See those three round discs atop the Verdesian in Battery Park City below? Those are heliostats directing sunlight into Teardrop Park South, Michael Van Valkenburgh's extension of his 2006 design across Murray Street. The south but north-facing park is nestled within the U-shaped Riverhouse by Ennead Architects, meaning it doesn't receive any sunlight for many months. Hence the heliostats, casting the spotlights on the paving at the bottom of the photo below.
Spending a few minutes in the park and seeing the heliostats in action -- they redirected themselves once when I was there -- I'm not sure they help bring natural light to the park as much as the surrounding buildings do, at least in terms of ambient light; notice the reflections from windows hitting the side of Riverhouse below. But Van Valkenburgh explains the reflected sunlight is to help trees and plants thrive in the space, aided by the computer programming that allows the heliostats to be focused on specific areas. A water feature is one such area that can re-reflect the light into the space, an indication of how the heliostats influenced the design.
Look out for more heliostats to be installed in the city, in particular as part of Van Valkenburgh's redesign of Jacob Javits Plaza, which I wrote about here.