Month: April 2018

2.3 Potential of solar energy

As we discussed in the previous article, Sun is a huge nuclear fusion reactor. It is a spinning ball of gases around which all the planets revolve. Its energy radiates out to space at a tremendous rate but declines with increasing distance from the Sun.

The amount of solar irradiance per unit area per unit time on a surface normal to the Sun’s rays at the Earth’s mean distance from the Sun (one astronomical unit away from the Sun) is about 1388 Wm^-2. This value is often known as the solar constant. Solar energy is partially absorbed and reflected back by the atmosphere. Therefore, solar constant is measured using satellites which allow to find out the amount of solar power received by Earth’s atmosphere before entering the atmosphere.

1388 Wm^-2 of solar power reaching the atmosphere means one square meter of the Earth’s atmosphere normal to the EM waves receives solar power equivalent to 14 light bulbs each rated at 100 W (28 light bulbs each rated at 50 W)!

The basic math of the Sun

Solar irradiance outside the Earth’s atmosphere~ 1388 Wm^-2

Distance from the Sun to Earth~ 1.5×10¹¹ m [1]

Surface area of a sphere having a radius of 1.5×10¹¹ m = 4π (1.5×10¹¹ m)²

= 2.8 10²³ m²

Luminosity of the (solar power at the Sun) Sun            = 2.8 10²³ m² 1388 W m^-2

= 3.9 10²⁶ W

Current global power demand                                                   = 17.5 10¹² W [6]

Note that,  

This implies that

• Our Sun generates 2.2×10¹³ times the global power demand. In other words, it generates 2.2×10¹³times energy that we consume and it is enough to light up 2.2×10¹³ Earth-like planets.
• The amount of energy generated by the Sun in a second is equal to the amount of energy consumed by us for 2.2×10¹³

Note that, 

So…

The amount of energy generated by the Sun in one second is enough to fulfill the entire global energy demand for almost 697615 years (at current rate of energy consumption)!

The solar irradiance at the Earth’s surface is always less than the solar constant largely due to the absorption and reflection of solar energy by some gases in the atmosphere. In addition, solar irradiance varies from place to place on the Earth’s surface, largely due to the fact that different places on the Earth are irradiated at different angles of incidence (Earth is not a disk but a sphere). However, our planet still receives more than enough energy from the Sun to meet our entire energy demand.

CONTINUED

2.2 Sun Vs. Two Key Challenges in Energy Sector  

Energy industry has always been an evolving research field. Researchers have been extensively working to develop new alternative energy technologies and to improve the energy efficiency of electrical appliances. Both attempts are crucial to find a solution capable of solving the energy crisis in future. Among many such research interests in the energy sector, two fascinating concepts have always been mind-bending.  

1. High-temperature superconducting materials

The electrical resistance of a superconducting material is exactly zero at any temperature lower than its critical temperature. As a result, superconducting materials conduct electricity with no energy loss as long as their temperature is maintained below their critical temperature. But no material has still been found to exhibit superconductivity at the room temperature. All known superconducting materials need to be cooled to very low temperatures which is an expensive and complicated mechanism. Any superconducting material with a higher critical temperature would certainly be able to save a substantial amount of energy which would otherwise have dissipated as Joule heating loss in transmission lines and electric circuits.

2. Commercial-scale fusion reactors

Fusion is simply the opposite of fission. Just like in a nuclear fission, an enormous amount of energy is released when light nuclei fuse into heavy nuclei. When lighter nuclei fuse into heavier nuclei, the sum of the nuclear mass after the fusion reaction would be less than that of resultant particles. This drop in the mass is converted into energy (kinetic energy of resultant nuclei and particles, radiation) according to the Einstein equation. Nuclear fusion is an unbeatable way of generating energy in terms of the amount of energy that could be gained per 1 kg of fuel. Further, one would be surprised to know that the amount of fusion fuels on the earth is unlimited!

Deuterium and tritium have been found to be the best nuclear fusion fuels. Deuterium can be cropped from sea water without any limit as it is a naturally occurring isotope of hydrogen. Abundance of deuterium is very low compared to that of Protium in naturally occurring water. But oceans are huge reservoirs holding 1.34 billion square kilometers of water [1]. In other words, oceans contain oceans of nuclear fuels which would be enough to provide energy for more than 40 billions of years at present rate of global energy consumption [2]. These facts have brought to light some mind-blowing information about the potential of fusion fuels contained in sea water leading many to anticipate nuclear fusion would be the most promising solution to the energy crisis in future.

Comparing potential of nuclear fusion energy to any other energy source is like trying to compare apples and oranges. But the bad story is that many technical challenges are yet to be overcome to build a commercial-scale fusion power plant. In order to build an economically/ practically feasible fusion reactor, the harvestable amount of energy must be always higher than the amount of energy needed to operate the reactor. But current technology is not capable of harvesting a reasonable amount of energy in nuclear fusion.

The idea of utilizing nuclear fusion energy was first emerged in1950s and was one of the mainstream research field in nuclear physics. Many believed that nuclear fusion was going to replace other forms of energy within next three decades. Researchers have been dreaming of self-sustaining, economically viable nuclear fusion power plants for decades and it still remains a dream, unfortunately.

We may have to wait just one more year, a decade, several decades or perhaps until 2100…

Who knows?

Nobody knows…..

But…

Even though we do not think of it…

We already have a massive fusion power plant in which tons of light nuclei fuse into larger nuclei generating a tremendous amount of energy each second.

Our planet is orbiting around it…

It is at the center of our orbit…

A huge natural fusion reactor…

The Sun!

Sun is the largest power plant in our solar system and is a huge spinning, gaseous ball.

It is a natural fusion reactor which operates 24 hours a day/ 7 days a week/ 52 weeks a year/ 1000 years a millennium, 10 millennia a hectocentennial…

And it does not shut down for maintenance in any circumstances.

Half of the earth is always receiving radiation from the Sun upon exposure to sunlight.

In order to ensure that each region on the earth receives solar energy, our planet is spinning while it is revolving about the Sun offering a golden opportunity to all the countries to harvest energy from a distant fusion reactor!

In next article, let us discuss the potential of solar energy and its capacity to quench our thirst for energy.

1. Eakins, B. W., & Sharman, G. F. (2010). Volumes of the World’s Oceans from ETOPO1. NOAA National Geophysical Data Center, Boulder, CO, 7.
2. Isaacs, J. D., & Seymour, R. J. (1973). The ocean as a power resource. international journal of environmental studies, 4(1-4), 201-205.

2.1 Solar energy: The best renewable energy source under the Sun

Earth, the one and only habitable planet in the solar system is rich in energy diversity. It is home to a variety of renewable energy sources, fossil fuels and nuclear fuels. Even though plenty of renewable energy is readily available around us we humans have been extensively drilling the earth for fossil fuels to fulfil the energy demand. As we previously discussed, this tendency has led to numerous environmental, ecological, social, and economic problems. Some damages we have done to the earth are extreme threats to the earth’s health and death threats to the living beings.

‘’Sooner or later, we will have to recognize that the Earth has rights, too, to live without pollution. What mankind must know is that human beings cannot live without Mother Earth, but the planet can live without humans’’- Evo Morales [1]

In our very first articles, we discussed manmade environmental damages and their impacts on the climate system. Then we realized that climate change was the most damaging upshot caused by our imprudent, irresponsible activities. We then moved on to discuss the anthropogenic causes of climate change and comprehended that overuse of fossil fuels was the most potent cause. All in all, switching to renewable energy was identified to be the game changer!

Thenceforward we discussed various sources of renewable energy in detail and realized that none of them would be sufficient to satisfy our increasing hungry for energy.  Finally, we concluded such renewable energy sources would be insufficient to replace today’s role of oil and thus to quench our thirst for oil.

However, as we learned in the last article, we are still not unlucky!

We are immensely fortunate to have access to a renewable energy source which is certainly capable of providing energy more than enough to fulfill the entire world’s energy demand.

It is solar energy!

Unlike other renewable energy sources, solar energy is everywhere and abundant!

Especially, it is easy to be harnessed.

And solar energy harvesting does not conduce to noise or air pollution.

What is solar energy?

Solar energy is heat and sunlight coming from the Sun. Simply, Sun is the place where solar energy emanates. Our Sun generates a tremendous amount of energy to nourish and light up its astronomical members, planets, moons, asteroids and comets. Energy generated by the Sun is irradiated out into the outer space in the form of electromagnetic (EM) waves and meets the Earth’s atmosphere at an average intensity in the range of 1361 W m^-2-1362 W m^-2 [2]. This amount is, however, reduced due to the absorption of solar radiation by various gases in the atmosphere before reaching the Earth’s surface.

All the indirect solar energy sources that we discussed in previous articles are also naturally derived from solar energy. However, the term ‘solar energy’ mostly refers to the use of solar radiation (sunlight/ heat) for practical applications such as electricity generation, water heating and space heating.

1. Morales, E. (2016). Sooner or later, we will have to recognize that the Earth has rights, too, to live without pollution. What mankind must know is that human beings cannot live without Mother Earth, but the planet can live without humans. People, Planet, and Progress Beyond 2015, 2, 133.
2. G.; Lean. J. L. (2011). “A new lower value of total solar irradiance: Evidence and climate significance” (PDF). Geophysical Research Letters. 38: n/a. Bibcode: 2011 GeoRL.38.1706K. doi: 10.1029/2010GL045777.