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The Earth receives extra power from the Solar in an hour than the entire of humanity consumes in a yr.

On this publish I’ll speak about a few of the science behind this attention-grabbing reality and I’ll additionally talk about how photo voltaic power is more likely to grow to be extra necessary sooner or later.

How a lot photo voltaic power hits the Earth?

The Solar generates power by nuclear reactions which occur at its dense hot core .It produces an enormous 382.eight trillion trillion (three.828  x  1026 ) watts of electromagnetic radiation (Williams 2018) principally within the type of seen mild, infrared and ultraviolet. As you get farther from the Solar, the depth (the ability per unit space) of its radiation falls.

The photo voltaic fixed is the depth of the Solar’s radiation at a distance of 1 astronomical unit (the common distance of the Earth from the Solar). It’s given the worth of 1,361 watts per sq. metre (W/m2). Nonetheless, as a result of the output of the Solar is barely variable, it fluctuates by zero.1% round this worth.

As proven above, the realm of a disc of the identical diameter because the Earth is 127,480,000,000,000  (1.2748 x 1014  ) sq. metres. So, the full power hitting the Earth in a single hour is given by

photo voltaic fixed x floor space of Earth-sized disc

1 361 W/m2 x 1.2748 x 1014 m= 1.73 x  1017 watt-hours.

 (This determine is commonly expressed as 173,000 terawatt hours (TWh), the place 1 terawatt is 1 trillion (1000,000,000,000) watts)

The overall power consumed by humanity in 2017 is barely lower than this at 160,000 TWh (Enerdata 2018). This determine contains not simply power used to generate electrical energy, but in addition power used straight for heating (for instance by burning firewood, coal, oil or fuel), used for transport (primarily petrol, diesel and aviation gas) and power utilized in industrial processes.  The overall quantity of electrical energy consumed in 2017 was roughly 22,000 TWh.

The potential for photo voltaic power.

There are two other ways of producing electrical energy from daylight. A method is to pay attention the Solar’s power utilizing mirrors onto a small space and use the warmth generated to provide steam to show a turbine which generates electrical energy. The opposite approach is use arrays of photovoltaic cells (extra generally often known as photo voltaic panels) to generate electrical energy straight from daylight. Nearly all of photo voltaic electrical energy is generated this manner and, as costs of photo voltaic panels proceed to fall and their effectivity will increase, that is the place the expansion might be.

The expansion of photo voltaic power (Our world in knowledge 2018)

One benefit that photo voltaic power has over different types of power is that it has an virtually limitless potential due to the huge quantity of power reaching the Earth from the Solar. As I’ll present subsequent it might be essential to cowl solely a comparatively small fraction of the Earth’s floor with photo voltaic panels to satisfy all of humanity’s power wants.

To calculate the dimensions of this space, the very first thing we have to take into account is the quantity of photo voltaic radiation which really reaches the Earth’s floor. Though the photo voltaic fixed is 1,361 W/m2, that is the depth of the radiation which hits the highest of the Earth’s ambiance. Even on a cloudless day not all this radiation reaches the bottom; some is mirrored again into area and a few is absorbed by the ambiance.

On a transparent day, if the Solar is straight overhead, the depth of the radiation hitting the bottom straight from the Solar is round 1,050 W/m2, on high of this an additional 70 W/m2 comes from the intense blue sky, giving a complete of 1,120 W/m2. (If is cloudy this determine might be decrease.)

The truth is, the Solar is straight overhead at a degree on the Earth’s floor provided that it lies within the tropics.  As proven beneath, when the Solar is decrease within the sky, the depth of the photo voltaic radiation is diminished as a result of its rays are unfold out over a bigger space and since they need to move via extra ambiance earlier than they hit the bottom. At evening when the Solar is beneath the horizon the photo voltaic depth is clearly zero.

The diagram above exhibits the variation within the photo voltaic depth on the equator, at an equinox when the Solar is straight overhead at noon. The time axis makes use of the photo voltaic time i.e. the Solar rises at 0600, is at its highest at 1200 and units at 1800. A cloudless day is assumed.

If we common out over a complete 24 hour cycle the quantity of photo voltaic radiation hitting the Earth’s floor (often known as the photo voltaic irradiance) on a transparent day on the equator on the equinox is roughly 340 W/m2. The most efficient solar panels on the market convert roughly 22% of photo voltaic irradiance to electrical power. Which means, averaged over a complete 24 hour cycle, the photo voltaic electrical energy which might be generated is 73 W/m2, which is roughly 5% of the photo voltaic fixed. At greater latitudes the Solar is decrease within the sky and so the quantity of photo voltaic electrical energy which might be generated is much less. The quantity of photo voltaic power is  diminished by cloud cowl. For instance, within the cloudy north west of Scotland the photo voltaic irradiance averaged out over a yr is just 72 W/m2, about one fifth of its worth on the equator.

If averaged out over 12 months and over all places on the Earth’s floor, then the common photo voltaic irradiance is 170 W/m2. Which means we would wish to cowl 586,000 sq. km of the Earth’s floor with photo voltaic panels to generate all of the world’s power wants, an space about 15% bigger than Spain. The main points of the calculation are given the notes on the backside of this publish. This quantity is comparatively small, solely zero.11% of the floor space of the Earth. Nonetheless, one problem is that nations which might generate probably the most photo voltaic power (significantly these in Africa) even have modest power consumption and plenty of densely populated nations, significantly these in Northern Europe, have excessive power consumption and obtain comparatively little daylight. For instance, if we had been to take the UK which has a small floor space, receives comparatively little daylight in comparison with the world common, and is densely populated with a excessive power consumption, we would wish to cowl about 5.2% of its floor with photo voltaic panels, which might be tough. Apparently the UK is ideally positioned for offshore wind farms and plans to generate 30% of its electricity in this manner by 2030.

Small scale solar energy

In the mean time, solar energy  not the biggest renewable supply of electrical energy. As proven within the chart beneath, in 2016 a complete of 5,877 TWh was generated by renewables. Of this, the overwhelming majority (four,023 TWh) was generated by hydroelectricity, adopted by 960 TWh by wind; photo voltaic power contributed 333TWh and the remaining 561 TWh by all different renewables mixed.

From Our world in knowledge (2018): the info excludes so referred to as ‘conventional biofuels’ e.g. burning wooden which can or might not be renewable

One clear benefit that solar energy has is that it’s attainable to generate electrical energy on a small scale. A single panel 4 metres sq. hooked up to a chargeable battery would be capable of generate and retailer sufficient photo voltaic power for lighting and cooking for a household in Africa. Photo voltaic panels haven’t any shifting elements and as soon as bought ought to work for many years.  It’s this potential to generate electrical energy on a small scale which will revolutionise the lives of a few of the poorest individuals in world, an concept I shall talk about additional in my subsequent publish.


I hope you have got loved this publish. To seek out out extra in regards to the Science Geek’s weblog, click on here or on the Science Geek Home hyperlink on the high of this web page.




Tilting photo voltaic panels

For small photo voltaic set up it is not uncommon to extend the common depth of the daylight by tilting the panel in direction of the Solar. For example, small arrays of photo voltaic panels within the UK are sometimes tilted to face south. It’s clearly tough to do that for the very massive arrays of photo voltaic panels discovered on photo voltaic farms.


Calculation of the realm of the world and the UK to lined I photo voltaic panels

In any massive construction which generates photo voltaic electrical energy there should be gaps between the photo voltaic panels. In these calculations I’ve assumed that one sixth of the realm of a photo voltaic farm/massive array of photo voltaic panels is not lined by panels.

Knowledge from Science Direct (2014) and Enerdata (2018)


Enerdata (2018) International power statistical yearbook 2018, Out there at: https://yearbook.enerdata.net/total-energy/world-consumption-statistics.html (Accessed: 23 February 2019).

Our world in knowledge (2018) International renewable power consumption over the long-run, Out there at: https://ourworldindata.org/renewable-energy (Accessed: 23 February 2019).

Science Direct (2014) The UK photo voltaic power useful resource and the impression of local weather change, Out there at: https://www.sciencedirect.com/science/article/pii/S0960148114002857(Accessed: 23 February 2019).

Williams, D. R. (2018) NASA Solar reality sheet, Out there at: https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html (Accessed: eight March 2019).


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