Question regarding where power goes

[winnie]

Just because our eyes don’t see any source of other radiation at night does Not mean their is no radiation coming at night on Earth

Radiation from space is always hitting the Earth from all directions, including at night. But the amount at night is not very much.

-Jon

 

[ggunn]

...the 'Hall Voltage' developed in a P-type semiconductor is the sort you get for a proton.

-Jon

Yes, but there are no free protons in semiconductors.

 

[hhsting]

Very true. But interestingly the Hall Effect for P-type semiconductors is the same as the Hall Effect for positive charges.

If you have a current of charges moving in a magnetic field, they get pushed to the side. When you have electrons move from right to left or protons moving from left to right you end up with the same 'conventional current' (from left to right). But if you add a magnetic field you will get a 'Hall Voltage' of opposite signs for electrons or protons.

In a P-type semiconductor the charge carrier is a 'hole', which is an absence of an electron. For a hole to move to the right what really is happening is an electron jumping to the left. But the 'Hall Voltage' developed in a P-type semiconductor is the sort you get for a proton.

-Jon

I dont follow. How does that work and semiconductor? Do MOSFET n type, p type or Bipolar transistor work that way?

 

[hhsting]

Yes, but there are no free protons in semiconductors.

Then what are they? Hall affect used to show what flows in metal and showed electrons and also sometimes positive charges. Do we have a second positive charge particle now other than proton?

 

[winnie]

There are numerous positive charged particles, but they are not relevant to this discussion.

The only 'free' charges in a metal or a semiconductor are electrons.

In a p-type semiconductor you have an excess of 'holes', which are essentially empty spaces that can hold electrons. These holes act in in this regard (the Hall Effect) as positive charges, even though what is really happening is electrons moving.

-Jon

 

[hhsting]

There are numerous positive charged particles, but they are not relevant to this discussion.

The only 'free' charges in a metal or a semiconductor are electrons.

In a p-type semiconductor you have an excess of 'holes', which are essentially empty spaces that can hold electrons. These holes act in in this regard (the Hall Effect) as positive charges, even though what is really happening is electrons moving.

-Jon

So holes are basically atoms which lost electron. So then the atom becomes positive overall? Hall affect observed that those positive charge are current. How does holes even create current? Only free charge particles are electrons.

 

[Carultch]

So holes are basically atoms which lost electron. So then the atom becomes positive overall? Hall affect observed that those positive charge are current. How does holes even create current? Only free charge particles are electrons.

It isn't the atom that has lost an electron. It is the lattice position that is missing an electron.

The go-to example to demonstrate p-type semiconductors is silicon doped with boron. Boron has 3 electrons in its outermost orbital, and silicon has 4 electrons in its outermost orbital. Only the outermost orbital is involved in bonding. Silicon makes single covalent bonds with each of its four neighbors, when forming the silicon crystal. If you replace a silicon atom with a boron atom in this lattice, you make it such that an electron is missing from the crystal lattice, from within the energy level involved in bonding.

The substance is still net neutral, because both silicon and boron contribute a single electron for every proton they each contain. But what happens is that by introducing a trace amount of boron atoms, you create an electron vacancy that the electrons each try to fill. This vacancy is called a hole, and the holes act as if they are positive charge carriers moving through the semiconductors.

 

[Carultch]

Let me ask you this. Can you have PV modules that react and provide electricity other than sunlight radiation? Such as x rays, gamma rays, UV rays all other types of radiation. I ask because then one can then generate power into night all sorts of radiation penetrate Earth night and day

It would be useless to make a terrestrial PV module that runs off X-rays and Gamma Rays, because these get blocked by our atmosphere. UV gets blocked by the atmosphere to a lesser extent, but UV has the added problem of also getting blocked by most kinds of glass.

PV cells are sensitive to both visible light and infrared light. This is where most R&D has focused for obvious reasons. Visible light is the most abundant in the sun's spectrum, and it is not just a coincidence that this is what is visible to humans. Those were the colors of light that were most critical to see for our survival.

There is a diminishing return to efforts of extending the spectrum of a PV cell, because the farther you get from visible light, the less energy is available in naturally existing sources that produce it. Eventually, you get to a frequency low enough where the radiation is so low in energy, that it cannot work with the working principle of semiconductor photovoltaics, and you'd need an entirely different kind of receiver to pick up energy from the radiation.

 

[hhsting]

It isn't the atom that has lost an electron. It is the lattice position that is missing an electron.

The go-to example to demonstrate p-type semiconductors is silicon doped with boron. Boron has 3 electrons in its outermost orbital, and silicon has 4 electrons in its outermost orbital. Only the outermost orbital is involved in bonding. Silicon makes single covalent bonds with each of its four neighbors, when forming the silicon crystal. If you replace a silicon atom with a boron atom in this lattice, you make it such that an electron is missing from the crystal lattice, from within the energy level involved in bonding.

The substance is still net neutral, because both silicon and boron contribute a single electron for every proton they each contain. But what happens is that by introducing a trace amount of boron atoms, you create an electron vacancy that the electrons each try to fill. This vacancy is called a hole, and the holes act as if they are positive charge carriers moving through the semiconductors.

So how can holes move? Is it holes or is it electrons moving in p type substrate that create current?

 

[jaggedben]

Who told electric current is just electrons? Electric current is movement of charged particles and their are two: protons and electrons. So then protons can also be involved or are moved.

Um, no. If the protons were moving on the wires that would be nuclear physics, not electrical engineering. But the elcectrons move back and forth in alternating current and may never get to the loads.

 

[ggunn]

So how can holes move? Is it holes or is it electrons moving in p type substrate that create current?

When a photon bumps an electron off its place in the crystal lattice of a semiconductor it creates an electron-hole pair. The electron has a negative charge and the hole has a positive charge by virtue of the fact that the atom to which the displaced electron was formerly attached now has more protons than electrons. When electrons move in one direction in an electric field, the holes they leave move in the other.

Imagine a bunch of spheres in a row in indentations in a plane. These are electrons and the indentations are atoms. Now knock a sphere in the middle of the line out of its indentation; the loose sphere and the now empty indentation are an electron-hole pair. The electron is inherently negatively charged and the hole is positively charged because the atom it was attached to now has one more proton than electrons.

Now introduce an electric field - positive on the left and negative on the right.. The freed electron goes haring off to the left unimpeded, but the still bound electrons also want to move to the left. The one to the right of the vacated indentation moves over into it, and then the next one in line moves over one indentation, and so on. The hole is therefore moving to the right. One electron to the left and one hole to the right for every electron-hole pair generated by a photon, an electric current a la the photoelectric effect.

This of course is a very simplified description of a complex process. It takes a lot of calculus to describe the math that drives it.

 

[wwhitney]

When a photon bumps an electron off its place in the lattice it creates an electron-hole pair.

That all make sense for a PV cell, but how do holes in p-doped semiconductors fit into the picture? The hole is neutral instead of positively charged. So does it do its job by allowing for a negatively charged anti-hole, paired with a positively charged hole elsewhere?

Cheers, Wayne

 

[zbang]

It's amazing how far this has come from the original discussion. (Can the mod's split the semiconductor discussion into another thread?)

 

[ggunn]

That all make sense for a PV cell, but how do holes in p-doped semiconductors fit into the picture? The hole is neutral instead of positively charged. So does it do its job by allowing for a negatively charged anti-hole, paired with a positively charged hole elsewhere?

Cheers, Wayne

Charge mobility in doped semiconductors is complex. You get into majority carriers, minority carriers, band gap physics, and the math careens into quantum mechanics. I had a pretty good grasp of it when I was just out of school, but many brain cells have expired since then. I will leave deeper explanation to anyone else who wants to jump down that rabbit hole.

 

[winnie]

My understanding is if you displace or move a proton or neutron you have the basics of a neuclear reaction, not electrical current.

Protons and neutrons are tightly bound in the nucleus of the atom. If you are ripping the nucleus apart or squeezing protons and neutrons together then you have a nuclear reaction.

But if _any_ charged particle simply moves from place to place you have an electric current.

In a chunk of copper, the charged particles that are free to move are electrons, and current in copper is motion of electrons.

You can move protons and neutrons without a nuclear reaction; simply walk across the room. You are not ripping s nucleus apart if you simply move the entire atom. If you have a positive ion (one with more protons than electrons) and it moves, you have a current from a net motion of a positive charge.

Positive ions currents are common in electrochemical reactions.

A nuclear reaction can create a current; both alpha and beta particles are charged and you can create a power source by having a radioactive source near an electrode. Charged particles from the decay create a current across the gap between the source and the collection electrode.

Jon

 

[zbang]

I'm a little surprised nobody mentioned this (me included)-
metallic bond
noun (Ccemistry)
the type of chemical bond between atoms in a metallic element, formed by the valence electrons moving freely through the metal lattice.

 

[CodeQuandary]

Which way a particular stream of power goes is a useless question to ask. Think instead of net power to building,
It is totally equivalent in every way if
a. The power goes out to POCO and all of the building power comes from POCO. Net to you is consumption minus production.
b. The power goes to the disco and back into the building and reduces the amount you buy from POCO. Net to you is consumption minus production.

The point of inetrconnection only matters if it goes out to POCO through a separate meter with a different rate, rather than through a net meter.

Generally in a net-metered environment, this answer is not a complete picture. If your energy use is less than or equal to what your solar system is producing, that electricity is never going through the meter. Period. No mystery. So any solar energy you use in real time in a net-metered system is sending electrons to whatever the end use is. Period. They don't sneak quietly through the meter and then back again. [to be clear: I don't personally think this is important, but it is what was asked]
As soon as you have asynchronous generation and use, the picture changes and it becomes meaningless to talk about electron origin.

 

[ggunn]

Generally in a net-metered environment, this answer is not a complete picture. If your energy use is less than or equal to what your solar system is producing, that electricity is never going through the meter. Period. No mystery. So any solar energy you use in real time in a net-metered system is sending electrons to whatever the end use is. Period. They don't sneak quietly through the meter and then back again. [to be clear: I don't personally think this is important, but it is what was asked]
As soon as you have asynchronous generation and use, the picture changes and it becomes meaningless to talk about electron origin.

I can't count the number of times I have been asked this question. Fundamentally it comes down to the difference between a current source , e.g., a grid tied PV inverter, and a voltage source, e.g., the grid or a battery. Nearly all the sources of energy we deal with are voltage sources, so most explanations of this effect for laypersons try to make it make sense in terms of voltage sources because that's what most people are familiar with. Those explanations can only go so far.

 

[CodeQuandary]

Generally in a net-metered environment, this answer is not a complete picture. If your energy use is less than or equal to what your solar system is producing, that electricity is never going through the meter. Period. No mystery. So any solar energy you use in real time in a net-metered system is sending electrons to whatever the end use is. Period. They don't sneak quietly through the meter and then back again. [to be clear: I don't personally think this is important, but it is what was asked]
As soon as you have asynchronous generation and use, the picture changes and it becomes meaningless to talk about electron origin.

Ai yi yi: I didn't read the whole thread (still haven't), but realize that my comment about the actual electrons was unhelpful/misleading, particularly in an AC system. I should have left it at energy.

 

[jaggedben]

Generally in a net-metered environment, this answer is not a complete picture. If your energy use is less than or equal to what your solar system is producing, that electricity is never going through the meter. Period. No mystery. So any solar energy you use in real time in a net-metered system is sending electrons to whatever the end use is. Period. They don't sneak quietly through the meter and then back again. [to be clear: I don't personally think this is important, but it is what was asked]
As soon as you have asynchronous generation and use, the picture changes and it becomes meaningless to talk about electron origin.

Oh, but some number of electrons absolutely do sneak quietly from the solar panels through the meter, and then some other electrons take their place sneaking back. Which is why I think Goldigger's way of putting it is more apt: It doesn't matter where the individual electrons go, we only really care about net power flow. Speaking in absolutes ("no electricity passes through the meter. Period.") isn't helpful.

From a practical point of view, there's also the case where total production exceeds consumption, but consumption isn't balanced across phases. In that case there may be power flow in both directions through the meter on different phases.