The Sun

From Thermal-FluidsPedia

(Difference between revisions)
Jump to: navigation, search
Line 10: Line 10:
[[Image:The sun.jpg|thumb|400 px|alt=Figure 1 The sun |Figure 1 The sun]]
[[Image:The sun.jpg|thumb|400 px|alt=Figure 1 The sun |Figure 1 The sun]]
-
The sun is a 1.4 million kilometer wide sphere of extremely dense, hot gas that resides approximately 150 million kilometers from the earth (Figure 1). Composed predominately of hydrogen and helium, its central temperature and pressure are estimated to reach 15-25 million kelvins and 300 billion atmospheres – conditions suitable for nuclear fusion to take place. As we will discuss later in [[Nuclear Energy|nuclear energy]], fusion involves combining atoms of hydrogen into a helium nucleus and heat. The sun loses mass at a rate of about 4.3 billion kilograms every second while producing an enormous amount of energy ([[#References|1]]). At its outer layer ionized gases both absorb and emit a continuous spectrum of radiation, causing this layer to be essentially opaque. Temperatures drop to about 5,800 K at the surface of the sun.
+
The sun is a 1.4 million kilometer wide sphere of extremely dense, hot gas that resides approximately 150 million kilometers from the earth (Figure 1). Composed predominately of hydrogen and helium, its central temperature and pressure are estimated to reach 15-25 million kelvins and 300 billion atmospheres – conditions suitable for nuclear fusion to take place. As we will discuss later in [[Nuclear Energy|nuclear energy]], fusion involves combining atoms of hydrogen into a helium nucleus and heat. The sun loses mass at a rate of about 4.3 billion kilograms every second while producing an enormous amount of energy ([[#References|a]]). At its outer layer ionized gases both absorb and emit a continuous spectrum of radiation, causing this layer to be essentially opaque. Temperatures drop to about 5,800 K at the surface of the sun.
==References==
==References==
-
(1) This loss of mass is nothing to worry about! By some estimates, the sun will have enough energy to support life on earth for another five billion years.
+
(1) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005
-
(2) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005
+
==Additional Comments==
 +
 
 +
(a) This loss of mass is nothing to worry about! By some estimates, the sun will have enough energy to support life on earth for another five billion years.
==Further Reading==
==Further Reading==
==External Links==
==External Links==

Revision as of 16:51, 18 July 2010

Give me the splendid silent sun with all his beams full-dazzling. ~ Walt Whitman (1819 - 1892)

Since ancient times, humans have demonstrated a basic understanding of solar energy by designing shelters that protected them from the cold of winter and the heat of summer. Socrates suggested that houses should be built facing south in order to maximize the heat of the winter sun. Anasazi Indians designed their dwellings under cliff overhangs, maximizing the solar gain in winter and providing shade in summer. The sheltering overhangs also reduced radiant heat loss at night and protected against cold winds. Furthermore, some houses were built with thick stone and clay walls and had small windows to retain heat during the day and release it gradually at night.

Today, solar power has been proven to be highly effective not only in providing heat to buildings and swimming pools, but also in cooling applications and for the generation of electricity. As with many other sources of energy, there are limitations on where this energy source can be used. The amount and intensity of solar energy available varies depending on geographical location, the position of the sun in the sky, weather conditions, and the orientation of the collector and surrounding objects. Solar energy can be used worldwide, especially in regions with high insolation. This includes large areas of Africa, Australia, the Middle East, Central and South America, and the southwestern United States.

In this chapter, we start by looking at the sun itself and the amount of radiation that can potentially be intercepted by various collectors on earth. We will discuss passive and active systems, as well as thermal and photovoltaic systems for utilizing solar energy for heating, cooling, and producing electricity.

Figure 1 The sun
Figure 1 The sun

The sun is a 1.4 million kilometer wide sphere of extremely dense, hot gas that resides approximately 150 million kilometers from the earth (Figure 1). Composed predominately of hydrogen and helium, its central temperature and pressure are estimated to reach 15-25 million kelvins and 300 billion atmospheres – conditions suitable for nuclear fusion to take place. As we will discuss later in nuclear energy, fusion involves combining atoms of hydrogen into a helium nucleus and heat. The sun loses mass at a rate of about 4.3 billion kilograms every second while producing an enormous amount of energy (a). At its outer layer ionized gases both absorb and emit a continuous spectrum of radiation, causing this layer to be essentially opaque. Temperatures drop to about 5,800 K at the surface of the sun.

Contents

References

(1) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005

Additional Comments

(a) This loss of mass is nothing to worry about! By some estimates, the sun will have enough energy to support life on earth for another five billion years.

Further Reading

External Links