The hard part is over for Fusion startups: Thank you Groundbreaking experience in 2022we know that controlled nuclear fusion reactions can generate more power than they consume. But now companies must prove their reactors can produce enough electricity to be profitable.
One option is to simply increase the temperature by generating more heat to produce more steam to spin a larger turbine. Another is to harvest electricity directly from the fusion reactions themselves, which promises to be more efficient.
Realty Fusion It announced on June 19 that its experiment had successfully powered a light bulb using electricity harvested directly from WHAM, a demonstration thermofusion device. The Wisconsin-based startup believes it is the first private company to publicly demonstrate such success.
“We can get power from plasma,” Realta Fusion co-founder and CEO Kieran Furlong told TechCrunch. The milestone shows “what’s possible,” he added.
Realta plans to use direct electricity conversion to heat the plasma in its reactor, a process that requires a lot of energy. Furlong estimates that direct conversion is about 90% efficient, meaning it will convert 90% of the potential energy into electricity. For comparison, about the steam turbines in today’s fission reactors 33% efficient. The more energy the company can harvest, the faster it will generate revenue.
Every power plant consumes some of the power it produces just to run, and fusion reactors are no exception. A big challenge facing fusion startups today is building reactors that can produce more energy than they consume. Efficiency gains from direct energy conversion should make it easier to overcome this hurdle.
About 20% of the energy from deuterium-tritium-fueled fusion reactions, which Realta plans to use in commercial reactors, is charged helium nuclei known as alpha particles. The startup has developed a prototype of an electrical converter and attached it to the end of its reactor. There, he was able to collect enough “alpha power” to generate several amperes of electric current at 100 volts, powering several light bulbs.
In a commercial-scale power plant, direct power converters must provide enough power to heat the plasma. “You’re basically able to circulate electricity,” Furlong said.
Ultimately, Furlong estimates that cycling can increase the overall efficiency of a commercial-scale power plant by 20% to 30%. “Spinning the power wheel, if you will, is very rewarding,” he said.
Although it is the first company to demonstrate direct energy conversion, Realta is not the only startup planning to incorporate this technology into its reactor. The Sam Altman-backed startup is key to the direct energy conversion plans for Helion, though it has yet to demonstrate it publicly.
Furlong said that generating electricity directly from the fusion reaction “really helps the economics” of the reactor design.
Realta raised earlier $36 million in Series A 2025 is managed by Future Ventures. Furlong said the company is in the midst of being promoted to a new era.
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