A solar future isn't just likely — it's inevitable

By David Roberts. Vox.com

I plan to write a great deal about the short-term prospects for clean energy, both economic and political, but I want to begin life here at Vox with an imaginative exercise, a bit of musing about what energy might look like in the future — not 10 or 20 years from now, but 50, 70, even 100 years ahead.

Obviously, predicting the far future is a mug's game if you take it too seriously. This post ismore about storytelling, a way of seeing the present through a different lens, than pureprognostication. But storytelling is important. And insofar as one can feel confident about far-future predictions, I feel pretty good about this one.

Here it is: solar photovoltaic (PV) power is eventually going to dominate global energy. The question is not if, but when. Maybe it will happen radically faster than anyone expects — say, by 2050. Or maybe it won't be until the year 3000, or later. But it'll happen.

The main reason is pretty simple: solar PV is different from every other source of electricity, in ways that make it uniquely well-suited to 21st-century needs. (Among those needs I count abundance, resilience, and sustainability.)

Solar PV is different from other energy sources — in one crucial way
Every other commercial source of electricity — besides solar PV — generates energy through roughly the same means: by spinning a turbine.

Coal plants, gas plants, nuclear plants, and concentrated solar power plants are all just different ways of boiling water to produce steam that spins a turbine. Wind power harnesses the wind to spin a turbine. Hydropower dams use flowing water to crank a turbine. These spinning turbines, in turn, provide mechanical force to an electric generator, which translates it into electrical current (this is done by moving electrical conductors through magnetic fields — see Faraday's Law).

Solar PV works differently: it converts sunlight directly into electricity. Photons of light excite the surface of a semiconductor, knocking electrons loose to become part of a charged electrical field, generating electromotive force that can be tapped by wires. (See: the photovoltaic effect.)

This difference sounds technical, but it is enormously consequential. It brings three obvious advantages, often touted by solar proponents.

First, a solar cell has no moving parts, so operation and maintenance costs tend to be very low. It has to be kept clean, but that's about it.

Second, a solar cell requires no fuel — so fuel costs are zero. Once the initial investment is paid off, and subtracting modest O&M costs, the power produced is free.

And third, a solar cell generates power without any pollution.

(Note: the manufacture and disposal of solar cells currently requires fuel and produces waste, so the above claims require a rather large footnote. But there's no reason in principle that solar PV cannot eventually be made using solar energy and composed entirely of recyclable or nontoxic components.)

Solar is the only truly distributed energy source
Solar PV's unique way of generating power has another important consequence: it can be highly distributed. Many utilities currently rely on big solar — constructing fields of panels miles long — but solar can also scale down to meters, even inches. Anywhere sun hits, some of it can be harvested for energy.

But not much energy. Indeed, skeptics of solar power often cite this feature as a weakness of PV technology. Even though there's enough cumulative sunlight to power human civilization thousands of times over, they note, it is still highly diffuse. The amount of energy in any given patch of sunlight is modest. So to gather the large amounts of energy necessary to run industrial civilization, solar cells would have to cover an enormous amount of surface area.

Solar skeptics are convinced that this puts an upper limit on solar's contribution. They believe civilization will always require concentrated fuels of some sort, simply because energy consumption is concentrated. They believe there's no way to gather enough diffuse renewable resources to power factories, hospitals, and other mainstays of Western life, which means the future of energy will either entail fossil fuels or nuclear power, both of which are energy-dense.

I think that's a mistake. In fact, being a passive harvester of diffuse energy will work to solar's advantage, not its disadvantage, in the long run.

To understand why, we have to project out past the limitations of today's solar PV technology. Current silicon panels — the ones that have been plunging in price thanks to China's largesse — are still relatively bulky and heavy. Their manufacture and disposal involves toxic chemicals. And the efficiency with which they convert sunlight to energy is low, around 10 to 15 percent.

But these limitations are not inherent to PV. Researchers are already experimenting with new,less-toxic materials. There are mass-produced panels hitting 20 percent efficiency. In lab conditions, solar cells have reached as high as 46 percent efficiency, more than three times today's average:

Most current solar cells come embedded in big black panels, but as they get smaller, they are starting to be integrated into other things — everything from buildings and roofs to roads, bus stops, and backpacks.

How solar power could become a dominant energy source
So let's try to think beyond the limitations of today's PV to a possible future — after another, say, 20 or 30 years of intense research, development, and deployment.

Imagine small, modular, highly efficientsolar cells embedded in all newly built infrastructure as a matter of course — buildings, bridges, parking lots, vehicles. Solar PV would no longer be a category of product in itself, but a routine feature of other products. As energy storage also gets cheaper, smaller, and better integrated, it will be worthwhile to capture and discharge small amounts of energy continuously.

The transfer of energy could become more distributed, as well, to better take advantage of all this solar power.For example, it will soon be possible for ordinary consumers to charge their electric vehicles without wires, just by parking in the right spot. According to a recent report by Navigant Research, "It is now clear that several major automakers are planning to bring wireless systems to market within the next few years, and a significant portion of the industry believes that wireless technology represents the future of plug-in electric vehicle (PEV) charging."

After a few decades of development, presumably wireless charging will get more efficient and smaller, as well. Imagine urban infrastructure in which wireless charging is everywhere — in curbs, benches, and buses — in which all electric devices are always being charged with sunlight that's always being collected and stored. Energy distribution could effectively become ambient.

Just as we expect all our devices to be connected to the internet today, uploading and downloading information, in the future we may expect all our devices and structures to be connected to this distributed energy net, harvesting, storing, and sharing the sun's power.

A future with distributed energy could look radically different from today
One often hears energy experts talkabout "distributed energy," but insofar as that refers to electricity, it usually just means smaller gas or windturbines scattered about — except in the case of solar PV. Only solar PV has the potential to eventually diffuse into infrastructure, to become a pervasive and unremarkable feature of the built environment.

That will make for a far, far more resilient energy system than today's grid, which can be brought down by cascading failures emanating from a single point of vulnerability, a single line or substation. An intelligent grid in which everyone is always producing, consuming, and sharing energy at once cannot be crippled by the failure of one or a small group of nodes or lines. It simply routes around them.

Will solar PV provide enough energy? Right now, you couldn't power a city like New York fully on solar PV even if you covered every square inch of it with panels. The question is whether that will still be true in 30 or 50 years. What efficiencies and innovations might be unlocked when solar cells and energy storage become more efficient and ubiquitous? When the entire city is harvesting and sharing energy? When today's centralized, hub-and-spoke electricity grid has evolved into a self-healing, many-to-many energy web? When energy works like a real market, built on millions of real-time microtransactions among energy peers, rather than the crude statist model of today's utilities?

Systems that use energy will co-evolve alongside this new model of energy production, storage, and sharing. They will be smarter and more efficient, not only in the incremental ways current technologies are becoming more efficient, but in stepwise, nonlinear ways, replacing whole systems rather than parts.

My optimistic view is that global energy demand will peak and start declining later this century, even as supply from ubiquitous solar PV and storage is rising. Eventually they'll meet in the middle, relegating other energy sources to the periphery, as backup.

This solar future is inevitable — the key question is how long it will take
This is all sci-fi for now, I realize, about changes that will certainly take many decades to unfold. But the changes follow inexorably from the logic of PV. As research, development, and deployment continue, as solar PV and storage become more integrated and omnipresent, they will fill the cracks left empty by a flawed and unjust global energy system. And from there, they will seep up and out, displacing dirty combustion, creating new models and energy services along the way.

It will be a long, fraught process. Any number of things could make a mockery of my prediction. Nuclear fusion or (just as likely) Tony Stark's arc reactor could render the conversation moot. A meteor could hit. Humanity could decide to abandon Earth for other planets. Whatever.

But if energy keeps evolving roughly along the paths that are visible now, the unique properties of solar PV will eventually propel it to dominance. We will find that in energy, as in so many other human systems, distributed power works better, to more people's advantage, than the concentrated kind.