Your Questions About Solar Cells

adminsta answers:

Don’t know the proper formula to calculate what the least amount of Silicon monoxide needed to produce the least amount of reflection.

But to the second part of the question. The more light that is being reflected, the less light there is being absorbed by the solar cell. The less light there is being absorbed by the solar cell, the less light there is being transformed into energy of another type by said solar cell.

In other words, the more light that is being reflected, the less efficient the solar cell will be, in regards to producing electricity.

adminsta answers:

Its very true that solar cell efficiency depends on the location where they are being used. This is primarily because of the tilt of the Earths axis as well as seasonal changes. Basically as you get closer to the poles the suns rays become more and more “spread” out because the land in those areas is facing away from the sun. On average days are shorter closer to poles as well because, depending on the location, they may never fully face the sun even in full summer, where as the equator directly faces the sun all year long. Weather can also have a big effect if you were to try and use solar cells in an area (Like Seattle WA) where its almost always cloudy.

However this is only one small problem that scientists are facing with solar cells right now. Right now they only can use a small percentage of the solar energy available. They are also extremely expensive compared to the amount of electricity they produce.

adminsta answers:

They are too expensive ,and the pay out will probably not be very good. Note of caution !! Mount them very sturdy as they have a lot of surface so a little wind can tare them up.

adminsta answers:

Light

adminsta answers:

Certainly the higher frequencies contain more energy. But photons with energy above the band gap energy of silicon are wasted.

Wikipedia:
Photogeneration of charge carriers

When a photon hits a piece of silicon, one of three things can happen:

1. The photon can pass straight through the silicon — this (generally) happens for lower energy photons,
2. The photon can reflect off the surface,
3. The photon can be absorbed by the silicon, if the photon energy is higher than the silicon band gap value.

This generates an electron-hole pair and sometimes heat, depending on the band structure.
When a photon is absorbed, its energy is given to an electron in the crystal lattice. Usually this electron is in the valence band, and is tightly bound in covalent bonds between neighboring atoms, and hence unable to move far. The energy given to it by the photon “excites” it into the conduction band, where it is free to move around within the semiconductor. The covalent bond that the electron was previously a part of now has one fewer electron — this is known as a hole. The presence of a missing covalent bond allows the bonded electrons of neighboring atoms to move into the “hole,” leaving another hole behind, and in this way a hole can move through the lattice. Thus, it can be said that photons absorbed in the semiconductor create mobile electron-hole pairs.

A photon need only have greater energy than that of the band gap in order to excite an electron from the valence band into the conduction band. However, the solar frequency spectrum approximates a black body spectrum at ~6000 K, and as such, much of the solar radiation reaching the Earth is composed of photons with energies greater than the band gap of silicon. These higher energy photons will be absorbed by the solar cell, but the difference in energy between these photons and the silicon band gap is converted into heat (via lattice vibrations — called phonons) rather than into usable electrical energy.

.

adminsta answers:

One has a means of attaching leads, or has leads for your electrical connection and the other you have to fabricate a means of making a connection to your cell’s conductive strips.

Depending on the amount of current the cell is to produce at peak will be your limiting factor, but something as simple as conductive tape (adhesive RF shielding for example) can work. Securing it could be done if you install them in a rabbeted frame to accept the panel and locate your conductive foil at each pole of the cell. Then a simple matter of securing a brass screw through that conductive tape with a simple wire loop under the head of the screw makes for a simple secure connection. While you could try to attach wire with a low wattage soldering iron, there are some instances where the cell could be damaged from the heat application.

Since it sounds like your cells will not be weather resistant, you will need to make a weather resistant frame for them, which makes the above a very simple method of attachment. .

adminsta answers:

Well that might get expensive. See you have solar power, which is direct current (dc) power that needs to be converted into alternating current (ac) power then back to dc power. So you will have to have power inverters and monitors and all that stuff or you will fry both of them. You know they make laptop bags now with flexible solar cells to charge your stuff without all that power loss and expensive equipment. The cord extends out from bag so you can charge it while using it. And you get it with the power rating it needs. That might be a better idea than spending a few hundred dollars on your idea.

adminsta answers:

For first generation solar cells they produce current at the sunlight wavelengths. See graph from the link. You can probably find a current vrs. Frequency plot somewhere but certain things have to be fixed for this to occur such as the incidence angle of the light and the exact type of cell. Normally you see plots of quantum efficiency. I got you started. Interesting science.