Download Current geothermal research at the IGS The Indiana Shallow

Geothermal Resources
Diagram showing the location of the core and mantle relative to the
earth's crust (Source: U.S. Geological Survey).
Thermal energy stored within the earth is known as geothermal energy.
Energy can be transferred into or removed from rocks and sediment, and the
resulting heat flow can be harnessed by engineered systems to produce
electricity or to heat commercial buildings and homes.
Heat from deep within the earth results from a combination of thermal energy
created during the formation of the earth and energy generated by the decay
of radioactive elements (for example, uranium and thorium) in the earth's core
and mantle (fig. 1). The thickness of continental crust in an area determines
how readily deep-sourced heat flow can be used for power generation and
direct use heating systems. In Indiana and much of the North American
interior, relatively thick continental crust inhibits the economic feasibility of
exploiting these high-temperature resources because of drilling costs and
inefficiencies associated with circulating fluids to extreme depths (greater than
10,000 feet).
An alternative approach is to use stored thermal energy from the sun. The
earth acts as a thermal battery and at relatively shallow depths (less than 500
feet) earth temperatures are generally stable and reflect the average annual
air temperature. Geothermal heat pumps can extract thermal energy and
transfer heat into buildings during winter months and inject excess heat back
into the ground during summer months. By exchanging heat with the earth,
properly designed systems are more efficient than conventional heating and
cooling systems. A demonstration of this technology can be seen in the
following video provided by the U.S. Department of Energy:
Current geothermal research at the IGS
At the IGS, we are studying deep geothermal conditions to evaluate basin
heat flow and shallow geothermal conditions to improve efficiencies of
geothermal ground-source heat pumps (GSHPs) in Indiana.
The Indiana Shallow Geothermal Monitoring
Network
Although software exists for GSHP installers to calculate optimal lengths and
configurations of ground-coupling geothermal systems, input parameters such
as soil thermal properties and earth temperatures must first be determined for
these applications to be optimal. The fundamental control on heat transfer for
a ground-coupled heat pump system is the thermal conductivity of the earth
materials within which the system is installed. Determining thermal properties
for typical unconsolidated sediments in the upper 6 feet of the ground will
support the design of more efficient systems by allowing GSHP installers to
tailor the configurations of their in-ground systems to specific geological
conditions and to account for seasonal fluctuations. For more information,
see: Indiana Shallow Geothermal Monitoring Network.
National Geothermal Data System
The Indiana Geological Survey is currently participating in a nationwide effort
to build a National Geothermal Data System (NGDS). This project will
facilitate the search for sources of renewable geothermal energy.
State-specific geothermal data are being compiled into an integrated publically
available (and searchable) national data system. For more information, see:
http://geothermaldatasystem.org/. Geologists at the IGS are also using these
data to perform regional-scale hydrogeologic studies and evaluate carbon
sequestration potential in the Illinois Basin. Several geothermal resource data
sets compiled for use with geographic information software can be
downloaded at the following IndianaMap Web site:
http://maps.indiana.edu/layerGallery.html.