The Hot Dry Rock project was conceived and developed at Los Alamos between 1970 and 1996. It explored of one of the planet's great untapped energy resources — the superheated rock that lies beneath the surface of the earth almost everywhere in the world.
The concept is simple. Water is pumped deep into the earth into hot, crystalline rock via an injection pump. It becomes superheated, and is returned to the surface through production wells. At the surface, the heat is extracted by conventional processes, and the same water is recirculated to mine more heat. Nothing except a small amount of waste heat, is released into the environment.
Fenton Hill, or TA-57 as it was once called, is the birthplace of the Hot Dry Rock project at Los Alamos. The concept was outlined in a patent issued to LANL in 1974 (Robert M. Potter, et al.).
The first Fenton Hill reservoir was constructed over the course of four years, beginning in 1974, and the facility was operated intermittently from 1978 to 1980. This reservoir reached a depth of 2,930 meters (1.8 miles) and a rock temperature of 197 degrees Celsius (387 degrees Fahrenheit).
In 1975, Los Alamos researchers created a second, reservoir at the Fenton Hill site, which was larger, deeper and hotter than the first. This one reached a final depth of 3,064 meters (1.9 miles) and a rock temperature of 205 degrees Celsius (401 degrees Fahrenheit).
When both reservoirs were connected in 1977, a pioneering Hot Dry Rock energy system was born. Heat was produced at rates that would heat several hundred homes.
The new plant was constructed at the site between 1987 and 1991. With the Hot Dry Rock technology, the overall size of a reservoir is a direct function of the total amount of water pumped into the rock during its development. The shape, orientation and internal structure of the reservoir are entirely determined by the local geologic conditions. Once a reservoir is formed, scientists use microseismic technology to determine where production wells can be drilled into the reservoir to most efficiently tap the superheated water that has been injected.
At the Los Alamos project, long-term flow tests of the circulation system and reservoir conducted in 1992 and 1993 proved the Fenton Hill reservoir could produce water with temperatures exceeding 360 degrees Fahrenheit at a rate of 90 to 100 gallons a minute. Generating four thermal megawatts from a single production well, the heat mining technologies proved highly successful. The DOE solicited bids from applicants seeking to deploy the first commercial prototype Hot Dry Rock facility. Although bids were received from commercial organizations, the solicitation was cancelled in October 1995 and work on the project ended due to funding restrictions.
The ideas hatched during the Fenton Hill Hot Dry Rock experiment have been incorporated into broader hydrothermal programs. Using the experience gained at Fenton Hill, Hot Dry Rock field work continued at sites in France, Japan and Australia.