Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Outlook for Geothermal Energy

The resource base (estimated total amount of energy) of geothermal energy is larger than the resource bases of coal, petroleum, natural gas, and uranium (uranium is used in the production of nuclear energy) combined.

The discovery and development of additional geothermal reservoirs depends on several factors. These factors include the depth, heat, and water content of a particular reservoir, as well as the permeability (property of having fractures that allow liquids to flow through) of the rock in the reservoir. The depth and heat of a geothermal reservoir cannot be changed, but the amount of water in the reservoir and the permeability of the rock can be increased. Private and government research projects underway in the United States, in Japan, and in Europe are focused on finding ways to increase the permeability and amount of water in certain types of hot rock (so that water can circulate more freely throughout the rock and become better heated).

Engineers are increasing the amount of water at The Geysers steam field in California by pumping treated wastewater from nearby communities down into it. This additional water increases the amount of steam available to produce electricity and provides nearby communities with an environmentally safe method for disposing of their wastewater.

The permeability of hot rock can be increased by hydraulic fracturing—injecting large volumes of water down into a well at a pressure high enough to break the rock. A second well is drilled nearby into the fractured rock. Cold water is pumped down one well, and once the water has heated, it is pumped up through the second well for use in a geothermal plant.