Compared to automobiles, public transit is already an earth-friendly alternative [PDF]. Now, the subway line running through Chile's capital is about to become even more energy efficient. As Fast Company's Co.Exist reports, Santiago's subway system will soon be the first in the world primarily powered by renewable energy.

In just a couple of years' time, up to 60 percent of Metro de Santiago's power will come from a new solar system being installed just south of Chile's Atacama Desert, some 400 miles away. The desert is the driest region on earth, making it the perfect place to harvest sunlight. Unlike other so-called solar systems that tap into their city's main power grid, the energy generated by this 100-megawatt system will be sent directly to the metro line. Up to 18 percent of additional energy that's used will be sourced from the San Juan wind farm nearby.

Santiago's subway is a major system, covering 64 miles and servicing about 2.5 million passengers a day. The upcoming transition to renewable energy is a sign that the benefits of solar are finally beginning to catch up with the costs. SunPower, the California-based company commissioned for the project, is using a pre-assembled system that can be installed quickly and cheaply. They're also working to build solar systems in America for a few of Apple's data centers and Stanford University.

Santiago's new solar field is expected to begin operation by the end of 2017.

[h/t Fast Co. Exist]