Geothermal Energy
Geothermal energy use involves the extrac
tion of heat from the earth either by using naturally occurring working fluids (water or steam) or by injecting working fluids that can absorb the heat. The first commercial use of geothermal energy as a source of electric power was in Italy in 1904. For many decades this natural resource remained untapped except at the Lardarello field in Tuscany. The most significant issue at this initial installation turned out to be erosion and corrosion of steam turbines and condensate systems. Other fields were not as easy to exploit as Lardarello. They involved not steam, but water dominated systems that needed binary systems or flash systems to put the heat into the power cycle. More problems with additional corrosion, erosion and new problems with scaling, excessive noncondensible gases, and plugging occurred at installations around the world. Dry steam plants, single flash plants, double flash plants, multi flash plants, binary plants, and total flow plants have been built or studied.
The history of geothermal energy in the United States dates back to the discovery of The Geysers in 1847 by William Bell Elliott. The field was first used as a resort but an attempt was made in the early 1920s to develop its potential for electric power production. Additional development was not pursued until PG&E’s first unit began operation at The Geysers in 1960. Jon began working on designs for plants at The Geysers in the 1975-1979 time frame, there were over 500MW in operation. The most significant issue at that time was the abatement of hydrogen sulfide emissions from the operating units. The emissions created not only an environmental air quality issue but also an issue with corrosion of electrical components and pumping and piping systems. Jon participated in corrosion coupon tests, and retrofit of existing units with systems to pipe the noncondensible gases to the cooling towers where they could be scrubbed. PG&E studied a number of retrofit systems/technologies for removing hydrogen sulfide but came to the conclusion that future units would have to be designed with surface condensers, rather than direct contact condensers, so that noncondensible gases could be separated and treated with a Stretford system that could remove the hydrogen sulfide. In 1978, eleven generating units were in operation at The Geysers. Four more were under construction. Six units were planned for the future. The first twelve generating units employed direct contact condensing for the main and ejector condensers. Initially units 13-15 were intended as low level direct contact main condensers.
About 70 percent of the engineering work on the Unit 13-15 condensers was completed before it was decided to change to surface condensers. Nowhere was there a surface condenser operating under conditions similar to those at The Geysers. Little was known about thermal performance, it was decided to implement a testing program. Jon designed a test facility to determine waterside fouling resistance, steam side fouling resistance, corrosive and erosive attack on 304 and 316L stainless steel and titanium tubes, and the heat transfer rates in different zones of the condenser. This test facility consisted of four bundles reaching halfway across the length of existing direct contact condenser Unit 7. Waterside fouling was minimal, and built up quickly over 10 to 15 days and then leveled off. When only waterside heat transfer was considered, the dirty tube to clean tube heat transfer ratio was approximately 80 percent. On the steam side, fouling resulted in a 3 to 10 percent drop in heat transfer rates in three of the four bundles. Additional fouling occurred in the steam side of bundle four due to sulfur deposits, probably from the direct water contact. These results were used to design the condensers for the new units. They were documented in a paper written by Jon and LL Forster of Ecolaire Condenser, Inc. in 1978, ASME publication78-JPGC-Pwr-18. Jon was the primary systems engineer for the design of Units 16-21. Not all of these units were built but I issued purchase specifications for Units 16-17 and purchased options for the equipment for the additional plants. He moved from PG&E to Northern California Power Agency to help with the management of their design contractor for their first geothermal unit that was then known as NCPA 2. The design largely duplicated PG&E designs, with insignificant differences.
While at Bechtel in the 1983 timeframe, he was responsible for the conceptual designs, and environmental permitting for the Puna Geothermal Venture project in Hawaii. A summary of this project’s design is included in a paper Jon co-authored with Maurice Richard, entitled Puna geothermal venture project ― Preliminary plant concept. The conceptual designs Jon prepared were for a direct steam plant design. The project was later acquired by Ormat, who applied their proprietary binary cycle technology (Organic Rankine Cycle) to the plant that was actually built. While at Bechtel, Jon assisted on the conceptual work for geothermal plants at the Salton Sea resource, the Canadian Meager Creek Resource and The Department of Water Resources plant at The Geysers.
The Management & Sustainability Blog provides additional information regarding the sustainability of The Geysers resource. The Geysers geothermal steam field peaked at about 1000MW and produces about 850 MW today. It still generates more geothermal power than any other field in the world. Worldwide, in 2000 there was 8661 MW of geothermal power capacity on-line. Calpine acquired all of the generating units from PG&E in 1999, at the time the California utility industry divested its generating assets.
By 2005 there was a modest increase to 8,932 MW of installed power capacity generating 56,951 GWh per year of green power, but there was considerable new development underway. At that time, the International Geothermal Association (IGA) projected that 10,700 MW would be online by 2010, and in 2005 GEA reported that this total could reach 13,500 MW by 2010 – representing a 50% growth in geothermal power since 2000. The number of countries utilizing geothermal energy in the year 2000 was 21; it could increase to 46 by 2010. Additional information can be obtained from the Geothermal Resources Council or the Department of Energy.