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Energy Basics. Stuff we all should know…. Historical aspects. Greeks and Romans initially used charcoal and wood to heat homes 2500 years ago, but switched to passive solar (with south facing windows, greenhouses ad low windows) when wood supplies fell.
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Energy Basics Stuff we all should know….
Historical aspects • Greeks and Romans initially used charcoal and wood to heat homes 2500 years ago, but switched to passive solar (with south facing windows, greenhouses ad low windows) when wood supplies fell. • In the USA, we started with wood for heating until 1880, then moved to coal. In the 1920’s we started using oil based technology and began the turbine era.
The Great Depression • The need for jobs and a national agenda spawned an age of big projects, such as the Hoover Dam, the Golden Gate Bridge and the Empire State Building
WWII • Nuclear discoveries brought the world a new possibility for electricity production. Nuclear fission.
What is Energy ? • Energy is the ability to do work • Work is exerting force over a distance • !st Law of Thermodynamics: Energy may be converted from one form to another, but will never be lost from the system. (Energy conservation) • 2nd Law of Thermodynamics: During that energy type conversion, some energy is converted to heat. Thus, the entropy increases. • Entropy is a measure of energy unavailable to do work in the system. Some heat is lost in the production and is entropy.
Lets convert human energy into work. • Lets measure it in watts. Then convert it to Horsepower ! • Lab Methods: We need your weight in Kg. (lbs X 2.2) • We need a stopwatch, a ruler, a calculator, and some good shoes ! • Formula: Watts generated / 746 = horsepower • We also need the total height of the stairs. (measure one stair and multiply by the number of stairs.
Set up : • Watts formula: • Wt (kg) X total climb (M) X 9.8 Time to climb stairs (sec) You will get two attempts to run up the stairs. Best time will count !
Solar Energy Plenty of it !
What kind of energy? • Nuclear reactions in the sun make thermal energy in the sun which is radiated to Earth as radiant energy which is again converted to thermal energy when it hits any object.
The Sun is by far the largest object in the solar system. It contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest)
Chemistry ! • The Sun is, at present, about 70% hydrogen and 28% helium by mass, everything else ("metals") amounts to less than 2%. This changes slowly over time as the Sun converts hydrogen to helium in its core. • Conditions at the Sun's core (approximately the inner 25% of its radius) are extreme. The temperature is 15.6 million Kelvin and the pressure is 250 billion atmospheres. At the center of the core the Sun's density is more than 150 times that of water.
Sunspots ? • The surface of the Sun, called the photosphere, is at a temperature of about 5800 K. Sunspots are "cool" regions, only 3800 K (they look dark only by comparison with the surrounding regions). Sunspots can be very large, as much as 50,000 km in diameter.
The Sun’s Power • The Sun's power (about 386 billion billionMegaWatts) is produced by nuclear fusion reactions. Each second about 700,000,000 tons of hydrogen are converted to about 695,000,000 tons of helium and 5,000,000 tons (=3.86e33 ergs) of energy in the form of gamma rays. As it travels out toward the surface, the energy is continuously absorbed and re-emitted at lower and lower temperatures so that by the time it reaches the surface, it is primarily visible light
What does the Sun’s energy do ? • The sun keeps us in place • The sun keeps the organization of the tides • The sun keeps us warm • The sun causes the weather and wind ! • The sun gives us energy (386 billion billion MW) • The sun grows plants (photosynthesis, oxygen, etc)
Really ? • Just 1 second of the Sun's energy output would power the U.S. for 9,000,000 years . • 1.0 seconds = 9 million years
The obvious question then…. • Why don’t we use the darned thing ??!!!!!!!!