SPEAKER_02: Amazing, fascinating stories of inventions, ideas and innovations. Yes, this is the podcast about the things that have helped to shape our lives. Podcasts from the BBC World Service are supported by advertising.
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SPEAKER_03: 50 things that made the modern economy with Tim Harford.
SPEAKER_00: Socrates believed that the ideal house should be warm in the winter and cool in the summer. With clarity of thought like that, it's easy to see how the great philosopher got his reputation. At the time, such a desire was easier to state than to achieve. Yet many pre-modern civilizations designed buildings to capture sunlight from the low hanging winter sun while maximizing shade in the summer. All very elegant. But that's not the kind of solar power that will run a modern industrial economy. And millennia went by without much progress. A golden thread, a book published in 1980, celebrated clever uses of solar architecture and technology across the centuries and urged modern economies racked by the oil shocks of the 1970s to learn from the wisdom of the ancients. For example, parabolic mirrors used in China 3,000 years ago could focus the sun's rays to grill hot dogs. Solar thermal systems would use winter sun to warm air or water that could reduce heating bills. Such systems now meet about 1% of global energy demand for heating. It's better than nothing, but hardly a solar revolution. A golden thread only briefly mentions what was, in 1980, a niche technology. The solar photovoltaic, or PV, cell, which uses sunlight to generate electricity. The photovoltaic effect isn't new. It was discovered in 1839 by Edmond Becquerel, a French scientist. In 1883, Charles Fritz, an American engineer, built the first solid state photovoltaic cells and then the first rooftop solar array in New York City. These early cells, made from a costly element named selenium, were expensive and inefficient. The physicists of the day had no real idea how they worked either. That required the insight of a fellow named Albert Einstein in 1905. It wasn't until 1954 that researchers at Bell Labs in the US made a serendipitous breakthrough. By pure luck, they noticed that when silicon components were exposed to sunlight, they started generating an electric current. Unlike selenium, silicon is cheap and Bell Labs researchers reckoned it was 15 times more efficient. These new silicon PV cells were great for satellites. The American satellite Vanguard 1 was the first to use them, carrying six solar panels into orbit in 1958. The sun always shines in space and what else are you going to use to power a multi-million dollar satellite anyway? Yet, solar PV had few heavy duty applications on Earth itself. It was still far too costly. Vanguard 1's solar panels produced half a watt at a cost of countless thousands of dollars. By the mid-1970s, solar panels were down to $100 a watt, but that still meant $10,000 for enough panels to power a light bulb. Yet, the cost kept falling. By 2016, it was half a dollar a watt and still falling fast. After millennia of slow progress, things have accelerated very suddenly. Perhaps
SPEAKER_00: we should have seen this acceleration coming. In the 1930s, an American aeronautical engineer named T.P. Wright carefully observed aeroplane factories at work. He published research demonstrating that the more often a particular type of aeroplane was assembled, the quicker and cheaper the next unit became. Workers would gain experience, specialised tools would be developed and ways to save time and material would be discovered. Wright reckoned that every time accumulated production doubled, unit costs would fall by 15%. He called this phenomenon the learning curve. Recently, a group of economists and mathematicians at Oxford University found convincing evidence of learning curve effects across more than 50 different products, from transistors to beer, including photovoltaic cells. Sometimes the learning curve is shallow and sometimes it's steep, but it always seems to be there. In the case of P.V. cells, it's quite steep. For every doubling of output, cost falls by more than 20%. And this matters because output is increasing so fast. Between 2010 and 2016, the world produced 100 times more solar cells than it had before 2010. Batteries, an important complement to solar P.V., are also marching along a steep learning curve. The learning curve creates a feedback loop that makes it harder to predict technological change. Popular products become cheap, cheaper products become popular, and any new product needs somehow to get through the expensive early stages. Solar P.V. cells needed to be heavily subsidised at first, as they were in Germany for environmental reasons. More recently, China seems to have been willing to manufacture large quantities in order to master the technology, leading to President Obama's US administration complaining that, rather than being too expensive, imported solar panels had become unfairly cheap. Solar panels are particularly promising in poorer countries with underdeveloped and unreliable energy grids and plenty of sunshine during the day. When the Indian Prime Minister Narendra Modi assumed office in 2014, for example, he announced ambitious plans to build large utility-scale solar farms, but also to establish tiny grids in rural villages with little or no access to the main grid. But now that solar P.V. has marched along the learning curve, it's competitive even in rich, well-connected areas. As early as 2012, P.V. projects in the sunny US states were signing deals to sell power at less than the price of electricity generated by fossil fuels. That was the sign that solar power had become a serious threat to existing fossil fuel infrastructure. Not because it's green, but because it's cheap. In late 2016 in Nevada, for example, several large casino chains switched from the state utility to purchase their power from largely renewable sources. This wasn't a corporate branding exercise. It was designed to save them money even after paying $150 million as a severance fee. The sun doesn't shine at night and winter storage remains a big challenge. As Socrates warned us, the wisest people understand that they know nothing. But the learning curve tells us that the ultimate triumph of solar P.V. seems likely. It is getting cheaper as it gets more popular and more popular as it gets cheaper. Socrates notwithstanding, that sounds like a recipe for success.
SPEAKER_03: An up-to-date guide to a fast-moving area is Chris Goodall's book, The Switch. For a full list of our sources, please see BBCWorldService.com slash 50things.
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