In Iceland and a few other countries, geothermal energy delivers a large part of the energy used for heating or cooling, through geothermal heat pumps. You may be surprised to hear that there are hundreds of thousands of buildings in the U.S. that are also hooked up to such systems. Geothermal energy is also applied at larger scales for electricity generation in various countries. Roland Horne, who leads the geothermal institute at Stanford University, gives an overview of existing and future geothermal energy systems. In future podcasts, we’ll take a closer look at the interesting Enhanced Geothermal Systems, aka Hot Dry Rock, which Roland discusses as a potentially important future energy source.