Rebuilding an entire planet’s energy system is a big job…The most basic problem is knowing what, exactly, you are trying to rebuild. Academic-research groups, think-tanks, charities and other concerned organizations try to keep track of the world’s wind turbines, solar-power plants, fossil-fueled power stations, cement factories and so on. To this end, they rely heavily on data from national governments and big companies, but these are often incomplete. The most comprehensive database covering American solar-power installations, for instance, is thought to miss around a fifth of the photovoltaic panels actually installed on the ground.

In a paper published in Nature, a team of researchers demonstrate another way to keep tabs on the green-energy revolution. Dr Kruitwagen and his colleagues have put together an inventory of almost 69,000 big solar-power stations (defined as those with a rated capacity of 10kw of electricity or more) all over the world—more than four times as many as were previously listed in public databases. This new inventory includes their locations, the date they entered service and a rough estimate of their generating capacity…

Pictures came from two sets of satellites, Sentinel-2 and SPOT, run by the European Space Agency and Airbus respectively. These peer down on the world, recording visible light and also the infrared and ultraviolet parts of the spectrum. The images amounted to around 550 terabytes of data, spanning the period between 2016 and 2018. That is enough to fill more than a hundred desktop hard drives. Sifting through this many pictures by eye would have been impractical. That is where the second technological trend comes in. Dr Kruitwagen and his colleagues trained a machine-learning system to spot the solar panels for them.

More generally, Dr Kruitwagen hopes that his eye-in-the-sky approach—which, despite the planetary scale of the project, cost only around $15,000 in cloud-computing time—could presage more accurate estimates of other bits of climate-related infrastructure, such as fossil-fuel power stations, cement plants and terminals for ships carrying liquefied natural gas. The eventual result could be the assembly of a publicly available, computer-generated inventory of every significant bit of energy infrastructure on Earth. Quite apart from such a model’s commercial and academic value, he says, an informed public would be one better able to hold politicians’ feet to the fire. 

Excerpt from Solar-cell census: An accurate tally of the world’s solar-power stations, Economist, Oct. 30, 2021