Can clean energy replace fossil fuels?

[Ad VanderVen]

If you search the net with the question: "Can clean energy replace fossil fuels?" then no clear answer is given. On the website https://blog.arcadia.com/top-7-questions-youve-asked-google-renewable-energy/ it is said:

Yes! However, despite falling costs, wind and solar only produce a little over 5.5% of the world’s electricity. A few countries, as well as several states in the U.S., have ambitious goals for reducing their greenhouse gas emissions. Germany, for instance, aims to run on 80% renewable energy by 2050. The shift to 100% clean energy will depend on small-scale progress and cooperation, but it is doable.

So if fossil fuels can be completely replaced by clean energy at all, it looks like it will take many decades to achieve this and the question is whether we have that much time.

My main question, however, is "Can fossil fuels be replaced by clean energy at all?"

 

[berkeman]

Have you read this helpful Insights article by @anorlunda? He covers many aspects of your question.

https://www.physicsforums.com/insights/renewable-energy-meets-power-grid-operations/

 

[hutchphd]

I was going to suggest:

https://www.physicsforums.com/threads/almost-plausible-solar-takeover-plan.989072/

 

[russ_watters]

So if fossil fuels can be completely replaced by clean energy at all, it looks like it will take many decades to achieve this and the question is whether we have that much time.

My main question, however, is "Can fossil fuels be replaced by clean energy at all?"

Electricity or all energy?

If the question is about electricity, the answer is simple: Of course it can*. There really are no significant technical challenges or fundamental limits preventing it. It's simply a choice to do it or not. We choose not to.

For other uses, like transportation, it isn't so simple and there are significant challenges.

[Edit]*Important caveat: people need to keep their eye on the ball when they define "clean". That can change the answer from a clear "yes" to a "probably no".

 

[f95toli]

This isn't really a technical question as such

The purely technical answer to the question "is it feasible to replace fossil fuels with alternatives that do not emit nearly as much CO2" is obviously yes. When people answer "no" to that (or similar) question they are really saying that they believe it would be too expensive and/or would negatively affect society in some other way (e.g. cause unemployment).

Hence, this is ultimately a political question and has to do with priorities.

 

[anorlunda]

I agree with @f95toli. It is a political question, not technical.

In the two Insights articles mentioned: The whole premise of the 2nd article is that we could make 100% solar PV electric work.

In the first article, the concluding paragraph said.

Even experimentation and change with fundamental markets are risky. We are talking about hundreds of billions of dollars per year. The incentive to steal, cheat, or manipulate is huge. If you remember, we already saw what happened in 2000 with disastrous rolling brownouts in California. There, the crooks proved to be more clever than the market designers, and much more clever than the regulators. Innovation and prudence do not mix well for vital services.

So, that article also focused on non-electrical-engineering-issues. The article deals with questions of financial stability, and the potential for criminal fraud.

 

[Vanadium 50]

wind and solar only produce a little over 5.5% of the world’s electricity.

There's your answer. Cut consumption by a factor of 20 and we're done.

If you say "but we can't just do that!", it means there are hidden constraints on what you think of as a solution. So long as they remain hidden, discussion is difficult.

 

[anorlunda]

If you say "but we can't just do that!", it means there are hidden constraints on what you think of as a solution. So long as they remain hidden, discussion is difficult.

Well said.

 

[russ_watters]

There's your answer. Cut consumption by a factor of 20 and we're done.

If you say "but we can't just do that!", it means there are hidden constraints on what you think of as a solution. So long as they remain hidden, discussion is difficult.

The first couple of constraints are typically easy, but after that, they can get a bit squirrely. It's always assumed that the electricity supply is reliable and sufficient for consumer demand, which really is one constraint.

 

[anorlunda]

Consumer demand is highly variable. In part it depends on the economy (demand has plunged since COVID). It depends on demand-side management that seeks to change people's habits. It depends on changing technology such as EVs. Look at the figure below and imagine that a big share of the energy in the transportation sector is shifted from fossil fuels over to the electric sector. Finally, it depends on population and affluence. As we raise people out of poverty, their demand increases and the transient demand change is even larger.

 

[Ad VanderVen]

When I ask the question can clean energy generation replace all energy generation by using fossil fuels, I mean all energy, including the energy needed to transport people and products by sea, road and air, as well as the energy that is necessary for the working of machines. as used in industry, road construction, etc.

Some say this is a political question. That is not true. It's a purely technical question and I haven't received an answer to that question yet.

If we stopped using fossil fuels around the world from tomorrow on, there would be a massive global famine within months and within a year the world population would drop from 7 billion to 1 billion, the number of people who lived on the planet before the discovery of the steam engine. It shows how the current size of the world's population largely depends on the use of fossil fuels.

Am I in favor of the use of fossil energy?. No, I am not, but if we cannot replace all energy generated by fossil fuels with clean energy within, say, one generation, then we really have a problem.

 

[Rive]

If we stopped using fossil fuels around the world from tomorrow on...

...that would be a new constraint added to the original question.

 

[Ad VanderVen]

...that would be a new constraint added to the original question.

No, it is not a new restriction added to the original question. I am only saying what the consequences would be if you would completely stop using fossil energy from tomorrow.

 

[russ_watters]

When I ask the question can clean energy generation replace all energy generation by using fossil fuels, I mean all energy, including the energy needed to transport people and products by sea, road and air, as well as the energy that is necessary for the working of machines. as used in industry, road construction, etc.

Then the answer is a simple "no". There are transportation uses that don't currently have technically viable non fossil fuel solutions, including large planes and ships.

 

[Ad VanderVen]

...that would be a new constraint added to the original question.

Do you mean the restriction: clean energy in one generation?

 

[f95toli]

When I ask the question can clean energy generation replace all energy generation by using fossil fuels, I mean all energy, including the energy needed to transport people and products by sea, road and air, as well as the energy that is necessary for the working of machines. as used in industry, road construction, etc.

Some say this is a political question. That is not true. It's a purely technical question and I haven't received an answer to that question yet.

Technically the answer is yes. If you really want to it is possible to make -in theory- carbon neutral (assuming you have a carbon neutral source of electrical energy) fuel for all types of transport including planes (which has been demonstrated). It is not financially viable because the world economy relies of cheap transportation and these fuels are still very expensive; but -again- this is still a political question.

If we stopped using fossil fuels around the world from tomorrow on, there would be a massive global famine within months and within a year the world population would drop from 7 billion to 1 billion, the number of people who lived on the planet before the discovery of the steam engine. It shows how the current size of the world's population largely depends on the use of fossil fuels.

And a hard-core environmentalist could hypothetically argue that this would be worth it if it saves the planet long-term. Again, this is not about technology but about what we prioritise which is ultimately a political question. Moreover, doing this "tomorrow" is clearly a very hard constraint which you did not include in your
original question.

 

[Ad VanderVen]

Then the answer is a simple "no". There are transportation uses that don't currently have technically viable non fossil fuel solutions, including large planes and ships.

Do you mean that there are currently no transportation uses with non-fossil fuel solutions, including large aircraft and ships? In that case, I welcome your clear answer. At least then we know where we stand. Many politicians argue that the introduction of alternative, clean energy is the solution to the climate problem. So that's not true. There is also a company that claims this solution even in one generation, namely the Swedish company Vattenfall.

 

[russ_watters]

Do you mean that there are currently no transportation uses with non-fossil fuel solutions, including large aircraft and ships?

Some transportation uses have non fossil fuel solutions (cars, for example), some don't.

In that case, I welcome your clear answer. At least then we know where we stand. Many politicians argue that the introduction of alternative, clean energy is the solution to the climate problem. So that's not true.

Well, you've set an arbitrary bar at 100%. I don't think it is widely believed that "the solution to the climate problem" requires 100%. Moreover, it isn't even a binary issue; any amount of conversion to non fossil fuel will have a positive impact.

So it doesn't look to me like you asked the right question for what you really want to know.

 

[Rive]

Do you mean the restriction: clean energy in one generation?

We are trying to answer your question. Could you please decide what is it?

Since we are able to synthesize a good replacement for almost every fuel and plastic out from 'thin air' (a bit of an exaggeration here) with only energy, in theory it is 'possible' to switch to clean energy.

A bit of a problem, that both the price and the environmental footprint would be terrible: several times (maybe several dozen times or more) higher than with fossil fuel. Then what would be the point?

At this point we did replace some fossil fuel/resources with 'clean' energy with reduced environmental footprint and acceptable price.

At this point we did 'replace' some fossil fuel/resources with 'clean' energy with actually increased environmental footprint and stupid price.

At this point we could replace some more (but decided not to) if 'clean' includes nuclear as 'CO2-free'.

So, what is your question?

 

[russ_watters]

Technically the answer is yes. If you really want to it is possible to make -in theory- carbon neutral (assuming you have a carbon neutral source of electrical energy) fuel for all types of transport including planes (which has been demonstrated).

I disagree. Demonstrating a short hop in a small electric plane does not suffice as proof you can replace jet airliners with battery powered ones.

"In theory" is just a way to avoid saying the actual technical solution does not currently exist.

 

[f95toli]

I disagree. Demonstrating a short hop in a small electric plane does not suffice as proof you can replace jet airliners with battery powered ones.

I wasn't thinking of electrical planes. I was referring to syntethic jet fuel (say kerosene made from biomass). This is not carbon neutral today, but as far as I understand that is more about costs that technical barrier.

 

[Ad VanderVen]

Technically the answer is yes. If you really want to, it is possible to make -in theory- carbon neutral (assuming you have a carbon neutral source of electrical energy) fuel for all types of transport including planes (which has been demonstrated). It is not financially viable because the world economy relies of cheap transportation and these fuels are still very expensive; but -again- this is still a political question.

I suppose by 'carbon neutral' you mean 'carbon dioxide neutral'. I don't think it is possible to make CO₂ neutral fuel, because the energy you get from the transition from C + O₂ to CO₂ is equal to the energy you need to convert CO₂ to C + O₂ . You could store the released CO2, but that also costs energy and this energy can also be equal to the energy released during the transition from C + O₂ to CO₂ . So I wonder where you got the information that it is possible to neutralize CO₂ emissions.

 

[fresh_42]

I find the entire thread nonsensical. If we will have used all fossil fuels, and they are limited, then we will work on other resources. Uranium isn't "clean" energy, so that is a separate discussion. But it will once be used up, too. Latest then we will run on solar energy input only - or fusion if we will manage to make it work. Whether this can be called "clean" is again a separate discussion. We will still have a lot of radioactive waste (the engines and tubes).

It is a simple calculation: Current energy consumption versus potentially usable solar energy. The answer is very likely a NO under the assumption of a non decreasing need and available energy density (container ships).

All the rest is politics, including the definition of "clean".

Case closed.

 

[Vanadium 50]

There are transportation uses that don't currently have technically viable non fossil fuel solutions, including large planes and ships.

Bring back blimps and clipper ships!

 

[Ad VanderVen]

Bring back blimps and clipper ships!

With the enormous amount of containers that we now transport?

 

[russ_watters]

I wasn't thinking of electrical planes. I was referring to syntethic jet fuel (say kerosene made from biomass). This is not carbon neutral today, but as far as I understand that is more about costs that technical barrier.

Oh, ok. I don't think I've ever seen a proposal/study of the requirements/feasibility of widescale implementation of that. Do you know of any you could link? EG., is the world capable of growing enough biomass for that?

 

[fresh_42]

Bring back blimps and clipper ships!

Hell, no! Did you forget the price of pepper in those days?

 

[f95toli]

Oh, ok. I don't think I've ever seen a proposal/study of the requirements/feasibility of widescale implementation of that. Do you know of any you could link? EG., is the world capable of growing enough biomass for that?

Sorry, no. I remember reading a bit about it when Virgin Atlantic flew their demonstrator a couple of years ago.
You get quite a few hits if you search for "jet fuel from biomass". As far as I understand they typically start with making ethanol, i.e. the "bio" bit is not very radical.

 

[russ_watters]

I find the entire thread nonsensical.

The framing of the issue by the OP might be weak, but it is the current mainstream view that climate change is the greatest threat to humanity we have now and maybe have ever had. So the issue of how to get away from fossil fuels is really, really important. I didn't think you disagreed with that.

If we will have used all fossil fuels, and they are limited, then we will work on other resources.

In the context of climate change, we don't have time to wait for running out of fossil fuels. We have to leave them in the ground, unused.

Uranium isn't "clean" energy, so that is a separate discussion.

This is why I said earlier we need to keep our eye on the ball. In the context of this discussion, "clean" means "carbon free" (or neutral). Having a goal of eliminating nuclear power because it isn't "clean", as Germany does, is equivalent to saying that it is nuclear power, not climate change, that is the greatest threat to humanity.

 

[f95toli]

I suppose by 'carbon neutral' you mean 'carbon dioxide neutral'. I don't think it is possible to make CO₂ neutral fuel, because the energy you get from the transition from C + O₂ to CO₂ is equal to the energy you need to convert CO₂ to C + O₂ . You could store the released CO2, but that also costs energy and this energy can also be equal to the energy released during the transition from C + O₂ to CO₂ . So I wonder where you got the information that it is possible to neutralize CO₂ emissions.

"Carbon neutral" means that there should be no net excess of CO2 at the end of a cycle. It does not mean that you can't "use" CO2. This is why growing plants and then burning them can -in theory- be carbon neutral even if the "burning" stage obviously generates a lot of CO2: the plants will have used exactly the same amount of carbon to grow (while releasing O2)
(and yes I know that growing biomass isn't actually carbon neutral because of land use etc, but the principle still holds)

 

[fresh_42]

In the context of climate change, we don't have time to wait for running out of fossil fuels. We have to leave them in the ground, unused.

This assumes that we agree on fighting climate change. I do not see that. And even if we do, it would require a form of compensation to switch from cheap to expensive energy which I do not see either. And if you argue, that cheap fossil fuel plus climate change exceeds the costs of clean energy by far, then my argument is, that we have different costs objects and hence different interests, which again will block progress.

All these involve political decisions, not physical ones. A physical subject would be the availability of lithium, copper and iron. Phosphor is interesting, too, but a different debate.

 

[russ_watters]

Sorry, no. I remember reading a bit about it when Virgin Atlantic flew their demonstrator a couple of years ago.
You get quite a few hits if you search for "jet fuel from biomass". As far as I understand they typically start with making ethanol, i.e. the "bio" bit is not very radical.

Fair enough, I'll probably look into it.

Also, the framing of the OP seems to have excluded financial considerations, but that's tough to do if a technology is really expensive. At some level the technological and financial challenges overlap (you hope technology can find a cheaper solution). One of the reasons I focus so much on electricity is that the financial constraints are practically nonexistent for carbon-free electricity, so we really should be able to choose to just do it. That we don't, is telling to me that people don't really believe climate change is a big problem. And if we won't even do it for electricity, replacing oil in transportation isn't a question that is really even on the world's radar.

 

[fresh_42]

That we don't, is telling to me that people don't really believe climate change is a big problem.

It is. The question is to whom!

 

[russ_watters]

It is. The question is to whom!

At the very least we can say it has been declared so by basically every government on the planet, by signing the Paris Agreement:
"Recognizing the need for an effective and progressive response to the urgent threat of climate change on the basis of the best available scientific knowledge..."

But few if any are taking steps that are commensurate with the declared importance of the problem. The irony of the location that gives the treaty its title should not be lost: in 1973, the Prime Minister of France decided it was in France's financial interest to rid his electric grid of foreign oil. So he basically snapped his fingers/stroked a pen, and it happened (they did stop a bit short, but not much). It was really easy to do.

[edit] The OP seems to be spun/constrained to generate a technical answer "no" to support a conclusion of "since it isn't possible to totally get off fossil fuels, we shouldn't even bother trying at all." But that isn't the prevailing technical framing and view of the issue. The prevailing view/framing is that is *is* possible to make a radical impact on the problem. And not just "possible" -- it should be easy.

 

[fresh_42]

"since it isn't possible to totally get off fossil fuels, we shouldn't even bother trying at all."

Well, this is definitely wrong. But the way to do so, and this is what I wanted to say, always inevitably ends up in a political discussion, because the transition costs, and the fact that different states have to give up different levels of luxury must be addressed. The current distribution of costs and cost objects will not work. And I see nobody dares to speak it out loudly, with little exceptions like Germany and nuclear power. My remark on the costs of pepper was only half way funny. It summarized the problem.

To discuss it on a pure scientific, non political level is in my mind only possible as fas as lithium and copper resources are involved, and even this is political.