From what I can gather, it uses some kind of rotational mechanism that is able to self-loop and provide excess energy; and it is fairly bulky and fairly well engineered. Somewhere, I saw that the return on investment (pay for unit from savings on electricity bill) is estimated to be between 3 and 5 years.
On their site, they say: "With the POWERJMD system, you will get an independent and almost free ecologic source of electricity. Even the most remote areas will have access to this electricity..."
And on their "goals" page, they say: "This new system has the potential to end the mass production of electric energy as we know it today."