How To Make Infrared Cooling Paint (Electricity Free Air Conditioning)

Summary

In this video, the creator explores how to make DIY paint capable of sub-ambient radiant cooling, potentially providing passive, electricity-free air conditioning. By using high-reflectance pigments like barium sulfate and leveraging the atmospheric infrared window, the paint can emit thermal energy into space. After experimenting with various methods, the creator compares their homemade paint to commercial options, achieving a significant improvement in cooling performance. The video also discusses practical applications for this technology, like cooling panels for buildings, and teases future improvements and experiments.

Takeaways

• 😀 Radiative cooling paints can passively cool surroundings by emitting infrared radiation into space, offering a form of electricity-free air conditioning.
• 🌞 Effective radiative cooling paints must have high reflectance in the visible spectrum to minimize absorbed heat from sunlight.
• 🌌 The key to effective radiative cooling lies in the paint's emission of infrared light at the right wavelength, allowing it to escape Earth's atmosphere into space.
• 🖌️ Ordinary white paint uses titanium or zinc oxide pigments, which reflect light but don't emit infrared light at the right wavelength for cooling.
• ⚗️ Barium sulfate and calcium carbonate are the best pigments for achieving sub-ambient cooling as they reflect light well and emit infrared radiation within the atmospheric infrared window.
• 🧪 The process of making barium sulfate for use in radiative cooling paint involves reacting barium nitrate with sulfuric acid to form the pigment, followed by washing and filtration to remove impurities.
• 🎨 When mixed with acrylic paint, the barium sulfate pigment creates a paint that can reflect sunlight effectively, but transparency issues arise due to the nature of the pigment when mixed with liquid.
• 🔬 Achieving high reflectance in paint requires not just good pigment but also maximizing light scattering, similar to the way snow reflects sunlight through tiny air pockets in ice.
• 🔋 The concept of cooling a building at night using radiative cooling paint could allow buildings to store cold energy and remain cooler during the day, like a thermal battery.
• 💡 There is still potential for improving radiative cooling paint by tweaking the formulation, including adding more pigment to improve its performance in direct sunlight and enhancing its infrared emission properties.

Q & A

What is the main concept behind sub-ambient radiant cooling paint?

Sub-ambient radiant cooling paint is designed to cool its surroundings by reflecting visible light and emitting infrared radiation at specific wavelengths that allow the heat to escape directly into space, leading to cooling even in direct sunlight.

How does the paint achieve sub-ambient temperatures?

The paint achieves sub-ambient temperatures by combining high reflectance of visible light with the emission of infrared radiation at wavelengths that pass through the atmosphere without being absorbed, allowing heat to be emitted into space.

Why is the atmospheric infrared window important for this cooling paint?

The atmospheric infrared window is important because it allows infrared light emitted by the paint to pass through the atmosphere with minimal scattering or absorption, ensuring the heat escapes into space instead of being reabsorbed by the Earth.

What are the two main pigments used in the best performing radiant cooling paints?

The two main pigments used in effective radiant cooling paints are calcium carbonate and barium sulfate. These pigments have good reflectance and emit infrared radiation at the right wavelength for cooling.

What was the issue with using barium sulfate in the initial paint mix?

The issue with barium sulfate was that it became transparent when mixed with the acrylic base, reducing the paint's reflectance and overall effectiveness. This transparency prevented the paint from achieving the desired cooling performance.

What modification improved the performance of the barium sulfate pigment?

The performance was improved by creating barium sulfate microspheres using a controlled chemical reaction with barium chloride and sodium sulfate. These microspheres were more reflective and less transparent, enhancing the cooling potential.

How did the snow-scattering effect contribute to the paint's effectiveness?

The snow-scattering effect works by introducing millions of tiny air gaps in the paint, which scatter light and increase reflectance. This increases the paint's ability to reject sunlight and boosts its overall cooling performance.

What was the result of combining barium sulfate microspheres with the snow-scattering acrylic mix?

Combining barium sulfate microspheres with the snow-scattering acrylic mix significantly improved the reflectance of the paint, making it much brighter than the original paint and improving its cooling performance in sunlight.

How did the paint perform under direct sunlight compared to off-the-shelf white paint?

Under direct sunlight, the DIY paint performed significantly better than off-the-shelf white paint. It was cooler by up to 20 degrees Fahrenheit, but still did not achieve sub-ambient temperatures, which are very challenging to reach in direct sunlight.

What were the challenges in achieving sub-ambient temperatures with the DIY paint?

The challenges included the heat conduction from surrounding materials and the difficulty of maintaining sub-ambient temperatures during direct sunlight. The paint was close to sub-ambient temperatures but couldn't fully achieve them due to these factors.

How can this cooling paint be used in practical applications?

This cooling paint can be used in passive cooling systems, such as radiative cooling panels that cycle air or water through them. These panels could be used to cool buildings or devices, especially by storing cooling potential at night to last throughout the day.

What are the potential future improvements for radiant cooling paint?

Future improvements include refining the pigment mix for better reflectance and infrared emission, creating more efficient methods for mass production, and developing cooling panels that can be used in homes or industries to lower energy consumption and reduce heat buildup.