Radiative Cooling Combats Climate Change By Using Space as a Heat-Sink

Urban environments are becoming increasingly sprawling and dense, resulting in more concrete and pavement than ever before.  The problem with that is the amount of heat absorbed by buildings and roads.  Surrounding areas become hotter, climate control systems must work harder, and greenhouse gas emissions skyrocket.  With that in mind, a team of researchers based out of the University of Maryland has come up with a simple but effective solution.  This is a recently developed material dubbed ‘cooling glass', which can help to mitigate this growing problem and its effect on climate change through radiative cooling.

The Radiative Cooling Breakthrough

Battling climate change isn't just about finding clean energy sources.  It is also about efficiently using the electricity we already create.  In this instance, cooling glass is a breakthrough that leverages the Albedo Effect and radiative cooling to essentially prevent thermal energy from the Sun from being trapped in typical building materials by reflecting it back into the emptiness of Space – a vacuum and limitless heat-sink that sits at a brisk -270ºC.

In its research article, the team states that it,

“…developed a randomized photonic composite consisting of a microporous glass framework that features selective LWIR [long-wave infrared radiation] emission along with relatively high solar reflectance and aluminum oxide particles that strongly scatter sunlight and prevent densification of the porous structure during manufacturing.”

The resulting product, or ‘cooling glass', is said to perform well in a variety of conditions, which, alongside a relatively easy manufacturing process, might just make it viable for large-scale applications in urban environments.

Source: www.cera.cool

As far as performance goes, the team indicates that,

“This microporous glass coating enables a temperature drop of ~3.5° and 4°C even under high-humidity conditions (up to 80%) during midday and nighttime, respectively.”

In doing so, the paper indicates that a building leveraging cooling glass has the potential to reduce its carbon emissions by as much as 10% annually.  When scaled across urban landscapes, this is significant.

While the idea of leveraging radiative cooling to battling climate change is nothing new, it is the performance and potential scalability of this new product that makes it particular interesting.

What is a ‘Heat-Sink'?

For those wondering, a heat sink is a device or substance that absorbs and dissipates heat from another object using thermal contact (either direct or radiant).  Man-made variants are commonly used in electronics and mechanical systems to manage temperature and prevent overheating.  In the case of cooling glass, it is through radiation into the vacuum of space that this thermal dumping occurs.

Here's an overview of the science behind heat sinks:

Thermal Conduction: The primary principle behind a heat sink is thermal conduction, a physical process where heat is transferred through a material. When a heat-generating component (like a CPU in a computer) becomes hot, it transfers its heat to the heat sink.

Material: Heat sinks are typically made from materials with high thermal conductivity, such as aluminum or copper. These materials effectively transfer heat away from the component and spread it out over a larger area.

Design and Surface Area: A key aspect of a heat sink's design is its surface area. Many heat sinks have fins or other structures to increase their surface area. This allows more air to come into contact with the heat sink, enhancing heat dissipation.

Convection: Air or liquid moving over the surface of the heat sink facilitates convective cooling. In passive cooling, natural air flow dissipates heat, while in active cooling systems, fans or pumps are used to increase the flow of air or liquid, respectively, enhancing the cooling effect.

Radiation: Heat sinks also dissipate heat through radiation. The heat absorbed by the heat sink is emitted as infrared radiation, which further helps in cooling the device.

The effectiveness of a heat sink depends on several factors, including the material's thermal conductivity, the design (especially the surface area), the ambient temperature, and the flow rate of air or liquid over the heat sink. By efficiently managing thermal energy, heat sinks play a crucial role in the reliability and longevity of electronic and mechanical systems.

What is ‘Radiative Cooling'?

Meanwhile, radiative cooling is a natural process where objects release heat in the form of infrared radiation. This process already plays a role in nature with the Earth's energy balance and has important applications in various technologies.

Here's a closer look at the science behind radiative cooling:

Infrared Radiation: All objects emit energy in the form of electromagnetic radiation, the intensity of which depends on their temperature. At the temperatures commonly found on Earth's surface, this radiation is mostly in the infrared spectrum. Radiative cooling occurs when an object, such as the Earth's surface or a building, emits more infrared radiation than it absorbs.

Emission into Space: One of the key aspects of radiative cooling is the ability of certain materials or surfaces to emit heat directly into space. This is possible because the atmosphere has specific ‘windows' that are transparent to certain wavelengths of infrared radiation, allowing this energy to pass through and escape into space.

Day vs. Night Cooling: Radiative cooling is most effective at night, as during the day, the absorption of solar radiation tends to offset the cooling effect. At night, without the input of solar energy, surfaces can cool down by emitting infrared radiation more effectively.

Relation to Albedo Effect: The albedo effect primarily concerns the reflection of visible sunlight, while radiative cooling is about the emission of infrared radiation. However, they are related in terms of energy balance. A surface with a high albedo reflects more solar radiation, absorbing less heat during the day. This can enhance radiative cooling at night, as there's less absorbed heat to be re-emitted. Conversely, a low-albedo surface heats up more during the day, potentially emitting more infrared radiation if it has high emissivity.

Applications: Radiative cooling has practical applications in passive cooling systems, such as in buildings and vehicles. It's also being explored for use in sustainable technologies, like the cooling panels discussed here, that can reduce reliance on electricity-powered air conditioning.

Radiative cooling is an important natural process that helps regulate temperature by emitting infrared radiation. While distinct from the albedo effect, which involves the reflection of sunlight, both contribute to the thermal dynamics of surfaces and play critical roles in both natural and engineered environmental systems.

Industry Players Tackling Climate Change

For those interested in learning which publicly traded companies are actively developing solutions to battle climate change, consider the following.

*Figures provided below were accurate at the time of writing and are subject to change.  Any potential investor should verify metrics*

1. FuelCell Energy, Inc.

FuelCell Energy, Inc. (FCEL +7.01%)

FuelCell Energy is a leader in the development and deployment of fuel cell technology. It focuses on designing, manufacturing, operating, and servicing highly efficient and clean fuel cell power plants. Its solutions are aimed at reducing reliance on fossil fuels and lowering carbon emissions, thereby contributing to the battle against climate change. The company's fuel cells provide a unique combination of clean, reliable, and efficient power generation, making them a valuable part of the transition to sustainable energy.

2. Brookfield Renewable Partners L.P.

Brookfield Renewable Partners L.P. (BEP +0.69%)

Brookfield Renewable Partners operates one of the world's largest publicly traded, pure-play renewable power platforms. Its portfolio includes hydroelectric, wind, solar, and storage facilities across North America, South America, Europe, and Asia. With a strong commitment to sustainability, Brookfield Renewable Partners focuses on long-term value creation through renewable energy assets, playing a significant role in the global shift toward clean, renewable sources of power to combat climate change.

3. ChargePoint Holdings, Inc.

ChargePoint Holdings, Inc. (CHPT +7.62%)

ChargePoint Holdings is at the forefront of the electric vehicle revolution, operating one of the most extensive and open EV charging networks. The company provides innovative and accessible charging solutions across multiple sectors, including residential, commercial, and public spaces. By facilitating the adoption of electric vehicles, ChargePoint Holdings is directly contributing to the reduction of greenhouse gas emissions and the shift away from fossil fuel dependence, marking a crucial stride in the fight against climate change.

Notable Companies Leveraging Radiative Cooling

While not publicly traded, there is a particularly noteworthy startup already working to implement and scale the science behind this cooling glass.  In fact, it was founded by the very same researchers behind this breakthrough.  This company is Ceracool.

Ceracool has developed a ‘radiative cooling paint,' which functions based on the same concept of the cooling glass.  The company touts its radiative cooling paint as offering “…free air conditioning by reflecting over 95% of solar irradiance and simultaneously emitting heat into the near-absolute-zero temperatures of deep space through the atmospheric transparency window.”  What makes this product particularly interesting is that it can be applied easily to surfaces prone to thermal build-up (roofs, roads, etc) by either spraying or brushing.

Another example of a privately held company innovating with radiative cooling technology is SkyCool Systems.

SkyCool Systems is a clean energy company developing advanced cooling solutions that leverage radiative cooling. Its approach involves a radiative cooling material that is integrated into a panel system designed to significantly enhance the efficiency of vapor-compression based cooling systems.  Like Ceracool, SkyCool Systems' pioneering work in this field represents a promising step forward in addressing the world's cooling challenges, offering both environmental benefits and energy cost savings.

Final Thoughts

At the end of the day, efforts surrounding climate change need to extend beyond solely tapping into sustainable energy sources.  While this is obviously a vital and important approach, it is essentially akin to juggling with one hand.  Rather, we need solutions that also address inefficiencies in our power consumption – which is exactly what radiative cooling products are about.  In an illuminating TedTalk from Aaswath Raman, he touched on the importance of addressing a potential feedback loop resulting from our cooling needs, and how radiative cooling may help.

Combined with other breakthroughs like back-contact micrometric photovoltaic cells, it should be interesting to see the resulting benefits of initiatives being undertaken by companies like Ceracool in the coming years.