The original “Hot Rocks” post focused on mainstream geothermal power, that is, hydrothermal resources, which are considered conventional geothermal resources because they can be developed using existing technologies. The natural formation of a hydrothermal resource typically requires three principal elements: heat, water, and permeability.
I called these the “low hanging fruit” because a large quantity of these have been identified and developed, but there are still many undeveloped hydrothermal resources still out there. Thus, in the first section below, we will focus on existing firms that develop all types of resources. In the following sections we will focus on unconventional geothermal resources.