Knowable Magazine · The dazzling history of solar power

Once fringe and futuristic, this renewable energy shines brightly today as a cheap and efficient source of energy. Still, it remains controversial ­— for much different reasons.


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How can we shine light on the future of an invention? If a novel technology really is novel, how can researchers begin to work out how it might fit into the world in the coming years or decades? After all, “prediction is very difficult, especially about the future.” That quote is from Niels Bohr. Maybe. No one knows for sure.

This is Knowable, and I’m Adam Levy.

We know what today’s technology looks like, and things are looking pretty bright for solar power. Solar is now the fastest-growing source of renewable power. In 2018 alone, almost 100 gigawatts of solar capacity were installed globally. If all these panels were working at their maximum capacity at the same moment, it would be more than enough to power all of Canada’s average electricity demands. But solar power hasn’t always been soaring. Step back just a few decades into the past, and solar was still futuristic. So what did the future of solar look like before we knew what it could become? Well the answer to that is controversial.

No, really. If you pick up the first-ever issue of the then-called Annual Review of Energy from 1976, you’ll find a paper imaginatively titled “Solar Energy.” Its abstract opens with this sentence:

It is widely recognized that the inexhaustible energy of the sun is received on the earth in sufficient quantities to make major contributions to the future energy needs of the world.

So far, so familiar. The vast amounts of energy the Earth receives from the sun still serve as an introduction to solar energy today. But then...

… it is yet uncertain and controversial whether we now have the means to economically collect and convert that solar energy into forms useful for our needs.

“Uncertain and controversial.” Was the future of this technology really in so much doubt? Well, yes. While researchers had been converting light into electricity using photovoltaics for some 20 years, applications of these approaches were still relatively new. In the 1950s and ’60s, solar power found a home on board many US and USSR satellites, where conventional power supplies would have been pretty inconvenient. But while the 1970s had seen progress, the technology was still viewed as unrealistic for conventional applications.

Kelly Sims Gallagher: “Really, at that time, that’s kind of where solar was. It was considered to be, you know, a very advanced kind of far-out technology.”

This is Kelly Sims Gallagher, who’s been researching energy technology innovation systems for around 20 years and is now based at the Fletcher School of Tufts University in Massachusetts. There’s a reason solar still seemed “far out” in the late 1970s: The cost was still steep: $20 per watt if your solar panel was running at full power. That’s around 90 2021 dollars. So if you wanted to buy enough solar panels to power a single 60-watt lightbulb, you’d have to fork over $5,000 of today’s money. Controversial indeed. Here’s Felix Creutzig of the Mercator Research Institute on Global Commons and Climate Change in Berlin, who studies solar power’s role in mitigating climate change.

Felix Creutzig: “Forty years ago, it was quite expensive. So you did know whether it was a real market-scale technology. So absolutely, yes, 40 years ago it was a controversial technology.”

But there’s more to learn from this 1976 paper than that solar power used to be expensive. For one, the motivations driving solar-energy development were different from today’s.

The rise in fuel prices in the 1970s.

Although the “cleanness” of solar relative to fossil fuels is touched on in this vintage paper, this doesn’t come with the same climate-change connotations it would today. While global warming was already being researched in the 1970s, it seems it wasn’t on these researchers’ radar, as you’ll find no mention of it here.

The paper states — as researchers point out today — that there are different ways of harnessing solar energy. For example, the energy can be captured by systems that convert it into heat, or into electricity, be that through…

photovoltaic, ocean thermal, or wind energy conversion

Now, personally, when I think of ocean thermal energy or wind turbines, I don’t necessarily think of the term “solar energy.” But the study correctly points out that:

Natural collection of solar energy occurs on the surface of the land and oceans of the earth, giving rise to wind and weather.

We may not describe these energy sources as “solar energy” today. But, sure, they do originate from that big glowing disk in the sky.

So how does the paper — that opened by reminding us of the controversy that solar power presents — finish? Well, with a surprisingly optimistic tone:

We expect that in the period after the year 2000 solar energy will have become one of the most conventional energy sources used in many regions of the world.

This statement may have felt deeply controversial at the time, but it didn’t remain that way for long. Just three years later, in 1979, President Jimmy Carter installed 32 solar panels on the White House roof. Carter also made a prediction about the year 2000, saying:

In the year 2000, this solar water heater behind me, which is being dedicated today, will still be here supplying cheap, efficient energy.

And his administration set a target to produce 20 percent of America’s energy from solar by the turn of the century.

These developments set the scene for one of the authors of the 1976 review to return to the topic in 1981. This review, titled “Solar Energy Technology — A Five-Year Update,” revealed solar power had become a big crowd pleaser.

If the United States selected its energy system by a popular vote, there seems no doubt that solar energy would win easily. The US public even believes that solar energy will grow rapidly enough to provide most of the nation's energy needs 20 years from now, a view that few if any of those closely involved with solar technology development find credible.

In this case, the expert was definitely right, as America has been slow to move away from its fossil-fuel infrastructure. Almost 40 years later and solar still is still only providing about 1 percent of US energy needs. But that doesn’t mean the author was filled with pessimism.

Still, the signifi­cance of the ultimate contributions of solar energy is not in doubt. The last five years have been a rapid start for what should be a continuing long-term commitment to the development of these technologies.

So what happened next? Well, the long-term commitment turned out to be more of a short-term fling. Another five years later, in 1986, and Reagan had gutted what he saw as fruitless research into renewables. And the solar panels on the White House’s roof weren’t destined to provide heat into the new century. By 1986, those were gone as well.

Commitments to developing and deploying solar power continued to flicker on and off around the world over the next decade. In 1996 (20 years after the first paper), we find a new review on solar power. The Annual Review of Energy had now become the Annual Review of Energy and the Environment. This review was titled “Progress Commercializing Solar-Electric Power Systems.” Just that title shows how the question of solar power’s potential had changed. And there had indeed been progress:

Between 1976 and 1992, prices for photovoltaic modules decreased by a factor of ten as cumulative production increased by a factor of 1,000.

Innovation was simultaneously boosting the efficiency of solar panels and lowering the costs of their production. But solar power was still a long way from becoming a bargain.

At module prices of $4.00-$4.50 per watt, and system costs approximately double that, PV systems are still relatively expensive for grid-connected applications.

And with these figures in mind, in 1996 solar’s future still wasn’t looking at all clear-cut. While the review two decades earlier projected that solar could be one of the world’s conventional sources of energy, this paper has more muted ambitions. For example, that for areas like the Mediterranean …

… solar power could supply 10%-25% of a local or regional electricity need within a 20-year period

At the time, it was hard to see how solar could compete with other energy sources without substantial subsidies. That said, though, the paper also suggests that subsidies should be removed from fossil fuels, a move that many environmental groups still call for to this day. The authors reasoned that this would ...

reflect the fact that they are a finite resource that is being depleted.

Today, the motivation for removing fossil-fuel subsidies is the complete reverse. We know we have enough fossil fuels to last many decades into the future. Here’s Kelly again, who we heard from earlier:

Kelly Sims Gallagher: “That was sort of the era of peak oil and the idea that we were going to run out of oil. It was before the shale gas revolution.”

Now we understand that fossil fuels are so plentiful that if we burned them all, vast areas of the planet would be made too hot for even human metabolism to cope. In 1996, the second Intergovernmental Panel on Climate Change report had recently been published, presenting evidence that humanity was altering the global climate. But even at this point, global warming was not the center-most motivation for a review on solar power. In fact, this 1996 study’s only mention of climate change is to point out that the United Nations Framework Convention for Climate Change calls for large-scale international cooperation. And back then, there seemed to vast optimism for such cooperation.

As the millennium approaches, humankind is approaching, for the first time, a global civilization.

Well, we’re now 21 years past the millennium. With the UK leaving the European Union, and America’s turbulent relationship with the Paris Climate Agreement, the Western world seems to have moved away from ideas of global cooperation. But the story for solar is much more positive. In the last decade, solar power usage has soared, shattering growth projections from the International Energy Agency time and time again. Governments around the world have put policies in place that incentivized solar energy, and Chinese manufacturers began exploring new ways to mass-produce panels at low costs.


And the costs have become staggeringly low. Today some solar panels cost a tiny 30 cents per watt — about 300 times cheaper than the “controversial” solar panels of 1976. In fact, solar is so cheap that the International Energy Agency recently declared it the cheapest source of electricity in history. As a result, it’s being rapidly deployed around the world. According to a 2019 review titled “Faster Than You Think: Renewable Energy and Developing Countries,” …

… renewable energy now dominates total investment in electricity power generation systems.

Here’s Felix Creutzig again, who you heard from earlier:

Felix Creutzig: “I think it’s a great story. Now it’s a technology that can be producing electricity at industrial scale and that’s a great thing.”

And for Kelly, there’s an important lesson to be learned from the journey that solar has been on.

Kelly Sims Gallagher: “Many people were very pessimistic about wind and solar, you know, and they were wrong. So I think we need to have faith in ourselves that we can accomplish pretty dramatic improvements in technology.”

So what next for solar? To reach the world’s agreed climate targets, emissions of greenhouse gases need to fall to net zero globallyas rapidly as possible. Ideally shortly after the middle of the century. Few doubt solar has a part to play in this transition, but how big its role will be remains unclear.

So what is the future for solar power? Well, whether solar can truly get out from under fossil fuels’ shadow will depend on governments continuing to drive innovation by incentivizing solar power. Without knowing what the world will do, the answer’s still controversial.

Felix Creutzig: “It’s still controversial whether PV will be delivering like 5 or 10 percent of primary energy in 2050 or 40 or 50 percent. There’s a huge gap between those numbers. The best thing here is to do it. And we can’t predict it, but we can change the trajectories ourselves.”

Make sure to subscribe to Knowable wherever you get your podcasts. Because in our next episode, we look back at our understanding of memory.

“Back then, there were a lot, a lot of questions, a lot of theories, and not too much testing of the theories.”

Don’t miss that episode, which is going live tomorrow. And if you enjoyed exploring the dazzling journey of solar power, be sure to write us a review on your favorite podcast app. It helps even more people hear our work. If you have any feedback on the show, do write to us at [email protected].

This podcast was made by Knowable Magazine from Annual Reviews, a journalistic endeavor dedicated to making scientific knowledge accessible to all. Through smart storytelling and sound science, Knowable aims to build understanding and fascination with the world around us. Knowable Magazine is free, and always will be. Read more at

In this episode you heard from Felix Creutzig and Kelly Sims Gallagher. There were also quotes from four papers: Frederick H. Morse and Melvin K. Simmons, 1976; Simmons, 1981; Raymond Dracker and Pascal De Laquil III, 1996; and Channing Arndt et al., 2019. I’m Adam Levy, and this has been Knowable.