How Solar Power Works


The sun is a nearly perfect sphere of hot, glowing gas. Its source of power lies buried deep in the central core, where a nuclear furnace rages nonstop, turning matter into pure heat and light. Slightly bigger than a typical star, the Sun is large enough by volume to swallow 1.3 million Earth. It contains 99.8 percent of all the matter in the Solar System and the force of gravity generated by this enormous mass keeps the planets trapped in orbit around it. Seen from Earth, the Sun is a life-sustaining source of light and warmth that shines steadily on us. Closer views, however, reveal a world of astonishing violence, its seething surface bursting with vast eruptions that hurl fiery gases into space. Scientists divide the Sun’s interior into three distinct layers: the core, the radiative zone, and the convective zone. All three are made solely of gas, but the gas gets hotter and denser toward the center. In the core, the temperature soars to 27 million °F (15 million °C) and the gas is 150 times denser than water (Dorling Kindersley, Knowledge Encyclopedia, DK Books).

It is therefore not astonishing that over the ages, man has worshipped the sun and viewed this nearby star as a god in the skies. In Africa, the Tiv people consider the sun to be the son of the supreme being, Awondo and the Moon Awondo’s daughter. The Barotse tribe believes that the sun is inhabited by the sky god, Nyambi and the moon is his wife. Even where the sun god is equated with the supreme being. In some African mythologies, he or she does not have any special functions or privileges as compared to other deities. The Ancient Egyptian god of creation, Amun is also believed to reside inside the sun. So is the Akan creator deity, Nyame and the Dogon deity of creation, Nommo (Wikipedia Encyclopaedia).

However, the sun is just one of God’s many creations. Psalm 148: 1-14 states that:

“Praise the Lord! Praise the Lord from the heavens; praise him in the heights! Praise him, all his angels; praise him, all his hosts! Praise him, sun and moon, praise him, all you shining stars! Praise him, you highest heavens, and you waters above the heavens! Let them praise the name of the Lord! For he commanded and they were created.”

God warns His children in Israel not to worship the sun as can be seen in Deuteronomy 4:19:

“And beware lest you raise your eyes to heaven, and when you see the sun and the moon and the stars, all the host of heaven, you be drawn away and bow down to them and serve them, things that the Lord your God has allotted to all the peoples under the whole heaven.”

 Although God warned his children not to worship the sun, He did not forbid us from harnessing or “harvesting” the sun’s energy. Indeed the sun is the source of light on our planet. Apart from being the source of light, the sun is also the source of heat and other forms of energy, including the energy stored in the foods we eat. The sun is also the source of fossil fuel (like coal and petroleum) vide plants. Over the decades, man has been able to turn bounty of sunbeams into useful electricity because the sun is like a power plant in the sky which bathes the earth in ample energy. The sun doesn’t give off carbon dioxide emissions like our earthly generator does and it never runs out of fuel. And the good thing is that God is not charging us for using it; it’s completely free.

How is solar energy harnessed?

The sun’s light contains energy and all lights do contain energy. Usually, when light reach an object, the energy turns into heat, like the warmth/heat you feel when you sit or walk in the sun. But when light hits certain materials the energy turns into an electrical current instead, which we can then harness for power. One hour of solar energy, where fully harnessed, can fulfil a whole year of energy need on earth! The sunlight reaches the earth’s surface in form of:

  • Light or the visible radiation (frequencies that produce the spectra violet to red while passing through a prism)
  • Heat or invisible infrared radiation (frequencies below [=infra] red spectrum)
  • High-frequency ultra-violet radiation (frequencies beyond [=ultra] violet spectrum). The use of the light needs no elaboration. The heat is the energy is what we use to dry clothes. It also runs the water-cycle (evaporation-cloud-rain).

Solar-electricity harnesses the first mode of light reaching the earth. This process of converting the light into electricity is called PV or photovoltaic.

How Do Solar Cells Work?

Solar cells convert light directly into electricity. On a sunny day, the electricity converted from an area of 1 square-meter can feed a 100W light-bulb. Solar cells or photovoltaic cells are generally silicon-based. Silicon is an element extracted from sand pieces that absorb the sunlight. One end of the Silicon (Si) piece is doped with Boron (B) which is considered as the Positive (+ve) end and the other end is doped with Phosphorus (P), which is the Negative (-ve) end. When light falls onto the solar cell, electrons are displaced from the atoms of silicon. However, the electrons tend to move towards phosphorus which attracts electrons (negative charges). Thereby, there is a surplus of electrons in the negative end and a shortage of electrons in the positive end. If a conducting line is formed up outside the cell between the positive and negative ends, an electrical flow is generated and a working circuit is constructed. This electricity is a direct current or DC (unidirectional flow) like a battery. But DC is not suitable for common use, so DC is converted through an inverter to alternating current or AC. This AC can be transformed into required voltage through a transformer. This process of converting sunlight into electricity is called the photovoltaic process. A combination of PV cells makes a PV module, a set of PV modules form a PV panel or commonly called solar panel. Even greater powers can be achieved through a collection of PV panels put together in an Array.

Early solar technology as we have just noted, employed large crystals made out of silicon, which produces an electrical current when struck by light. Silicon as an element can do this because the electrons in the crystal “get up and move” when exposed to light instead of just wiggling in one place to make heat. The silicon turns a good portion of light energy into electricity, but it is expensive because big crystals are hard to grow. Newer materials use smaller, cheaper crystals, such as copper-indium-gallium-selenide, that can be shaped into flexible films. This “thin-film” solar technology, however, is not as good as silicon at turning light into electricity.

 What is the Process or the Steps of Harnessing Solar Energy?

In summary, the process of harnessing solar energy takes the following pattern:

  • Of course, it starts with the Sun radiating light.
  • The PV cells convert solar radiation into electricity.
  • This electricity is like battery-generated electricity (unidirectional flow of current) or the DC.
  • The inverter converts direct current (DC) into alternating current (AC).
  • The transformer guarantees that the voltage of the electricity coming from the inverter is the one we require.
  • The distribution scheme receives electricity produced by the system and combines it with other electric sources.
  • There could be electric meters to measure the amount of electricity produced.

(Ref: http://www.solarenergyhome.co.uk/solar_energy_works.htm)

 What are the Advantages of Solar Energy over Conventional Energy?

Solar energy has the following advantages over conventional energy:

  • The energy from the sun is virtually free after the initial cost of installation has been recovered.
  • Depending on the utilization of energy, paybacks can be very short when compared to the cost of common energy sources used.
  • Solar and other renewable energy systems can be stand-alone; thereby not requiring connection to a power or natural gas grid.
  • The sun (especially in the tropics) provides a virtually unlimited supply of solar energy.
  • The use of solar energy displaces conventional energy; which usually results in a proportional decrease in greenhouse gas emissions.
  • The use of solar energy is a largely untapped market.
  • Other technologies that are Beneficial when using Solar Energy

What’s the difference between how a plant captures light energy and how man does it with solar cells?

Plants absorb the light, and [they use] that electron to change a chemical bond inside their cells to actually make fuel. Right now there is no solar cell that can do that although research is ongoing in that area. If a solar cell could work like plants, it would be a very big advance for mankind. It’s a very active topic right now among researchers.

How efficient are current solar cells at capturing light energy?

The power efficiency of a typical crystalline silicon cell is the average of 22 to 23% range. This implies that they convert as much as 23% of the light striking them into electricity. Rooftop solar cells are lower than that and somewhere between 15 and 18%. The most efficient solar cells are the ones attached to satellites and their power efficiency is almost 50%.

 What is the place of solar energy in Nigeria and the African continent?

The estimated average sunshine hours in Nigeria are six hours per day. Hence, this country does have rich potentials for solar power production. Given Nigeria’s solar potentials, solar thermal applications, for which technologies already exist in the country, include solar cooking, solar water heating for industries, hospitals and households, solar evaporative cooling, solar crop drying, solar incubators and solar chick brooding.

The Nigerian National Energy Policy which came into effect in the April 2003 recognizes the use of renewable energy sources such as hydro, solar, wind, biomass amongst other sources of renewable energy sources. In particular, the Nigerian National Energy Policy recognizes the need for the nation to harness the hydropower potential available in the country for electricity generation. It also recognizes the need for Nigeria to integrate solar energy (in particular) into the country’s energy mix. Furthermore, Nigeria’s Electric Power Policy developed by a 23-member Electric Power Sector Reform Implementation Committee (EPIC) and approved by the Federal Government of Nigeria, in the year 2001, specifically states in Section 7.1 (i) that the rural electrification policy shall include a full menu of rural electrification options, such as grid and off-grid, mini-grid, non-thermal, renewables etc. NERC, pursuant to the powers granted it under the Electric Power Sector Reform Act No. 6 of 2005, licensed the first renewable power project above 1MW namely; the 5MW solar project located in Jos, Plateau State, Nigeria (Ref: http://science.nasa.gov/headlines/y2002/solarcells.htm).

On the continent, South Africa seems to be the most promising country utilising solar energy. Global Information Company IHS has released an analysis which paints South Africa as the world’s most attractive emerging country for solar energy, pointing to the country’s target of 8.4 GW of solar PV capacity by 2030 combined with the country’s successful large-scale tendering process in moving towards that goal. (Ref: http://cleantechnica.com/2014/01/31/south-africa-worlds-attractive-solar-energy-country/#oZ2152Ml3VXgy4IH.99)

What are the challenges of using solar energy?

Right now, solar energy only accounts for a tiny portion of Nigeria (and the rest of the world’s) total electricity generation because it is more expensive when compared to alternatives like cheap but highly polluting petroleum products. Solar power is about seven times as expensive compared to what people pay for petroleum products. In order to have a hope of replacing fossil fuels, scientists need to develop materials that can be easily mass-produced and convert enough sunlight to electricity to be worth the investment.

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