Passive Cooling vs. Active Cooling — What’s the Difference?

active passive cooling
A common problem in product design — particularly in electronics — is managing thermal conditions for optimal efficiency. The core of the challenge is designing energy-efficient microprocessors and printed circuit boards (PCBs) that will not overheat.

A frequently overlooked aspect of thermal management problem solving is architectural design. Whether it’s a private home, an office building, or a dedicated server room, architectural considerations can have a huge impact on the thermal management solutions available. 

To tackle and alleviate the difficulties and inefficiencies that arise as a result of heat, engineers employ different cooling systems to manage conditions. These systems can be divided into two main categories: those with active and with passive cooling techniques. But what is the difference between them?

Passive Cooling

The advantages of passive cooling techniques lie in the energy efficiency and lower financial cost, making it an astute systems design choice for the thermal management of both buildings and electronic products such as laptops, televisions, boxes, etc. 

Passive cooling achieves high levels of natural convection and heat dissipation by utilizing a heat spreader or a heat sink to maximize the radiation and convection heat transfer modes. In architectural design, natural resources like wind or soil are used as heat sinks to absorb or dissipate heat. This leads to proper cooling in electronic products and thermal comfort in homes or office buildings by keeping them under the maximum allowed operating temperature. A growing trend in this regards can be witnessed in what is commonly known in the industry as passive houses.

To sum it up — passive thermal management is a cost-effective and energy-efficient solution that relies on heat sinks, heat spreaders, heat pipes or thermal interface materials (TIM) to maintain optimal operating temperatures.

Active Cooling

Active cooling, on the other hand, refers to cooling technologies that rely on an external device to enhance heat transfer. Through active cooling technologies, the rate of fluid flow increases during convection, which dramatically increases the rate of heat removal.

Active cooling solutions include forced air through a fan or blower, forced liquid, and thermoelectric coolers (TECs), which can be used to optimize thermal management on all levels. Fans are used when natural convection is insufficient to remove heat. They are commonly integrated into electronics, such as a computer case, or are attached to CPUs, hard drives or chipsets to maintain thermal conditions and reduce failure risk.

The main disadvantage of active thermal management is that it requires the use of electricity and therefore results in higher costs, compared to passive cooling.

Why Use a Thermal Analysis Software?

Early in the design phase, a thermal analysis software can be used to virtually test fans, blowers, heat sinks, chips, PCBs and even server rooms and buildings, for a better thermal management.

By performing early-stage thermal simulations, designers can predict the airflow, temperature distribution, and heat transfer in systems. These analyses reduce the number of unnecessary physical prototypes, resulting in design process efficiency and significantly reduced costs. In this public project, a heat sink design was analyzed through conjugate heat transfer simulation, with the purpose of optimizing it to ensure proper cooling.

Thermal analysis software can also help you make an informed decision when considering active and passive cooling techniques. This workshop recording and its step-by-step tutorial will help you compare active and passive cooling of a Raspberry Pi house by performing a simulation. Access the SimScale platform for free to follow this tutorial. Create an account or start a free 14-day trial.

To learn more about how engineering simulation can be used in electronics design, download this case study for free: Thermostructural Analysis of a Chip. 

SimScale is the world's first cloud-based simulation platform, enabling you to perform CFD, FEA, or thermal analyses. Sign up for the 14-day free trial and join the community of 70 000 engineers and designers. No payment data required.