Thread: question about solar power

Ok, I have been wondering about this question a bit, and though I haven't gotten much beyond the very basic physics classes for engineers (im computer science and we don't take much in the way of physics) I am intrigued to know an answer to this question. Photo voltaic cells use sunlight/photons to create electricity, I don't know the actual physics behind it off hand though I have seen/read about it before. Now my question is, since it is using energy from the sun, would it not also mean that the energy taken from the light would decrease the amount it could be used to warm things? Thereby giving the ability to not only use this energy in an effective manner, but say put it on the top of your house and it would in turn decrease (maybe not by much, but albeit some) your cooling costs? Just wondering, thanks.

If I understood your question right, then as far as this scenario is concerned, all of the energy that reaches us from the sun is in the form of electromagnetic waves (such as light). Heat (as defined by the collective kinetic motion of particles within the medium) cannot propagate directly through space, as it contains no such particles to 'mediate' through; it is a vacuum. Therefore the energy is transferred in the form of electromagnetic waves, best though of in this case as light particles, photons.

When these photons reach Earth they can either:

> reflect off of the surface of an object,
> be absorbed by an object

If they absorb into an object they will transfer their energy to it (They are absorbed by a particular atom, and interact with one of the atoms electrons, sometimes causing the electron to dislodge from the atom altogether if the energy is high enough). The nett effect of millions of such collisions is a general increase in kinetic energy (heat) of the object.

However in the case of a photo voltaic cell, an electric field is present and dislodged atoms are acted up by it, within a semiconductor, causing a current to flow.

Without the electric field, (as in normal everyday objects), the only useful product of this energy transfer is the heat. Some 'solar' cells are simply comprised of black pipes filled with water, such that the heat will convert it to steam etc...electricity. (These are not photo voltaic)

As for the exact dynamics of the process within the semiconductor, and the affect of the electric field, this page should be of use:

http://www.solarbotics.net/starting/...l_physics.html

Therfore any photons interacting within the domain of the electric field will produce a current, while others (absorbed by the frame perhaps) will simply produce a heat. This heat will be of no spectacular magnitude (probably more if you simply paste your roof black)

Also energy is conserved, so if you had to choose between painting your roof black or covering it with solar cells, then choose the solar cells, hook them to a central heating system and insulate your roof properly. This is what most of us do, except perhaps without the solar cells.

bit4bit

Um...In so far as much as the light isn't hitting your house to deposit that energy on your roof. So, yeah, if you cover yer roof with canopy of solar panels, you'll be keeping the sun off the roof, so the house won't heat up.

Problem is, the solar panels will heat up, plus it depends on how the panels are attached. If they are like normal house-mount solar panels, they sit almost right on the roof, which means they'd just transfer their heat to the roof. If they're mounted on a frame above the roof, there will essentially be a small oven effect underneath from the hot panel.

Nothing a bit of roofing insulation can't fix.

Originally Posted by groovydude

Ok, I have been wondering about this question a bit, and though I haven't gotten much beyond the very basic physics classes for engineers (im computer science and we don't take much in the way of physics) I am intrigued to know an answer to this question. Photo voltaic cells use sunlight/photons to create electricity, I don't know the actual physics behind it off hand though I have seen/read about it before. Now my question is, since it is using energy from the sun, would it not also mean that the energy taken from the light would decrease the amount it could be used to warm things? Thereby giving the ability to not only use this energy in an effective manner, but say put it on the top of your house and it would in turn decrease (maybe not by much, but albeit some) your cooling costs? Just wondering, thanks.

You are so well mannered with your quesion in not asking why humanity as a species has not evolved yet to ADAPT to what the sun already provides the planet.

Cute.

Conservation of energy says that any energy converted to electricity isn't converted to heat. The solar panels aren't 100% efficient, so they do still heat up though. I wonder if solar panels or white paint heats up more?

In having researched, as much as medicine allows, our evolution in history, "something happened" to humanity that suggested we have arrived at a civilization that tries to harness the energy of the sun, while all other life forms seems perfecty adapted.

I am guessing that "that which enforces us to harness the energy of the sun", namely our modern social world, civilisation, has something inherently wrong about it for us as a people to be almost forced, for our survival, to harness the energy from the sun in a science-tech manner. I am guessing what is wrong with civilisation is the very science we use: it's not the right one. We have forgotten something.

Originally Posted by streamSystems

In having researched, as much as medicine allows,

In what way is medicine a restriction on your research?

Originally Posted by streamSystems

"something happened" to humanity that suggested we have arrived at a civilization that tries to harness the energy of the sun, while all other life forms seems perfecty adapted.

Waffle.
What is the something that happened?
What is the evidence for the something that happened?
What are other life forms perfectly adapted to?
What is the similarity between our desire to harness solar energy and the adaptation of other life forms, that allows you to contrast them?
What possible relevance has your post to the question raised in the opening post?
Do you intend to knock all threads off course with irrelevant, nonsensical posts, or are you targeting certain kinds of post?

That "something" that happened was humanity's incorrect employment of a thing we call science, the employment of a less than perfect science leading to a less than perfect (ecosystem unfriendly) technology.

(look, I get the message: I will add a post after thoroughly researching the concept (of whatever it is I am posting), citing at least a few substantiated equations and associated literary scholars of scientific wisdom).

(yet I will reply to my posts aready made.............just to finalise them)

I also apologise for the way I present my posts, namely as open ended questions that aim to then focus in on whatever issue someone is interested in debating. It is a carry-over style from my Medical schooling. Sorry. I forget that scientists are more closed ended with their presentation and research.

I will make a deal with you though, given my abstract nature of posts: I won't jump in on anyone's post.

If I post something, you don't like it, "ignore it".

I won't jump in on someone else's post.