I can't find an official source, but Bob Greenyer of the Martin Fleischman Memorial Project mentioned it in this video presentation. Tom Bearden was a controversial scientist and retired military man (forget what rank) who was adamant that energy can be released from the vacuum:

There is enough energy inside the space in this empty cup to boil all the oceans of the world. This is a fact well known to the scientific community, and was, for example, a favorite quote of Nobel Prize winning physicist Richard Feynman.

Two Nobel prizes were awarded in 1957 to Lee and Yang for substantiating the extraction process for this energy.

— Tom Bearden (referring to "Broken Symmetry")

He believed that research into and access to this "free" energy was being suppressed so as not to disrupt the control mechanism of forced energy scarcity.

While the page is derogatory in tone, prominently labelled pseudo-science, his rationalwiki page actually does a good job of summarizing things he was involved with and stated over the years, for anyone unfamiliar:

https://rationalwiki.org/wiki/Thomas_E._Bearden

He wrote numerous technical books I've never read, but I've watched some lectures he gave while looking to directed energy weapons. You can get a sense of what he was about from this article that considers his work in line with that of Nikola Tesla:

https://files.catbox.moe/18fv9l.pdf