Can we power the world with renewable energy alone? Or is it just a pipe dream?
The short answer is yes, but it won't be easy, to say the least.
There is an old adage "where there's a will there's a way" that pretty much sums up the main barrier to achieving this.
A better question might be "will there ever be the will to power the world through renewables alone?". That is a much harder question to answer, let alone to begin to address.
If the will, both political and societal, can be achieved then it would, in theory, be possible.
Necessity is the mother of all invention
Whether a global consensus with all human beings on the planet (unlikely) could be achieved or progress is driven by profit motives akin to a new 'gold rush', only then it will be possible to build a renewable-only future.
But the reality of the world might force us into making this huge overhaul of our current energy-generation mix. As utilitarian as fossil fuels are as a fuel source, they are, by their very nature, finite.
Although estimates of fossil fuel reserves tend to be revised every decade or so as new sources are found or others suddenly become economically viable, there will be a time when they are exhausted. This is inevitable.
Other driving factors include the debate over the effects on the Earth's climate. This has, unfortunately, become highly politicized and has generally become a partisan bone of contention.
That aside, the basic finite nature of our current energy sources will require us to find alternative sources. Renewables might just be the perfect solution.
It's probably likely that then, and only then, will humans seriously look at alternatives to supply our thirst for energy.
After all, for all the "virtue signaling", to borrow a phrase, over "saving the planet", it is highly unlikely, most will give up their current lifestyles to reduce their general energy consumption needs.
Nobody is likely to stop driving their cars, use their smart devices or the internet, or stop using energy-hungry home appliances anytime soon. And why should they?
Afterall one of the key motives for human technological development is our desire to make life that little bit easier and, probably, more importantly, save our only real asset - time.
To this end, we must find a way of producing energy in such a way that can be sustainable in long-term.
Renewables might just be the key
Whilst there has been a lot of hype around renewables for several decades, the main barriers at present tend to be political and economic in nature. There are vested interests for and against which muddy the waters making it hard for a clear consensus to be formed.
There is a great discussion on just this issue here.
But there are some genuine concerns about the technical issues with renewable technologies over more conventional systems like coal power stations.
They are, by their very nature, intermittent in their ability to generate power and, by extension, this inhibits but doesn't rule out, their reliability as a power source.
Most experts agree that a future renewable-only energy generation infrastructure would be mixed, or hybrid, with solar, wind, tidal, hydro-, geothermal and, most-likely nuclear, all working to compliment one another.
In all cases, some form of energy storage will be desirable which could include batteries, gravity storage (like a dam's reservoir) and any other myriad of methods imaginable. Entrepreneurs, like Elon Musk, believe this is the way to go.
By his estimates, it would take about 100 of his giga-factories (solar generation and battery storage under one roof) to power the entire world.
Renewable technology has some inherent issues
Solar-based renewables, for example, are great when the sun shines and tend to provide about 20 W/m2 on average. When night falls, however, they are rendered completely useless in and of themselves.
In contrast, coal-fired and nuclear power stations can run 24/7, 365 days a year.
Wind-based renewables struggle when there is no wind - no wind, no power. For example, wind generation in Germany for 2012 varied by orders of magnitude depending on wind strength from 0.115GW to a maximum of 24GW.
Another promising renewable energy source, energy crops, promise to be a great alternative fuel source if you have enough space to grow the crop. This is generally out of the question in European countries but fine for places like Brazil with large open spaces.
Space requirements are also a problem for other renewables as most tend to take up a lot of space. For example, if all roofs in the UK were to have solar panels it would be enough to provide 5% of the country's energy needs.
It has also been estimated that a solar farm the size of Texas would be enough to provide all the power the U.S. needs but is that practical in reality?
Wind farms are worse for energy production per m2, requiring, on average, 2.5 W/m2 in windy areas. To be solely reliant on this form of renewable would take up a lot of space on land.
Obvious solutions to that are to place them offshore which many countries, like the UK, are investing in heavily.
But, as with anything, you'll either see the above issues as a deal breaker or an opportunity for improvement. Many of the above apparent limitations can, and likely will, be resolved.
For example, adding energy storage to solar farms would eliminate the issue of no solar generation at night. Their energy generation efficiency can, and inevitably will be improved dramatically notwithstanding any application's maximum efficiency of course.
But isn't renewable energy more expensive than conventional energy generation?
A recent study by Stanford and UC Davis analyzed the current state of renewable technologies with an eye to see if it would feasible to completely run the world off it.
In their estimation, it should not only be possible but will only increase costs modestly compared to current rates.
More importantly, they concluded that it would also be possible, using 100% renewable technology energy generation, to save 2.5 to 3 million lives per year.
Their strategy envisaged a world where at least 90% of energy demand could be met with large-scale wind and solar generation.
Of the remaining 10%, 4 percent could be provided by geothermal sources and hydroelectric, 2 percent from wave and tidal and the remainder should be possible from fuel cells - most likely hydrogen-based.
They also foresaw the need to keep conventional power-generation systems until they could be replaced with renewable technologies. By 2030, so they say, all new power-generation plant could be from renewable sources only.
By 2050 all existing power plants could be readily converted to renewable alternatives completing the 100% conversion plan. The University of Pennsylvania generally agree and go on further to provide some quantifiable estimates of required systems.
By their estimation, a 100% renewable world would need, as a ballpark,
"3.8 million large wind turbines, 90,000 utility-scale solar plants, 490,000 tidal turbines, 5,350 geothermal installations, and 900 hydroelectric plants."
Once its all up and running, so they believe, it should cost less (in real terms) than current fossil fuels and nuclear power per kW.
Which country uses the most renewable energy?
According to the Climate Council , the country that uses the most renewable energy is...
Iceland with an almost 100% reliance on renewable energy generation for its needs. Of course, it has a bit of an advantage with the abundance of geothermal energy resources given the island's very unique geology.
Next up is Sweden who are pushing forward with zeal to deliver on their promise to achieve 100% renewable energy generation.
They set themselves the task of achieving this goal ASAP in 2015 and quickly made huge investments in solar, wind, energy storage, smart grids, and clean transport.
Next up in a close third place is Costa Rica with an impressive 99% renewable energy generation, as of 2016. They achieved this by heavily investing in a mixed strategy of hydroelectricity, geothermal, solar, wind and other renewable technology.
They also benefit from abundant geothermal resources on their doorstep. They aim to be on par with Sweden by as early as 2021.
And finally, in fourth place, is Nicaragua which is well on its way to achieving 90% power generation from renewables. This came after a concerted effort over a decade to invest in and build wind and solar generators with no subsidiaries or increases in consumer costs.
All of these nations truly are the masters of the art of "where there is a will, there is a way". An inspiration for us all irrespective of your opinion on renewable power generation.