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Solar Energy Forums

Lance Said:

Global Warming - basic calculations?

We Answered:

Crude oil contains about 6119 megajoules (MJ) per 42-gallon barrel.
Pure unblended gasoline contains about 130 MJ per gallon, less if its an ethanol blend.
One metric tonne of coal contains 24,137 MJ.
http://www.eia.doe.gov/kids/energyfacts/…

Above the atmosphere, the Sun's energy contains about 1365 Watts per square meter, when that square meter is at right angles to the Sun's rays. (One watt is one joule per second.) Down here on the ground, you have to contend with clouds and dust, and atmospheric scattering, so you're lucky to get 1000 watts per square meter. So theoretically, a one-square-meter area that is at right angles to the Sun at all times might receive about 43 MJ on a clear day. But a photovoltaic panel is generally only 15% to 20% efficient, so you'd get much less than that: maybe 8 MJ per day. And most solar panels are "passive" meaning that they don't follow the Sun during the day, and therefore don't usually get the Sun's rays at right angles, so you have to allow for that too.

Solar-to-heat conversion systems are generally about the same level of efficiency as photovoltaics (15-20%), although some recent installations of solar-heated Stirling engines have demonstrated direct efficiencies as high as 30%.
http://www.nrel.gov/docs/fy04osti/33875.…

Nearly all the Sun's energy is in the visible range of the spectrum.

Eva Said:

What is the cause of gravity? And if possible, what is the opposing force to gravity?

We Answered:

Centrifugal

Ivan Said:

Is there a sensible, happy, medium?

We Answered:

I'm sorry but I fail to understand where you are coming from.

How can there be a happy medium between right and wrong? It is right to protect the environment for future generations; it is wrong to damage the environment wilfully or even thoughtlessly.

Where I agree with you is in suggesting that hectoring is bad tactics. Those who urge us to try harder are not wrong or pursuing a party political agenda; they are right but getting their tactics wrong. Instead they should consider setting a good example of a simple less damaging lifestyle and should then demonstrate that it is more fun than trying to keep up with the wasteful spending habits of their neighbours.

I am glad that you are making efforts to reduce your impact on the environment. You have made some sensible choices. Please do not be put off by those who hector for greater efforts. How about setting them a more effective example?

Best wishes

Renee Said:

What did we learned from the two typhoon Ondoy & Peping?

We Answered:

No doubt Manila and Luzon will learn a lesson about flood control and disaster pre-paredness. .. for a time. Same thing happens in the USA, coastal communities go a long time without a big storm and become very relaxed and fail to prepare even when a major storm appears to be heading right toward them. Hurricane Andrew did a lot of damage to south Florida in 1990, so Florida was very concerned abour hurricanes and flooding, changed the building codes, and other precautions.. which may explain why Katrina and other storms in 2004 did relatively little damage to Florida, who had flooding, evacuation and releif plans well rehearsed. New Orleans had not seen a major storm for a very long time, and unfortunately was unprepared for Katrina, which caused a lot of damage and loss of life. Storms happen. Everyone and every home, and every community should have a plan on what to do when they happen. The Red Cross /Red Cresent is really good at helping communites to prepare for disasters, and they need volunteers to do thier job.

Claire Said:

Information and Advice for My Green Future?

We Answered:

Going green is a very good idea. and interesting one too because it is sort of new. There are many different types of new available energy sources. I am quite interested in majoring in some kind of Engineering, but not sure which. I think materials engineering is pretty good too. u examine the properties of materials and compare them and experiment with them. who knows, maybe u could create a new cheap energy source!
good luck!

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