From the article, “...the earth has a charge... of 4.5 megawatt hours...”
That’s enough to light ten thousand standard light bulbs for 4.5 hours, or about 0.005 to 0.01 times the output of an average coal, gas or nuclear fired power plant.
In Tesla’s time that probably seemed like a lot of power.
In addition to making one terrible business decision, Tesla lived about 25-50 years too early. Were he able to conduct his experiments, with the knowlege of Einstein, Bohr, Heisenburg and others in hand, the practical results would have been, in my opinion, orders of magnitide greater.
As it is, Tesla’s writings probably contain pointers to advanced phenomena, some of which might be exploitable for useful amounts of cheap energy, but finding and leveraging them is difficult because of Tesla’s pre-standard nomenclature, his secrecy, and his ability to rely on his memory, reducing the quantity of surviving notes.
http://www.spinspace.com/biophysics/haarp.htm
there’s lots of stuff like this on the net...I don’t know what to make of it, but it’s interesting.