■ Thermal Management Tends to Increase Weight
When you try to strengthen thermal management, components tend to increase.
Making metal thicker.
Making heat sinks larger.
Adding cooling plates.
Adding more heat dissipation sheets.
Inserting thermal insulation materials.
These measures can be effective for heat.
However, the weight increases accordingly.
In other words, thermal management tends to go hand in hand with increased weight.
■ Weight Reduction Makes Thermal Management More Difficult
Conversely, prioritizing weight reduction makes thermal management more difficult.
For example,
making metal parts thinner.
Making heat sinks smaller.
Reducing the heat dissipation area.
Replacing parts with resin.
Then it becomes lighter.
However, the ability to release heat can decrease.
In other words, making it lighter can make it harder to cool.
■ Heat and Weight Reduction Tend to Be a Trade-Off
In thermal management, materials are needed to carry heat.
In weight reduction, you want to reduce materials.
At this point, the two tend to collide.
In other words, it is a relationship in which you want to add to release heat,
but you want to reduce to lighten.
This is the difficulty of heat × weight reduction.
■ In EVs, Weight Reduction Directly Affects Driving Range
In EVs, weight affects driving range.
When the vehicle body becomes heavier, the energy required for driving increases.
In other words, even if more batteries are loaded, the vehicle becomes heavier accordingly and efficiency drops.
If too many thermal management components are added here, the weight increases further.
However, batteries and inverters require thermal management.
In other words, in EVs, the challenge of wanting to manage heat but not wanting to make it heavier
always exists.
■ EV Batteries Require Thermal Management and Weight Reduction at the Same Time
In EV batteries,
● Heat dissipation materials
● Thermal insulation materials
● Insulating materials
● Flame-retardant materials
● Cooling plates
● Protective materials, and so on are used.
These are necessary for safety and performance.
However, they all add weight.
That is why, in EV batteries, how to make the necessary thermal management work as lightly as possible is important.
This is not simply material selection, but also a matter of structural design and process design.
■ In Robots, Weight Determines Motion Performance
In robots, weight is extremely important.
When they become heavier, a vicious cycle arises in which
● Motor load increases
● Power consumption increases
● Batteries become larger
● Operating speed drops
● Joint load increases
● Heat generation increases
In other words, in robots, becoming heavier can increase heat even further.
As a result of adding thermal management components and making it heavier, motor load increases and it generates even more heat.
This is a typical contradiction of heat × weight reduction.
■ In Wearable Devices, Weight Determines the Experience
In wearable devices, weight directly affects the user experience.
A heavy smartwatch.
Heavy AR glasses.
Heavy earbuds.
That alone means they will not be used for long periods.
However, wearable devices also contain AI processing, communication, batteries, and sensors.
Naturally, they generate heat.
In other words, in wearable devices,
the challenge of wanting to make it lighter, but not wanting it to get hot
becomes extremely strong.
■ In Aerospace, 1 g Matters
In the aerospace field, weight is extremely important.
In satellites, drones, and aircraft, weight directly affects fuel efficiency, flight time, and launch costs.
However, electronic devices, batteries, communication equipment, and sensors generate heat.
Furthermore, convection cannot be used in space, so thermal management is difficult.
In other words, in aerospace,
materials that are light and can control heat are strongly required.
■ Metals Cool, but They Are Heavy
Copper, often used in thermal management, has high thermal conductivity.
But it is heavy.
Aluminum is lighter than copper, but its thermal conductivity is lower than copper’s.
In other words, in material selection,
the balance between thermal conductivity and weight must be considered.
Copper is not necessarily optimal.
Nor is aluminum necessarily optimal.
Judgment is required depending on the application.
■ Graphite Can Be Advantageous for Weight Reduction
Graphite sheets are lighter than metals and make it easy to spread heat in the in-plane direction.
That is why they are an effective option in smartphones, wearable devices, and so on.
However, graphite has directionality.
Care is also needed regarding electrical continuity, particle shedding, cracking, and processability.
In other words, graphite is
a material that can spread heat lightly, while on the other hand
also being a material that requires care in how it is used.
■ Aerogel Can Be Advantageous for Lightweight Thermal Insulation
Aerogel is attracting attention as an extremely light material with high thermal insulation.
In EVs, ESS, aerospace, and so on, it is expected to be used to block heat.
In particular,
it is an effective candidate when you want to stop heat lightly.
However, because it
・Is brittle
・Tends to shed particles
・Is difficult to process
・Can be expensive
ingenuity is needed to use it in volume production.
■ Lighter Materials Can Be Harder to Process
Lightweight materials are not necessarily easy to handle.
For example, there are challenges such as being
・Thin
・Soft
・Brittle
・Easily stretched
・Prone to shedding particles
・Prone to warping
In other words, with lightweight materials,
not only being light,
but also being handleable in volume production is important.
■ Thinness and Lightness Are Similar but Not the Same
Making something thinner often makes it lighter.
However, making it thinner can reduce strength or make processing more difficult.
In addition, in thermal management, making it too thin can lead to insufficient step absorption and contact.
In other words, satisfying
thin
light
cools
can be applied at the same time is not easy.
■ In Heat × Weight Reduction, Composite Materials Become Important
To achieve both heat management and weight reduction, composite materials rather than single materials are often used.
For example,
● Graphite + insulating film
● Aluminum foil + adhesive material
● Heat dissipation sheet + lightweight base material
● Aerogel + protective film
● Ceramic filler-loaded resin, and so on.
In other words, in weight reduction and thermal management,
layered structures are more important than materials alone.
■ Weight Reduction Is Not Irrelevant Even in AI Servers
Because AI servers are large equipment, weight reduction may seem largely irrelevant.
In reality, however, there are constraints on rack weight, cooling mechanisms, maintainability, transportability, and installation.
In addition, the more cooling components increase, the more complex the structure becomes.
In other words, even in AI servers,
the balance between cooling capacity and mountability, weight, and maintainability is important.
■ The Researcher's Perspective: Think About Heat × Weight Reduction in Terms of Performance per Weight
In research and development, not only simple thermal conductivity but also
performance per unit of weight is important.
For example, even with the same heat dissipation performance, achieving it at half the weight has great value.
Especially in EVs, robots, aerospace, and wearable devices,
expectations are rising for
lightweight high thermal conductivity materials
lightweight thermal insulation materials.
■ The Shop-Floor Perspective: The Lighter the Material, the More Unruly It Is in Volume Production
On the shop floor, lightweight materials can be difficult to handle.
For example,
● Floating during transport
● Getting curl from winding
● Stretching
● Tearing
● Warping
● Shedding particles
● Sticking due to static electricity
● Unstable positioning on automated machines, and so on.
In other words, with lightweight materials, not only material performance but also
transportability
suppliability
processing stability
are important.
■ Problems That Tend to Occur in Volume Production for Heat × Weight Reduction
In volume production processes, the following kinds of problems can occur.
● Wrinkles in thin materials
● Lifting of lightweight materials
● Deformation during die-cutting
● Warping during lamination
● Misalignment during winding
● Meandering during supply to automated machines
● Poor compatibility with adhesive materials
● Edge crumbling
● Deformation during transport
These affect not only thermal performance but also ease of assembly and yield.
In other words, with heat × weight reduction,
how to handle light materials stably is extremely important.
■ OTIS's Perspective
OTIS is not a company that develops lightweight materials themselves.
However, we may be able to contribute in the area of processing lightweight thermal management materials into a form that can be used in volume production processes.
What matters from OTIS’s perspective is
● Thin-film processing
● Processing of lightweight sheet materials
● Graphite processing
● Evaluating the processing of aerogels
● High-precision die-cutting
● High-precision lamination
● Lamination of dissimilar materials
● Reel supply
● Designing supply formats for automated processes
Lightweight materials are difficult to handle precisely because they are light.
That is precisely why technology that feeds light materials stably into volume production processes is important.
■ What OTIS Can Do
At OTIS, through
● Thin-film heat dissipation material processing
● Graphite sheet processing
● Metal foil processing
● Evaluating the processing of lightweight thermal insulation materials
● High-precision die-cutting
● Microfabrication
● High-precision lamination
● Stacking of irregular shapes
● Reel supply
● Designing supply formats for automated processes
and more, we may be able to contribute to bringing heat × weight reduction countermeasure components closer to a state in which they can be used in volume production.
Especially in EVs, robots, wearable devices, aerospace, and smart devices, lightness, thinness, thermal performance, and mass producibility must be considered at the same time.
■ Outside OTIS's Expertise
On the other hand, OTIS is not a company that specializes in
● Development of lightweight materials themselves
● CNT material development
● Graphene material development
● Aerogel manufacturing
● Overall structural design
● Dedicated thermal simulation analysis
However, in the area of making lightweight thermal management materials into a form that can be used in volume production processes,
we may be able to play an important role.
■ Industries Where This Technology Will Be Important
★★★★★ EVs and batteries
★★★★★ Robots
★★★★★ Wearable devices
★★★★★ Aerospace
★★★★☆ Smartphones
★★★★☆ Drones
★★★★☆ AI servers
■ Summary
Thermal management is not about simply making things heavier
To release heat, you want to add materials.
Making metal thicker.
Adding heat dissipation components.
Adding cooling structures.
However, that leads to increased weight.
On the other hand, prioritizing weight reduction too much makes it harder for heat to escape.
In other words, the essence of heat × weight reduction is the contradiction of
wanting to add to cool
wanting to reduce to lighten.
In future EVs, robots, wearable devices, and aerospace, materials and structures that are light and thin yet can still control heat will be required.
And it is not enough for those materials to be high-performance.
Being able to feed light materials stably into volume production processes in the intended shapes
— only when that works does it become true thermal management.
Column Supervisor: Koji Kakumoto (President, OTIS Co., Ltd.)
After studying abroad and working in planning and development at a trading company, he joined OTIS Co., Ltd. in 2011. While primarily working in the Corporate Planning Department, he has also served concurrently in manufacturing and technical divisions, and since 2018 has served as President, working to drive business growth and strengthen the organization.
This article is a general technical explanation intended for educational purposes and does not refer to any specific company, product, or technology.
