Devices and methods for concentrated radiative cooling

An air conditioning system comprising:

• an air conditioner;
• a pre-cooling coil comprising a heat exchanger operatively connected to the air conditioner to supply pre-cooled return air to the air conditioner;
• and
• a preconditioning heat exchanger operatively connected to the pre-cooling coil to supply chilled water to the heat exchanger of the pre-cooling coil to pre-cool the return air,
• wherein the preconditioning heat exchanger comprises a water loop that flows through a concentrated radiative cooling device, the concentrated radiative cooling device comprising:
• a pipe forming a portion of the water loop to be cooled, the pipe having exterior surfaces configured to be exposed to sunlight from first directions;
• a radiative cooling coating on the exterior surfaces of the pipe, the radiative cooling coating configured to lose thermal energy from the pipe, the radiative cooling coating comprising a solar-reflective infrared-emissive paint that contains nanoparticles, is free of a polymeric matrix, and does not contain a metallic component, the radiative cooling coating exhibiting high emissivity for wavelengths of 8 to 13 micrometers and high reflectance for the solar spectrum wavelengths of 0.3 to 3 micrometers, wherein the radiative cooling coating is configured to radiate the thermal energy from a first of the exterior surfaces in the first directions and a second of the exterior surfaces in second directions that are different from the first directions;
• and
• an elongated reflector having a concave cross-sectional V-shape with an opening opposite a rounded valley of the concave cross-sectional V-shape, wherein the pipe is nested within the opening and the opening is not covered, wherein the concave-cross-sectional V-shape defines a surface configured to reflect the thermal energy radiated from the radiative cooling coating on the second of the exterior surfaces and redirect the thermal energy in the first directions, and wherein the elongated reflector has a high reflectance for wavelengths of 5 to 30 micrometers;
• and
• a temperature sensor configured to sense temperature of the pre-cooled return air from the heat exchanger of the pre-cooling coil, wherein the air conditioner is configured to turn on if the temperature of the pre-cooled return air is higher than a set point and to turn off if the temperature of the pre-cooled return air is lower than the set point.