begin the process. It is suitable for wide range of material, but it is flammable under high temperature so you can see the burning cautions at the rear of a superglue tube. One common point for these adhesives is that they formed thermoset instead of thermoplastic in the curing process.
Lets first have a look at epoxy, which usually consists of epoxy resin + hardener. It is easy to use, simply mix the resin with the hardener together so that the end parts of the adhesive (diepoxy and diaming) are joined, and apply them on adherents. It wouldn't take long to polymerise, so you have to act fast before they cure, or simply make everything ready before you mix them togethher. However you may find that it is very hard to remove the adhesive from the substrates once it cured, so always act wisely and carefully.
The next one, anaerobic, which means 'no oxygen or lack of oxygen'. So the polymerisation basically happens when there is little or no oxygen at the surrounding. Apply the adhesive on the adherent, but the adhesive will remain as it is when there is oxygen around. But once there is a lack of oxygen, the process initiates and it happens just within a flash of seconds. So this process is usually used for thin closed gaps.
Super glue is a type of adhesive which cure very fast as well. The water vapours in the surround atmosphere act as initiator to begin the process. It is suitable for wide range of material, but it is flammable under high temperature so you can see the burning cautions at the rear of a superglue tube. One common point for these adhesives is that they formed thermoset instead of thermoplastic in the curing process.
Saturday 11 May 2013
Adhesive bonding
Adhesive bonding is another option if you would like to join 2 or more parts together. It is similar as glue-ing parts together without the need of high temperature involved in the process. This joining process fit in many applications in the industry because it can bond almost all materials.
There are many types of adhesive bonding available in the shop out there. We will talk about some of the common types available. Super glue is one of them and it can be purchased in most stationery shops. The technical name for super glue is cyanoacrylates. It has low viscosity and generally not cheap if you consider its volume. When super glue is exposed to the air, it undergoes rapid polymerisation reaction. The moisture in the atmosphere acts as initiator and the process can finish in just a few seconds.
Another common adhesive is epoxy which consists of both epoxy resin and hardener. They are usually sold together as a set. Epoxy can be used in a wide variety of different materials such as metals and polymers. At low temperature, epoxy is very brittle but at high temperature, it becomes stronger and more durable.
Always bear in mind that before applying adhesive on the materials, some preparations are required. Basically you have to make sure the adherent surface is clean and ready to hold the adhesive. This is important to make sure a strong bonding is formed between the adherent and adhesive interface. For example, a metal piece usually tends to have an oxide layer on its surface. If this oxide layer is not 'wipe out', the adhesive will stick on this oxide layer instead of the adherent real surface. Sometimes other contaminants might occur as well, so make sure you remove them beforehand. In case the surface is rough and unbalanced, a file can be quite handy in smoothening the surface. A smooth surface is more desirable in adhesive bonding because the adhesive can spread more evenly and cover a larger surface area. Don't look down at these small tips, they are very useful if you want to make sure the adhesive really does its' work.
There are many types of adhesive bonding available in the shop out there. We will talk about some of the common types available. Super glue is one of them and it can be purchased in most stationery shops. The technical name for super glue is cyanoacrylates. It has low viscosity and generally not cheap if you consider its volume. When super glue is exposed to the air, it undergoes rapid polymerisation reaction. The moisture in the atmosphere acts as initiator and the process can finish in just a few seconds.
Another common adhesive is epoxy which consists of both epoxy resin and hardener. They are usually sold together as a set. Epoxy can be used in a wide variety of different materials such as metals and polymers. At low temperature, epoxy is very brittle but at high temperature, it becomes stronger and more durable.
Always bear in mind that before applying adhesive on the materials, some preparations are required. Basically you have to make sure the adherent surface is clean and ready to hold the adhesive. This is important to make sure a strong bonding is formed between the adherent and adhesive interface. For example, a metal piece usually tends to have an oxide layer on its surface. If this oxide layer is not 'wipe out', the adhesive will stick on this oxide layer instead of the adherent real surface. Sometimes other contaminants might occur as well, so make sure you remove them beforehand. In case the surface is rough and unbalanced, a file can be quite handy in smoothening the surface. A smooth surface is more desirable in adhesive bonding because the adhesive can spread more evenly and cover a larger surface area. Don't look down at these small tips, they are very useful if you want to make sure the adhesive really does its' work.
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