American Scientist

Humans weren’t the only ones who needed to stay cool during 2023’s record-breaking heat waves. Many machines, including cell phones, data centers, cars, and airplanes, become less efficient and degrade more quickly in extreme heat. Machines generate their own heat, too, which can make hot temperatures around them even hotter.

No machine is perfectly efficient—all machines face some internal friction during operation. This friction causes machines to dissipate some heat. That dispelled heat mixes with the external temperature, so the hotter it is outside, the hotter the machine will be.

Cell phones and similar devices with lithium-ion batteries experience decreased performance when operating in climates above 35 degrees Celsius (95 degrees Fahrenheit). This throttling is by design to avoid overheating and increased stress on the electronics.

Designs that use innovative phase-changing fluids can help keep machines cool, but in most cases heat is still dissipated into the air. So, the hotter the air, the harder it is to keep a machine cool enough to function efficiently. Plus, the closer together machines are, the more dissipated heat there will be in the surrounding area.

We are engineering researchers who study how machines manage heat, as well as ways to effectively recover and reuse heat that is otherwise wasted. Technologies for reducing, capturing, and reusing heat could help prevent mechanical failures and weakened infrastructure systems during an era of rising temperatures.

Deforming Materials

Higher temperatures, either from the weather or from the excess heat radiated from machinery, can cause materials in machinery to deform. To understand why, consider what temperature means at the molecular level.

At the molecular scale, temperature is a measure of how much molecules are vibrating. The hotter the temperature, the more the molecules that make up everything from the air to the ground to materials in machinery vibrate.

As the temperature increases and the molecules vibrate more, the average space between them grows, causing most materials to expand. Roads are one place to see this happen—hot concrete expands, gets constricted, and eventually cracks. This phenomenon can happen to machinery, too, and thermal stresses are just the beginning of the problem.

Travel Delays and Safety Risks

High temperatures can also change the way oil in your car’s engine behaves, leading to potential engine failures. For example, if a heat wave makes it 16.7 degrees Celsius hotter than normal, the viscosity of typical car engine oil can change by a factor of three.

Fluids such as engine oils become thinner as they heat up, so if it gets too hot, the oil may not be thick enough to properly lubricate and protect engine parts from increased wear and tear.

Additionally, a hot day will cause the air inside your tires to expand and raise the tire pressure, which could increase wear and the risk of skidding.

Airplanes are also not designed to take off at extreme temperatures. As it gets hotter outside, air expands, making it thinner or less dense. This reduction in air density decreases the amount of weight the plane can support during flight, which can cause significant travel delays or flight cancellations.

Battery Degradation

In general, the electronics contained in devices such as cell phones, personal computers, and data centers consist of many kinds of materials that all respond differently to temperature changes. These materials are all located next to one another in tight spaces. So as the temperature increases, the types of materials deform differently, potentially leading to premature wear and failure.

Waste heat from power plants could support 27 percent of residential air-conditioning needs.

• Facebook
• Twitter

Lithium-ion batteries in cars and electronic devices degrade faster at higher operating temperatures. Heat increases the rate of reactions within the battery, including corrosion reactions that deplete the lithium levels, which in turn reduces the battery’s storage capacity. Tests conducted by Recurrent (a company that provides car and battery information for the secondary electric vehicle market) found that electric vehicles can lose about 20 percent of their range when exposed to sustained 32-degree-Celsius (90-degree-Fahrenheit) weather.

Data centers full of computer servers dissipate significant amounts of heat to keep their components cool. On very hot days, fans must work harder to ensure chips do not overheat, and in some cases, powerful fans are not enough to cool the electronics.

When the data centers need a stronger cooling system, they often turn to evaporative cooling. This method sends incoming dry air from the outside through a moist pad. The water from the pad evaporates into the air and absorbs heat, which cools the air. This technique is usually an effective and economical way to keep chips at a reasonable operating temperature. However, evaporative cooling can require a significant amount of water, which is problematic in regions where water is scarce. Water for cooling can add to the already intense resource footprint associated with data centers.

Air conditioners struggle to perform effectively as it gets hotter outside—just when they’re needed the most. On hot days, air conditioner compressors have to work harder to send the heat from homes outside, which in turn disproportionately increases electricity consumption and overall electricity demand. For example, in Texas, every increase of 1 degree Celsius creates a rise of about 4 percent in electricity demand.

Heat leads to a staggering 50 percent increase in electricity demand during the summer in hotter countries, posing serious threats of electricity shortages or blackouts, as well as higher greenhouse gas emissions.

Reusing Heat

Heat waves and warming temperatures around the globe pose significant short- and long-term problems for people and machines alike. Fortunately, there are ways to minimize the damage.

One is to ensure that machines are kept in air-conditioned, well-insulated spaces out of direct sunlight. Another is for consumers to use high-energy devices, such air conditioners and electric vehicle charging stations, during off-peak hours when fewer people are using electricity.

Individual changes at the consumer level will not solve the problem alone, so scientists and engineers are developing ways to use and recycle the vast amounts of heat dissipated from machines. One simple example is using the waste heat from data centers to heat water. Waste heat could also drive other kinds of air-conditioning systems such as absorption chillers, which use heat as energy to support coolers through a series of chemical- and heat-transferring processes.

In both of these examples, the energy needed to heat or cool something comes from heat that is otherwise wasted. Indeed, one of us (Garimella) collaborated on a 2011 study that found that waste heat from power plants could support 27 percent of residential air-conditioning needs, which would result in a dramatic reduction of overall energy consumption and carbon emissions.

Extreme heat can affect every aspect of modern life, and heat waves aren’t going away in the coming years. However, there are opportunities to harness extreme heat and make it work for us.

This article was adapted from a version previously published on The Conversation.