Data centers’ waste heat holds untapped potential

Reusing waste heat from data centers for heating purposes often sparks debate due to concerns about the economic feasibility and long-term sustainability, especially when it comes to existing data centers.

However, just like using heat pumps in older buildings, there are proven, mature ways to put waste heat to use that should not be overlooked in the pursuit of carbon neutrality.

Even low-grade waste heat — at around 25°C/77°F — can offer significant advantages as a preheat source for heat pumps, particularly when the average outdoor temperature during the heating season is at least 15°C/59°F lower.

As a leading player in the data center industry, NTT DATA’s Global Data Centers division is exploring best practices and innovative approaches to using waste heat — not only when building new data centers but also at our many existing data centers.

Before we take a closer look at these concepts, let’s first establish the fundamental parameters that help explain the full picture.

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Waste heat and its key parameters

Data centers operate 24x7 to enable smooth-running digital services. They generate a significant amount of hot air or water as a byproduct of cooling IT systems — often referred to as waste heat. The thermal output can be repurposed for practical uses such as heating office buildings and homes or powering industrial processes.

By capturing and redirecting this waste heat, data centers can significantly reduce their environmental impact and contribute to more sustainable energy practices.

Unfortunately, sometimes the amount of heat that can be reused is calculated based on inaccurate assumptions, which can lead to unrealistic expectations or an inability to meet legal requirements.

Maximum thermal IT load

A key parameter when it comes to defining the size of a data center is the maximum IT load that it can host. When we calculate the waste heat, this translates to the maximum theoretically achievable thermal IT load of the data center. The real thermal IT load depends on the real IT load, which generates the usable waste heat.

Utilized thermal energy and full load hours

Utilized thermal energy refers to the total amount of heat transferred from a data center over a defined period, typically expressed in kilowatt-hours (kWh).

Dividing the utilized thermal energy (kWh) by the maximum thermal power of the installed heat-exchange system (kW) yields the full load hours. This value assists in planning and optimizing heat generation and dissipation.