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Will Renewable Energy Ever Meet All Our Energy Needs?
Lasrick writes "Dawn Stover has another great piece detailing why renewable energy will never provide us with all our energy needs. She deconstructs the unrealistic World Wildlife Fund report (co-written by several solar companies) that claims renewables will be able to provide 100% of the energy needs of several countries by 2050. From the article: 'When renewable energy experts get together, they tend to rhapsodize about the possibilities, believing that this will somehow inspire others to make their visions come true. But ambitious plans to power entire countries on solar energy (or wind or nuclear power, for that matter) don't have a snowball's chance in Australia. Such schemes are doomed to fail, and not because of the economic "reality" or the political "reality" -- however daunting those may be. They are doomed because of the physical reality: It's simply not physically possible for the world's human population to continue growing in numbers, affluence, and energy consumption without trashing the planet.'"
Err... you do know that Australia has alpine areas right? http://en.wikipedia.org/wiki/Australian_Alps
Work smarter, not harder.
Until you define "needs", the question is pretty meaningless.
his article is sort of an IQ test: if you agree with him, you fail
for instance
quote "Take solar power.... In only one hour, the sun delivers as much energy to Earth's surface as humanity consumes in a year....astrophysicist Tom Murphy calculates that, even with an annual energy growth rate of only 2.3 percent, a civilization powered by solar energy would have to cover every square inch of Earth's land area with 100-percent-efficient solar panels within a few hundred years. "
I mean, do I really have to go thru all of hte problems with this one statement ?
'When renewable energy experts get together, they tend to rhapsodize about the possibilities, believing that this will somehow inspire others to make their visions come true.
Those aren't experts.
"First they came for the slanderers and i said nothing."
The summary cites solar, wind, and nuclear as not being able to power cities. This is due to the fact that cities need power when they need it, and can't wait for the power to be there intermittandly. Therefore, viable options fall under the designation "baseload" power (power that you can have whenever - and in most cases wherever), and the summary's mention of solar and wind are rightly not grouped in this category.
Incorrectly, however, the summary mentions nuclear, which is in fact a primary form of baseload power along with coal, gas, or hydro. Nuclear could, can, will, and does power entire cities, in fact, Chicago is roughly over 90% powered by Nuclear energy (rough statistic - http://en.wikipedia.org/wiki/List_of_power_stations_in_Illinois).
Renewable Energy can NEVER satisfy 100% of the total energy requirement to run the current human civilization.
However, if we deconstruct the way we use energy we would find that up to 80% of the energy we are using ended up in waste heat.
No matter it's in the industrial setting or electricity generation or even the fluorescent light bulbs that we are using right now, waste heat is generated.
If, and only if, we can get our technology to improve to the level that waste heat is minimized to, let's say 10% or less, then, we will see that we do not need that much energy input anymore.
This has a ripple effect ... The less energy we need, the less load on the electricity grid and the less need to construct power plant ... and so on ...
Muchas Gracias, Señor Edward Snowden !
It should be obvious to anyone that you can't grow society forever without hitting some limit. Whether the limit is energy, or something else is rather moot. Talk about using all the energy in the galaxy is rather overboard.
So... at some point we have to stop growth. But there is no will anywhere to do so. Only when we run hard into the limits will growth stop, and then by necessity. So, all this talk about how we must change is itself just "visionary" fluff. There isn't going to be much actionary. We can't even agree on emissions to make much progress on that. He is asking for a lot more, and thus it is a lot less likely to happen.
Yes. Fast forward far enough and we're either extinct or running off renewables. Non-renewables are temporary, pretty much by definition. Stupid question.
It has been a long time since we had a world war
They used to occur on a regular basis until ww2 put an end to the cycle
I will be amazed if in 20 years any more than 50% of all these fiddly little generators are still maintained and working. Just look at what's left of the old wind farms in CA and HI. It would be nice if they kept them up though, to give my boy something to do when the new armies of H1B's finally take the entire tech industry back home with them.
Strange things are afoot at the Circle-K.
...on how you look at the problem.
Cover every roof in the United States with photovoltaics at today's efficiency levels and you'll generate roughly as much energy as the entire civilization consumes. And lots of places in the world have roofs other than just the United States....
But, though there's no problem with resource availability, there are two huge practical concerns. First, such a project would be massively expensive. Second, it generates electricity, which is not readily useable for transportation with today's infrastructure.
Neither of those problems are insurmountable. Though solar photovoltaics aren't cheap, they're not as expensive as many petrochemical alternatives being seriously considered, such as tar sands. That is, we might not be able to afford widespread PV adoption, true...but, if we can't afford it, we won't be able to afford anything else when the existing wells run dry.
(As a side note, we're already scraping the bottom of the oil barrel. Remember Deepwater Horizon? Imagine you're standing on the shore of the Colorado River in the middle of the Grand Canyon. A mile above you is the rim; that's how far below the ocean surface the wellhead was. Several miles above the rim is an airliner flying past. That's how far through solid rock the well was bored before it reached the oil deposits. That's how desperate we already are today for oil...loooooong gone are the days when you had to be careful in Texas with a pickaxe lest you start a gusher. Yes, we've got lots of oil left -- about half as much as the planet's total original reserves, in fact. But -- duh! -- we went for the easy-to-get-to, high-quality half first, and what's left increasingly fits the definition of, "dregs.")
The problem with transportation fuels is more pressing. At the very least, with enough input energy, you can extract CO2 from the atmosphere and turn it into fuel (via the Fischer-Tropsch process, for example) that you can put back into a tank to burn it again, so we have alternatives. The catch, of course, is that it takes a lot of excess energy to do so, and so won't be cheap.
TL/DR: Yes, we can run our society on solar power. No, it won't be cheap. No, we won't have any better alternatives. Yes, that means we're facing some tough times in the not-too-distant future.
Cheers,
b&
P.S. Even worse than the looming transportation fuel shortage is the looming petroleum-based fertilizer shortage. That double whammy is going to result in lots of people starving to death. b&
All but God can prove this sentence true.
"No one energy will ever meet "all" of our energy needs. Theres a reason why we still use wind and hydro energy despite centuries/millenia."
Oil comes from Sun
Aeolic comes from Sun
Hydro comes from Sun
Thermal comes from Sun
Solar -obviously, comes from Sun
Only energy that doesn't come from Sun is nuclear.
On a long enough timeline, all energy is renewable.
Once the next comet hits and wipes out humanity, it'll only be another couple million years until our graveyards turn into the next oil deposits.
This signature is false.
This is a classic case of weighting down an opponent's thesis with extra assumptions, and then using those assumptions to shoot it down.
The basic question is, "is it possible to meet the world's current energy needs using renewables?"
The question the author is answering is, "is it possible to to meet the world's energy needs using renewables, assuming continued exponential growth forever?"
The answer to the second question is obviously "no", unless you're an economist. But the author only attacks the "exponential growth forever" idea, and says nothing about the first question, which is far more interesting.
No. The current status of renewable energy (geothermal, hydroelectric, wind, solar, etc.) can in no way support our current consumption habits.
Can a more widely implemented renewable energy/less-polluting energy infrastructure support a society that uses less energy? Likely. Or some of us are going to have to die to make room for the bigger consumers lest we all die.
The plan?
(1) Assume all fossil-fuel-burning energy plants will shut down in 50 years.
(2) Begin plans to install the most regionally appropriate renewable energy power plants to support those areas.
(3) Calculate the energy shortfalls and make plans to supplement with the most reasonable nuclear options (insert arguments about recycling waste, using thorium, etc.)
(4) Select a demo site, implement, learn, discuss, implement better.
"If something cannot go on forever, it will stop," -Herbert Stein
The absurd comment about ...with an annual energy growth rate of only 2.3%... reminds me of the population growth people a couple decades back who claimed that if the population keeps growing at this rate, by blah-blah-blah date the population of earth will be expanding at the speed of light.
Conclusion, population will not continue to grow at that rate, energy growth will not continue perpetually at 2.3%.
Of course we may want to influence *how* things stop. Stopping a car by applying the breaks is generally preferred over accelerating full-speed into a cliff.
~~~~~~~
"You are not remembered for doing what is expected of you." - Atul Chitnis
Any economic model that is not in line with the laws of physics is flawed. No matter how much you pretend otherwise, there is only so much gold in Fort Knox.
When our name is on the back of your car, we're behind you all the way!
geothermal energy comes from thermonuclear thorium reactions in the molten layers of the earth. thorium comes from supernovas thorium reactions come form the sun. so yes all energy comes from the sun, or more correctly the suns that existed before ours was formed.
https://www.gnu.org/philosophy/free-sw.html
...just as soon as all the non-renewable resources are gone.
A more accurate synopsis of her argument is this:
"Since population growth and per capita economic growth are dependent on ever-increasing energy consumption, it is physically impossible for renewable energy to provide an indefenite supply of unlimited energy. Therefore, demand reduction is the only really-long-term answer."
While I actually agree with this position, it's freaking worthless. First off, the author's argument and the WWF paper are speaking to entirely different time scales. It's functionally equivalent to saying we shouldn't waste time advocating the use of seat belts because they don't protect pedestrians. Scope matters!
The second and larger issue here is that her counter-argument is just as reality-deprived as she claims the WWF paper to be. In her conlcusion, she states simply, "To which I say: Why don't we just not do it?" i.e. why don't we exert self-control as a species and stop growing. Stop adding to total population. Stop increasing per capita consumption. It simply doesn't matter how true that is on paper. I find it amusing that she name checks the Do the Math blog which has been linked on Slashdot previously. The blog is compelling and well-written. It also avoids the flippant suggestion that converting to a zero-energy-growth global society will somehow be as obvious as a Nike commercial. The "reality check" is that the reckoning over energy consumption will be painful. Death and violence are in the cards long before equilibrium is reached. Human beings have the capacity to plan for the future and execute on those plans, but the number of years forward we are motivated to act upon have finite congnitive limits. The climate change issue is a recent-but-not-exclusive example of these limitations at work.
There is of course an amusing logical fallacy in her argument as a whole. If we are to ever reach the equilibrium she seeks, whether that is by design or through painful reaction, that equilibrium would have to be completely fueled by renewable resources, since we must eventually run out of the non-renewable ones. Doh!
Still, I'm glad this got posted to Slashdot. Undeneath her specific arguments there is a clear undercurrent. "Physicists are smarter than all the rest of you because we deal with real stuff so all of you can suck it." That kind of attitude definitely belongs here.
It's energy storage. Energy storage is the ultimate limiting factor on human civilization. Anyone that can crack the energy storage problem will be very, very wealthy.
Stars and supernovas aren't quite a renewable resource, except possibly through initiating a new "big bang" and rebooting the universe. The universe ultimately uses energy and moves to increased entropy. New stars are formed, but the pool of matter and energy to form them from is limited; some is lost over time (think of loss to black holes, for example... no real way to recover matter once it reaches that state.)
If renewable energy doesn't exist, then the whole premise that any civilization--human or otherwise--could be powered entirely by renewable energy is moot.
Oil alone accounts for 160 exajoules of the world's energy budget a year (about 30 billion barrels of oil - a year). The book referenced in this wikipedia entry ( http://en.wikipedia.org/wiki/Cubic_mile_of_oil ) explains it in terms that are easily understandable. Google and a calculator should do the rest.
We're literally out of gas by 2100 or thereabouts (Russia might still be fracking useful quantities but nobody else will be). While there will still be coal, natural gas and oil here and there, there won't be enough that's cheap enough, or with a high enough net energy to support a large scale industrial civilization. After that, those of us that haven't starved will be using biomass, wind, solar and hydro because that, as they say, will be that. There will. however, be many fewer of us to use it. Perhaps a LOT fewer, depending on how enthusiastic we are with nuclear weapons as tools of diplomacy.
Please do not read this sig. Thank you.
But we can't afford the energy (or money, same thing) to build out nuclear. It's called the energy trap and we're in it.
thegodmovie.com - watch it
You are a dolt, I know you are anonymous but please never post such idiocy again. I'm not going to defend the Agenda 21 comment, but will attack your Capitalism comment. Go read a book and learn something about economics. Every economy works where no income = no purchases. There is not a single exception to the rule going back to the bartering days. And don't even start with the Welfare check bullshit that normally follows. Welfare would still be money in exchange for goods, but the source of money would change.
Funny that Karl Marx and the rest of the Communist bunch bickered about how bad Capitalism was.. and look how they operate? With currency in exchange for goods. The difference is that of course "The Party" controls what goods are available and who can get what goods. But the use of money works the same. It is a requirement for any economy. And be honest. Communism and Party control is way more unfair than "Capitalism" (assuming Capitalism is being used in it's true form, not the monopolistic leech fest we see called Capitalism today).
If you want to attack the conspiracy theory, that's fine and dandy. But if you do so in the future, at don't use false economic statements (easily debunked false economic statements).
-The wise argue that there are few absolutes, the fool argues that there are no probabilities.
No matter how much you pretend otherwise, there is only so much gold in Fort Knox.
I remember years ago learning that there is about a ton of gold in every cubic mile of sea water. That's gold that isn't economically feasible to extract. But that just demonstrates that there's a hell of a lot of gold that isn't in Fort Knox.
The article is full of lies, damned lies, and murderous discourse:
As Derek Abbott has reported elsewhere in the Bulletin, nuclear power is not globally scalable because of the limited availability of the relatively scarce metals used to construct reactor vessels and cores, which appears to be a harder limit than the supply of uranium fuel.
Nuclear fission reactors are made of steel and concrete. Neither are particularly rare. The fuel is not rare either and exploration only began in full swing in the XXth century. Fast reactors, thorium, etc further make the notion that nuclear has hit some kind of a wall laughable. There are only 80 years known reserves of uranium left because no one has bothered prospecting for more. Why waste time doing it when you have so much of it for so cheap? In the 1990s many uranium mines closed because of the abundance of blended down nuclear warhead stockpiles from the former USSR. You couldn't give it away. Only now have these mines started entering in service again.
billions of rooftop photovoltaic systems, millions of jumbo-size wind turbines, hundreds of thousands of wave devices and tidal turbines, tens of thousands of concentrated solar power plants and photovoltaic plants, thousands of geothermal plants, and hundreds of hydroelectric dams. But the construction work doesn't end there, because population and living standards are expected to continue rising after 2030. At best, such a plan simply kicks the can down the road.
Try doing the math assuming 18% efficient solar PV power and place the panels in deserts where there is a lot of solar insulation and the land is worth next to nothing and see how much land area you need. You would be surprised. This efficiency is today regularly achieved by both silicon PV and CIGS and I would not be surprised if they managed to do it in other roll to print technologies as well. Wind can easily power 20% of current energy needs economically. The dams are useful for flood control and ensuring a safe water supply even if they did not generate any power. Making a global energy grid is as impossible as it was impossible to make a global communications grid.
astrophysicist Tom Murphy calculates that, even with an annual energy growth rate of only 2.3 percent, a civilization powered by solar energy would have to cover every square inch of Earth's land area with 100-percent-efficient solar panels within a few hundred years.
A few hundred years ago we did not have global maritime trade or steam engines. Or viable electricity for that matter. The Earth's land area is 1/3rd of its total surface area and there are other surfaces in the solar system besides that. This with current technology. With future technology we could be harvesting energy from black holes or anti-matter for all we know.
There's another way to approach the problem: start with supply instead of demand, and work backward from there. In his book Sustainable Energy -- Without the Hot Air, physicist David J.C. MacKay calculates how much energy could sustainably be produced in the United Kingdom with a massive expansion of existing technology. The total turns out to be less than the nation's energy consumption, which suggests to MacKay that the only path forward is to reduce demand -- through energy efficiency improvements, for example -- until it balances with supply. To which I say: Why don't we just not do it? Let's not build any new power plants except to replace old, inefficient ones. Let's not dig up all the oil. Let's not drive to work alone. Let's not eat meat every day. Let's not turn the thermostat up so high. Let's not buy so many things we don't really need. And above all, let's not accept continued energy growth as a necessary or even desirable way of life.
Yes let us freeze, starve, and stop having children while ignoring the prime directive of the natural world to satisfy some max
That "reality check" need a reality check on more than snowballs; example: http://en.wikipedia.org/wiki/Grid_parity
Most of the world is heading in a few more years to being able to make solar power more cheaply than getting power from the grid (the parts that are not already there, like much of India).
I'm all for living within our current energy means in a reasonable way (and I abhor the pollution from mining and burning coal and oil), but she cites a calculation that projects exponential growth on Earth forward a few hundred years, calculates we will need to cover the whole Earth in solar panels (and then the Galaxy), and then concludes from that somehow that we should stay the way we are. That just does not seem to be a healthy emotional space to be in.
She's probably against self-replicating space habitats that can duplicate themselves from sunlight and asteroidal ore, too? Even if it would mean quadrillions of people could live in the solar system and the survival of some aspect of humanity might be better assured? From the 1920s by J.D. Bernal on that:
http://vserver1.cscs.lsa.umich.edu/~crshalizi/Bernal/world/
Maybe we should all move back to live in trees in Africa? Or maybe that is too "advanced" compared to flopping around in muddy tidal flats?
There are always at least four issues to a resource question:
* How much stuff do we "want" based on cultural expectations?
* How efficiently can we use what we have to make what we want?
* How should we divide all that up?
* How can we expand the scope of what we are doing to new types or resources or new areas to find them in?
That is the complexity of the issue and she stakes out a position without discussing the possibilities or why she prefers one over the other. There might be a case to be made in the direction she tries to go (e.g. the Amish may have an overall happier community-oriented way of life), but she did not make it.
A 21st century issue: the irony of technologies of abundance in the hands of those still thinking in terms of scarcity.
Once upon a time, before about two and a half centuries ago in point of fact, renewable resources did provide all of our energy needs. They kept our shelters warm enough to fight off hypothermia--our most important need. They allowed us to grow our food with the aid of solar powered animals--our third most important need. And with that food we had strength and energy enough to do what was necessary to secure clean water sources and/or make alcohol--our second most important need. So if survival of the species is what is meant by "needs" here, then experience would show that the answer is yes. Certainly, the renewable resources still retained scarcity enough to justify killing one another, as though we needed an excuse, but that has and always will remain true even when we are awash in cheap energy, massive industrial capacity, and so much food that price supports are used to ensure farmers have enough money to eat. But our species needs for survival were met by renewable resources.
But if "needs" is expanded to include everything we now do with the large quantities of cheap solar energy stored in fossil fuels, then the answer is no. We once had solar powered vehicles and farm equipment: i.e. horses, mules, asses, camels, and oxen. But since we want to go further in a day than those solar powered vehicles can take us--and most of us in the developed world, myself included, often need to do so in economies structured as ours--then we now seem to need non-renewable resources.
This is question begging. It will of necessity prompt debate, and that fruitless, so long as the key terms remain undefined. To define these key terms, however, may be the more uncomfortable problem. If, on the other hand, you tell me what "needs" means, then most else is simple calculation.
> assuming Capitalism is being used in it's true form, not the monopolistic leech fest we see called Capitalism today
That is its true form. Capitalism asserts the same patterns over time.
If we can reduce the energy consumption of a device, it just means we get to use that energy for other devices, potentially more powerful.
Consumption of energy will still increase even if devices are made more energy-efficient.
That's a possibility. Another possibility is that there are only so many devices needed by a person.
Lighting, cooking, refrigeration, washing, cleaning, heating, viewing, communicating, listening, transporting, making, destroying, storing.
That's pretty much it.
Pervasive robotics is the only thing that could create a change in that model.
Anecdotally I've reduced the number of devices and increased efficiency over time. I've done that while adding four people to my family. That won't hold true for long as my children grow but gone are the days of having a device for everything. Now they are all combined into just a few high efficiency devices. A smartphone, laptop, tablet and TV are all that is needed. The TV is only used a few hours a day by the kids which will get less and less as they become more independent and social life takes over.
So fewer devices, more efficient energy use - even the appliances are far more efficient and really how many refrigerators can you use? Washer dryer? Dishwasher, vacuum cleaner, toaster, microwave, coffee maker. The list isn't that long and you soon run out of things to buy. Sure you upgrade for efficiency or features every 4-5 years but you just don't buy two coffee makers anymore, you get a Keurig and make a cup at a time regular or decaf or special roast or tea.
This trend will continue. The big cost is in the manufacturing of new stuff though. That's where the robotics make a difference in a good way (discounting the labor competition) as they are far more efficient than people. They can run at off peak hours, don't require lighting (infrared would work fine), dont need creature comforts or heated work spaces.
So if we can mature past the wealth based society, robots can do all the work and we'll have plenty of energy for strategic and creative pursuits.
A fool throws a stone into a well and a thousand sages can not remove it.
No, I'm not one of those people. I'm fully aware if the fiat nature of currency, and that banks create money by lending it to you primarily on their estimation of your capacity to repay it. Nevertheless, there are only so much resources available (be it gold, or oil, or brown cows that give chocolate milk) and any economic system that ignores that fundamental rule of physics is flawed.
When our name is on the back of your car, we're behind you all the way!
It's also not a real law - it's a heuristic leading from human behavior. There have been plenty of weird instances in human history where changes in supply or demand didn't show the expected direct influence on the opposing factor. But there aren't local exceptions to physics, and there are fewer ways to artificially manipulate the terms in global energy equations than there are in even large economies.
From the article:
We simply don't have an alternative to fossil fuels that can be rapidly scaled up, doesn't require a daunting input of raw materials and energy, and has a relatively low output of air-polluting emissions.
To which I say malarkey, bologna, and BS. This is an opinion, backed by no data. Here is a counter opinion. Which has data, which we like.
From that article:
NREL's research showed that one quad (7.5 billion gallons) of biodiesel could be produced from 200,000 hectares of desert land (200,000 hectares is equivalent to 780 square miles, roughly 500,000 acres), if the remaining challenges are solved (as they will be, with several research groups and companies working towards it, including ours at UNH). In the previous section, we found that to replace all transportation fuels in the US, we would need 140.8 billion gallons of biodiesel, or roughly 19 quads (one quad is roughly 7.5 billion gallons of biodiesel). To produce that amount would require a land mass of almost 15,000 square miles. To put that in perspective, consider that the Sonora desert in the southwestern US comprises 120,000 square miles. Enough biodiesel to replace all petroleum transportation fuels could be grown in 15,000 square miles, or roughly 12.5 percent of the area of the Sonora desert (note for clarification - I am not advocating putting 15,000 square miles of algae ponds in the Sonora desert. This hypothetical example is used strictly for the purpose of showing the scale of land required). That 15,000 square miles works out to roughly 9.5 million acres - far less than the 450 million acres currently used for crop farming in the US, and the over 500 million acres used as grazing land for farm animals.
The TL;DR version is that we could replace all car gasoline consumption in the United States with farms equivalent to 15% the size of the Sonora Desert, using land that you can't farm on anyways, which would be a 100% carbon neutral 100% solar solution.
The article also says:
Never mind the infrastructure required for transmitting solar electricity to all who need it, and storing some for a rainy day.
Biodiesel stores nicely even in the dark. See? Not a problem.
The person who wrote this article is simply unimaginative.
Weaselmancer
rediculous.
Not Fiat - more a Yugo, a Travant, or on a good day a Friday afternoon after a few too many drinks at the pub British Leyland Jaguar.
International oil and resource trading in US dollars seems to be what kept it alive under Reagan and is kept the dollar going in the crash a few years ago. Once the Norwegains, Arabs, Chinese and other big movers of US dollars decide to use something else it's screwed, but since there's now obvious alternative it keeps afloat.
Probably because anyone can make grammatical errors. I try to re-read before posting and correct the errors I notice, but I am far from perfect. How come people like you use fallacy to attack arguments instead using facts or debate?
-The wise argue that there are few absolutes, the fool argues that there are no probabilities.
It's not really 'weird instances'... you're describing Jeavon's Paradox
In a nutshell, it states that increased efficiency of a resource actually increases the depletion of said resource. e.g, as MPG of cars increases via efficiency, more people will accept longer commutes, resulting in a net increase in the use of fuel.
You stereotypers are all the same...
1) If we wait for nature to turn our energy consumption into an S-curve, the process will be extremely unpleasant for the people involved (constraints due to resource scarcity have a habit of fueling some rather nasty conflicts). It seems to me that we're better served to point out the problem so that we can try to find a way to limit our own energy use intentionally so that we can do it in a less painful way.
2) Even if population growth stops, energy growth doesn't necessarily. Per capita energy use has been increasing for pretty much all of human history. And, there's no reason to think that we aren't going to keep inventing new technologies that need ever more energy. (And, I should note here that most improvements in energy efficiency work by reducing the amount of energy that goes to waste heat, not by reducing the amount of energy required for the purpose for which we're expending energy. CFLs and LED light bulbs put out the same amount of energy in light as do incandescents; but, they give off less heat, for example.) If this continues, we'll still have a problem.
3) Expanding into the galaxy still has a non-exponential limit on our growth. In that case, at best we increase the available space and energy resources quadratically, since our outward expansion is limited by the speed of light.
4) Human ingenuity does not trump physics. If there are no new energy resources to tap, no amount of cleverness will allow growth in energy use to continue. And, please note, zero point energy is not a magical reservoir of unlimited energy waiting to be tapped.
5) I don't have to believe that today's conception of physics is 100% correct (and, in fact, I can tell you with 100% certainty that our current understanding of physics is, at best, incomplete) to be extremely confident that there aren't major unknown sources of available energy that can supersede the output of the sun. I can conclude this because the only phenomena that are not fully explained by known physics are things that couple only extremely weakly to the ordinary matter we are able to exert direct control over. So, any major untapped sources of energy either don't exist or are not accessible in any practical way.
6) Even ignoring the point that cold fusion is total nonsense (fusion in general is not; but, cold fusion has been shown, time and again, to be totally unsupported by the evidence), any energy source reliant on materials present on Earth will be, at best, a temporary solution. Eventually, solar will be the only source practically available.
7) Finally, TFA doesn't need to consider "a lot more obvious possibilities" when they can all be dismissed as having far less total energy available than the sun. Maybe other technologies can allow us to use energy faster than the sun outputs for a time; but, ultimately, that's just putting off the inevitable limitations for a finite (and, frankly, surprisingly short) time, unless we learn to stem our energy use.