Section I. Power Engineering

Worldwide Installed Geothermal Electric Capacity

Introduction

PARTI

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One is tempted to talk of the seven ages of geothermal development. From prehistory, natural hot springs have been used by man for bath­ing and cooking, and there is some evidence of piped systems as early as the 14^th century, but the second age — the managed exploitation of heat from the Earth — really began about one hundred years ago with the first piped heating systems in Europe and USA. These were fol­lowed closely by the first steps in commercial power generation (as early as 1904 in Italy), which developed quietly but unspectacularly up to the time of World War II. The third age (ca. 1950-1970) was a period of slow consolidation, with systems developing slowly but — above all - with far greater detailed knowledge of the underground and its ex­ploration emerging, primarily through the oil industry.

The fourth age (1973-1980) was the golden age of geothermal en-^ergy. Spurred by the first oil shock and with a solid foundation of geo­logical knowledge, geothermal power stations began to appear in more than 30 countries. During this period, the growth rate of worldwide installed capacity touched 14% per year, and averaged 8.5%. Similar though less spectacular development occurred also in direct geother­mal heating applications.

Part of the reason for this enthusiastic development was the reliability

⁵¹ geothermal resources. Unlike the other sustainable energy sources

^icn ^ wind or solar, geothermal resources provide firm power, 24 hours

^3er day, 365 days per year. It is not unusual to find geothermal plant

Unit 6. Geothermal Energy

with annual availability factors in excess of 98%, so load factors can be high, the energy supplied by geothermal is some 3.5 times greater thaJ for wind plant. This firmness in itself can be a considerable asset td the utilities.

By the early 1980's, however, fossil fuel supplies had stabilized and prices were falling in real terms. For a technology that required a highj initial capital investment and achieved its returns in terms of saving on fossil fuels, that was bad news. Coupled with the fact that this was a period of high interest rates and that — at least in new areas -J the geological risk (and hence risk to the invested capital) is high, 1985-1 1995 was essentially a period of stagnation for geothermal development]

There is evidence that this situation is now changing, and that wd may be entering into the sixth age of geothermal development — ond in which the environmental and other advantages of geothermal del velopment (by comparison with other energy sources, be they fossil oi renewable) begin to be recognized by a wider public. If this is true, wd can expect this sixth age to merge imperceptibly into a seventh agej early in the next century when new technologies — for whicl the research started in the 1970's — will extend the opportunities for geothermal usage to geographically and technically wider areas.

Not only are the better geothermal zones increasingly well under-l stood, but techniques of exploration and interpretation are becoming increasingly sophisticated — thanks, again, to the hydrocarbons industry which relies on essentially the same range of technologies. Geother-j mal's really strong point, however, is its potential to be environmen-1 tally friendly.

By operating geothermal systems as a closed loop, and reinjecting the contaminants along with the cooled water, the environmental iml pact can be reduced almost to zero.

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