# Charging Africa

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Once, I heard about that the Sun releases 1,7x10^17 J per year and our most advanced solar cell can take out 43% of the energy that came form the Sun.

So if we put many solar cells in Africa, specifically in the Saara Desert, that has 9 200 000 km^2 we could produce enough energy to power all Africa.

But even if we just put the solar cells on top of the houses, they could still have enough power to live without power that comes from a generator that runs with oil or some kind of fuel and stops working when they need.

Some kids would be able to study at night and have better grades, consequently have better lives.

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A number of sites have made a similar point about the relatively small area needed for this

There are, of course, other problems one would have to solve (e.g. getting the energy to its destination, storage, etc.)

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3 hours ago, Danilo_Rocha2 said:

Once, I heard about that the Sun releases 1,7x10^17 J per year

That's certainly not correct value..

Earth gets ~ 1370 W/m^2 (in atmosphere). And is ~ 150 mln km away from the Sun.

~1370 W/m^2 × (~150×10^9 m)^2 × 60s × 60 × 24 × 365.25 = ~9.728 × 10^32 J

3.846×10^26 W

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24 minutes ago, swansont said:

3.846×10^26 W

OP said "per year"..

We should calculate the energy which truly arrives to the Earth's surface. With inclusion of day-night variations. With analysis of angle (majority of the land is in the Northern Hemisphere)

Edited by Sensei
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Or you take the engineering approach and just read-off provided numbers: https://globalsolaratlas.info/map. If I remember correctly, the tool even has a "mark an area and integrate" functionality.

I'd like to say something constructive here. But I find it hard to make out what this thread is about, or to add anything meaningful on this very vague level. I mean: Yes, solar panels generate electricity. Yes, you can put them on rooftops. And yes, there is lots of sun in the equatorial regions. And to Swansont's post: Yes, there are problems in detail. Transport and storage are somewhat generic problems, and they are at least easy to handle - any scenario calculation in the planning phase will implicitly include them. Rather specific problems to solar power in the Saharan regions seem to be sand, corruption and a perception of modern-day colonialism when rich white guys try to tell Africans what they should be doing.

The idea of exploiting the solar power opportunities in the Sahara region is obviously not new. My personal favorite idea in "think big" is a world-grid with a solar power belt around the whole equator, btw. In Germany, the Desertec initiative was very well known. They planned to generate electric power in Africa and export it to Europe (sounding like modern-day colonialism: check). To my knowledge, the project died in 2014 when most major industry partners quit. I don't know why it failed, but the common rumors are about drop in renewable energy generation costs within Europe and worries about generating your power in regions that are considered politically unstable (-> Arab spring and the civil wars that followed and are still ongoing).

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32 minutes ago, timo said:

Rather specific problems to solar power in the Saharan regions seem to be sand, corruption and a perception of modern-day colonialism when rich white guys try to tell Africans what they should be doing.

And the main problem of the Sahara is water.

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30 minutes ago, SergUpstart said:

And the main problem of the Sahara is water.

I never heard that mentioned as an issue for actual projects. But yes, maybe. How, specifically, do you think that lack of water is a problem for solar power projects?

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32 minutes ago, timo said:

How, specifically, do you think that lack of water is a problem for solar power projects?

This means that there is a problem of a sufficient number of electricity consumers in this region.

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2 hours ago, SergUpstart said:

This means that there is a problem of a sufficient number of electricity consumers in this region.

Because electricity is famous for being used at the location where it’s generated?

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2 hours ago, swansont said:

Because electricity is famous for being used at the location where it’s generated?

And then you need to look at what is more profitable, to lay a power line from the Sahara to Europe or to build wind farms on the European coast.

Here is the latest news on this topic  https://www.bbc.com/news/world-europe-55931873

In addition, the power line from the Sahara to Europe must cross the sea. Communication cables and oil and gas pipelines are laid under water, but I haven't heard about underwater high-voltage power lines. This is what the insulation of an underwater high-voltage cable should be. In addition, the construction of wind farms on the European coast creates jobs in Europe.

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27 minutes ago, SergUpstart said:

And then you need to look at what is more profitable, to lay a power line from the Sahara to Europe or to build wind farms on the European coast.

Profitability wasn’t the point under discussion, nor was powering Europe, or job creation.

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18 hours ago, Sensei said:

That's certainly not correct value..

Earth gets ~ 1370 W/m^2 (in atmosphere). And is ~ 150 mln km away from the Sun.

~1370 W/m^2 × (~150×10^9 m)^2 × 60s × 60 × 24 × 365.25 = ~9.728 × 10^32 J

Correction: it must be multiplied by 4 PI.

~1370 W/m^2 × (~150×10^9 m)^2 × 4 × 3.14159265 × 60s × 60 × 24 × 365.25 = ~1.222 × 10^34 J per year.

22 hours ago, Danilo_Rocha2 said:

Some kids would be able to study at night and have better grades, consequently have better lives.

..and they could work online, and be paid by western country companies, work as e.g. software engineers. Therefore they also need fast reliable Internet connection with the rest of world. This way they won't have to abandoned homes and searching for a better life in the Europe risking losing life in travel.

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37 minutes ago, Sensei said:

Correction: it must be multiplied by 4 PI.

~1370 W/m^2 × (~150×10^9 m)^2 × 4 × 3.14159265 × 60s × 60 × 24 × 365.25 = ~1.222 × 10^34 J per year.

I don’t understand your calculation. 150 million km is the distance to the sun, not the size of the earth. Why are you multiplying by the square of this, to get an energy from an energy per unit area?

You should multiply by the projection of the area of the earth facing the sun, which would be pi* r^2, where r is the radius of the earth. And that’s the energy hitting the earth, while to OP talks of the energy emitted by the sun

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1 hour ago, swansont said:

I don’t understand your calculation. 150 million km is the distance to the sun, not the size of the earth. Why are you multiplying by the square of this, to get an energy from an energy per unit area?

It the opening post Danilo said "Once, I heard about that the Sun releases 1,7x10^17 J per year".. but gave incorrect value.

3.846×10^26 W is calculated from ~1370 W/m^2 × (~150×10^9 m)^2 × 4 × 3.14159265. It is value that you gave earlier in this thread too. But you didn't multiply by the number of seconds per year to match OP units "J per year".

What energy Sun releases per second, or per year, is one thing. What arrives to the Earth is another thing. It gets tricky to calculate what really reaches Earth surface as you have to take into account latitude, longitude, altitude, weather, reflectivity of surface (e.g. white snow reflects light) etc. etc.

What is the origin of Danilo's data i.e. 1.7 × 10^17 J.. ?

1370 W/m^2 × 3.14159265 × (6,370,000m)^2 = ~ 1.75 × 10^17 W.. So it is energy per second (without taking into account angle), not per year as Danilo wrote. At noon, and in the best weather possible conditions.

Edited by Sensei
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Problems yes, but this is the big one, even though it is a single small word.

23 hours ago, swansont said:

There are, of course, other problems one would have to solve (.................storage, etc.)

1

The basic problem is this.

Nearly all forms of 'environmental' electricity generation are a form of collection of low density energy and are inherently low voltage.
This requires the parallel working of many units of generation, whether wind farms or solar or other.

All this low grade supply has to be commoned up to a single output, which is technically very difficult and can be very wasteful if not done well.

How would this work on a massive scale in the Sahara ?

2

9 hours ago, timo said:

specific problems to solar power in the Saharan regions seem to be sand

Not just sand but in particular sandstorms !

3

2 hours ago, SergUpstart said:

In addition, the power line from the Sahara to Europe must cross the sea. Communication cables and oil and gas pipelines are laid under water, but I haven't heard about underwater high-voltage power lines. This is what the insulation of an underwater high-voltage cable should be.

You are right, transmission is a difficulty, and needs to be at high voltage to avoid losses. Note my point 1 for the necessary technology to achieve this.

However how do you think transmission takes place from

Quote
2 hours ago, SergUpstart said:

build wind farms on the European coast.

Which are mostly offshore  ?

Further, you may like to know that the UK already buys (nuclear generated) electricity from France via a massive underwater cable across the English Channel.

On 2/6/2021 at 8:36 PM, Danilo_Rocha2 said:

But even if we just put the solar cells on top of the houses, they could still have enough power to live without power that comes from a generator

4

So what happens when the sun isn't shining ie at night ?

Yet again a storage and recovery issue

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42 minutes ago, Sensei said:

It the opening post Danilo said "Once, I heard about that the Sun releases 1,7x10^17 J per year".. but gave incorrect value.

Yes, we both posted information attempting to show this

Quote

3.846×10^26 W is calculated from ~1370 W/m^2 × (~150×10^9 m)^2 × 4 × 3.14159265. It is value that you gave earlier in this thread too.

But (150 x 10^9 km)^2 isn’t an area with any physical meaning, so it makes no physical sense to multiply it by the power per unit area

It does make sense ( sort of) to calculate the power per unit area using the 1/r^2 nature of the radiation, but if that’s what you did you’ve skipped some steps

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2 hours ago, Sensei said:

.and they could work online, and be paid by western country companies, work as e.g. software engineers. Therefore they also need fast reliable Internet connection with the rest of world. This way they won't have to abandoned homes and searching for a better life in the Europe risking losing life in travel.

They have the internet, the problem is more about the numbers of computers and the level of the technology and also the teacher that give lessons about this kind of stuff.

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1 hour ago, swansont said:

But (150 x 10^9 km)^2 isn’t an area with any physical meaning, so it makes no physical sense to multiply it by the power per unit area

Inverse square law is e.g.

$P = \frac{P_0}{4 × \pi × r^2}$

From total power of the Sun P0 we get P in W/m^2.

And it (P) is what we can measure using physical devices.

To get total power of the Sun (P0) we have to reverse inverse square law equation to:

$P_0 = P × 4 × \pi × r^2$

This is also used to measure distance to stars. Earth due to orbiting the Sun is 300 mln km nearer to the star and half year later it is 300 mln km farther from it. Brightness of the star periodically changes due to increased or decreased distance, so we can deduce r (distance).

Edited by Sensei
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9 minutes ago, Sensei said:

Inverse square law is e.g.

My objection is not based on my having questions about the inverse square law. No need to explain it to me.

You could have just said you were calculating the surface area of a sphere at the distance of the earth.

But when you just throw numbers up, without an equation or units or explanation, the method is not always clear.

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2 hours ago, studiot said:

The basic problem is this.

Nearly all forms of 'environmental' electricity generation are a form of collection of low density energy and are inherently low voltage.
This requires the parallel working of many units of generation, whether wind farms or solar or other.

All this low grade supply has to be commoned up to a single output, which is technically very difficult and can be very wasteful if not done well.

In the current situation in the global economics, environmental energy can become the lifesaver that will help to bring it out of a depressed state. Because it can create a lot of jobs.

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4 minutes ago, SergUpstart said:

In the current situation in the global economics, environmental energy can become the lifesaver that will help to bring it out of a depressed state. Because it can create a lot of jobs.

No one said that it is not a beneficial or desirable process.

But this is a technical discussion about technical issues involved in achieved a desired objective.

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Not just because of the energy but because it could help the economy in this countries.

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52 minutes ago, Danilo_Rocha2 said:

Not just because of the energy but because it could help the economy in this countries.

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Hyperloop is like a train but it travels in a tube in vacuum and it can reach 1100 km/h

It was Elon's idea.

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