84
votes
Why don't solar panels contribute to global warming?
The purpose of solar cells is to generate electricity. This can replace the electricity generated by burning fossil fuels for electricity. The fact that it's becoming practical to run vehicles on ...
- 1,213
59
votes
Accepted
Why are solar panels kept tilted?
First, not every solar panel in India is oriented towards the south or tilted at 45°. One of the world's largest photovoltaic power stations is installed in Kamuthi (9.3°N, Southern India), with pv ...
- 1,847
42
votes
Accepted
Why is silicon used for making solar cells?
Si is among the most abundant materials on Earth and widely used for processors as well. There are very few other materials that can even theoretically compete with that. Germanium and GaAs won't be ...
- 731
30
votes
Accepted
What is different in the morning sunlight so it doesn't produce as much electricity as at noon?
When the sun is near the horizon, the sun rays have to travel through more air to get to you than when it's directly overhead. This phenomenon is known as atmospheric extinction, and this page has a ...
- 47k
25
votes
Why is silicon used for making solar cells?
On the topic of germanium versus silicon, a smaller band gap is not a good thing in a solar cell.
The maximum theoretical efficiency of a single-junction solar cell in natural, unfocused sunlight is ...
- 17.1k
22
votes
Accepted
Why don't solar panels contribute to global warming?
Simple back-of-the-envelope calculation:
This figure shows our best estimates of the radiative forcing from different anthropogenic (human-caused) phenomena:
It shows that the radiative forcing from ...
- 6,148
17
votes
Why are solar panels kept tilted?
Cleaning issues aside, the best orientation of a solar panel is the one that maximizes solar exposure.
It can be fixed or change periodically if a motor mechanism is provided. If it is static, then ...
- 3,216
10
votes
Accepted
If energy is supposed to be a scalar, why does this logic of solar panels work?
Energy is a scalar, but the flow of energy is not. It is a vector, and indeed for EM radiation it is the Poynting vector.
The Poynting vector is the flow of energy per unit time per unit area i.e. ...
- 351k
10
votes
Why don't solar panels contribute to global warming?
solar panels increase the efficiency of how we 'harvest' this solar
energy, reflecting less of it back into space, and turning more of it
into en energy (in this case, electrical
I’m no expert, ...
- 200
7
votes
Why are solar panels kept tilted?
Because in northern hemisphere sun is at the south (it moves from east to west - but always on the south side of the sky), by tilting the solar panel towards the sun (to the south) you increase energy ...
- 2,359
6
votes
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What kind of engine is a photovoltaic solar cell?
In response to light a solar cell generates an electrochemical potential which provides the thermodynamic driving force for extraction of work. This is the fundamental operation of a solar cell and is ...
- 3,289
6
votes
Is silicon a semiconductor or insulator?
The difference between semiconductors and insulators is a quantitative rather than a qualitative one. The principal division here is between the insulators and the metals: the former have the last ...
- 57.4k
6
votes
Accepted
How hot can the focal point of a convex lens get under the full sun?
The theoretical maximum is exactly the surface temperature of the Sun, by thermodynamic arguments that the 2nd Law cannot be violated. We will, of course, fail to reach this limit by far. Long before ...
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5
votes
Why don't solar panels contribute to global warming?
The benefit of a solar panel power plant as a replacement for coal(or other fossil fuel) power plant is manifold:
1) less fossil fuel is burned, so it can be used differently, for example as a source ...
- 35.5k
5
votes
Why is silicon used for making solar cells?
Raw material of germanium is about 100 to 1000 times more expensive than silicon.
Furthermore, the science and engineering of silicon is well established.
Also, you don't actually use silicon to ...
- 3,106
5
votes
Why is silicon used for making solar cells?
Since silicon exists in abundance (I believe around circa 25 % of Earth's crust is made from silicon), the industry has come to accept it as a standard.
International Technology Roadmap for ...
5
votes
Accepted
How do photovoltaic panels obey the law of conservation of energy?
As already mentioned in the comments, the energy comes from the absorbed photons. A photon has a frequence-dependent energy
$$E=hf$$
where $h$ is Planck's constant and $f$ is the frequency.
Being ...
- 3,649
5
votes
Accepted
Is silicon a semiconductor or insulator?
In Physics, it is meaningless to ask if a particular substance is an insulator, a semiconductor, or a metal as far as the electronic transport is concerned.
The reason is that the electronic ...
4
votes
Materials for use in a solar cell
When light is absorbed in a semiconductor, the excited electrons will quickly relax to the conduction band edge. The extra energy of the absorbed photon compared to the bandgap of the semiconductor is ...
- 101
4
votes
Where does the electricity, generated by a solar panel, go if you don't use the electricity?
Answering this nine-year-old question because IMO, it deserves a low-level (physics-based) answer, and the others tend toward higher-level (more practical) explanations.
A Photovoltaic cell is a P/N ...
- 13.7k
4
votes
Why don't solar panels contribute to global warming?
This crude approximation is essentially correct:
Two things affect the total sum of energy on earth: radiation into space will drain energy (and is limited because of the presence of atmosphere). ...
- 428
4
votes
Why is silicon used for making solar cells?
I am not an expert on semiconductor physics but from some internet research I have found out that money is not always the deciding factor. Germanium is also sometimes used in semiconductors and has ...
- 156
4
votes
Would this work as a way to get more energy from sunlight?
The shortcoming of the arrangement you suggest is that the plant, or solar panel, would only experience the ideal frequency at a single point on the rotation of the wheel. There would be points on the ...
- 25k
4
votes
Accepted
Why don’t illuminated series connected (photo-)diodes bias each other?
Here is something to get you started.
Firstly let's make a simple SPICE model for a single solar cell. We have a current source in parallel with a diode, we also have a voltage source which we will ...
- 3,289
4
votes
Accepted
Why is exciton diffusion a problem in organic photovoltaics and not in inorganic photovoltaics?
For most semiconductor, e.g. GaAs, a exciton has binding energy about 6 meV ($0.006 eV$) and with a binding length about $200 \dot{A}$. That is a very loosely binded state, can be broken into free ...
- 4,146
4
votes
What is different in the morning sunlight so it doesn't produce as much electricity as at noon?
If I understand your drawing, at all measurement times the sun is fully abvoe the horizon and the solar panel is always perpendicular to the line-of-sight to the sun.
In this case, what you are ...
- 10.9k
3
votes
Accepted
Do III-V based photovoltaics "glow" (photo-luminesce) when illuminated but not loaded?
III-V photovoltaics will indeed photoluminesce quite nicely (particularly if not loaded). As you note, they are direct band gap materials so if there is any overlap of electrons and holes you can get ...
- 7,331
3
votes
Why don't solar panels eventually reach electrical charge equilibrium?
Your understanding is not wrong - except for the bit where the electrons end up with a greater potential. This means that when you close the circuit, they will want to travel around the circuit - and ...
- 118k
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