Nanomaterial-enhanced fluids for challenging cooling applications

FlexeGRAPH’s CTO, Shannon Notley, introduces the company’s nanomaterial-enhanced fluids for cooling in automotive and computing applications.

FlexeGRAPH, an Australian-based start-up, has developed a family of nanomaterial-enhanced fluids to replace existing water and glycol-based liquids used in challenging cooling applications. The patented, breakthrough technology allows 60% improved conductivity compared with market-leading materials, providing unprecedented performance for liquids used in applications where managing and directing high thermal loads is critical. The products are non-toxic and environmentally friendly, allowing use in sensitive applications, and can be flexibly formulated with corrosion inhibitors to provide seamless compatibility with existing cooling systems.

The challenges of keeping cool

Electrical devices such as computers and batteries in phones, vehicles, and large-scale energy storage installations generate a lot of heat in normal use. This is because the flow of electricity in a circuit is not perfectly efficient. As the electrons move along they encounter some resistance, resulting in the generation of heat. The greater this internal resistance is, the greater the amount of heat generated. This phenomenon, known as Joule or Ohmic heating, has been exploited in many technologies of the past 100 years, including the incandescent light bulb and in the heating elements of electric toasters. In these applications, the high resistance is necessary to produce the desired heating effect; however, in many other applications, including Li-ion batteries or computer chips, any increase in temperature is problematic.

Efficient ways to keep these electronic components cool are critical to ensure safety and optimum performance. This is particularly true for energy-dense systems such as the batteries used in electric vehicles (EVs). These batteries, based on Li-ion chemistry, are susceptible to overheating when rapidly charged or discharged, leading to potentially catastrophic failure if the heat is not managed effectively.

This necessarily places a limit on how quickly batteries can be charged, presenting a challenge for the uptake of EVs. Indeed, range anxiety could be eliminated if charging time was reduced to minutes. Currently, the strategies used to manage these thermal loads in vehicles include air cooling and liquid cooling using similar fluids to those established long ago for internal combustion engines. Using air is simple and cheap but largely ineffective for large battery vehicles. Liquid cooling of batteries and other components within the electric powertrain is now far more common than using air-cooled systems.

Liquid-cooling systems typically use water glycol-based fluids for heat transfer that were originally developed for the internal combustion engine more than 90 years ago. Although there have been some advances since relating to improvements in the life cycle of the coolant and corrosion inhibition, the heat transfer performance has remained unchanged during this time. This has resulted in a fundamental design and performance limitation of both traditional internal combustion engine and electric powertrain vehicles that are liquid cooled.

The FlexeGRAPH solution

FlexeGRAPH has developed a nanofluid-based coolant that provides the first advance in heat transfer performance for some decades. FlexeGRAPH fluids can be used in existing systems to provide enhanced heat transfer; however, the greatest potential lies ahead, with an unprecedented design freedom for thermal engineers in state-of-the-art systems. Using nanofluids to cool EV batteries will allow faster charging, a critical consideration for transport and logistics companies where lost time, and hence costs, can be reduced.

High thermal conductivity nanofluids coolants such as those produced by FlexeGRAPH have other important advantages for electric powertrain vehicles, as well. The capacity loss of the battery with extensive charge-discharge cycling can be reduced as the system remains cooler, potentially extending the lifetime of the most costly component in the EV, the Li-ion battery pack. Furthermore, it is possible not only to cool the battery system more effectively with a nanofluid coolant but also to heat it when necessary. This is of great importance in cold climates where damage to the battery electrodes can occur when charging at sub-zero temperatures.

Whilst nanofluid heat transfer agents have featured in the scientific literature for some time, there have been limited commercial outcomes until recently. Some of the challenges have included the high cost in comparison to the established commoditised liquids, the limited improvements in heat transfer ability, and the lack of compatibility with other ingredients in coolant formulations. These factors have been compounded by the tendency of the nanomaterials to sediment over time, resulting in fouling of components and performance reduction. FlexeGRAPH has addressed these issues by harnessing their expertise in nanomaterial synthesis and minerals processing. In particular, the long-term stability of the advanced formulations under temperature and pressure extremes is a feature of their products. Coupled with a low-cost, scalable production method for the key ingredient, graphene, this has allowed FlexeGRAPH to gain traction in the rapidly growing EV coolant market.

Alternative applications

There is a clear and present need to charge batteries faster; however, heat transfer nanofluids can also provide benefits in other areas. Currently, FlexeGRAPH is working with partners to develop a solution for internal combustion engines used in high-performance applications in defence and motorsport. Furthermore, there are niche applications in enhanced cooling of industrial systems such as welding torches used in automated production to allow greater throughput. Another area is in geothermal heating applications, where improved thermal properties of the fluids can reduce the depth of wells required to provide adequate heating.

The other major target for FlexeGRAPH’s products is the high-performance computing market. Here, it is becoming increasingly common for direct-to-chip liquid cooling of servers. This is driven by the relatively high cost of power, where in some cases up to 40% of the electricity consumed in a data centre is used to simply cool the enclosures. This situation is exacerbated by the rapid expansion of high-power computer operations associated with blockchain and cryptocurrency mining. Proliferation of cloud-based applications and storage in addition to developments in AI will also continue to add to the baseload power requirements.

In all of these related cases, the liquid coolants employed are again similar to those developed for the internal combustion engine. It depends somewhat, though, on the temperature range over which the coolant is required to be a liquid. FlexeGRAPH flexible formulations enhance these diverse applications based on our platform technology.

About FlexeGRAPH

FlexeGRAPH was established in Canberra, Australia in 2017 but has already rapidly expanded its operations into Europe through the formation of a subsidiary in Sweden. This allows FlexeGRAPH to be closer to the target markets in automotive applications and computing. Furthermore, the supply chain for chemicals is well developed, providing the ideal partnering opportunities to leverage distribution channels. The Australian operation continues to focus on R&D around applications, formulations, and scaling manufacturing. The current production capacity for global operations is more than 1,000kg per year of nanomaterials.

The company continues to explore new opportunities and markets. Right now, the focus is on water and glycol systems, but under active development is the next generation of enhanced nanofluids based on dielectric fluids. These fluids will be able to transfer heat directly from electrified components as these liquids are thermally conductive yet electrically insulating. With this in mind, FlexeGRAPH aims to become the dominant player globally in nanofluid-based coolants, setting a new standard for thermal management performance.

 

Shannon Notley

Founder and CTO, FlexeGRAPH

Flex-G Proprietary Ltd

+61 437770825

shannon.notley@flexegraph.com

http://flexegraph.com/

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