What is thermochromic, thermotropic, and photochromic glass
Thermochromic, thermotropic, and photochromic glass are all types of smart glass that change their properties in response to environmental stimuli. However, they differ in the type of stimulus they respond to and the mechanisms by which they change.
1. Thermochromic Glass
Thermochromic glass changes its tint based on temperature. When the temperature reaches a certain threshold, the glass darkens or becomes tinted, reducing the amount of light and heat entering the space. This feature helps regulate indoor temperature by blocking excessive sunlight on hot days, reducing the need for air conditioning. Once the temperature drops, the glass returns to its transparent state, allowing more light to pass through. This type of glass is useful for energy savings, as it adjusts passively without needing external controls.
Key Features:
- Changes based on temperature.
- Automatically darkens when hot and becomes clear when cooler.
- Reduces glare and solar heat gain in buildings.
2. Thermotropic Glass
Thermotropic glass, like thermochromic glass, responds to temperature changes, but it works through a different mechanism. In thermotropic glass, a special layer embedded in the glass changes its transparency based on the temperature. At lower temperatures, the layer remains transparent, but as the temperature rises, the layer scatters light, causing the glass to turn opaque or milky. Unlike thermochromic glass, which darkens, thermotropic glass becomes more diffused to reduce the heat and light entering the building.
Key Features:
- Responds to temperature changes.
- Becomes opaque or diffused when temperatures rise.
- Ideal for controlling solar heat gain and privacy.
3. Photochromic Glass
Photochromic glass changes its tint in response to light intensity, particularly ultraviolet (UV) light. When exposed to strong sunlight, the glass darkens, reducing glare and light transmission. This type of glass is commonly used in photochromic lenses for eyeglasses, but it can also be applied to windows. Photochromic glass is effective at automatically adjusting to varying light conditions, though it does not respond to temperature as thermochromic or thermotropic glass does.
Key Features:
- Changes based on UV light intensity.
- Darkens in strong sunlight and becomes clear in low light conditions.
- Commonly used in eyewear but can be applied to buildings for managing light.
Comparison:
- Thermochromic: Changes tint based on temperature, typically darkening the glass.
- Thermotropic: Becomes opaque or diffused based on temperature to scatter light.
- Photochromic: Responds to UV light, darkening the glass when exposed to sunlight.
Each type of glass offers specific advantages depending on whether you're managing heat, light, or privacy and whether the trigger is temperature or light.