Seems to me with hundreds of billions now thrown away on so-called alternatives, the only thing holding us back is that no viable alternative yet exists.
Ever wonder why ethanol is used in gasoline? I wonder every day! It takes about 1 gallon of gasoline to get the cellulose in corn to break down at a high enough temperature to produce about 1 gallon of ethanol. The trouble is oil can run out. Corn is replaceable. In the geological time span, oil is replaceable, but I think that won't happen until the next few ice ages, lol. Make sense? Ask any farmer's son in Vermillion, South Dakota, lol.
If more people used alternative energy, the cost would go down. It would offset the cost of research & implementation. If car companies made electric cars & sold them for $20,000 instead of $50,000, they'd sell so many, they'd recover their costs & then some. It's expensive now because it's not common place. Or as common as it should be. There's hydroelectric dams everywhere. They seem to do the trick. It's not really about complete replacement, it's more replacement where practical. That's the idea.
Atomic, Hydroelectric, wind, solar, geothermal, recycled materials for construction (being more cost effective and efficient in maintaining thermal temperature inside buildings reducing heating / cooling costs, thereby reducing energy consumption. It's more than viable. It's the gradual implementation that's inevitable. If it were done over night, the world would stop turning for a short time, lol. Gradual but progressive momentum is what's occurring. Would you buy an electric car if you knew you could pay it off in 2 or 3 years laugh as you drive by a gas station knowing you'll never have to do that again?
Let me put it another way: Citizens of middle eastern countries don't pay taxes. Their leadership drives the rest of the world insane. They're sitting on a cache of what makes the world go round. Suppose we got to the point where dependency on them diminished to the point where they had to pay taxes. Their gov'ts would have to change their tune.