A Question About Solar Energy?

Question

I'm doing a project on solar energy. The only thing I have not found was the efficiency of solar energy compared to other kinds of existing or future/possible kinds of energy. Does anyone know of any sites or any facts that would help me? It'd be greatly appreciated. Thank you so much in advance.

Answer 1

The kinds of solar cells you and I can buy "off the shelf", right now, are in the 18%- 22% efficiency range.

The kind of solar cells that fly on the international space station (ISS) -- which are the most efficient production cells in the world -- are still only 27.5% efficient. With concentrators (little Fesnel lenses), they can possibly reach about 35%. These efficient cells are *very* expensive and not practical for public use.

Here's a link to the ISS solar cell manufacturer.
http://www.emcore.com/product/space_photovoltaic.php

Click on "download Datasheet" to compare different types.

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Answer 2

It's going to be a taboo subject but if you talk about how many watts it takes of energy to build a solar cell and the amount of energy that cell puts out in it's life time. You will find out How dumb of a idea it is to make solar cells to "save the earth". They're a reason why solar cells cost so much money. There is a reason why power companies don't build solar farms. If it was really that easy to get "free energy" after 7 years they would all be doing it.
For the "few" that do it now it's because they got large grants from the government, so its basically free.

Answer 3

Some people say that solar power is not practical, since to get enough power you would have to cover the entire country with solar cells. Is this true? A square meter of solar cells can deliver about 150 watts. A gigawatt, the output of a typical nuclear power plant, would take 7 square kilometers. (Can you verify that number?) This may sound big, but it really isn't. California has a typical peak power use (during the day, largely to run air conditioners) of about 50 gigawatts of electrical power; to produce this would take 350 square kilometers of solar cells. This would take less than one thousandth--that's one tenth of one percent--of the 400,000 square kilometer area of California. Besides, the solar plants would probably be placed in a nearby state, such as Nevada, that gets less rain and doesn't need the power itself.

Others complain that solar energy is available only during the day. What do we do at night? Of course, it is during the day that we have the peak power demand, to run our factories and our air conditioners. But if we are to convert completely to solar cells, then we will need an energy storage technology. Many people think that large hydrogen fuel-cells might provide that.

Answer 4

There's no "standard nuclear reactor", but if we take a 1 GW nuclear plant, it can generate about 8 terawatt-hours/year. A 200 watt solar panel can generate about 1 kilowatt- hour/day, or 365 kwh/year, so that's about 21 million 200 watt solar panels. However, the power output from the nuclear plant is controllable by the operators, where solar panels only operate at full output for a few hours/day (on clear days - less if there's cloud). Therefore, to compare the two, you have to factor in some kind of energy storage or backup which will increase the cost of the solar installation (perhaps by a factor of two or more). Despite claims of solar being cheaper than coal now, when one compares apples to apples (i. e. total energy produced, and controllability) solar is still several times more expensive than coal, and about twice as expensive as nuclear even in the U. S. A gram of U-235 can make usable energy equal to three metric tons of coal. Solar energy production has no hazardous by-products, but manufacture of the panels can involve some very hazardous materials like fluorine (for silicon panels) or cadmium (for CdTe panels). This is part of the reason panel manufacture has gone to Asia - they have fewer environmental regulations and it's easier to dispose of the byproducts of production. DK

Answer 5

Efficiency doesn't really have meaning in this context. If your input energy would otherwise be wasted, as in the example of cellulosic fiber, or solar, do you really care what your conversion ratio (efficiency) is? Perhaps the question is: what is the cost per kwh of electricty from these various sources.

Until photovoltaics are able to be manufactured more cheaply, they will be one of the more expensive sources of electricity. They do have many applications in there current form, mosty for off grid application like remote houses that would have to pay the cost of extending the power grid, or way way of the grid, like in geosychonous orbit on a satellite.

Answer 6

I've always heard and gone by 30-40% efficiency.

There is new solar technology in the works that is going to make solar energy more practical soon.

Answer 7

Here's one site that talks about 40% efficiency for conversion of solar energy into electricity.
http://www.energy.gov/news/4503.htm