This Engine Sucks Energy From Deep Space Without Leaving the Ground

Deep space may provide hidden sources of energy, such as dark matter, for fueling futuristic spacecraft. Before we reach that stage, however, a new experimental engine suggests it’s already possible to tap into deep space as a potential energy source—albeit on a smaller scale that likely won’t support interstellar travel.

Indeed, the purpose of the new engine, described in a Science Advances paper published on November 12, is far less ambitious—but it still marks an important step forward. So far, its primary purpose is to ventilate greenhouses and other buildings. Known as a Stirling engine, the simple device converts differences in heat to mechanical energy.

What’s special about this particular engine, however, is that it uses the depths of space to provide the required chill. The “warm†part is the natural warmth on Earth, whereas the “cold†part is something “very, very cold but also very far away: deep space,†the team, two engineers at the University of California, Davis, explained in a statement.

“It doesn’t actually have to touch space physically; it can just interact radiatively with space,†added study senior author Jeremy Munday in the release.

But how does that even work?

First, consider how Stirling engines work. Unlike many other engines, Stirling engines are surprisingly efficient when “only small temperature differences exist…such as that between a hot cup of coffee and its surroundings,†Munday explained. The key is to ensure that the warm and cold parts of the engine are clearly separated, he added.

Creating the new engine only required one simple modification. Munday and his co-author and graduate student, Tristan Deppe, fabricated a simple panel to serve as a heat-radiating antenna. They then propped a commercially available Stirling engine on the square antenna, which ended up being slightly larger than a laptop.

Simply, the side facing the ground was connected to the soil with an aluminum mount to ensure it absorbed heat from Earth’s surface, according to the paper. The side facing the night sky, on the other hand, was covered in a special type of paint that enabled it to capture infrared radiation from deep space and the Sun.

“The reason that this is unlike any other technology is that a lot of engines work on temperature difference, but usually things that are nearby,†Munday explained in a video introducing the engine. “For us, we have the warm Earth that’s nearby, but the cold of space is very, very far. And the leap we’ve taken is that, well, even though these things are separated far away, we can radiatively couple them.â€

Tiny engine, cosmic power

Over a year, Munday and Deppe set apart a plot of land to test their device outside the lab. They found that after sunset, their setup created about an 18-degree Fahrenheit (10-degree Celsius) temperature difference in the two sides of their square antenna.

This was enough of a heat gradient to generate at least 400 milliwatts of mechanical power per square meter—enough energy to directly power a fan and a small electrical motor, according to the paper.

For the researchers, however, the most promising experiment was one they conducted inside a small greenhouse. For this test, they replaced the engine’s flywheel with a custom fan blade and monitored whether the setup could help ventilate a greenhouse at night.

To their surprise, they found that the fan provided enough airflow to regulate the temperature of the greenhouse. Since this is just the first prototype, continued improvements and scaling up of the technology “could provide an entirely passive method of ensuring healthy breathing air in public places and promoting plant growth by regulating humidity and CO2 levels in greenhouses and growhouses,†the paper noted.

UC Davis has filed a provisional patent for the design, according to the release.