Solar Energy

Question 1

How hot is the Suns surface?

Answer 1

Sun’s surface T ~ 6000K

Question 2

How dose the earth receive energy?

Answer 2

Earth’s receives E through
radiative E transfer:
§ 47% visible light
§ 45% infrared
§ 8% ultraviolet and shorter
( X- and Gamma-rays )

Question 3

What is TSI?

Answer 3

TSI (‘solar constant’) =insolation at the top of the atmosphere =
S0=1360.8± 0.5 W/m

Question 4

What is the Milky way galaxy?

Answer 4

A flattened, disk-shaped mass in space estimated to contain up to 400 billion stars; a barred-spiral galaxy; includes our Solar System.

Question 5

Where is our solar system located?

Answer 5

Our Solar System is embedded more than halfway out from the galactic centre, in one of the Milky Way’s spiral arms—the Orion Spur of the Sagittarius Arm.

Question 6

What dose our solar system consist of and where is it located?

Answer 6

Our Solar System of eight planets, four dwarf planets, and asteroids is some 30 000 light-years from this black hole at the centre of the Galaxy and about 15 light-years above the plane of the Milky Way.

Question 7

What is the definition of Gravity?

Answer 7

the mutual attraction exerted by every object upon all other objects in proportion to their mass, was the key force in this condensing solar nebula.

Question 8

How was our solar system formed?

Answer 8

According to prevailing theory, our Solar System condensed from a large, slowly rotating and collapsing cloud of dust and gas, a nebula. Gravity, the mutual attraction exerted by every object upon all other objects in proportion to their mass, was the key force in this condensing solar nebula. As the nebular cloud organized and flattened into a disk shape, the early protosun grew in mass at the centre, drawing more matter to it. Small eddies of accreting material swirled at varying distances from the centre of the solar nebula; these were the protoplanets.

Question 9

What is the Planetesimal Hypothesis

Answer 9

The planetesimal hypothesis, or dust-cloud hypothesis, explains how suns condense from nebular clouds. In this hypothesis, small grains of cosmic dust and other solids accrete to form planetesimals that may grow to become protoplanets and eventually planets; these formed in orbits about the developing Solar System’s central mass.

Question 10

What is solar wind?

Answer 10

Solar wind is a flow of electrically
charged particles from Sun’s outer
corona (~ 3-4 days to reach Earth).

Question 11

What are sunspots?

Answer 11

Sunspots are caused by magnetic
storms on the Sun. They are often
more than 12 times Earth’s diameter
(their temperatures are less than the
temperatures of their surroundings).

The Sun’s most conspicuous features are large sunspots, surface disturbances caused by magnetic storms. Sunspots appear as dark areas on the solar surface, ranging in diameter from 10 000 to 50 000 km, with some as large as 160 000 km, more than 12 times Earth’s diameter.

Question 12

What dose the earths magnetosphere do?

Answer 12

The Earth’s magnetosphere deflects
the solar wind.

As the charged particles of the solar wind approach Earth, they first interact with Earth’s magnetic field. This magnetosphere, which surrounds Earth and extends beyond Earth’s atmosphere, is generated by dynamo-like motions within our planet. The magnetosphere deflects the solar wind toward both of Earth’s poles so that only a small portion of it enters the upper atmosphere.

Question 13

What is Solar wind Magnetosphere Ionosphere
Link Explorer (SMILE)

Answer 13

Solar wind Magnetosphere Ionosphere
Link Explorer (SMILE), an
ESA collaborative mission with China
that will investigate the Sun-Earth
connection. Launch planned for 2023.

Question 14

What are the Auroras?

Answer 14

Outbursts of charged particles
(coronal mass ejections, CME)
cause most spectacular auroras

§ Collisions of particles with
elements in the atmosphere
produce colours (O2 - yellow and
green, N2 - red, violet, and blue)

A spectacular glowing light display in the ionosphere, stimulated by the interaction of the solar wind with principally oxygen and nitrogen gases and few other atoms at high latitudes; called aurora borealis in the Northern Hemisphere and aurora australis in the Southern Hemisphere.
These lighting effects, known as the aurora borealis (northern lights) and aurora australis (southern lights), occur 80–500 km above Earth’s surface through the interaction of the solar wind with the upper layers of Earth’s atmosphere. They appear as folded sheets of green, yellow, blue, and red light that undulate across the skies of high latitudes poleward of 65°

Question 15

What percentage of matter from the original solar nebula did the sun capture?

Answer 15

The Sun captured about 99.9% of the matter from the original solar nebula. The remaining 0.1% of the matter formed all the planets, their satellites, asteroids, comets, and debris

Question 16

What is fusion and how does it relate to the Sun?

Answer 16

The Sun’s abundant hydrogen atoms are forced together and pairs of hydrogen nuclei are joined in the process of fusion. In the fusion reaction, hydrogen nuclei form helium, the second-lightest element in nature, and enormous quantities of energy are liberated—literally, disappearing solar mass becomes energy.

Question 17

What is the solar cycle?

Answer 17

The solar cycle is the periodic variation in the Sun’s activity and appearance over time

Question 18

What is the Soar Minimum/Maximum?

Answer 18

A solar minimum is a period of years when few sunspots are visible; a solar maximum is a period during which sunspots are numerous.

Question 19

What are Solar Flairs?

Answer 19

Solar flares, magnetic storms that cause surface explosions, often occur in active regions near sunspots.

Question 20

What are prominence eruptions

Answer 20

prominence eruptions, outbursts of gases arcing from the surface, often occur in active regions near sunspots.

Question 21

What does the sone constantly emit?

Answer 21

The Sun constantly emits clouds of electrically charged particles (principally, hydrogen nuclei and free electrons) that surge outward in all directions from the Sun’s surface.

Question 22

What experiment did the Apollo XI astronauts do in 1969

Answer 22

Because the solar wind does not reach Earth’s surface, research on this phenomenon must be conducted in space. In 1969, the Apollo XI astronauts exposed a piece of foil on the lunar surface as a solar wind experiment (Figure 2.3). When examined back on Earth, the exposed foil exhibited particle impacts that confirmed the character of the solar win

Question 23

What are Coronal Mass ejections?

Answer 23

In addition, massive outbursts of charged material, referred to as coronal mass ejections (CMEs), contribute to the flow of solar wind material from the Sun into space. CMEs that are aimed toward Earth often cause spectacular auroras in the upper atmosphere near the poles.

Question 24

What is the essential solar input to life

Answer 24

The essential solar input to life is electromagnetic energy of various wavelengths, traveling at the speed of light to Earth.

Question 25

What is the electromagnetic spectrum

Answer 25

Solar radiation occupies a portion of the electromagnetic spectrum, which is the spectrum of all possible wavelengths of electromagnetic energy.

Question 26

What is a wavelength?

Answer 26

A wavelength is the distance between corresponding points on any two successive waves.

Question 27

What is Frequency?

Answer 27

The number of waves passing a fixed point in 1 second is the frequency.

Question 28

What is the radiant energy composition that the Sun emits?

Answer 28

The Sun emits radiant energy composed of 8% ultraviolet, X-ray, and gamma-ray wavelengths; 47% visible light wavelengths; and 45% infrared wavelengths.

Question 29

What is Wien’s Displacement law?

Answer 29

An important physical law, Wien’s Displacement Law, states that all objects radiate energy in wavelengths related to their individual surface temperatures: the hotter the object, the shorter the mean wavelength of maximum intensity emitted. This law holds true for the Sun and Earth.

Question 30

How hot is the Sun’s surface?

Answer 30

The Sun’s surface temperature is about 6000 K (6273°C), and its emission curve is similar to that predicted for an idealized 6000-K surface

Question 31

What is a blackbody?

Answer 31

A blackbody is a perfect absorber of radiant energy; it absorbs and subsequently emits all the radiant energy that it receives

Question 32

What kind of wavelenghts do the Earth and Sun emit?

Answer 32

To summarize, the Sun’s radiated energy is shortwave radiation that peaks in the short visible wavelengths, whereas Earth’s radiated energy is longwave radiation concentrated in infrared wavelengths.

Question 33

What is the thermopause?

Answer 33

The region at the top of the atmosphere, approximately 480 km above Earth’s surface, is the thermopause (see Figure 3.1). It is the outer boundary of Earth’s energy system and provides a useful point at which to assess the arriving solar radiation before it is diminished by scattering and absorption in passage through the atmosphere.

Question 34

How much of the Suns totaly energy output reaches earth?

Answer 34

Earth’s distance from the Sun results in its interception of only one two-billionth of the Sun’s total energy output. Nevertheless, this tiny fraction of energy from the Sun is an enormous amount of energy flowing into Earth’s systems.

Question 35

What is Insolation?

Answer 35

Solar radiation that is intercepted by Earth is insolation, derived from the words incoming solar radiation. Insolation specifically applies to radiation arriving at Earth’s atmosphere and surface; it is measured as the rate of radiation delivery to a horizontal surface, specifically, as watts per square metre (W·m−2).

Question 36

What is the Solar Constant?

Answer 36

The solar constant is the average insolation received at the thermopause when Earth is at its average distance from the Sun, a value of 1372 W·m−2.* As we follow insolation through the atmosphere to Earth’s surface (Chapters 3 and 4), we see that its amount is reduced by half or more through reflection, scattering, and absorption of shortwave radiation.

Question 37

What is the Subpolar point?

Answer 37

Earth’s curved surface presents a continually varying angle to the incoming parallel rays of insolation (Figure 2.8). Differences in the angle at which solar rays meet the surface at each latitude result in an uneven distribution of insolation and heating. The only point where insolation arrives perpendicular to the surface (hitting it from directly overhead) is the subsolar point.

Question 38

Where is the subpolar point located?

Answer 38

During the year, this point occurs only at lower latitudes, between the tropics (about 23.5° N and 23.5° S), and as a result, the energy received there is more concentrated. All other places, away from the subsolar point, receive insolation at an angle less than 90° and thus experience more diffuse energy; this effect becomes more pronounced at higher latitudes.

Question 39

What is the differences in the energy recieved above the equator and the poles?

Answer 39

The thermopause above the equatorial region receives 2.5 times more insolation annually than the thermopause above the poles. Of lesser importance is the fact that, because they meet Earth from a lower angle, the solar rays arriving toward the poles must pass through a greater thickness of atmosphere, resulting in greater losses of energy due to scattering, absorption, and reflection.

Question 40

Why are days and nights longer on the poles?

Answer 40

In June, the North Pole receives slightly more than 500 W·m−2 per day, which is more than is ever received at 40° N latitude or at the equator. Such high values result from long 24-hour daylengths at the poles in summer, compared with only 15 hours of daylight at 40° N latitude and 12 hours at the equator. However, at the poles the summertime Sun at noon is low in the sky, so a daylength twice that of the equator yields only about a 100 W·m−2 difference.

In December, the pattern reverses, as shown on the graphs. Note that the top of the atmosphere at the South Pole receives even more insolation than the North Pole does in June (more than 550 W·m−2). This is a function of Earth’s closer location to the Sun at perihelion (January 3 in Figure 2.1d). Along the equator, two slight maximum-insolation periods of approximately 430 W·m−2 occur at the spring and fall equinoxes, when the subsolar point is at the equator.

Question 41

What is net radiation?

Answer 41

net radiation, which is the balance between incoming shortwave energy from the Sun and all outgoing radiation from Earth and the atmosphere—energy inputs minus energy outputs.

Question 42

What are isolines?

Answer 42

The map uses isolines, or lines connecting points of equal value, to show radiation patterns

Question 43

In middle and high latitudes, poleward of approximately 36° N and S latitudes, net radiation is negative. Why?

Answer 43

This occurs in these higher latitudes because Earth’s climate system loses more energy to space than it gains from the Sun, as measured at the top of the atmosphere. In the lower atmosphere, these polar energy deficits are offset by flows of energy from tropical energy surpluses

Question 44

Of interest is the –20 W·m−2 area. Why?

Answer 44

Of interest is the –20 W·m−2 area over the Sahara region of North Africa. Here, typically clear skies—which permit great longwave radiation losses from Earth’s surface—and light-coloured reflective surfaces work together to reduce net radiation values at the thermopause. In other regions, clouds and atmospheric pollution in the lower atmosphere also affect net radiation patterns at the top of the atmosphere by reflecting more shortwave energy to space.

Question 45

What is Seasonality?

Answer 45

Seasonality refers both to the seasonal variation of the Sun’s position above the horizon and to changing daylengths during the year. Seasonal variations are a response to changes in the Sun’s altitude, or the angle between the horizon and the Sun.

Question 46

What is alititude

Answer 46

The angular distance between the horizon (A horizontal plane) and the Sun (Any point in the sky.)

Question 47

Where can the Sun be found directly overhead?

Answer 47

The Sun is found directly overhead (90° altitude, or zenith) only at the subsolar point, where insolation is at a maximum. At all other surface points, the Sun is at a lower altitude angle, producing more diffuse insolation.

Question 48

What is the Sun’s declination?

Answer 48

The Sun’s declination is the latitude of the subsolar point. Declination annually migrates through 47° of latitude, moving between the Tropic of Cancer and Tropic of Capricorn latitudes. Although it passes through Hawai‘i, which is between 19° N and 22° N, the subsolar point does not reach the continental United States or Canada; all other states and provinces are too far north.

Question 49

What is daylength?

Answer 49

The duration of exposure to insolation is daylength, which varies during the year, depending on latitude.

Daylength is the interval between sunrise, the moment when the disk of the Sun first appears above the horizon in the east, and sunset, that moment when it totally disappears below the horizon in the west.

Question 50

What is noteworthy about the daylength in the North and South Poles?

Answer 50

At the North and South Poles, the range of daylength is extreme, with a 6-month period of no insolation, beginning with weeks of twilight, then darkness, then weeks of pre-dawn. Following sunrise, daylight lasts for a 6-month period of continuous 24-hour insolation—literally, the poles experience one long day and one long night each year!

Question 51

How do seasons happen?

Answer 51

Seasons result from variations in the Sun’s altitude above the horizon, the Sun’s declination (latitude of the subsolar point), and daylength during the year. These in turn are created by several physical factors that operate in concert: Earth’s revolution in orbit around the Sun, its daily rotation on its axis, its tilted axis, the unchanging orientation of its axis, and its sphericity (summarized in Table 2.1). Of course, the essential ingredient is having a single source of radiant energy—the Sun.