Geothermal and other non-traditional energy sources

Lecture index: Geothermal, hydroelectric, tidal and wave energy, geologic components of biofuels, other energy sources.


Yellowstone is one of the better known geyser fields, fueled by the earth's internal energy. This image of an eruption where groundwater has been transformed into steam, a striking demonstration of the amount of energy locally available.

Heat capacity of rocks - Heat capacity is a basic descriptor of the energy content of a given material. For granite it is estimated at .19 calories/gram C° ( 1 kg = 1000 grams, which with a density of 2.5 gm/cc would be a cube of rock roughly 7.36 cm on a side, or 2.89 inches on a side the energy associated with a 1° C temperature change would be 190 calories. Since water is the transporting medium its heat capacity is important also, and is aout 1 calory/gram C°. Remember that water is less dense than rock, but even per unit volume there is a greater calory change associated with a 1° change in T. With this information you could estimate how much energy is a cubic kilometer of rock.

Geothermal gradients are important:

A suite of geothermal maps -

Types of Geothermal energy:

Northern California geothermal power plant at The Geysers. Image source:

What is controlling the pattern here? Source:

Video of hot well out of control in Yellowstone:

USGS Fact Sheet on U.S. geothermal power:


This is a traditional approach. Remember previous discussion on effects of dams on river systems. Mountainous countries such as Norway have abundant hydroelectric resources. Pump storage, where another energy source is used to pump water up to a reservoir which can then be released later to produce electricity when it is needed, is also a possibility.

Glen Canyon Dam - Image source:

Diagram of typical arrangement for hydroelectric power. Image source:

Tidal and wave energy

This is more non-traditional, and a related question is as to why? Below are some considerations

Large sand waves (mega-ripples) caused by tidal currents in and out of San Francisco Bay. Image source:

Geologic components of biofuels

We don't have time to address in detail, but there is a geologic element here in that soil, water and fertilizers are involved in the production of many biofuels.

What is the relative efficiency of solar panels versus photosynthesis and plants?

Other energy sources

We won't discuss in detail in this particular class, but can be quite important, especially locally.

The significance of energy storage:

There is a significant array of energy possibilities in the future, but many have specific site requirements and environmental considerations. Linked energy systems and smart grids are research focal points.