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Modeled impact of large-scale wind and solar farms in the Sahara

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Re: Modeled impact of large-scale wind and solar farms in the Sahara

#51

Post by clairity »

kryogen1c wrote: post #46

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.

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.

Re: Modeled impact of large-scale wind and solar farms in the Sahara

#52

Post by pesmhey »

wongarsu wrote: post #6
jameskilton wrote: post #3

> 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...

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).

I’d like to offer a comparison that may put it into a different perspective for you. Imagine saying that a 1 TB hard drive is excessive, 20 years ago. Sure, contemporaneously, but we sure did find some useful ways to put all that excessive hard drive space to use.

Re: Modeled impact of large-scale wind and solar farms in the Sahara

#53

Post by pmwhite »

state_less wrote: post #29
abecedarius wrote: post #20

Earlier quoted context omitted.

How would you go about it? Lots of high-voltage lines, or is there something else that'd make more sense for this unusual setup?

Distributed generation seems like it would make sense (with current tech). Italy and Spain could help here. Maybe you could go from Tunisia to Europe, but supplying African countries seems more attainable. It'd be nice if you could turn the energy into a gas like methane, pull CO2 out of the atmosphere in the process. Good for the atmosphere and you could transport gas over long distances. https://en.wikipedia.org/wi…

I wonder if hydrogen is practical to transport in large quantities. My guess is no.

Your idea of methane, if it could be done efficiently, seems more likely.

Re: Modeled impact of large-scale wind and solar farms in the Sahara

#54

Post by delecti »

pesmhey wrote: post #52
wongarsu wrote: post #6

Earlier quoted context omitted.

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).

I’d like to offer a comparison that may put it into a different perspective for you. Imagine saying that a 1 TB hard drive is excessive, 20 years ago. Sure, contemporaneously, but we sure did find some useful ways to put all that excessive hard drive space to use.

One really good example would be water desalination. I'm sure the neighbors of the Sahara could use a glut of fresh water.

Re: Modeled impact of large-scale wind and solar farms in the Sahara

#55

Post by jessaustin »

xyzzyz wrote: post #50
krupan wrote: post #42

Earlier quoted context omitted.

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 beca…

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 R…

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

Re: Modeled impact of large-scale wind and solar farms in the Sahara

#56

Post by sampo »

nwallin wrote: post #47
satya71 wrote: post #33

Earlier quoted context omitted.

I don't have the numbers. But intuitively, AC should be less energy as it's energy transfer. Heating is usually directly adding energy to the living environment. You can get heating using heat pumps (some southern US homes have this type) but it doesn't work very well when it's too cold outside. Europe should have more heating than US, with it's more northern location.

Electric heaters are more efficient than traditional air conditioning units. Transferring heat from inside a 80F house to the 110F air outside is not very efficient, only about 30-60%. On the hand, an incandescent light bulb is a ~99% efficient heater. The only energy that is "lost" is the light which is radiated out the window. Space heaters and electric radiators are 100% efficient. Additionally, heat pumps are can…

> Transferring heat from inside a 80F house to the 110F air outside is not very efficient, only about 30-60%.

This is wrong. Modern heat pumps can easily have efficiency over 400%.

Re: Modeled impact of large-scale wind and solar farms in the Sahara

#57

Post by rossdavidh »

krupan wrote: post #23
xyzzyz wrote: post #21

Earlier quoted context omitted.

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

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.

It is in fact still a matter of active debate as to whether or not the Sahara is natural. Some evidence suggests humans may have played a role in its expansion to current size, at least: https://www.sciencedaily.com/releases/2017/03/170314111320.h...

Re: Modeled impact of large-scale wind and solar farms in the Sahara

#58

Post by xyzzyz »

nwallin wrote: post #47
satya71 wrote: post #33

Earlier quoted context omitted.

I don't have the numbers. But intuitively, AC should be less energy as it's energy transfer. Heating is usually directly adding energy to the living environment. You can get heating using heat pumps (some southern US homes have this type) but it doesn't work very well when it's too cold outside. Europe should have more heating than US, with it's more northern location.

Electric heaters are more efficient than traditional air conditioning units. Transferring heat from inside a 80F house to the 110F air outside is not very efficient, only about 30-60%. On the hand, an incandescent light bulb is a ~99% efficient heater. The only energy that is "lost" is the light which is radiated out the window. Space heaters and electric radiators are 100% efficient. Additionally, heat pumps are can…

> Transferring heat from inside a 80F house to the 110F air outside is not very efficient, only about 30-60%.

Where did you get this number from?

Re: Modeled impact of large-scale wind and solar farms in the Sahara

#59

Post by sampo »

weberc2 wrote: post #28
xyzzyz wrote: post #22

Earlier quoted context omitted.

We have less AC, but we have more heating, which is more energy intensive than AC.

I’m doubtful about both of these claims (Europe has more heating than the US and that heating is more energy-intensive than AC). The latter seems particularly hard to believe given how efficient heating is compared to A.C.

Here is a study from 2013 in Environmental Research Letters. Comparing Minneapolis and Miami, the coldest and the warmest metropolitan areas in the US. Minneapolis uses (per capita) 3.5 times more energy for heating and AC (mainly heating) than Miami (mainly AC).

"This finding suggests that, in the US, living in cold climates is more energy demanding than living in hot climates."

http://iopscience.iop.org/article/10.1088/1748-9326/8/1/0140...

Part of the difference is that, heating is usually directly burning oil or gas, so the efficiency is 1:1, whereas cooling can have efficiency 4:1 because heat pumps just move heat. But you need electricity to run a heat pump, and generating the electricity is at about 0.5:1 efficiency. So if all Minneapolis switched to heating with heat pumps, they could bring the difference down from 3.5 to 1.8. But still living in Miami is more energy efficient.

Re: Modeled impact of large-scale wind and solar farms in the Sahara

#60

Post by nimos »

nwallin wrote: post #47
satya71 wrote: post #33

Earlier quoted context omitted.

I don't have the numbers. But intuitively, AC should be less energy as it's energy transfer. Heating is usually directly adding energy to the living environment. You can get heating using heat pumps (some southern US homes have this type) but it doesn't work very well when it's too cold outside. Europe should have more heating than US, with it's more northern location.

Electric heaters are more efficient than traditional air conditioning units. Transferring heat from inside a 80F house to the 110F air outside is not very efficient, only about 30-60%. On the hand, an incandescent light bulb is a ~99% efficient heater. The only energy that is "lost" is the light which is radiated out the window. Space heaters and electric radiators are 100% efficient. Additionally, heat pumps are can…

The coefficient of performance (efficiency) of an AC at that temperature range would still be well over 1. Probably around 3-4 depending on the unit and refrigerant. [0] ACs are very efficient for the same reason heat pumps are efficient. They are just moving energy around.

[0] https://www.researchgate.net/publication/242172797_A_Compari...

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