Categories : Energy Teaching People - What and How Tools for Society Uncategorized

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In part one of this series we identified, in broad terms, two forms of energy available to us: arriving energy and stored energy. The arriving energy comes from the sun and, if not stored, must be used right away. Of course, it must be transformed into a useful form of energy except, perhaps, for the warming it provides and assisting in our ability to see. One might argue that it causes winds and other atmospheric changes, but this too is conservation. So what are the forms of stored energy even if not readily to do work?


Beyond solar and wind, there are geothermal and hydro. Geothermal, in loose terms, is the hot water stored in the earth. Actually it is more than hot water. It includes the hot water and hot rocks found within a few miles of earth’s surface and in the extremely hot molten rack called magma deeper in the earth. It is heat. Hydro, on the other hand, is potential energy stored in water that can be harnessed from its downward flow caused by the weak force field called gravity. Some might argue that hydro energy is not stored energy but caused by the solar energy generating rain storms that move the water to higher elevations. But when the water is moved, it acquires stored (potential) energy.


Continuing, we find fossil fuels, nuclear, fire and food. The fossil fuels have chemical compounds that, when broken down, generally release heat that must be transformed, for the most part, into a form more useful for human directed machine work or converted into another useful form. Of course, sometimes the heat is used directly as in a home gas heating system (very local “climate” control). Nuclear is similar except that the energy comes from breaking down the nucleus of an atom as opposed to a chemical bond.


Fire and food can be considered together if you eliminate the burning of fuel in a car engine. As used here it refers to the burning of things such as trees and other recently living things. Like food, these things are made by plant cells using carbon dioxide (CO2) and the solar energy of the sun. The solar energy is stored and some of the “bad” CO2 is converted into “safe” molecules with carbon.


There is another source of energy that also needs to be considered: the battery. In simple terms a battery has two plates that create an electromagnetic field. The plates either have an abundance of electrons (negative) or a great shortage of electrons (positive). In everyday terms you externally connect the negative terminal of one plate to the positive terminal of the other plate and the electrons move or flow, – electricity.


You can buy a battery at the store and there are two types. In one type the chemistry cannot be reversed – the battery “dies” when all of the surplus electrons have moved. The other type is called rechargeable. By applying electrical energy to the battery in the right manner you can reverse the flow of electrons inside for later usage. Your cell phone, car, and some lawn lights have rechargeable batteries. We take them for granted and really do not consider the external energy needed to recharge or replace the battery’s potential energy. It’s sort of like pumping water uphill.


In everything we do we are doing work with energy to heat something or to move something. To this process there is an attribute called efficiency. Consider the movement of something. You want to pick up a box at the grocery store and move it to your abode. At the store you pick up the box, put it in your shopping cart, pay for it, move it to your car and put it on the front seat. Then you drive your car home and physically take the box inside. Every step of this process takes energy. Your body has to move, push the cart and so on. Your body is “burning” energy, converting some of its stored energy into movement. But some of the energy is lost as heat from your body and the total energy consumed is the sum of the energy moving the box and the energy that is lost. Efficiency is the amount of energy used for actually moving the box divided by the total energy consumed expressed as a percentage. In the case of the human moving the box the efficiency is probably very high or, at least, acceptable. But how about the car?


Assume you have a gasoline powered car and an electricity powered car. Also assume the trip is 10 miles. I am going to do some math and scaling from 10 is an easier process if you want to do it. A Chevy Bolt (electric) requires about seven kWh (kilowatt-hours) to make the trip. Converting, this is 10.8 million joules. A gallon of gasoline has 127 million joules of potential (stored) energy. If your car gets 25 miles per gallon, it will consume 50.8 million joules (useful or lost). Assuming the electric car is 100 percent efficient, the gasoline car powered car is only 21 percent efficient. The rest of the energy released by burning the gasoline is lost in waste: lost energy contributing to increased entropy, lost physical waste products, and CO2 emissions.


Simplistically, just convert everything to electricity. But from where does the electricity come? In the world, 65.3 percent of electricity (2016 number) is generated from fossil fuels. In the United States it is 66.2 percent (2014 number). And in France the number is 9.3 percent (2006 number). How can we change the numbers? Is it solar, wind, hydro, geothermal, nuclear, or something else?

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 Posted on : June 18, 2019
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