A history of hot dry rock geothermal energy systems

Abstract

This is a short history, so far as it can now be assembled, of early speculations and observations concerning the existence and origin of natural heat in the earth's crust; of some of the many methods proposed to extract and use it; and of recent investigations designed to develop and demonstrate such methods. It is probably only the preface to a much longer history—still to be written—of mankind's beneficial use of this, one of earth's oldest, most plentiful, most widespread and secure energy sources.