Belgium’s Solar Tunnel over a 2.1-mile stretch of the Paris-Amsterdam rail line is expected to generate annually 3,300 MWh of clean energy. (Photo courtesy Enfinity)

Belgium’s Solar Tunnel over a 2.1-mile stretch of the Paris-Amsterdam rail line is expected to generate annually 3,300 MWh of clean energy. (Photo courtesy Enfinity)

Belgium’s Solar Tunnel over a 2.1-mile stretch of the Paris-Amsterdam rail line is expected to generate annually 3,300 MWh of clean energy. (Photo courtesy Enfinity)