Expert Interview with Dr. Aritra Ghosh of Exeter University

We are joined today by Dr. Aritra Ghosh, Post Doctoral Fellow in Renewable Energy at the Environment and Sustainability Institute (ESI) at the University of Exeter.

Dr. Aritra Ghosh

1. In your research work into smart glass technologies, what is your area of expertise?

I have worked with PDLC and SPD systems and mostly on topics which are beneficial for end-users. e.g. samples are prepared but it is unknown how they behave when they will be installed in a building.

Real-world experiments assure the practical behaviour of the window. How will this window control heat flow (to limit electricity bills), daylighting (to control the use of artificial light and allow daylight with sufficient level)?

My responsibility is to explore and help end users, such as architects, building engineers and interior designers.

2. How many smart glass technologies are there and how would I choose between them?

Smart glass technology is a fascinating name. You can differentiate between them in terms of their activation: i.e. electrical, thermal or light.

PDLC, SPD and EC need an electrical supply, whereas thermochromic, thermotropic and phase change materials need ambient heat to change the colour of the window.

Photochromic is activated by light. There is another type which is known as gasochromic technology, which works under the presence of hydrogen gas.

3. What are the commonalities and differences in how these smart glass technologies work?

I believe occupant or end-users choice will get priority for selecting those technologies. Smart switchable windows possess more than one transparent state. You can get a complete opaque state which will reduce the need for curtain, blinds, shading devices etc; also you can get complete transparent state.

Now occupant choice will play a key role. Electrically powered PDLC, SPD and EC can change their colour whenever you want just by making it switch ON and OFF.

On the other hand, it is impossible to control the change of colour for the thermally activated or light-activated smart windows.

Electrically powered windows can also be integrated into building energy management systems and powered by Photovoltaics (PV).

If you don’t consider this as is an obstacle then thermally or light actuated technologies are a good choice due to having no need for electrical power.

The power requirement of an electrically activated window is not high. 1 square metre consumes less than 5W of power. PDLC, SPD works under AC power supply while EC needs DC power.

PDLC and SPD both become transparent and EC becomes coloured (opaque) when the powered. EC shows a memory effect which means it keeps it’s coloured state, EC doesn’t consume continuous power. SPD and PDLC need continuous power to keep them transparent.

4. What are the main benefits of smart glass for end-users?

Traditional single and double glazing units are not the future when smart glasses are in the market. In my point of view, more than one transparency state beats other static transparent windows. PDLC, SPD and EC can be powered directly from PV systems. Changes of transparency or colour of the window allow different level of solar heat and light. This can save monthly energy cost (utility bill).

5. Where do you see the smart glass sector going in the next 5-10 years?

I am confident that in the next 5 years more they will dominate the domestic building sector. Their aesthetic look and Privacy and colour changing property will draw attention from the sector who even does not bother about climate change or sustainable environment.

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