A fusion reactor capable of producing limitless clean energy is up and running in Germany.

The Wendelstein W7-X fusion energy device known as a stellarator produced its first batch of hydrogen plasma when it was started earlier this year.

The device essentially works like a star in a jar, harnessing the near infinite power of the sun. Since then scientists have been monitoring the device and recording readings, according to a study in the journal Nature Communications.

Once the technology is viable it could be incorporated into power plants across global cities allowing Earth to run on limitless clean energy indefinitely.

The W7-X is the world's largest stellarator and is currently operated by Max Planck Institute for Plasma Physics in Germany.

However, its development has been an international effort with scientists from the US Department of Energy's Princeton Plasma Physics Laboratory (PPPL) working in collaboration with German officials.

Principal research physicist for the advanced projects division of PPPL, David Gates, issued an email stating the W7-X was running as planned.

"This lays the groundwork for the exciting high-performance plasma operations expected in the near future," Gates said.