Alternative Energy (Solar/Wind)/Solar Energy

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Question
Hi,

My son is doing a science project on solar energy, and we decided we should ask an expert!  Specifically, can you describe the process, and pieces, to explain how the suns' light goes from hitting the panels to when you flip on a light switch.  I realize you have answered this before, but it would help if he has his own response to put into his report.  Thank you so much in advance for taking the time to explain this as best you can.

Dustin (& James!)

Answer
Hello Dustin and James,

What it takes for a solar system to work is all dependent on the application.  Solar energy encompasses heating of water (solar hot water system), an area (solar oven) or air (solar space heating units).  But the most popular solar right now is solar electricity.  It turns out that this is the most versatile but also has the lowest efficiency of solar conversion.   As we search for alternative sources of electrical generation, it turns out that solar electric has a few positive traits.  It is modular (can shape systems to the demand), low visual impact (in most cases just flat panels against the roof) and low maintenance requirements (no moving parts and if designed and installed correctly will last 30+ years with a component replacement every decade or so).

A typical solar system used to heat water is 85% - 95% effective in collecting the energy from the sun and using it.  A solar electric system has a 15% to 20%  efficiency.  Where solar electric shines the most is in its usages.  You have a very limited use of hot water in a house, while electricity is used through out the house in many different ways.

A solar electric system can be as simple as a panel connected directly to an electrical load like a solar power fan.  The sun hits the panel, causing a flow of electricity that is then used to power a motor connected to the fan blades.

Another popular simple solar system is the solar lighting you see around gardens and walkways.  This adds a battery to the mix and usually some from of charge control component that keeps the battery from overcharging and breaking.  The sun energy is used to charge the battery which in turn powers the lighting.

In the two examples above, all the parts are using the same kind of electricity.  This kind of electricity is DC or Direct Current which is a flow of electricity (or actually electrons) in one direction (Negative to Positive).  The Negative is due to an excess in electrons which is a negatively charged particle and the positive is an atom lacking electrons so in its balance it has positive charge from the excess protons in the atom.

A solar wafer on a panel is a type of semi-conductor which creates a excess of electrons on one side of the PnP semi conductor plate and a deficit of electrons on the other side.  This occurs when the photon energy of the sun strikes the different materials on each side of the semi conductor and effectively "energize" the atoms so that the outer rings change their energy state.  If you introduce a path (wire) from one side to the other, the electrons will flow through that path.  As long as the sun is on the panels, the state change process will continue.

Now most of your home runs on AC electricity also called Alternating Current.  This is because electricity from a generator flows in two directions.  Power plants are just huge generators that turn 60 cycles a second or 60 hertz here in the U.S.  As the armature passes through the magnetic field it causes the electrons to move down the wire. The best way to repeat something in motion is to put it in a circle.  The armature will pass through the positive end of the magnetic field and then the negative end of the magnetic field as it rotates.  The electrons are then alternatively pushed then pulled, so too the electricity in wire in your home is also alternating or pushing and pulling.

For the DC electricity to work in your AC electricity home, you need a special electrical component called an inverter which changes the electrical input DC to an AC output synced with 60 hertz of the utility.  It also has to match the voltage which is the electrical pressure, but I am not going to get into those details.

The only other part in a solar system that I haven't covered are the switches and over-current protection devices; both of which stop the flow of electricity either by desire or because of a need to kill the flow for safety concerns.

I hope this is what you are looking for.  In school work assignments, it is my preference that you paraphrase what was said instead of just copying and pasting so that this information has the chance to permeate the mind.

Thank you - Marshall  

Alternative Energy (Solar/Wind)

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Marshall Scott

Expertise

I am knowledgeable about residential solar pool heating, moderately knowledgeable about residential solar electric systems, and can resource answers in solar hot water and battery back up PV systems, but personally have little experience. I review questions when I get a chance During the PEAK SOLAR SEASON (May - September) , my replies will be delayed as I am usually working 60+ hours a week.

Experience

Solar pool heating and solar electric systems

Education/Credentials
BA in Psychology which has nothing to do with solar. Various trainings and presentations on solar and 8 years experience.

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