We are all seeing the start of an energy crisis.  Petroulum will not last us forever and we are realizing that truth.  There are other energy possibilities to move and each has its own pros and cons.  Someday we will have to move ourselves to a new set of energy resources.  Solar is a strong possibility for being a key energy resource.

Why is solar such a strong possibility?  First of all, it is all around us.  Solar power can be delivered on the small scale to power a little calculator or expanded to cover acres of land and power thousands to millions of houses.  It is a free stable fusion reactor for every one, large and small.  it has been combining hydrogen isotopes for billions of years before the human race existed and will continue for billions more.  It is scalable, and unlike many other energy resources, it can be converted directly into usable energy.  What I mean is that it is possible to convert sun light directly into electrical energy without the need to boil water or heat gases.  There are no pollutants while the solar cells are in operation, which is unlike most fossil fuels.

Monocrystalline silicon solar cell

Solar energy like all other forms of energy, has its problems.  For one, it is limited by time of day and weather.  If it is night or bad weather the amount that solar panels produce is drastically dropped.  This makes it difficult at best to see a full electric grid based off of solar alone.  Another degrading factor is the expensive materials needed in make many of the solar cells in existence today.  The common solar cell that has a blue tint is made from highly purified silicon.  Silicon is common, for example most of the sand on a beach and quartz crystals are made of silicon oxide.  The problem is purifying it so that it is usable in solar panels.  Another problem that is less often discussed is that many of the higher efficiency solar cells use relativity toxic elements.  Some of these include Cadmium, Selenium and Arsenic.  During normal operation the chemicals are bound up and are relatively safe, but if disposed of improperly, they can lead to toxic leakage.

These facts support solar energy to be a part of the solution but not the whole solution.  In the end, we will need a combination of other energy sources to stem this energy crisis.  There are advances that would help improve the position of solar power.

I want to discuss some of the possibilities that will help solar energy.  Understand that I have a distinct bias that is due to my present research.  One of these possibilities that will help solar technology is the advent of quantum dot solar cells.  I will start by breaking up the term.  Quantum dots are little balls of material.  Imagine taking a quantum sized ice cream scooper to a material.  This ball of material has properties that are different from the material from which it came due to its small size.

Quantum dots, all excited using ultraviolet light and photoluminescencing various colors of light. The emitted light changes depending on the quantum dot's size due to quantum confinement. Reds are the largest dots and blues are the smallest.

One of these properties is called quantum confinement.  I tried to discuss it on the video blog earlier, but here is a different perspective on it.  Think of an unruly kid.  If one gives them a whole in which park to play, they will slowly wander various places and rarely travel in a straight line until they tire themselves out.  Now if it is a rainy day outside and they are confined to a house, they become a little more energetic, while not having a good method to let go of that energy.  They get into trouble and you ground them to their room.  Now, they get super energetic and start to become loud letting out some of that pent in energy.  If you attempted to confine them any further, well you get the point.  As one confines the kid he/she becomes more energetic.  In a quantum system the electron acts in much the same way, as one closes the barriers around the electron, it becomes more energetic.  This is a side effect of the uncertainty principle.  As you confine its position in space, its momentum becomes less confined.  That is to say, there is the electron but I now do not know how fast it is going.  In quantum dot solar cells, this allows us to tune the electrons energies by confining them.  This causes the energy of light that it can absorb efficiently to increase.

Another useful property of quantum dot solar cells is called self purification.  Just as it sounds quantum dots purify themselves.  If you have ever shaken a container of sand you know that as you shake it, the heavier large grains will make their way to the bottom as lighter smaller grains work their way to the top.  Quantum dots do much of the same thing.  If there is an impurity, it is able to shift around due to the “shaking” of atoms around it.  This shaking is from room temperature heat that shakes all atoms around us.  As it shifts around, there is a chance that it makes it to the surface, which is a nice comfy stable spot for it.  When it is on the surface, it is out of the rest of the material and does not effect its properties.  This does not happen in large materials because there is too much material between the impurity and the surface, but in quantum dots the impurities only have to jump a few hundred times to make it to the surface.

Helpful resources:

Wiki: Solar Cells

Quantum Dot Blog Post

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