How Solar At High Altitudes Could Power Entire Countries, Even In Winter

Solar panels above Davos test the electricity generated at different angles in snowy conditions. © 2019 EPFL/CRYOS

Solar power is the world's fastest growing source of energy, but obvious problems remain. New research suggests, if properly located, it could play a surprisingly large role in powering countries far from the equator during the winter. 

Solar is now usually the cheapest way to generate electricity during daylight hours. It's also increasingly practical to store energy for night time use. Winter, however, remains more of a challenge. It's one thing to store electricity for 12 or even 16 hours, quite another to hold onto it for months of darkness.

According to Dr Annelen Kahl of the Ecole Polytechnique Federale de Lausanne, however, that may not be necessary, at least in places with high mountains. Kahl and colleagues have modeled the use of solar panels in Switzerland. In Proceedings of the National Academy of Sciences, they argue if panels are placed correctly we can “shift a significant amount of electricity generation from the summer to the winter months.”

The secret is to put the panels at high altitude and angle them closer to vertical than is usually done.

There's an obvious reason to put solar farms up mountains. The less atmosphere, particularly fog, between the panel and the Sun, the more light it collects. However, it's also cheaper to collect energy closer to where it will be needed, so panels usually get installed lower down slopes – often on the roofs of existing buildings.

That may make sense when only a small portion of our electricity comes from sunlight, but Kahl argues that as we move towards fully renewable grids, timing becomes as important as quantity of power. Using satellite data from thousands of locations across Switzerland, the authors show the differences between summer and winter sunlight shrink with elevation. Once you get above 2,500 meters (8,200 feet) there's more sunlight during winter than at lower elevation during summer – enough to keep the lights on.

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