Check out the curious cases of "Coral Castle", and the electricity generator built by Tariel Kapanadze. Yes, it is possible to build device to harvest the EM field in your basement, once you figure out how to.
You might ask why those genius at MIT, Stanford, or Princeton have not figure out a way to harvest those energies? Well, as a matter of fact, many scientists and investors have produced working prototype during the past 50 years.
But why have not those knowledge and technologies become available commercially?