It seems to me that these patents attempt to take advantage of this energy. That says to me, any spaceship utilizing such energy, would have to be quite large. And, you can't compress a vacuum. If you compress a vacuum, it gets smaller, and still has nothing in it. It's simply smaller and thus contains less energy.
re: “However, quantum physics calculates that a one cubic centimeter of vacuum still contains about 0.000000000000000000000000002 kilowatt hours (kW-h) of energy. “
It’s energy (energetic particles) that are just ‘transiting through’ ... look what shows up in a Wilson cloud chamber for instance:
https://www.youtube.com/watch?v=a9tl7O7AWhE
re: “Note that one kW-h of electricity costs you about a dime. “
14 cents per on my last bill. And that does not include the “carrying charge” (delivery charge, for the lines, etc) tacked on to the tune of 2 or 3 cents per KW, plus misc charges, and tax.
Overall, I’m looking at over 19 cents/kWh lately.