Thanks to Barry Mead for posting the following comment regarding the work of Garett Moddel who claims that energy can be directly harvested from the vacuum using specially designed diodes that employ the Casimir effect.
I sent emails to Garett Moddel and he confirmed that the primary thing holding up the mass production of this device is reliability. The devices work great when they are first produced, but quickly break down and become useless. Until he gets more research money to analyze how and why the cells break down over time there will not be a wide-spread industrial roll out of this technology. I wish a rich backer would take a strong interest in this device so we could get over this reliability hurdle and bring this great technology to a useful marketable product.