What is Smart Glass?

Smart glass is any glazing material with coatings, laminations or embedded electronics that can affect its optical, electrical or thermal properties.

In a Nutshell

‘Smart glass’ is a family of products that can change their optical, thermal or electrical properties when triggered.

The ‘trigger’ can be a natural phenomenon like heat, light or pressure, leading to what we call passive smart glass, such as photochromic and thermochromic glass.

When the trigger is an electrical signal, for example from a building management system, we call it active smart glass. Examples include liquid crystals, suspended particle devices (SPD), electrophoretic, and electrochromic glass.

Further examples include:

  • transparent photovoltaic glass which converts sunlight into clean electricity, while maintaining a view to the outside world
  • microfluidic glass for the healthcare sector
  • augmented-reality wearables
  • holographic automotive dashboards
  • RF-shielding glass to protect sensitive electronics

There is a lot here, so let’s break this topic down, one step at a time:-

What is Glass?

Glass is an amorphous material (Greek: ‘without shape’), which does not follow a continuous pattern in its internal structure. It is normally transparent, brittle and chemically inert.

Crystalline materials, on the other hand, are organized typically in a lattice form. In nature, examples of crystals include snowflakes, diamonds and table salt. 

All crystals are solids, whereas amorphous materials can be solids, liquids or gasses.

In fact, we consider glass to be neither a solid nor a liquid!

Visible light passes through most glazing products (both amorphous and crystalline) which can be engineered to block infrared (i.e., solar heat) and ultraviolet.

Smart Glass 

Smart glass is a glazing material with augmentations, such as surface coatings or nanostructures, internal laminations or embedded electronic circuits.

We find applications in windows, transportation, appliances and consumer devices.

We now describe the taxonomy further:-

Passive Smart Glass

Natural stimuli can trigger passive technologies into changing their optical properties. Examples include heat or light from the sun, changes in chemical composition, or changes in pressure.

Here are some further examples:

  • Thermochromic glass (triggered by heat)
  • Photochromic glass (triggered by visible light and UV)
  • Piezochromic glass (changes in pressure)
  • Gasochromic glass (changes in gaseous concentrations)
  • Mechanochromic glass (changes in mechanical force)

Some of the above are still in the R&D stage, but promise interesting applications across the chemical, pharmaceutical and industrial sectors.

Both thermochromic and photochromic glass have found applications in building facades, in eye wear and in transportation. This can minimise air conditioning costs and reduce discomfort and glare for passengers and building occupants.

The biggest advantage of passive materials is that they do not need cabling, which saves on installation costs in buildings and reduces weight in vehicles. The disadvantage is that they are harder to control ‘on-demand’, based on user needs.

Active Smart Glass

This type of smart glass operates electrically and thus can connect to building management systems (BMS) and the internet.

Recent advances include building facades driven by artificial intelligence based on building occupancy or sky conditions.

Active technologies include:-

Electrical Safety and Smart Glass

Condensation in insulated glazing units can cause short circuits in high-voltage smart glass, such as liquid crystal and SPD glass, introducing potential safety concerns.

Even though electrochromic and electrophoretic technologies operate at safer voltages (typically 5-15Vdc), they still require protection against short-circuits and radio-frequency (RF) noise.

Smart Glass Powered by Sunlight

Potentially the most exciting technology is transparent photovoltaic (PV) smart glass, since we can combine it with the above technologies to drive the glass using clean energy.

Some windows include opaque PV modules installed on the exterior of the frame. 

Some hide the PV layer transparently inside the smart glass, providing a seamless integration and obviating the need for any cables at all.

Yes, you heard that right: the interior PV layer is transparentconductive and energy-generating!

Use Cases

Smart glass use cases include:

  • privacy screens in a bank or hospital that are triggered by human presence
  • auto-tinting facades for buildings or vehicles that block glare under strong sunlight
  • retail displays or storefronts that can hide objects from view for security reasons
  • display cases for art & luxury items that can reduce light exposure damage which can result in colour fading
  • ‘heads-up displays’ with visual information projected onto aircraft or automotive glass that reduces accidents by keeping drivers focussed on the road ahead

Smart Glass Suppliers

If you are looking for manufacturers, distributors or installers of smart glass products or services, look no further than our parameterised search.

The screenshot below shows a search for suppliers of photovoltaic glass. This can be filtered further if you specify product attributes, such as minimum transmittance, U-value or haze:

Smart glass marketplace search for manufacturers, distributors and installers

Smartglass World Marketplace Search for transparent photovoltaic (PV) smart glass manufacturers, distributors and installers

If you press the ‘Show Results’ button, this will produce a list of companies, which you can contact by posting a request on the Marketplace.

Outlook

Terminology is important.

Recent legislation in the US has confused the term ‘electrochromic’ with ‘any electrically-activated smart glass’, which is not accurate.

Smartglass World was created to educate customers and industry players in the technologies and applications available.

The industry should pay heed to using terminology accurately, so that customers have clarity about which smart glass technology is best suited to their needs.

References

1. “Green Nanotechnology” – Smith & Granqvist – ISBN-13: 978-1420085327, URL

2. Colour and the Optical Properties of Materials – Richard Tilley – ISBN-13: 978-0470746950, URL

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