Energy & Sustainability Science
Amazingly simple magnetic heat-switching valve
Bahl-Erikson Valve.png

Here’s an interesting article about a very clever gizmo by two scientists at Denmark’s Risø National Laboratory for Sustainable Energy. It’s being hyped as a totally original invention, but the idea is so conceptually simple that I have a hard time believing it’s entirely new under the sun. Still, though–very cool.

So, quick science review: If you take a magnetic material and heat it up, eventually it stops being magnetic. The temperature at which this happens is called the “Curie temperature” (named for Monsieur, rather than Madame, Curie). The process is completely reversible: Cool the stuff down again, and its magnetism returns. And it turns out, with modern manufacturing, a very wide range of Curie temperatures is possible depending on the specific materials involved.

What Danish scientists Christian Bahl and Dan Eriksen have done is exploit the Curie effect to create a simple, heat-switching mechanical valve: At low temperatures, a magnetic attraction keeps the spring-loaded flapper in one position, but at temperatures above the Curie point, the magnetic attraction is annulled and the spring drives the flapper into the other position. Like other devices commonly called “magnetic valves,” the Bahl-Erikson valve has the advantage that it can be operated without introducing any holes into the valve case, which is handy if you’re working with nasty or delicate materials. Unlike other magnetic valves, however, it does not require any kind of external power to operate, and hence is more reliable as a failsafe.


I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and My work has also appeared in ReadyMade, c't – Magazin für Computertechnik, and The Wall Street Journal.

View more articles by Sean Michael Ragan