A wise man once said… “Anything is possible that is not forbidden by the Second Law of Thermodynamics.” Spoken by a true visionary and researcher. My personal interests are in discerning what is most economic to do TODAY.
Currently, the most nearly economic large scale source of renewable earth energy for the USA may be the use of geopressured hot waters to generate electricity from closed cycle turbines. No new technologies are necessary. What is required is a careful, detailed geologic analysis of the very best areas to establish such a test plant, obtaining a thorough cost estimation for the necessary engineering of well design, physical facility analysis, and the organizing of joint support of industry and governmental cooperation.
It is clearly possible to do TODAY; our task is to see if it can be done as an economic investment today.