In a quest to cut the cost of clean electricity, power utilities around the world are supersizing their solar farms.

Nowhere is that more apparent than in southern Egypt, where what will be the world’s largest solar farm — a vast collection of more than 5 million photovoltaic panels — is now taking shape. When it’s completed next year, the $4 billion Benban solar park near Aswan will cover an area 10 times bigger than New York’s Central Park and generate up to 1.8 gigawatts of electricity.

That’s roughly the output of two nuclear power plants combined and almost double the planned capacity of the vast Villanueva facility now growing in the Mexican state of Coahuila — currently the largest facility in the Americas. (The largest solar farm in the U.S. is the 580-megawatt Solar Star facility near Los Angeles.)

The 579-megawatt Solar Star projects are two solar installations in Kern and Los Angeles counties in California. Woody Welch / SunPower

But Benban probably won’t hold on to its title for long.

China is planning to build a two-gigawatt solar farm in the northwestern province of Ningxia, and the state of Gujarat in western India recently gave the go-ahead for a five-gigawatt facility. Japan is even talking about putting a large-scale solar farm in space.

The bigger, the cheaper

“There are huge savings for larger projects,” says Benjamin Attia, a solar analyst with Wood Mackenzie, an energy consulting firm based in Edinburgh, Scotland. “Logistics, transport, construction and installation all benefit from scale economies. We’ll start to see more solar parks of one and two gigawatts, and potentially even 10 gigawatts in the future.”

The plunging cost of solar panels is part of the cost-savings equation. A 2017 report from the U.S. National Renewable Energy Laboratory found that the cost of photovoltaic systems shrank by a factor of five from 2010 to 2017. Even the punitive tariffs on Chinese solar panels enacted earlier this year by the Trump administration are unlikely to slow the spread of large-scale solar, which in the U.S. is already cheaper and much cleaner than coal.

“Governments have wised up,” says Attia. “They just want the cheapest, fastest way to add new electricity supplies. For nuclear, procurement can take a decade. For gas, it’s up to four years. If you’re talking solar and things go smoothly, you can build a reasonably large project in 18 months.”

Solar power is now a particularly attractive option for developing countries. When solar panels were more expensive, only rich nations could afford the subsidies and tax breaks that allowed solar farms to make financial sense. In many sunny parts of the world, solar power is now competitive with other power sources without financial assistance (and that's also true for parts of the U.S. and other developed nations).

Some of the biggest new farms, including Benban, are set up so that the panels are owned and operated not by a single utility but instead shared by dozens of firms. This arrangement helps reduce the red tape associated with permits and regulations, says Attia, and allows even small solar start-ups to benefit from economies of scale.

The key role of Infrastructure

But even if the cost of solar panels continues to fall, there are upper limits to the size of future solar parks. A solar farm is only useful if the electricity it generates can reach the homes and factories that need it, often hundreds of miles away. Electricity transmission grids can struggle to cope with the intermittent power that massive new wind and solar farms generate.

“Typically, those locations are going to be pretty remote,” says Daniel Kirschen, professor of electrical engineering at the University of Washington in Seattle. “The grid around new solar or wind farms will not be very strong. So you’re going to need to reinforce the grid, and that can get quite expensive.”

China, in particular, has grappled with the infrastructure problem, and in the past has been unable to use up to 30 percent of the electricity generated by newly built solar farms. One possible solution is to build so-called supergrids that move electricity over vast distances to ensure that it’s not wasted.

A grid to connect China, Korea, Russia and Japan is being proposed, and a planned European supergrid could span the continent by the late 2020s.

Where the sun never sets

Not every nation is able to join the solar revolution, of course. Crowded, cloudy Japan, for example, has neither the open spaces nor the reliable months of sunshine needed for gargantuan solar parks. So it’s looking to build a solar power station where the sun always shines and space is not an issue: outer space.

Japan’s space agency, JAXA, is working to put into orbit a one-gigawatt orbital solar farm that can generate power 24 hours a day. Starting in the 2030s, the solar space station would beam down energy as microwaves to a human-made island covered with billions of antennas. The agency has already demonstrated a system that can beam energy a few hundred yards, though questions remain about the practicality and safety of space-based power stations.

Space-based solar power aside, the biggest rivals to massive solar parks on Earth are likely to be the small solar panels installed atop houses and in backyards.

Large solar farms account for the vast majority of panels installed around the world, but in developed countries like the U.S. and Germany, household solar power has about an equal share. Homeowners can sell power back to the grid, or even store it locally using batteries originally developed for electric cars. Solar micro-grids are also becoming popular in developing nations that lack good rural power connections or are prone to extreme weather events.

However humans tap into solar energy, the good news is that there is plenty of it. More of the sun’s energy strikes the Earth’s surface in two hours than we consume in all forms every year. A solar park covering just 2 percent of the Sahara could provide the globe’s entire energy needs — assuming we could build a planetary supergrid to access it.

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