Solar Power Uses

Solar power is used a number of different ways, of course. There are two very basic kinds of solar energy:

Solar thermal energy collects the sun's warmth through one of two means: in water or in an anti-freeze (glycol) mixture.

Solar photovoltaic energy converts the sun's radiation to usable electricity.

Two kinds of solar energy and Five ways they can be used.

Here are the five most practical and popular ways that solar energy is used:
Small independent solar photovoltaic systems. We see these used everywhere, from calculators to garden lights. Portable units can be used for everything from RV appliances while single panel systems are used for traffic signs and remote monitoring stations.

Solar pool heating. Running water in direct circulation systems through a solar collector is a very practical way to heat water for your pool or hot tub.

Solar thermal energy using glycol to heat water. In this method (indirect circulation), glycol is heated by the sun's rays and the heat is then transferred to water in a hot water tank. This method of collecting the sun's energy is more practical now than ever. In areas as far north as Edmonton, Alberta, solar thermal to heat water is economically sound. It can pay for itself in three years or less.

Integrating solar photovoltaic energy into your home or business power. In many parts of the world, solar photovoltaics is an economically feasible way to supplement the power of your home. In Japan, photovoltaics are competitive with other forms of power. In the US, new incentive programs make this form of solar energy ever more viable in many states. An increasingly popular and practical way of integrating solar energy into the power of your home or business is through the use of building integrated solar photovoltaics.

Large independent photovoltaic systems. If you have enough sun power at your site, you may be able to go off grid. You may also integrate or hybridize your solar energy system with wind power or other forms of renewable energy to stay 'off the grid.'

http://www.thesolarguide.com/solar-power-uses/

- Xin Yun

SUMMARY OF WHAT WE COVERED SO FAR

-the operation of a solar panel
-how light energy from the sun is converted into solar energy for use
-the needs for solar energy
-pros and cons of using solar energy
-whether solar energy could become the main energy source in the future
-an insight into whether people might becom reliant on the use of solar energy
-the use of solar energy

any more to add on?

yuzhen

Solar cell physics -- the photovoltaic effect, applied

Sunlight is composed of photons, which can be thought of as "packets" of energy (the amount of energy in a photon being proportional to the frequency of its light). When photons strike a solar cell, the vast majority are either reflected or absorbed (some really high-energy photons will blow right through, but they're of no concern here). When a photon is absorbed, its energy is transferred to the semiconductor -- in particular, to an electron in an atom of the cell. If enough energy is transferred, the electron can escape from its normal position associated with that atom. In the process, the electron causes a hole (i.e., an empty spot where the electron used to be) to form. Each photon with enough energy will normally free exactly one electron, and one hole. Note that both electrons and holes are mobile, and as such can be current carriers.

Figure 1. The effect of the electric field in a PV cell (diagram courtesy of How Stuff Works )

The simplest solar cells have 3 active layers -- a top junction layer (made of N-type semiconductor ), an absorber layer (a P-N junction), and a back junction layer (made of P-type semiconductor). Thanks to the P-N junction, the cell has it's own built-in electric field. This electric field provides the voltage needed to force electrons and holes freed by light absorption to flow in their own directions (the electrons to the N-type side, and the holes to the P-type side). If we provide an external current path, electrons will flow through this path to their original (P-type) side to unite with holes the electric field sent there, doing work for us along the way. The electron flow provides the current, and the cell's electric field causes a voltage. With both current and voltage, we have power, which is just the product of the two.

Figure 2. Operation of a photovoltaic cell (diagram courtesy of How Stuff Works )

After a moment's thought, you can see that two additional layers must be present in a solar cell --electrical contact layers -- to allow electric current to flow out of and into the cell. The electrical contact layer on the face of the cell where light enters is generally present in some grid pattern and is composed of a good conductor such as a metal. The grid pattern does not cover the entire face of the cell since grid materials, though good electrical conductors, are generally not transparent to light. Hence, the grid pattern must be widely spaced to allow light to enter the solar cell but not to the extent that the electrical contact layer will have difficulty collecting the current produced by the cell. The back electrical contact layer has no such restrictions -- it need simply provide an electrical contact and thus covers the entire back surface of the cell.Additionally, an antireflective coating is generally applied to the top of the cell to reduce reflection losses, and a cover plate of some kind is often installed to protect the cell from damage while out in the real world.

http://www.solarbotics.net/starting/200202_solar_cells/200202_solar_cell_physics.html

- Yee Ting