Friday, September 5, 2008

Solar Power and Greenhouse Gases:
A Weighty Subject

Let's set the record straight: Solar power is not a totally green source of electricity but it is 89% in that direction. The present day manufacturing of photovoltaic (PV) system components must use existing power sources mostly generated by burning fossil fuels. Later, as more clean, renewable energy is produced this 11% will diminish proportionally. Solar is undoubtedly the avenue to pursue.

As solar bypasses fossil-fueled electricity it prevents greenhouse gas emissions by the ton. This is hugely significant because burning coal, oil and natural gas for electricity makes the most pollution on the planet. Carbon dioxide released from burning petroleum makes the most impact on the environment as it traps heat in the atmosphere raising mean temperatures. Granted, Earth has a history of warm and cold eras but the rapid heating since the 1950s is unprecedented. The vast preponderance of scientists agree it is a man-made phenomenon caused by burning fossil (carbon-rich) fuels.

Let's review how carbon dioxide is weighed in a way to which we can all relate. A gallon of gasoline weighs about six pounds (a gallon of water, 8.33 lbs) but produces about 19 lbs of carbon dioxide after burning. Sounds impossible, right? The calculation is interesting.*

Consider a single molecule of octane, a typical hydrocarbon found in gasoline. Octane consists of eight atoms of carbon and 18 atoms of hydrogen, written as C8H18. If you break down the octane and mix it with enough oxygen (O2), you've got the ingredients--the atoms of carbon, hydrogen, and oxygen--to make eight molecules of carbon dioxide (CO2) and nine molecules of water (H2O). The eight molecules of CO2 weigh about three times more than the one molecule of octane you started with. (This does not violate the law of conservation of mass because the weight of oxygen from the air is added to the weight of the carbon from the gasoline.)

Estimating this way is not hard and fast so some assumptions must be made. The Environmental Protection Agency first determines how much carbon is in each particular kind of gasoline and then comes up with a weighted average based on consumption levels for each variety. Using this method, EPA estimates a gallon of gas contains an average of 2,421 grams of carbon which can produce 8,877 grams of CO2. They multiply that number by 0.99 to account for the carbon that doesn't react fully with the oxygen. Their result: 8,788 grams, or about 19.4 pounds.

Applying the same basic calculation to fossil-fueled electricity generation and developing countries adding new coal-fired plants by the week, global warming appears out of control. Solar and wind power are the key components to the solution.

* How Gasoline Becomes CO2.

Photos courtesy FreeFoto:


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