PV Gap

Douglas Said:

Why is it fine to short circuit solar panels?

We Answered:

Because they have a high internal resistance, which limits the current and prevents damage.

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Willie Said:

how long does it take for a solar panel to make one watt?

We Answered:

There are no accurate answers to your question yet.
The final answer is : No, you don't want to buy it. Several reasons.

A normal single family home uses about 500 to 600 kiloWatt-hours or kWh in one month. One kWh is 1/ 1000 of a MegaWatt hour. So the discussion here is off by at least a factor of 1000 or more.
The 500 to 600 kWh/ month is about 7000 kWh per year. Apartments and Condo's use much less energy.

Your instantaneous power need is the issue. When you turn on your microwave, you use about 1000 Watts to 1500 Watts. When the toaster is on -- you use about 1000 Watts. The hair dryer, maybe 1500 Watts. If you want all three of those on at the same time, and some lights --- you will need about 30 or 40 solar panels that you described.

Then --- another problem -- the solar panel only puts out 12 Volts DC. Not the 120 Volts AC that you really need for your microwave and hair dryer. So now you add several thousand dollars for an "inverter" (an electronic device) to convert 12 Volt DC to 120 Volts AC.

Next problem --- Now maybe you decide that you want to watch TV at night, or read a book under your desk lamp. The sun is not shining -- therefore, no power. Now you need several thousand dollars for battery back-up storage. This is similar to having a rack of about "40 car batteries" sitting in your garage. Maybe $100/ battery, and you need 30 or 40 --- that's about another $3,000 or $4,000.

Bottom line: You will need a 2 or 3 kW Solar system to operate your home. At about $9,000 per kW, that's about $20,000 to $25,000 for the entire system installed (although, no batteries, yet). And these systems fail over time. The inverter will fail in 6 to 10 years. The batteries will last maybe 5 years. The solar panels themselves degrade to about 80% of full output at the ten year point.

Your current electric bill which is maybe $60 to $80/ month, or $800 to $1000/ yr. It is much cheaper to just keep getting the dependable power from the utility grid, rather than worrying about a cloudy day interrupting re-runs of American Idol. Hope this helps.

These Solar Systems (PV's) take a long time to pay back, and they degrade over time, and can get destroyed in one big wind storm, or hail storm. Not a good idea.

Clifton Said:

which solar panels are better, amorphous vs polycrystalline. whats is the pro's and con's?

We Answered:

Amorphous panels tend to be less efficient, cheaper, and can be flexible (depending on the backing material). I'm not sure if there are many rigid amorphous panels available nowadays

In most situations the choice will come down to cost, so I wold go for the cheapest.
Less efficient panels however will mean a larger area of panel for the same output so mounting may be more difficult.