
Modeled impact of large-scale wind and solar farms in the Sahara - joeschmoe3
https://phys.org/news/2018-09-large-solar-farms-sahara-vegetation.html
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jameskilton
> The wind and solar farms simulated in the study would cover more than 9
> million square kilometers and generate, on average, about 3 terawatts and 79
> terawatts of electrical power, respectively.

This study is looking at a combined farm size that's almost as large as all
the land mass in the US.

[https://en.wikipedia.org/wiki/List_of_U.S._states_and_territ...](https://en.wikipedia.org/wiki/List_of_U.S._states_and_territories_by_area)

~~~
wongarsu
That seems a bit excessive, considering that the world energy consumption is
only about 18 terawatts (and only about 3 terawatts of that are electrical
right now).

~~~
Analemma_
If countries like China, India, Malaysia, Nigeria etc. start to have per-
capita energy use close to that of the United States, global energy
consumption could easily double or triple even without any increase in
population.

I said "if", but I really should say "when", because this is what's expected
to happen as these countries modernize and start getting things like air
conditioning on the same scale as US households. 79 TW of capacity will become
a necessity sooner than you think.

~~~
spacenick88
Almost no one in Europe has per-capita energy use anywhere close to the US, so
why would China? And I don't think it's just that we have less AC, though
that's surely the strongest contributor.

~~~
wongarsu
For reference for anyone curious: the US has a final energy consumption of
6.0kW per capita, the EU average is about 2.9kW. (2009 data)

At that point, China was at 1.3kW/citizen, Africa at half that, India on the
level of Africa and the middle East slightly below the EU with 2.3kW.

Wikipedia [2] uses world bank data instead which seems to measure differntly,
but the relations are roughtly the same.

1: [https://www.eea.europa.eu/data-and-maps/figures/final-
energy...](https://www.eea.europa.eu/data-and-maps/figures/final-energy-
consumption-million-toe-3/ener16_table_01)

2:
[https://en.wikipedia.org/wiki/List_of_countries_by_energy_co...](https://en.wikipedia.org/wiki/List_of_countries_by_energy_consumption_per_capita)

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tasty_freeze
I'm confused by your wording and by wikipedia. Watts are a measure of power,
not energy. kWh is a measure of energy.

~~~
wohlergehen
In the same sense as your server has an "energy consumption" of 2000W, i.e. 1W
<=> 356*24/1000 kWh/a.

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strainer
I would not have guessed that the solar arrays beneficial effect on
precipitation is dependent on them not being too efficient and so releasing
more heat than bare desert (which is very reflective).

From the article - "The precipitation increase in our solar farm experiments
is due to the relatively low conversion efficiency of the panels (15%, typical
current conversion efficiency for photovoltaic panels), which results in
albedo decrease. However, if solar panel efficiency and the associated
effective albedo are high enough to lead to an albedo increase relative to the
background environment (as, for example, a 45% efficiency would), the climate
impact would be surface cooling with precipitation suppression, similar to the
impact of overgrazing in the desert. Assuming an intermediate conversion
efficiency higher than 15% for solar panels (e.g., 30% efficiency) results in
negligible albedo change and, thus, insignificant climate impacts."

[^]
[http://science.sciencemag.org/content/361/6406/1019](http://science.sciencemag.org/content/361/6406/1019)

~~~
DoctorOetker
I still consider it a win even if solar panels reach 45% efficiency: surplus
energy can be used to desalinate and transport seawater for irrigation, or by
condensing it from air (releasing the heat of condensation)

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wongarsu
>"The greater nighttime warming takes place because wind turbines can enhance
the vertical mixing and bring down warmer air from above," the authors wrote.

That's actually a very interesting effect. I guess the votices generated by
wind farms quite beneficial in a desert region.

It would be interesting to see what effect wind farms have on desertification.
Given that two large factors are fertile ground blowing away and desert sand
being blown onto fertile land, I imagine wind farms might be beneficial for
slowing down desert growth.

~~~
reaperducer
_I guess the votices generated by wind farms quite beneficial in a desert
region._

Unless you're an ectothermic creature (like a lizard, tortoise, snake, etc...)
which relies on the cool of night to hunt food and find water.

~~~
e40
Yeah, I was thinking that the cool temps at night are necessary for
condensation. Without it, the plant and animal life in the region could be
devastated.

~~~
BurningFrog
If we're talking about deserts, there is next to no plant and animal life, and
part of the goal of this would be to change that.

~~~
reaperducer
You are grossly misinformed about deserts.

~~~
village-idiot
Humans tend to know less about environments that kill us rapidly.

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rossdavidh
While interesting, I have my doubts as to the reliability of any prediction
model for a case such as this. It would be a case quite a bit outside the
historical data which the prediction model is based on, and it's not like
weather and ecological systems are nicely linear and well-behaved systems to
predict.

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sandworm101
What they do not model is the local effect of the cities that will need to be
built to service all these panels. 9,000,000 square KM is a gigantic area.
Millions of people will be needed to maintain these farms. Those people will
need to either live locally or be transported regularly. The study should
model how the presence of those people in such a relatively underpopulated
area will impact local climate.

1 person per km2 = 9million people. But I'd bet you would need a couple dozen
people for every km2 of solar farm, and associate infrastructure, meaning
perhaps 100 millions people. And then all the people to provide services to
those people ... this is like building a few new countries from scratch.

~~~
ebikelaw
Solar utility installations in California that I’m familiar with employ fewer
than 1 person per square km.

~~~
sandworm101
And how do they keep all those panels clean? Who maintains the transformers
when they break? Who swaps out the panels as they reach their life expectancy?
It isn't just the night watchman, but the entire community of people involved
in any large outdoor installation.

~~~
ebikelaw
Like any utility, you don't need a guy just hanging around waiting for the
transformers to explode. You truck him in every 50 years when that actually
happens. It's time domain multiplexing, essentially.

~~~
mikeyouse
The cleaning is largely a solved problem too.. You don't need 50 $10k/year
people with squeegees, you just need one person in a $50k truck.

[https://www.alibaba.com/product-detail/China-Road-tunnel-
wal...](https://www.alibaba.com/product-detail/China-Road-tunnel-wall-
cleaning-
vehicle_60770674771.html?spm=a2700.7724857.normalList.5.63a52b09SAEP3y)

~~~
ebikelaw
If there’s one job that robots are certainly going to take, it is solar panel
squeegee guy.

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ngcc_hk
Can the energy used to water desalination from the sea ?

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krupan
"A new climate-modeling study finds that a massive wind and solar installation
in the Sahara Desert and neighboring Sahel would increase local temperature,
precipitation and vegetation. Overall, the researchers report, the effects
would likely benefit the region."

Beneficial to who or what? Beneficial in what ways?

~~~
xyzzyz
You can continue reading the article to learn the answers, you know.

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krupan
Sorry, I think the point I was trying to make was, do we really want to
transform this unique geography? I live in Utah and if someone came here and
said, "you know all this red rock and sand in the south, we could change that
into a lush green landscape," there'd be massive opposition to that idea.

~~~
xyzzyz
Do you think there would a massive opposition if someone came here and offered
changing 2% of Utah into lush green landscape? I believe this change would be
welcome, as people like some variety. Now, area of Utah is 2% of Sahara's
area, so we could literally transform some patch of Sahara of the size of
Utah, and still have 98% of it untouched, and get enough electricity to power
most of Europe.

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krupan
You haven't followed the recent Bears Ears controversy, have you? :-)

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krupan
Here's another example. I grew up in Washington state. We have dams on a lot
of rivers in the Northwest generating clean renewable energy before anyone had
ever heard of climate change (Grand Coulee is the most famous). They literally
did change the barren desert of Eastern Washington into a fertile farming
breadbasket with the irrigation water and power they provide. Despite that,
there are people who hate them because they changed the rivers into a series
of lakes and are threatening the wild salmon population.

Pick any part of the Sahara and transform it and some species unique to that
area, some native people, some curious weather pattern, some unique geologic
formation will be lost and people will be upset.

~~~
xyzzyz
I'm quite familiar with the dams, I live in Washington myself, and visited
them multiple times. I agree that someone will always be upset, but this is
generally true about every change ever. The point is to do changes that are
most beneficial to the most, don't carry extremely serious side effects, and
are net win over the alternative, which in this case is keeping burning coal.
There's still plenty of coal left in Roslyn fields, and if not for the dams,
it would probably continue to be extracted today.

~~~
jessaustin
Surely that coal is as big an argument for Saharan solar farms as it is for
Washington dams?

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kryogen1c
I have always been alarmed that I've never seen the weather effects of solar
and wind power discussed - they are by definition removing energy (randomly)
from the global climate system. As one of the least understood and most
complex systems that _drastically_ impact our lives, this should be cause for
concern.

~~~
clairity
that energy loss to solar and wind power is a miniscule percentage of the
energy available, which is provided by the sun and most of which gets radiated
away anyways. no need to worry about it for another 5 billion years or so.

~~~
kryogen1c
The concern is not the output of the sun, but energy moving in an unplanned
(and unplannable fashion).

In other words, solar panels shade ground that would have been sunned.
Windmills change atmospheric differential pressure by removing windspeed.

The best case scenario is these changes are negligible, but that is a luck-
based result. We have no idea because global climate is not effectively
modelable.

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peterashford
You're worried that we haven't discussed the results of something that you
admit is not effectively modelable?

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kryogen1c
Yes.

Just because something is difficult to model doesn't mean the outcome/results
can't be wildly dangerous. We should still try and guess the impacts of our
actions, but it seems like no one is concerned.

