E-COATING - Turning Glass Waste into Valuable Passive Cooling Material
E-COATING - Embrace Green, Keep Comfort
E-COATING - Embrace Green, Keep Comfort
Background Problems in Hong Kong: Urban Solid Waste Problems & HVAC Electricity Consumption Problems
E-COATING prototype samples for testing
Outdoor prototypes. (Left: without E-COATING applied on roof; Right: with E-COATING applied on roof)
Waste Glass Yield Infographic
What it does
E-COATING is an eco-friendly solution created from waste glass. It can be applied to the exterior roofs and walls to reduce the heat absorption of buildings, reducing the amount of electricity consumed on cooling and associated greenhouse gas emissions.
In Hong Kong, air-conditioning accounts for 31% of total electricity consumption. Besides, over 470,000 glass bottles end up in landfills every day. These staggering figures sparked my imagination. One scorching hot day, as I walked in the sun and a cloud provided momentary shade, I wondered if we could harness the cooling power of clouds by using waste glass as pigments in highly reflective coatings for buildings. This would reduce their cooling load and help combat global warming. Then we started to prove the idea based on our previous research outcome related to radiative cooling. We aim to transform waste glass into a valuable material.
How it works
Think of E-COATING as a thick cloud for your building. It has an impressive ability to block and reflect sunlight - about 95% of it. This is achieved by controlling the sizes of the fragmented glass used in the coating. When sunlight hits the coating, the light scatters and bounces off the tiny glass fragments thousands of times. This constant bouncing and scattering sends most of the incoming heat right back where it came from. E-COATING is also designed to continuously emit a type of heat called infrared thermal radiation. This heat is released at specific wavelengths, between 8-13 micrometers, which makes it very special. Because this particular type of heat can easily pass through Earth's atmosphere and dissipate into space, instead of getting trapped by greenhouse gases. This reduces the need for energy-consuming air conditioning systems, leading to lower energy usage overall, making the building a more comfortable and sustainable place to be.
The initial phase is to collect glass bottles from waste bins. We had to ensure that we had a sufficient quantity for our experiments. These bottles were then shattered into pieces and meticulously ground into a powder. A series of repeated experiments were conducted to determine the correlation between the milling time and the size distribution of the glass powder. Then, we proceeded to the screening stage to identify VOC-free binders and additives that were both feasible to use and had a minimal environmental impact. After shortlisting potential binders, we conducted further experiments to determine their refractive indices, which would affect the optical properties of the E-COATING. After that, we start to make the prototypes of the E-COATING. This needs a careful balancing act of mixing the raw materials in the right proportions. But, the application process proved more challenging than we anticipated. In the testing phase, we encountered several hurdles, such as cracking, peeling, and chalking of the coating. However, these setbacks provided valuable insights for improvement. We began refining the formulation, adjusting the ratio of binders to additives, and experimenting with different application methods. And also optimize the coating's performance and stability.
How it is different
E-COATING is distinguished from traditional exterior wall coatings by offering not only basic coating properties, but also a free cooling effect. If E-COATING is applied on 10% of rooftops area of Industrial Parks (~405M m^2) in China, the saved electricity (~77.6B kWh) would be able to power ~15.7M Chinese households annually. This would also reduce 55.1M tonnes of carbon dioxide emission per year, which is equivalent to the amount of carbon fixed by 4.59B trees per year. By using recycled glass as pigments, we eliminate energy-intensive processes in the product life cycle, such as raw material extraction and synthetic pigment manufacturing. Also, the production cost of E-COATING would be lower than the same type of coating products in the current market, our customers do not need to pay for the extra high cost to participate in environmental protection. E-COATING's water-based formula also emits no VOCs. This creates a more environmentally friendly community.
Our R&D goals include completing various standard tests for E-COATING, identifying mass production methods, conducting field testing in real scenarios, enhancing the applicability and versatility of E-COATING, developing E-COATING in different colors using different colored recycled glass bottles and investigating new E-COATING formulas for indoor use. From a business perspective, we are going to start a company and connect with organizations, as well as spend time identifying and optimizing the supply chain. We are willing to build up a large collaborator network and connect with likeminds to generate an impact in the world.
Professor Charles K. Kao Student Creativity Awards 2023, Champion (Postgraduate Group)