No chiller required. You can install a dry cooler with a glycol system and use a duel coil AC unit. With this system you utilize free cooling when the glycol is under the free cooling set point (when OAT is colder), (running glycol through the free cooling coil), or when the OAT rises and the (glycol warms up), the unit will divert the glycol through an internal heat exchanger. In mechanical cooling mode the unit can handle much warmer glycol temps. Liebert, Canatal, Schults (ATS units), Ecosare, all make duel coil units. There may be more companies making duel coil units as well.
Some companies do a much better job at energy savings then others in the method that the unit utilizes free cooling mode. Units that use a fixed set point to switch from free cooling to mechanical and vise versa are not as energy efficient as others that factor in other parameters. If your area is large enough require more then one unit to cool the space many can be networked together to allow them to utilize free cooling on both units first before switching to mechanical cooling. Networking the units also have other benefits.