is a very simple thing: a square piece of silicon typically 182 millimetres on each side and about a fifth of a millimetre thick, with thin wires on the front and an electrical contact on the back. Shine light on it, and an electric potential—a voltage—will build up across the silicon: hence “photovoltaic”, or. Run a circuit between the front and the back, and in direct sunlight that potential can provide about seven watts of electric power.
And it shows no signs of stopping, or even slowing down. Buying and installing solar panels is currently the largest single category of investment in electricity generation, according to the International Energy Agency , an intergovernmental think-tank: it expects $500bn this year, not far short of the sum being put into upstream oil and gas. Installed capacity is doubling every three years.
The silicon foundries of China lack salesmen with Boulton’s verve . But when it comes to exquisite chemical purity and physical flawlessness, the wares they provide to serve the world’s desire for power should be enough to make anyone silicon mad. That said, the manufacturers benefit from the fact that they are key to their country’s industrial strategy. There have been some bankruptcies, but the Chinese government has extended cheap loans to many overextended firms. Gregory Nemet of the University of Wisconsin-Madison notes that the solar-cell market typically catches up with the overcapacity thus created within a couple of years. The current oversupply will see whether this remains the case.
Cheap, plentiful, acceptable energy which is emissions-free at the point of generation; it might seem that the climate crisis is solved. There is a catch, though—in fact, two. Consumers want to be able to draw power at night. And the grids to which they look for it work on the basis of a “merit order”: everyone supplying the grid at a given time is paid the price needed to attract the marginal supplier of power.
Batteries and other storage technologies allow arbitrage across time rather than space; energy generated at midday, when grid prices are low, can be sold back when the Sun sets and prices are higher. What is more, batteries, like solar cells, are mass producible and targets of Chinese industrial policy. As a result they are moving down an experience curve even steeper than solar’s.
Adani Green Energy, one of the world’s largest solar developers, has obtained the rights to build solar farms on two vast tracts of land in India, one in Gujarat, near the border with Pakistan, the other in Rajasthan. Each of them is large enough to take some 30of solar panels, says Sagar Adani, the company’s boss and the nephew of the larger Adani Group’s founder, Gautam Adani.