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 Subject: Solar Power Category: Science > Technology Asked by: wilbur111-ga List Price: \$4.50 Posted: 25 Mar 2003 07:07 PST Expires: 24 Apr 2003 08:07 PDT Question ID: 180693
 ```What area of solar panels would be required to satisfy the whole world's present energy needs. E.g. Panels the size of Turkey might be enough. Maybe of only Quatar. I suppose the latitude at which the panels would be placed would make a difference, but I'm not after anything too mathematical, just a nugget of information. Saying that, though, I'm not scared of maths. Also, though, would there be any adverse affects of having such a large reflective surface in one place - such as, literally, covering the whole of a desert with solar panels? Increased global warming, perhaps? Would it be better to have several smaller sources? And, if you get into this question, how do the costs of obtaining the energy through solar compare to obtaining the energy through oil? E.g. the costs of big cables going across the world. Thanks```
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 ```hello wilbur111, Here are some good pointers, however the effects of the panels on global warming or the costs relative to oil, were not readily available within the scope of a \$4.50 question, but the sites below should give you some ideas. "If the whole world consumed 500 quadrillion BTU's of energy in 2000, and that's only a bit generous, than a square of photovoltaic cells 200 miles on a side would have produced 100% of the world's energy requirements in that year. That's assuming 8 watts of output per square foot of PVs, 6 hours of sun a day year-round, and 70% efficiency after transmission and conversion." http://www.ecoworld.org/Home/articles2.cfm?TID=259 Another possibility is to collect the sunlight in space and 'send it' back to earth: "But the technological challenges posed by the system are great. In order to harvest as much energy as possible, the satellites would need large surfaces of panels, measuring on the order of 7 miles long and 3 miles wide-over 21 square miles each." http://hcs.harvard.edu/~hsr/pdfswinter2003/bechis72-75.pdf "The solar energy released by the sun may seem like the best source of energy for the world. It has many benefits: it is free, it does not pollute, is very reliable when the sun is shining, and it is very safe. With all of these benefits, it may seem odd that there are extremely few solar power plants on earth. The reasons that solar power plants do not power the world are summed up in two reasons: cost and reliability. Solar plants made of solar cells are extremely expensive to build. Thousands of square feet of solar cells are required to generate enough power for even a very small town. A large city simply doesn’t have enough room for a solar plant, or enough money. The second main reason is the unreliability of the plants. If the plant has a few cloudy days, there will be no electricity for the town. This is not an option for many towns or cities. In the modern age of today, we need to have power 24 hours a day, 7 days a week, not only on sunny days, sometimes at night." http://www.smartown.com/sp2000/energy_planet/en/trad/solar.html Another alternative: "With oceans covering 60 per cent of the planet, wave power offers a source of energy that's still untapped - just 0.1% of the ocean's energy could power the world for five years." http://www.tve.org/earthreport/archive/03Sep2000.html Best regards THX1138```
 ```The location makes a big differece. Arizona, USA would likely produce twice as much energy as Turkey even though Turkey is a bit larger. This is because there are fewer cloudy days in Arizona. Close to the Equator also helps but any very sunny location in the torrid zone is good, and there are a few good semi tropical locations such as Arizona. At present even 30% of the world's needs is impractical as storing energy from afternoon to early evening (peak demand) is costly, dangerous and/or not tested large scale. At present the cost of big cables around the world would likely far exceed the cost of the solar panels and the land they occupy. The known reserves of some of the elements (copper) are not sufficient. The line losses are often more than half at distances over about 200 miles, so many smaller sources is better than several locations and one location for the Earth is far more costly. Liquid nitrogen temperature super conductors may be competitive with copper wire for high tension power lines soon, but I have not heard any encouraging reports. I think one problem is the line explodes if super conductivity is lost for more than one second, unless the power input to the line can be cut in less than a second. With solar panels about 20% of the energy become electricity, perhaps 40% becomes heat and about 40% is reflected back into the sky. The direction of the reflected beam changes thoughout the day, even if the solar panels are stearable, so I don't think there would be important environmental problems except the mine tailings from producing the raw materials and the land under the solar panels. I have participated in perhaps 70 alternative energy threads at www.abuzz.com You probably can locate them with key words such as solar power tower. When you find one where ccpoodle participated (that's me), click on ccpoodle and you can skim though the 3600 threads I have been in. At least 30 are about alternative energy. Neil```
 ```Here are my comments on the THX comment. The arithmetic may be correct, but some of the assumptions are over optimistic. In the North Temperate zone, December and early January, the 6 hours per day is not realstic, as the pannels produce only about 1% as much power when the sun is close to the horizon, even if the pannels are stearable. So for about 7 weeks each year annother energy source is needed especially as these are peak demand weeks in most of the North Temperate zone. The 70% efficiency may not be achievable even for customers within 10 miles of the solar array and may be as low as 20% conversion and delivery efficiency for cities at 40 to 60 degrees North or South latitude that are typically 1000 miles from a good location for obtaining solar energy. The solar power sattelites would be incredibly costly to build and keep running. What do you think about a one square KM rectenna receiving ten billion watts next door to your house? That is average 10,000 watts per square meter = one watt per square cm. Hot spots could be ten times more, like inside your microwave oven. A 1.2 KM wide death ray, 24/7. The rectenna can be larger, reducing the power density to non-leathal, but land near lots of energy customers is typically expensive. Whole body exposure to 1000 watts per square meter makes you feel a bit warmer, and the health effects are still being debated. As far as I know a one megawatt (enough for about 500 homes) tide or wave generating facility is yet to be built. Apparently there are many problems before either can compete with oil. Neil```
 ```Thanks very much for all your responses. All good stuff and none of you official researchers. Thanks.```