Methods and apparatus for light attenuation and heat management using electrophoretic media

A switchable light modulator for use in a window of an enclosure for light attenuation and heat management, comprising:

• a first light-transmissive substrate for receiving incident sunlight;
• a first electrode layer on one side of the first light-transmissive substrate;
• a second light-transmissive substrate;
• a second electrode layer on one side of the second light-transmissive substrate;
• a light-transmissive polymer structure between the first electrode layer and the second electrode layer, the light-transmissive polymer structure including a base superposed on the second electrode layer and a wall structure extending orthogonally from the base defining a plurality of cells, each of the plurality of cells including a plurality of wells in the base;
• an electrophoretic medium contained in each of the plurality of cells, said electrophoretic medium comprising a plurality of charged reflective pigment particles and a plurality of charged absorptive pigment particles dispersed in a non-polar solvent;
• and
• a controller configured to apply a set of driving voltages between the first and second electrodes to drive the electrophoretic medium among a plurality of optical states including:
• (a) a first set of optical states for reducing transmittance of thermal radiation from the incident sunlight through the switchable light modulator into the enclosure by spreading the plurality of charged reflective pigment particles across each cell proximate the first electrode layer and positioning the plurality of charged absorptive pigment particles between the plurality of charged reflective pigment particles and the second electrode layer in varying arrangements to achieve open, tinted, and closed states,
• (b) a second set of optical states for promoting transmittance of thermal radiation from the incident sunlight through the switchable light modulator into the enclosure by concentrating the plurality of charged reflective pigment particles in the wells in the polymer structure and positioning the plurality of charged absorptive pigment particles between the plurality of charged reflective pigment particles and the first electrode layer in varying arrangements to achieve open and tinted states, and
• (c) a third set of optical states for reducing transmittance of thermal radiation out of the enclosure during nighttime operation by spreading the plurality of charged reflective pigment particles across each cell and spreading the plurality of charged absorptive pigment particles across each cell between the plurality of charged reflective pigment particles and the first electrode layer.