Why Do Data Centre Servers Generate So Much Heat? And How Will We Get to “Cool” Servers?

1. The Physical Origin of Heat: Joule’s Law

Every server within a data centre is made up of electronic components: processors (CPUs and GPUs), memory modules, hard drives, network cards, power supplies, and so on. All these devices operate via the flow of electric current. However, according to the laws of physics — particularly Joule’s Law — when an electric current flows through a conductor, part of the energy is dissipated as heat.

This phenomenon occurs because no material is a perfect conductor. There is always some resistance to the flow of electrons, and that resistance converts part of the electrical energy into thermal energy.

Additionally:

• Processors, which are the computational core of the server, perform billions of operations per second. This intense workload results in substantial electrical activity, which translates into localised high temperatures.
• RAM and hard drives also generate heat due to the constant reading and writing of data.
• Power supplies do not convert all incoming energy into usable energy; some of it is lost as heat.

When this process is multiplied by thousands of servers operating simultaneously, it creates a highly demanding thermal environment that must be managed with sophisticated cooling systems.

Joule’s Law explains that when an electric current passes through a conductor, part of the electrical energy is converted into heat: Heat = I² × R × t Where: - I = current - R = resistance - t = time This heat generation is inevitable in any electronic system. In data centres, where thousands of components operate simultaneously in enclosed spaces, the cumulative heat is enormous.

2. Why Can’t This Heat Be Avoided with Current Technology?

• Limitations of miniaturisation: As transistors shrink, power density (energy per unit volume) increases, raising temperatures. The close proximity of components also encourages heat accumulation.
• Limited energy efficiency: Although it has improved over time, today’s chips are still inefficient, more than 50% of the electrical energy is lost as heat.
• Performance requirements: Modern servers are designed to maximise performance, not to minimise heat. Processing speed is often prioritised over thermal efficiency.

3. How Much Heat Does a Typical Server Generate?

A 1kW server produces approximately 3,412 BTU/h, equivalent to a standard oil-filled household radiator. A rack with 40 servers could easily generate 80kW, enough to heat an entire 800 m² home.

Cold climate advantage: Data centres located in colder regions like Iceland or Northern Sweden benefit from natural cooling, significantly reducing energy use for refrigeration.

4. Current Examples of “Cool” Solutions

a) Direct Liquid Cooling (DLC)

• Coolant flows through cold plates attached to processors. • Used by companies like Meta (Facebook) to reduce air conditioning needs.

b) Immersion Cooling

• Servers are submerged in dielectric liquid that transfers heat efficiently. • Example: Microsoft’s Project Natick, a submerged data centre in the sea.

c) Energy-Efficient Chips

• ARM-based processors (e.g. Amazon Graviton) consume less power. • Google TPUs process AI tasks more efficiently than traditional GPUs.

d) A Shift in the Computing Paradigm

• Optical computing: Uses light instead of electricity to process information. Still in the experimental phase, but promises to eliminate much of the heat generated.

• Quantum computing: While it currently requires extremely low temperatures, future advancements could allow certain types of calculations to be performed with far less energy.

5. What Does the Future Hold?

6. Conclusion: The Path to “Cool” Servers

Servers may never stop generating heat entirely, but the key lies in:

- Designing systems that produce less heat per operation

- Managing thermal loads with smarter, more efficient techniques

- Leveraging location, architecture, and software intelligence to reduce cooling needs

In short, the future of data centres is not just faster — it's cooler.

Joaquin Rodriguez Antibón.