Solar Panels on Half the World’s Roofs Would Power the Planet

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By Siddharth Joshi, James Glynn, and Shivika Mittal

Rooftop solar panels are up to 79 percent cheaper than they were in 2010. These plummeting costs have made rooftop solar photovoltaics even more attractive to households and businesses who want to reduce their reliance on electricity grids while reducing their carbon footprints.

But are there enough rooftop surfaces for this technology to generate affordable, low-carbon energy for everyone who needs it? After all, it’s not just people who own their own houses and want to cut their bills who are in need of solutions like this. Around 800 million people globally go without proper access to electricity.

Our new paper in Nature Communications presents a global assessment of how many rooftop solar panels we’d need to generate enough renewable energy for the whole world—and where we’d need to put them. Our study is the first to provide such a detailed map of global rooftop solar potential, assessing rooftop area and sunlight cover at scales all the way from cities to continents.

We found that we would only need 50 percent of the world’s rooftops to be covered with solar panels in order to deliver enough electricity to meet the world’s yearly needs.

We designed a program that incorporated data from over 300 million buildings and analyzed 130 million km² of land—almost the entire land surface area of the planet. This estimated how much energy could be produced from the 0.2 million km² of rooftops present on that land, an area roughly the same size as the U.K.

We then calculated electricity generation potentials from these rooftops by looking at their location. Generally, rooftops located in higher latitudes such as in northern Europe or Canada can vary by as much as 40% in their generation potential across the year, due to big differences in sunshine between winter and summer. Rooftops near the equator, however, usually only vary in generation potential by around 1% across the seasons, as sunshine is much more consistent.

This is important because these large variations in monthly potential can have a significant impact on the reliability of solar-powered electricity in that region. That means places where sunlight is more irregular require energy storage solutions—increasing electricity costs.

Our results highlighted three potential hotspots for rooftop solar energy generation: Asia, Europe and North America.

Of these, Asia looks like the cheapest location to install panels, where—in countries like India and China—one kilowatt hour (kWh) of electricity, or approximately 48 hours of using your laptop, can be produced for just 0.05p. This is thanks to cheap panel manufacturing costs, as well as sunnier climates.

Meanwhile, the costliest countries for implementing rooftop solar are the U.S., Japan and the U.K. Europe holds the middle ground, with average costs across the continent of around 0.096p per kWh.

Rooftop solar panels look like they’d be equally useful in areas with…



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