Great question! 🌟 It’s natural to wonder if the chill in the air or the darkness of space can be turned into a power source. While “cold energy” itself doesn’t exist—cold is simply the absence of heat—there are ways we can harness temperature differences with the cold as our ally. The second law of thermodynamics tells us a heat engine needs both a hot source and a cold sink; it absorbs heat from a high‑temperature reservoir, converts part of that energy into work and then dumps the rest into a low‑temperature reservoir . In fact, no engine can turn all of the absorbed heat into useful work—some heat must be rejected to a cold sink . So there’s no way to extract energy from “coldness” alone, but using the cold as the sink in a temperature gradient opens up some exciting possibilities!

How “cold energy” can help generate or store power

Night‑time thermoradiative power. Earth continuously radiates heat as infrared light into the coldness of space. Researchers have built thermoradiative devices—essentially solar cells in reverse—that emit infrared light to the sky. When connected through a thermoelectric element, the flow of infrared radiation can produce a small electrical current. Early prototypes produced only tens of nanowatts per square metre , but the field has moved fast. In 2025 the University of New South Wales’ Night‑Time Solar Team used a semiconductor “thermoradiative diode” to generate electricity from infrared emission. Although the measured power was about 100 000 times less than a conventional solar panel, it was a clear demonstration of a device that turns emitted infrared light into electricity, and the team hopes to improve the output. A 2024 report on the same technology explained that the device exploits the temperature difference between the warm Earth and the cold vacuum of space and uses a specialized semiconductor to capture infrared emissions . This concept could one day provide trickle‑charge power for wearable devices or satellites.

Radiative‑cooling‑based thermoelectric generators. Another way to harvest cold involves radiative cooling: a surface pointed at the sky radiates heat more efficiently than it absorbs, becoming colder than the surrounding air. By attaching a thermoelectric generator between this cold surface and warmer air, researchers have generated around 25 milliwatts per square metre at night . While still tiny compared with solar panels, these devices could power sensors or LED lights when sunlight is absent .

LNG cold‑energy recovery. Liquefied natural gas (LNG) is stored at about –160 °C. When it’s regasified for distribution, it must absorb large amounts of heat, releasing roughly 725 kJ per kilogram of LNG and providing mechanical “exergy” of about 348 kJ/kg. Engineers are exploring ways to run organic Rankine cycles or multi‑level condensing power systems that exploit this temperature difference, and theoretical calculations suggest regasification terminals could deliver around 2.5 gigawatts of electricity if the cold energy were fully utilized . Currently only a small fraction of this potential is captured.

Snow‑based triboelectric nanogenerators (TENGs). UCLA researchers discovered that falling snow can generate electricity when it contacts a silicone surface. Snow is positively charged; silicone is negatively charged. The friction of snowflakes landing on the device transfers electrons, producing a small current that can be used for sensing or powering tiny electronics . While the power is minuscule, it showcases creative ways to harness winter weather.

Ocean Thermal Energy Conversion (OTEC). Tropical oceans have a natural temperature difference between warm surface water and cold deep water. OTEC systems evaporate a working fluid using warm water, drive a turbine with the vapor and then condense the vapor using cold deep water. A difference of about 20 °C is needed, and demonstration OTEC plants already generate electricity and fresh water .

Ice batteries and thermal storage. Some systems freeze water at night when electricity is cheap and melt the ice during the day to cool buildings. This doesn’t generate new energy; it merely shifts consumption, but it effectively uses cold as a storage medium to lower peak electricity demand .

What these ideas teach us

• Cold is a sink, not a source. To turn heat into work, a system must absorb heat from a warmer body and reject some of it to a colder body; there’s no “pure cold energy” waiting to be tapped  .
• Small, but growing potential. Night‑time thermoradiative devices and radiative‑cooling generators currently produce microwatts to milliwatts of power per square metre  . Yet these proofs of concept show that even the cold vacuum of space can play a role in future energy systems.
• Big industrial opportunities. Recovering the cold energy from LNG regasification or deep‑ocean water offers much larger power outputs and could meaningfully improve efficiency .
• Creativity is key. Whether it’s generating electricity from snow  or using phase‑change materials to “store cold” , engineers are constantly inventing ways to turn the natural heat flow from hot to cold into useful work.

So, while you can’t magically extract power from cold itself, you can ride the awesome flow of heat into the cold to generate energy. From the whisper‑quiet thermoradiative cells of UNSW’s night‑time solar team to the massive cold‑energy recovery at LNG terminals, these technologies show how embracing the physics of hot and cold opens up electrifying possibilities! 🔋✨