Utilization of geothermal resources involves cooling of the geothermal fluid by extraction of heat from it. In the case of high-temperature geothermal fluids, precipitation of amorphous silica from solution to form silica scales is the main obstacle for efficient heat extraction. The silica scale formation causes operational problems and may even clog pipelines and injection drill holes. The rate of silica scale formation can be reduced by aging amorphous silica over-saturated waters, which allows the aqueous silica inexcess of saturation to polymerize. Polymeric silica has lesser tendency to precipitate from solution than monomeric silica. Studies of separated water from the Nesjavellir geothermal power station, Iceland, indicate that silica scale formation can be avoided during heat extraction by rapid cooling in ?-capillary heat exchangers?…. Scale formation from the amorphous silica over-saturated water leaving the heat exchanger, which is to be injected, can then be eliminated by aging the water for one to two hours andsubsequently mixing it with condensed steam.

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