Does the world really need 'more power'?

[DarkMattrHole]

The answer should depend on the result. If the result is more of what's going on and what's going up, like pollution, extinction, and temperature, then no, the world doesn't need more power, and the solution lies elsewhere.

If we can stop polluting with particles and gassing out as we consume power, we can defeat catastrophic global warming, and continue to consume more and more power for quite a while. But at some point the absorption of energy for consumption at the surface will once again begin the rise of global temperature to a catastrophic level.

Solar panels will absorb the sun's energy where it is transported to the surface for release. Even orbiting solar panels beam warming energy to the surface where it is consumed by society. So there's a theoretical limit. So I'm wondering what that limit looks like.

If you could beam clean energy into the lights and toasters, and ovens and dryers and all of industry, how much bigger could a pollution-free powered world get than we are now? Without upsetting the planet?

 

[anorlunda]

It sounds like you're planning to make Earth like Trantor (the fictional planet in some Isaac Asimov's novels). On Trantor the 45 billion people lived below ground because they used so much energy that the surface nearly glowed red.

Climate is not the only problem. We are running out of fresh water, and fish stocks, and habitat for animals, and food, and arable land, and minerals, and rare Earth elements, and every other kind of non-renewable resource imaginable. Isn't it obvious that the base problem is not energy but global population?

 

[DarkMattrHole]

Ya it's pretty obvious, and the food that we eat also determines how big we should be, so with lots of people around we need them to be mostly herbivore.

 

[berkeman]

Ya it's pretty obvious, and the food that we eat also determines how big we should be, so with lots of people around we need them to be mostly herbivore.

But, but, I don't want to be a herbivore. Well, except, Beyond Burgers and Morning Star "meats" aren't bad. I suppose I could survive on those...

 

[DaveC426913]

You can optimize the resource/waste footprint for an average person on the planet, but that can only go so low. There is a minimum amount required, and will strongly depend on advancements in clean technology.
New technology costs money, so the efficiency of the technology will be compromised by how much we're willing to spend (as a race and as individuals).

The problem is, it's a losing battle. Population growth will always result in the total power requirement of the planet rising inexorably.

Either we emigrate to other planets, or we emplace some sort of population control.

 

[DarkMattrHole]

Well, we all wear pants and stop at stop signs...

 

[berkeman]

Well, we all wear pants and stop at stop signs...

"We", paleface? I wear a loincloth at some Cosplay events...

(well, not really, but I'm on standby at a number of Cosplay events)

 

[Algr]

Ya it's pretty obvious, and the food that we eat also determines how big we should be,

So we need our scientists working on that shrink ray then.

 

[DaveC426913]

So we need our scientists working on that shrink ray then.
View attachment 270590

I'd offer the alternate modern-day example of Damon in Downsizing ... except that the story has virtually nothing to do with downsizing - it's merely a plot vehicle to drive a completely unrelated story.

 

[Algr]

Apparently that film script started out very different. Originally it was about the dangers of letting government have too much power over you. I never actually saw the final film - I could tell it was going to forget it’s premise and go off into something else.

 

[mfb]

This is a physics forum...

Earth receives about 170 PW of radiation from the Sun, and emits the same amount back to space at ~300 K. Increasing the surface temperature by 1 K (while keeping the rest constant) increases emissions by 4/300 or 2 PW. That's the amount we could continuously add as heat while limiting its temperature effect to 1 K. That's e.g. ~700 TW of electricity from fusion, or 35 the current rate of global energy (not electricity!) consumption. With solar panels the balance depends on the surface you put them on.

 

[DrStupid]

Increasing the surface temperature by 1 K (while keeping the rest constant) increases emissions by 4/300 or 2 PW. That's the amount we could continuously add as heat while limiting its temperature effect to 1 K.

As the surface temperature cannot be increased without increasing the temperature of the bottom layers of the atmosphere, the counter-radiation from the atmosphere to the ground will increase too. The amount we could continuously add as heat while limiting the temperature effect to 1 K is not the 2 PW of additional emission but the difference between this additional emission and the additional counter-radiation.

However, it is possible to increase the ratio between emission and absorption by emission at wavelengths that are not blocked by greenhouse gases.

 

[BWV]

The problem is, it's a losing battle. Population growth will always result in the total power requirement of the planet rising inexorably.

Either we emigrate to other planets, or we emplace some sort of population control.

but The universally observed trend of the past 100y or so is that population growth declines as power consumption increases. Most of the developed world now has birthrates below replacement. If the trend continues, shortly global fertility rates will fall below replacement

 

[anorlunda]

If the trend continues, shortly global fertility rates will fall below replacement

That's the low estimate, but not the only estimate. From Wikipedia

But even by the low estimate, 7 billion is far too large a population.

How many people is too many? That's a difficult question. Existing estimates tend to focus only on food, not on water, habitat, climate and the holistic problem. One possible clue is the famous "hockey stick" curve that shows global CO2 starting to rise around 1800. In 1800, the world population was about 1 billion.

 

[BWV]

That's the low estimate, but not the only estimate.


But even by the low estimate, 7 billion is far too large a population.

How many people is too many? That's a difficult question. Existing estimates tend to focus only on food, not on water, habitat, climate and the holistic problem. One possible clue is the famous "hockey stick" curve that shows global CO2 starting to rise around 1800. In 1800, the world population was about 1 billion.

why is 7 billion too many? CO2 began to rise in the 19th century because that was when coal began to be widely used, cannot impact CO2 levels over the long term by burning wood

 

[DaveC426913]

Most of the developed world now has birthrates below replacement. If the trend continues, shortly global fertility rates will fall below replacement

The graph suggests it could be a century or two before that happens.

Regardless, it is a bad assumption that trend will continue linearly. It is more likely to approach one asymptotically. There is a vast gulf between parents deciding to have one child instead of two - and parents deciding to have no children at all.

That 1.0 replacement won't break easily. Or soon.

View attachment 270629

 

[gmax137]

There is a vast gulf between parents deciding to have one child instead of two - and parents deciding to have no children at all.

That 1.0 replacement won't break easily. Or soon.

What matters for global population is the average. If everyone decided to have no children at all, population would go to zero in about 100 years as everyone died without any reproduction. But nobody thinks that's what will happen.

If everyone had one child instead of two the total would decrease much more slowly (with a "half life" of maybe 20 - 30 years?). Remember, replacement is not one child, it is two (one for each person, two per couple).

 

[BWV]

replacement is slightly more than two, to account for mortality

 

[anorlunda]

The problem with depending on birth rates to control population is that it doesn't work well in undeveloped countries. Wikipedia says that Africa alone is projected to have 4.5 billion people by 2100.

 

[BWV]

The problem with depending on birth rates to control population is that it doesn't work well in undeveloped countries. Wikipedia says that Africa alone is projected to have 4.5 billion people by 2100.

So what then do you propose?

And African birthrates are falling in line with development, just as it has in the rest of the world

https://www.google.com/publicdata/e...NGA:BWA:GHA&ifdim=world&hl=en&dl=en&ind=false

 

[DarkMattrHole]

Earth receives about 170 PW of radiation from the Sun, and emits the same amount back to space at ~300 K. Increasing the surface temperature by 1 K (while keeping the rest constant) increases emissions by 4/300 or 2 PW. That's the amount we could continuously add as heat while limiting its temperature effect to 1 K. That's e.g. ~700 TW of electricity from fusion, or 35 the current rate of global energy (not electricity!) consumption. With solar panels the balance depends on the surface you put them on.

Thanks, mfb. So with a totally clean energy source, about 35 times the energy consumption would be possible in theory, before we destabilize the climate from excessive energy release at the surface. That sounds like a comfortable margin. But if that weren't enough, if we had a mechanism to actively beam energy out to space at a frequency that passes through the atmosphere without being trapped, we could even increase that margin further, although it sounds like that would never be required.

 

[DarkMattrHole]

As the surface temperature cannot be increased without increasing the temperature of the bottom layers of the atmosphere, the counter-radiation from the atmosphere to the ground will increase too. The amount we could continuously add as heat while limiting the temperature effect to 1 K is not the 2 PW of additional emission but the difference between this additional emission and the additional counter-radiation.

However, it is possible to increase the ratio between emission and absorption by emission at wavelengths that are not blocked by greenhouse gases.

Thanks, DrStupid. So does that mean when the counter-radiation is taken into account, the actual figure becomes somewhat less than the calculated 2 PW?

 

[DrStupid]

So does that mean when the counter-radiation is taken into account, the actual figure becomes somewhat less than the calculated 2 PW?

Yes. As around 50 % of the emitted radiation comes back, it will be 1 PW.

 

[mfb]

No, that is taken into account already. The atmosphere doesn't suddenly become a heat source. If it radiates 2 PW more to space then it receives 2 PW more from the ground. That's the net change.

That's the low estimate, but not the only estimate. From Wikipedia

The estimates are perfectly in agreement. A fertility rate that falls below replacement at some point in the 21st century means the population reaches its maximum in the same range, and starts decreasing at the end of the century. We already passed two important milestones:
* The relative increase per year reached its peak in the 1960s at 2.2% per year. We are down to half of that, 1.1% per year.
* The absolute increase per year reached its peak ~2013.

Most estimates are in the range of 10-11 billion for 2100. That's 50% more than today, but not catastrophically more. We can't support all of them by burning coal and oil, clearly, but with nuclear power and renewable energy the CO2 emissions from energy use can be kept low. Other CO2 sources are still an issue.

Ya it's pretty obvious, and the food that we eat also determines how big we should be, so with lots of people around we need them to be mostly herbivore.

Or make meat in the lab.

 

[DrStupid]

No, that is taken into account already. The atmosphere doesn't suddenly become a heat source. If it radiates 2 PW more to space then it receives 2 PW more from the ground.

No, that's not taken into account. The 2 PW are not the additional heat flow from the surface to the atmosphere but the additional black body radiation emitted from the ground. That results in 1 PW more radiation into space, 1 PW more counter-radiation from the atmosphere back to the ground and an increase of the steady state surface temperature by 1 K.

 

[mfb]

That results in 1 PW more radiation into space

That's not the scenario I considered. Make your own scenario if you want to consider half the change.

 

[DrStupid]

That's not the scenario I considered.

It is:

Earth receives about 170 PW of radiation from the Sun, and emits the same amount back to space at ~300 K. Increasing the surface temperature by 1 K (while keeping the rest constant) increases emissions by 4/300 or 2 PW.

Let’s see in detail what that means:

Earth receives about 170 PW radiation from the sun. 30 % (corresponding to 51 PW) is directly reflected back into space. 23 % (corresponding to 39 PW) is absorbed by the atmosphere and 47 % (corresponding to 80 PW) is absorbed by the ground. The surface emits 245 PW (evaporation and convection included). 20 PW of this emission goes directly into space and 225 PW are absorbed by the atmosphere. The atmosphere emits 99 PW into space and 165 PW back to the ground. All emissions into space add to 170 PW.

The 245 PW emission from the ground correspond to a surface temperature of 305 K. Increasing the temperature by 1 K results in the relative increase by 4/300 that you mentioned above. Neglecting rounding errors this is fully consistent with your scenario.

But now comes the difference: The relative increase of 4/300 corresponds to 3.3 PW additional emission from the ground. That is more than the 2 PW you mentioned above and which I referred to in my pervious posts (because I didn't check your numbers). It seems you applied the relative increase of 4/300 to the total incoming 170 PW from the Sun. That makes no sense because it has been calculated for the thermal emission from the ground. It is limited to thermal emission and to a similar increase of the temperature.

0.3 PW of the additional emission go directly into space. 3.0 PW are absorbed by the atmosphere. Now it gets complicate because I need to estimate the radiation from the atmosphere without a proper climate model. Assuming that the major part of the counter-radiation comes from the bottom layers of the atmosphere suggests that this radiation will also be increased by 4/300 because these layers are also warmed up by 1 K. This is a conservative estimation because it neglects the temperature gradient in the atmosphere which would result in an even higher increase. That gives 2.2 PW additional counter-radiation. Thus, there are just 0.8 PW left to be emitted into space. Together with the 0.3 PW direct emission from the ground there remains a total increase of about 1 PW emission into space. That is the additional power that can be released into the environment without increasing the surface temperature by more than 1 K.

 

[BWV]

Ultimately nuclear power - fission or fusion - is a dead end as too much of the energy is lost to heat? This article mentions 30% for fission, about as efficient as coal

http://www.electrical-efficiency.com/2012/09/nuclear-power-energy-efficiency/

however it is not clear to me how this compares to solar or wind. PV panels are ~20% efficient, but don't think that means 80% is ‘new’ excess heat added to the atmosphere

 

[mfb]

Ultimately nuclear power - fission or fusion - is a dead end as too much of the energy is lost to heat? This article mentions 30% for fission, about as efficient as coal

So what? The problem of coal is not the produced heat. It's the CO2. We won't run out of fuels for fission or fusion any time soon, so efficiency isn't a major issue.

That makes no sense because it has been calculated for the thermal emission from the ground.

It's a more rough approximation. Thanks for working that out in more detail. My point was "it's way beyond today's energy use" - which is true even with the additional factor 2 you calculated.

 

[russ_watters]

Ultimately nuclear power - fission or fusion - is a dead end as too much of the energy is lost to heat? This article mentions 30% for fission, about as efficient as coal

How do you determine a threshold for "too much" that makes them a "dead end"? I'm not sure what that even means or why it should be relevant at all, since ultimately all of the energy we produce becomes heat anyway.

however it is not clear to me how this compares to solar or wind. PV panels are ~20% efficient, but don't think that means 80% is ‘new’ excess heat added to the atmosphere

Most solar panels are dark in color, so that does mean that basically all of the energy that isn't turned into electricity is dissipated as heat. But you'd probably want to compare that to the albedo of the ground or roof the panel is installed on.

For wind, the efficiency is better; somewhere around 50%.

 

[russ_watters]

Ultimately the question in the OP comes down to a value judgement because of the word "need". How we decide to live and use our resources is a choice based on what we want for a standard of living.

As far as I know, most if not all developed countries are currently reducing their energy intensity (energy use per person), but developing countries have a long way to go to reach the energy intensity and level of development of the developed countries. But even the developed countries could increase their energy intensity in the future if energy gets cheaper and cleaner. We can always find new ways to expend energy.

 

[BWV]

So what? The problem of coal is not the produced heat. It's the CO2. We won't run out of fuels for fission or fusion any time soon, so efficiency isn't a major issue.It's a more rough approximation. Thanks for working that out in more detail. My point was "it's way beyond today's energy use" - which is true even with the additional factor 2 you calculated.

The question was in regard to this hypothetical future where CO2 emissions are reduced / eliminated, but total energy consumption is such that we have to worry about warming the planet simply from waste heat

 

[DrStupid]

The question was in regard to this hypothetical future where CO2 emissions are reduced / eliminated, but total energy consumption is such that we have to worry about warming the planet simply from waste heat

This is an issue for Kardashev Type I civilisations and above. We are currently at 0.7 and growing with around 0.1 per century. That means the hypothetical future you are talking about is in around 300 years. It doesn't make much sense to speculate about it. It would have been easier for George Washington to discuss our current technical and environmental problems.

 

[BWV]

This is an issue for Kardashev Type I civilisations and above. We are currently at 0.7 and growing with around 0.1 per century. That means the hypothetical future you are talking about is in around 300 years. It doesn't make much sense to speculate about it. It would have been easier for George Washington to discuss our current technical and environmental problems.

Well yes, but we are near the end of science, so won't know that much more 300 years from now

 

[Ophiolite]

Well yes, but we are near the end of science, so won't know that much more 300 years from now

That is an assessment overturned by events each time it is made. Perhaps this time will be different, but I suspect not.