Rooftop solar panels are up to 79% cheaper than they were in 2010. These lower costs have made rooftop PV more attractive to households and businesses who want to reduce their reliance on grid electricity while reducing carbon emissions.
But are there enough rooftops for this technology to generate low-carbon energy at an affordable cost to everyone who needs it? After all, it’s not just people who own their homes and want to lower their bills who need solutions like this. About 800 million people worldwide live without adequate access to electricity.
Our new paper in Nature Communications It provides a global assessment of how many rooftop solar panels we need to generate enough renewable energy for the entire world – and where we need to place them. Our study is the first to provide such a detailed map of global rooftop solar potential, assessing surface area and sunlight cover at scales all the way from cities to continents.
We found that we only need to cover 50% of the world’s rooftops with solar panels in order to provide enough electricity to meet the world’s annual needs.
We’ve designed a program that combines data from more than 300 million buildings and analyzes 130 million square kilometers of Earth — nearly the entire surface area of the planet. This estimated how much energy could be produced from the rooftops of the 0.2 million square kilometers on that land, an area roughly the size of the United Kingdom.
We then calculated the electricity generation potential of these surfaces by looking at their location. In general, rooftops located in higher latitudes such as northern Europe or Canada can differ up to 40% in generation potential throughout the year, due to the large differences in sunlight between winter and summer. However, rooftops near the equator typically differ only in generation potentials by about 1% across seasons, where sunlight is more uniform.
This is important because these large differences in monthly potential can have a significant impact on the reliability of solar-powered electricity in that area. This means that places where sunlight is erratic require energy storage solutions – leading to increased electricity costs.
Our results highlighted three potential hotspots for rooftop solar power generation: Asia, Europe and North America.
Of these, Asia appears to be the cheapest location to install panels, where – in countries like India and China – a kilowatt-hour of electricity, or roughly 48 hours of laptop use, can be produced for just 0.05p. This is thanks to the cheap panels manufacturing costs, as well as the sunny climate.
Meanwhile, the most expensive countries to implement rooftop solar are the United States, Japan and the United Kingdom. Europe occupies a middle position, with costs across the continent averaging around 0.096 pence per kWh.
Rooftop solar panels appear to be just as useful in sparsely populated areas as they would in urban centres. For those who live in remote areas, panels help to augment or even replace the supply from potentially unreliable local networks. And for those in cities, the panels can significantly reduce air pollution from burning fossil fuels for energy.
It is necessary to point out that the global electricity supply cannot depend on a single source of generation to meet the demands of billions of people. Thanks to the changing weather and our planet’s day and night cycle, the mismatch between solar energy supply and demand is inevitable.
The equipment to store solar energy when you need it is still expensive. In addition, solar panels will not be able to provide enough power for some industries. Heavy manufacturing and mineral processing, for example, require very large currents and specialized conduction of electricity, which solar energy will not yet be able to provide.
Despite this, rooftop solar has tremendous potential to alleviate energy poverty and return clean, pollution-free energy into the hands of consumers around the world. If solar energy costs continue to fall, rooftop panels may be one of the best tools yet to decarbonize our electricity supply.
Assessment of the global electricity generation potential from rooftop photovoltaics
Introduction of the conversation
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