INTERNATIONAL GEOTHERMAL DAYS OREGON 1999

Transcription

1 VOL. 20, NO. 4 DECEMBER 1999 ISSN INTERNATIONAL GEOTHERMAL DAYS OREGON 1999

2 Vol. 20, No. 4 December 1999 GEO-HEAT CENTER QUARTERLY BULLETIN ISSN A Quarterly Progress and Development Report on the Direct Utilization of Geothermal Resources CONTENTS International Geothermal Days John W. Lund Small Power Plants: Recent Developments in Geothermal Power Generation in New Zealand Michael Dunstall Geothermal Heat Pumps Four Plus Decades of Experience R. Gordon Bloomquist Curing Blocks and Drying Fruit in Guatemala Luis Merida Italian Geothermal District Heating Systems Roberto Carella Stories from a Heated Earth Page PUBLISHED BY GEO-HEAT CENTER Oregon Institute of Technology 3201 Campus Drive Klamath Falls, OR Phone: geoheat@oit.edu All articles for the Bulletin are solicited. If you wish to contribute a paper, please contact the editor at the above address. EDITOR John W. Lund Typesetting/Layout - Donna Gibson Graphics - Tonya Toni Boyd WEBSITE FUNDING The Bulletin is provided compliments of the Geo-Heat Center. This material was prepared with the support of the U.S. Department of Energy (DOE Grant No. FG01-99-EE35098). However, any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the view of USDOE. Cover: Conference field trips: (top) Wineagle 600 kw (net) binary power plant, Litchfield, CA and (bottom) Group photo at Medicine Lake (Glass Mtn.), CA. SUBSCRIPTIONS The Bulletin is mailed free of charge. Please send your name and address to the Geo-Heat Center for addition to the mailing list. If you wish to change your Bulletin Subscription, please complete the form below and return it to the Center. Name Address Zip Country

3 INTERNATIONAL GEOTHERMAL DAYS OREGON 1999 John W. Lund Geo-Heat Center For the first time, the International Summer School on Direct Application of Geothermal Energy (ISS), International Geothermal Days - Oregon 1999", was held outside of Europe. A total of 114 participants from 30 countries attended the conference on the Oregon Institute of Technology campus from October 9 to 16, 1999, including a large delegation of city mayors and provincial governors from Turkey. The conference, hosted by the Geo-Heat Center, was supported by funds from the U.S. Department of Energy and donations from Fuji Electric Corporation of America, Calpine Corporation, Ormat International, Inc. and the Shaw Historical Library Foundation. The Conference was composed of the following sessions: International Workshop on Small-Scale Power Projects International Workshop on Geothermal Heat Pumps International Course on Direct Utilization of Geothermal Energy Evening Seminar on Computer Software for Geothermal Heat Pumps Evening Seminar on HEATMAP Computer Software Utilization Four field trips were also undertaken to nearby geothermal projects and geologic sites: Crater Lake National Park (for early arrivals) Medicine Lake, CA to visit the potential sites of two 50-MWe geothermal power plants (Fourmile Hill by Calpine Corporation and Telephone Flats by CalEnergy Company geothermal projects). This field trip also included a visit to Lava Beds National Monument. Direct-use projects in the Klamath Basin, including the Oregon Institute of Technology mini-heating district, the Klamath Falls district heating system, a local residential heating system using a downhole heat exchanger, and a combined greenhouse and aquaculture heating project. A final field trip from Klamath Falls to Reno, NV visiting along the way two potential geothermal projects at Canby, CA, and a hybrid plant (wood waste and geothermal) and binary geothermal plant (Wineagle) near Litchfield, CA. This conference was also the 10 th anniversary of the International Summer School founded by Dr. Kiril Popovski of St. Clement Ohridski University, Bitola, Macedonia, and the 25 th anniversary of the International Geothermal Conference on Multipurpose Use of Geothermal Energy held on the Oregon Institute of Technology campus - and was the start of the then Geo-Heat Utilization Center. The founders of the Center, Gene Culver, Paul Lienau and John Lund all made presentations at both conferences.. The first official function of the conference was the Medicine Lake field trip lead by David McClain, a consultant from Portland, OR. His detailed knowledge of the environmental work and local geologic setting for the two power project provided interesting discussion for all, especially during our stop for lunch at Medicine Lake under beautiful fall weather. Subjects from the impact of noise from the power plants and the visual impact of the power line, to addressing local Indian and summer resident s concerns were presented and explained how they would be mitigated. We ended the day by visiting several geologic structures in Lava Beds National Monument, including a chance to cool off in Skull Cave - a large collapsed lava tube. A reception was held that evening on the OIT campus, hosted by the Shaw Historical Library Foundation. The conference was officially opened on Monday by welcome talks from the President of Oregon Institute of Technology, Dr. Martha Anne Dow, the Mayor of the City of Klamath Falls, Todd Kellstom, and the chairman of the Klamath County Commissioners, Steve West. Dr. Kiril Popovski, representing the International Summer School and Dr. John W. Lund, representing the Geo-Heat Center, also welcomed the attendees and presented some of the background history on the conference. The one and a half day session on Small-Scale Electric Power Generation was introduced with an excellent summary paper by Ron DiPippo (see Vol. 20, No. 2). His paper was followed by the topic of slim hole drilling presented by Jim Combs and John Pritchett. Liz Battocletti presented material on financing, and then Gordon Bloomquist and David McClain discussed legal, institutional and environmental issues. That evening, a dinner, complete with local Native American, Wocus Bay Singers, dancers and drummers, was hosted by Calpine Corporation. The audience participated in one of the ring dances and drumming - to the delight of all. For many, this was their first exposure to Indian culture and traditions. The next day, power plant case histories were presented by Dan Schochet of Ormat, Ken Nichols of Barber- Nichols, Richard Campbell on the Mammoth, CA project developed by Ben Holt Company, Gerardo Hiriart on CFE projects in Mexico, Yuri Esaki on projects in Japan, Mike 1

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6 Dunstall on New Zealand experience (inculed in this issue) and Josefino Adajar on projects in the Philippines. This was followed by a half-day session on geothermal heat pumps. Kevin Rafferty of the Geo-Heat Center started off by presenting US experiences with commercial applications. This was followed by an overview paper of European experience present by Ladsi Rybach of Switzerland, Burkhard Sanner of Germany and Goran Hellstrom of Sweden. Gordon Bloomquist presented material on case studies of commercial/institutional installations in the U.S. (included in this issue). Computer applications were then presented by Gary Phetteplace of the U.S. and Burkhard Sanner of Germany, followed by an evening workshop on computer applications. There was lively discussion during all of these presentations, as this was the first time the subject had been presented at an International Summer School conference. To break up the indoor presentations, a local field trip of direct-use sites in the Klamath Basin was held at midweek. In additional to John Lund, Toni Boyd and Kevin Rafferty of the Geo-Heat Center, the field trip was enhanced by commentary from Gene Culver, retired from the Geo-Heat Center, Brian Brown, a local consulting mechanical engineer, Bruce Masl and Ray Gibson (retired) from the OIT Physical Plant, and Manny Molina of the city of Klamath Falls. The participants were divided into two groups and visited the OIT wells and heating systems, an individual home downhole heat exchanger system (Dick and Doris Pope), the city of Klamath Falls district heating system, including the newly completed Klamath County Courthouse, and downtown sidewalk snow melt system. Lunch was arranged by the city at a local park, and then we drove south of town to visit the Liskey Ranch where geothermal water is used to heat a greenhouse complex (Vicky Azcuenaga) and topical fish rasing ponds (Ron Barnes - who can be reached at <gotfish@aol.com>). That evening a dinner was hosted at the local country club by Fuji Electric Company and Ormat International. Our English/Spanish interpreter, Paul (Pablo) Lewis, provided the entertainment by singing Mexican songs of his own composition. The last two days of the formal part of the conference were presentations on the direct utilization of geothermal energy. The first set of presentations were on general aspects of direct utilizations, including an overview of the technology by John Lund, downhole heat exchangers experience by Gene Culver, district heating design by Orhan Mertoglu, greenhouse design by Kiril Popovski, aquaculture pond design and refrigeration by Kevin Rafferty, industrial applications by Paul Lienau, timber drying by John Lund, pavement snow melting design by Brian Brown, an innovative concrete block and fruit drying facility in Guatemala by Luis Merida (included in this issue), and an introduction to HEATMAP district heating design program by Gordon Bloomquist. This was followed by a computer workshop on the use of HEATMAP presented by Bob O Brien of the Washington State University Energy Program. That evening, the Mayor of the City of Klamath Falls, Todd Kellstrom, hosted a reception at the Ross Ragland Community Theater in downtown area - a building that is also geothermally heated. 4 These general presentations were then followed by specific examples of district heating design in Iceland (E. Gunnlaugsson), USA (T. Boyd and B. Brown), France (C. Boissavy), Romania (M. Rosca and C. Bendea), Slovakia (O. Vana and O. Halas), Hungary (M. Arpasi), Lithuania (V. Rasteniene and F. Zinevicius), Italy (R. Carella included in this issue), China (Zhu Jialing) and Japan (Y. Yusa). General and greenhouse system potential and design were presented by representatives from Albania (A. Frasheri), France (C. Boissavy), Argentina (A. Pesce), Bulgaria (S. Fournadzieva and K. Bojadzieva), Macedonia (S. Popovska), Portugal (A. M. Rodrigues), India (D. Chandrasekharam), USA (B. Gordon) and Italy (C. Campiotti). The final evening, a western style dinner complete with cowboy hats, bandanas and sheriff badges, was hosted by OIT. Entertainment was provided by Belles and Beaus line dancers, again with audience participation. Certificates were presented to participants and lecturers. The final field trip was from Klamath Falls to Reno, set to arrive in time for the start of the Geothermal Resources Council Annual meeting. The all-day bus tour with nine cars following, toured a potential district heating project in Canby, CA (Dale Merrick) and Kelly Hot Springs flowing at 400 gpm (25 L/s) at 187 o F (86 o C) (Sal Pantano). A lunch stop was held in Alturas, CA where several schools are heated with geothermal energy. The park for lunch was reserved by the Alturas Chamber of Commerce. After lunch and a 1.5-hour drive, we toured the Operation Energy Corporation/Honey Lake Power Company biomass/hybrid power plant near Litchfield/Wendel, CA. This plant built in 1989, uses geothermal water for the condensate preheater (1.5 MW) and then wood chip waste as the main fuel to produce 35.5 MWe of power. The massive plant was down for maintenance, but we were still impressed with its unique type of operation. Afterwards we toured the Wineagle Developers binary power plant which uses 1,000 gpm (63 L/s) of 230 o F (110 o C) geothermal water to produce a net output of 600 kwe. The plant was design by Barber-Nichols Engineering Co. From there, the nine trailing cars descended on the lone gas station at Litchfield, and almost overwhelmed the facility. All finally arrived in Reno safely and scattered to the various motels. Some participants left the next day, and other stayed for the GRC meeting. Two volumes of the proceeding are available: Small-Scale Electric Power Generation & Geothermal Heat Pumps - 19 papers of 192 pages. Direct Utilization of Geothermal Energy - 36 papers of 226 pages. Each can be ordered from the Geo-Heat Center for $15.00 or $25.00 for both plus postage. Copies of the three field trip guides are also available free of charge. The four papers in this issue of the Quarterly Bulletin, were presented at the conference, but arrived too late to be included in the Proceedings. Many thanks to all the participants - a few photographs are included for your enjoyment.

7 SMALL POWER PLANTS: RECENT DEVELOPMENTS IN GEOTHERMAL POWER GENERATION IN NEW ZEALAND Michael Dunstall Geothermal Institute, The University of Auckland, Private Bag 92019, Auckland, New Zealand WHAT IS SMALL SCALE? None of the recent New Zealand power plant developments truly qualify as small on a field wide basis. The size of the individual units in these projects is however, quite small. Over the last four years fourteen geothermal generation units have been installed in New Zealand, eleven of these having a capacity of less than 5MWe. Prior to the recent period of activity three small units were installed at Kawerau; each of these units were also less than 5MWe in output. All the recent construction has been undertaken by individuals, local power companies, or by trustees of local Maori tribes, often as joint venture projects. New Zealand's first two geothermal power stations, Wairakei and Ohaaki, were both large. They were built using NZ Government money in 1958 and 1989 respectively. RECENT NEW ZEALAND DEVELOPMENTS Four new geothermal stations have been erected in New Zealand since One plant (Poihipi) uses conventional steam turbine technology, while the three smaller plants (Rotokawa, Ngawha and Mokai) use binary cycle technology. Two older binary cycle plants also operate at Kawerau. Poihipi: Mercury-Geothermal (July 1996) This 55-MW power station was imported to New Zealand as a second hand unit, having been built for the Geysers geothermal field but never run. The complete power plant was reconfigured to generate at 50Hz (60Hz is used in the USA) and has been erected in the western part of the Wairakei geothermal field, tapping a shallow steam zone. Electricity output is restricted by a resource consent that does not allow the plant enough steam to run fully loaded 24 hours per day. To get the maximum possible revenue it is run at high load 14 hours per day, when electricity tariffs are high, and runs at very low output (~3MW) during the night. It is New Zealand s only non-base load geothermal station. Rotokawa: Transalta (September 1997) The Rotokawa geothermal field is located in the Taupo Volcanic Zone (TVZ) and contains wells with some of the hottest downhole temperatures (>320EC) recorded in New Zealand. Wellhead pressures at Rotokawa are also very high, with some wells showing over 70 bar when shut in. The field is bisected by the Waikato River and covers a wide area, estimated at somewhere between 17 and 30 km 2. The field is thought to be one of the largest in New Zealand, containing an estimated 2700PJ of useable heat (Hunt, 1998). Fracture permeability is the main means of fluid movement at Rotokawa as the andesitic reservoir rocks are relatively impermeable. The wells are generally good producers providing high temperature fluids with high enthalpy. Because of the high enthalpy, the power station installed at Rotokawa has an output double that of the Ngawha plant, while processing about the same mass flow. Silica content at Rotokawa is high so the fluid separation pressure is maintained at barg to prevent scaling problems. The non-condensable gas contains a considerable quantity of H 2 S, but due to the relatively small size of the development this does not produce an odour nuisance when the gas is vented to atmosphere. The Rotokawa power station (Fig.1) utilises a 16MW steam turbine which exhausts at just over 1 barg to two aircooled ORMAT binary cycle units. The hot brine from the separator is used in a third ORMAT binary cycle unit. Total output of the plant is 24MWe. The plant is supplied by two production wells, about 1000m deep. After two-phase transmission the steam and water are separated at the power plant, passing separately through the units, and are then recombined before reinjection. Three shallow reinjection wells are used (~400m); a relatively impermeable layer exists between the production and reinjection horizons preventing cold fluid returns. Figure 1. Rotokawa Power Station (24 MW). Several of the wells in use at Rotokawa were drilled by the New Zealand Government during the early eighties and have since been sold to the project. Some new wells have also been drilled. Three other Government funded wells remain unused at Rotokawa, because they are unsuitable for produc- 5

8 ton or reinjection, or because they are too far away from the plant to be viable. Rotokawa field also has three abandoned exploration wells that were drilled by the Crown. These wells were cemented after corrosion of the casing by acid fluids at shallow level. This region of acid fluids has now been delineated and covers only a small area of the field, near steam heated surface features. This type of corrosion is not expected to cause problems in the remaining wells. Ngawha: Top Energy (July 1998) The Ngawha geothermal field is the only high temperature geothermal field in Northland New Zealand. Compared to high temperature fields in the Taupo Volcanic Zone (TVZ) the Ngawha field has a number of differences. Reservoir pressures are somewhat higher due to a confining layer near the surface. The reservoir is also mainly greywacke rocks, which are often found as low permeability basement rocks in the TVZ fields. At Ngawha these rocks are extensively fractured, providing very good permeability in wells which intersect fractures and very poor permeability in others. High boron, high non condensable gas and high mercury levels characterize the fluids at Ngawha, which are also at relatively low temperature (230EC) and enthalpy (~ 970kJ/kg). The low enthalpy means that while the wells produce high mass flow rates the electrical potential per well is lower than is typical in the TVZ. Calcite scaling was observed during early production tests at Ngawha and is expected to be an ongoing concern during development of this resource. The resource area is approximately 15km 2, and the stored heat has been quoted as 1400PJ (similar in size to Ohaaki) (Hunt, 1998). The current development at Ngawha consists of two air-cooled ORMAT binary cycle units, with a combined output of just under 10 Mwe (Fig. 2). The units are supplied with steam and hot water from two production wells, about 1000m deep. Steam and water are separated at the wellpad before transmission because of the steep terrain that must be traversed. Separation pressure floats between 10 and 17 barg. The steam and hot brine are passed through separate heat exchangers in the power plant. Flows are then recombined before being pumped to disposal in two reinjection wells with depths of about 1300m. Noncondensable gases are vented to the atmosphere. All the wells in use at Ngawha were drilled by the New Zealand Government during the early 1980s. A further ten unused wells drilled to depths up to 2300m and one abandoned well exist at Ngawha. This early drilling program reduced the economic risk of development considerably. However, the existing wells were drilled for exploration and are quite widely spaced. This meant that approximately 7000 m of steam-field piping was needed to connect the system (Fig.3). Figure 3. Long pipelines were needed to connect the widely spaced wells at Ngawha. One of the wells used for fluid production at Ngawha was completed in an unusual manner. Up until its recent removal, NG9 (Fig.4) was New Zealand s only dual- Figure 2. Ngawha Power Station (10 MW). 6

9 completion well. The upper feed zone discharged through the annulus between the 8 5 / 8 production casing and an inner 5 1 / 2 casing. The lower feed discharged through the 5 1 / 2 casing. Although the two zones could feed to the surface separately they were combined before phase separation when the Ngawha development commenced. The dual-completion has since been removed, increasing the well output. Figure 4. NG9 wellpad - a dual completion. Mokai: Tuaropaki Trust (October 1999) The Mokai resource has many similarities to the Rotokawa resource. The power development is also similar. Mokai was confirmed by drilling in the 1980 s after geophysical measurements suggested the presence of a large geothermal reservoir. The wells drilled at that time were some of New Zealand s largest producers, with MK5 having sufficient output for about 25MW of electric power. The resource area is estimated to be 12-16km 2, containing stored heat of 2700PJ (the same figure attributed to Rotokawa) (Hunt, 1998). The wells are high temperature (over 300EC), have high wellhead pressure (>50bar), and produce high silica fluids. Gas levels at Mokai are however quite low compared to other fields in the Taupo Volcanic Zone. The current development at Mokai uses four production wells with depths between 1000 and 1500m. Three shallower reinjection wells (<800m), drilled in the outflow tongue of the reservoir, are used for fluid disposal. Two further wells were drilled during the exploration of Mokai in the 1980s, but these are not used in the current project. The hybrid power plant at Mokai (Figs. 5 and 6) is similar in concept to the Rotokawa plant. Steam separated at 21 barg is used in a 29 MW steam turbine that exhausts at about 1 barg to four ORMAT binary plants, where the steam is condensed. A further two ORMAT binary plants make use of hot brine from the separators, which are located on the power plant site. The brine and condensate mix before being pumped to the reinjection wells. The ORMAT units are aircooled and, as with other developments in New Zealand, the non-condensable gas is vented to atmosphere. Figure 6. Overview of Mokai Power Plant - 50 MW. 7

10 Figure 5. Mokai Power Plant (50 MW). Kawerau: BOP Electricity (1989, 19991) The Kawerau geothermal field is the only geothermal field still operated on a commercial basis by the New Zealand Government, with day-to-day operation by Century Drilling and Energy Services Ltd. The primary use of steam from the Kawerau field is for direct use at the Tasman Pulp and Paper Company mill. Geothermal steam is used in clean steam heat exchangers to provide mill process steam. It is also used for timber drying in high temperature kilns in the nearby Tasman Lumber plant and a small quantity is used to heat a greenhouse located in the steamfield (see Vol. 19, No. 3, 1998). An 8 MWe atmospheric back-pressure turbine at the mill is used for load balancing to smooth out the mill steam demand, allowing well output to be changed gradually (Hotson, 1994). Development of the Kawerau field began in the early 1950 s with steam production for use in the mill predating electricity generation at Wairakei. The resource area is estimated to be 19-35km 2, containing stored heat of 1300PJ (about the same figure attributed to Wairakei). The field poses no special difficulties for utilisation, having a moderately high temperature of about 270EC. Some very productive wells have been drilled at Kawerau and these have generally had a long life. Today there are five production wells operating, with an average depth of about 1000m. Some wells tend to produce calcite scale but this is controlled by injection of inhibitor chemicals or cleaned out in periodic work overs (Bloomer, 1998). Non-condensable gas levels are moderate, and variable venting of these gases provides a convenient method of control in the clean steam heat exchangers. Up until the late 1980s, water from the separator plants was flashed to atmospheric pressure and dumped in the Tarawera River. Steam condensate from the mill heat exchangers was also dumped to the river. In 1989, two 1.3MWe ORMAT units were installed to make use of the separated water supply from separator plant 21 on the east side of the river, and reinjection of some waste brine was started. This first ORMAT plant was named TOI (Tarawera ORMAT Installation) (Fig 7) and was capable of cooling the brine from 180EC to 108EC. After some initial teething problems these units proved reliable and the decision was made to install another unit (TG2) on the western side of the river, utilizing fluid from separation plant 35. TG2 is larger than TO1, with 3.5 MWe output from a single unit. This plant is also a newer design than the TO1 units and includes a recuperator between the turbine and the condenser. The outlet temperature of brine from TG2 is 95 o C. All three plants use air-cooled condensers and run unattended. Figure 7. Tarawera ORMAT Installation 2.6 MW (Kawerau field - east side of Tarawera River). 8

11 Three reinjection wells are currently in use at Kawerau, accepting about 25% of the water produced in the field; the remainder flows to the river. All the condensate from the mill heat exchangers is now collected and, after stripping the non-condensable gases, is used as a source of clean feed water for all of the mills boilers. The field has 23 unused wells of varying age and 12 abandoned wells. LOW EXPLORATION RISK FOR DEVELOPERS The four recent power developments in New Zealand, and the older Tarawera ORMAT plants, have all presented a relatively low exploration risk for the developers. In three cases, Ngawha, Rotokawa and Mokai, a number of productive wells already existed and the New Zealand Government had carried out a substantial amount of scientific work from the early 1960s until the 1980s. Most of the scientific information about these fields was in the public domain and available free to the developers. The wells themselves were also sold to the developers at a reduced cost. While this sounds simple enough the well ownership issue was very complex and involved considerable legal wrangling. In the case of the Poihipi development the plant was built in the western area of the Wairakei steam field so quite a lot was already known about this resource. At Kawerau, the hot water resource used in the ORMAT power plants had been pouring into the Tarawera River for 35 years. Despite the scientific and drilling work which had already been done some developers chose to reduce exploration risk even further by using No steam - No reward contracts when drilling new wells. New Zealand has quickly shifted from a position where one Government owned company controlled power generation and distribution, to a competitive system for generation and retailing of electrical energy. Some background to these regulatory changes is needed to understand the circumstances that led to the recent activity in geothermal power plant construction. NEW ZEALAND ELECTRICITY SYSTEM New Zealand s electricity network is highly interconnected through a national grid of high voltage power lines and an undersea DC cable linking the North and South Islands. However, the grid has a limited capacity to carry power north, where most of the demand exists. Over 50% of New Zealand's population live north of an East-West line through Lake Taupo (Fig. 9). WHY THE RECENT SURGE IN DEVELOPMENT? There have been many regulatory changes in the past ten years in New Zealand which have had an impact on geothermal development (Fig 8). Changes in resource management and electricity industry regulations have had the main impact. Figure 9. Location of major power stations and population (load center) in New Zealand). Figure 8. Geothermal exploration and field development Through these rapid changes a number of new interested parties have emerged. The system has a high reliance on hydro stations (which generate 60-70% of the power), many of which lie on the South Island, well away from load centres. Traditionally, thermal generation has been used to meet peak loads and this has been at high marginal cost. This situation is now changing somewhat with the proliferation of high efficiency gas turbine combine cycle and co-generation plants. 9

12 Figure 10. High temperature geothermal fields. New Zealand s high temperature geothermal fields are in a strategically good location, near load centres on the North Island (Fig 10). Ngawha is the exception to this, lying in Northland, but is relatively strategic to that area, which has no major power stations following the closure of the Marsden Point oil fired stations. NEW ZEALAND ELECTRICITY MARKET New Zealand s electricity market has also undergone a period of rapid change while continuing to show about 3% annual demand growth. Electricity is now sold 1/2 hourly on a wholesale market, where competitive retail and generation sectors bid for the supply and purchase of electricity. In theory, an electricity retailer can now make electricity sales in any part of the country, but in practice retailers have mainly stuck with their traditional local customers. Distribution of electricity on a national level is handled by TransPower, the grid operator, and at a local level by smaller distribution (lines) companies. RESOURCE MANAGEMENT AND ELECTRICITY REFORM Up until 1988, the Geothermal Energy Act 1953 was the main legislation controlling the development of geothermal resources for electricity. It was set up to allow development at Wairakei and gave the Minister of Energy, through the Ministry of Works and the New Zealand Electricity Department, quite sweeping powers. The Minister may authorise search for geothermal energy and give power to enter land. The Public Works Act also gave the Government power to take land needed for geothermal development, although this was never used. The Geothermal Energy Act was amended in 1988 when the Ministries were converted into State Owned Enterprises (Government owned companies). The regulations covering safe use of geothermal passed to the Health and Safety in Employment Act 1992 and allocation of geothermal resources for utilisation fell under the newly created Resource Management Act 1991 (RMA). The purpose of the RMA was 10

13 to promote the sustainable management of natural and physical resources and required resource managers to have regard to efficient use and development of natural and physical resources and to have regard to any finite characteristics of natural and physical resources (Bloomer, 1994). Mineral resources were specifically excluded from the RMA but geothermal was included. Geothermal resources now have to be managed in a sustainable and efficient way. This had never been a requirement in New Zealand before. Sustainable Management is defined as...managing the (use of) resources in a way, or at a rate, which enables social, economic, and cultural well being... while; meeting the reasonably foreseeable needs of future generations; safeguarding the life-supporting capacity of air, water, soil and ecosystems; and avoiding, remedying or mitigating any adverse effects of activities on the environment. Electricity Industry reform has also had a major impact. In 1996 part of the Electricity Corporation of New Zealand (ECNZ) was split off to form a competitor in the generation market. The new company was called Contact Energy. Rules were also put in place to ensure that the dominant players could not shut independent power producers out of the market. This year the Electricity Reforms Act (April 1999) has had a major impact. The remaining ECNZ assets were split into three competing state owned enterprises (Meridian Energy, Genesis Power, Mighty River Power) and Contact Energy was sold. Local power companies were also forced to split into energy companies (retailers) or distribution companies (lines companies). It is no longer possible to own a substantial share of a generating company and a lines company in New Zealand. The national grid operator (TransPower) is at present untouched and still owned by the New Zealand Government. PREVIOUS INVESTMENT BY THE GOVERNMENT The historical investment in geothermal exploration made by the New Zealand Government during the period is now coming to fruition. Excluding those wells drilled at Wairakei and Ohaaki, 124 investigation wells were drilled over this time. In many fields these wells proved the resource. The scientific effort that was put into these fields was also substantial and almost all of the information is in the public domain. Of the 124 wells drilled between 1950 and remain, and the Crown has an ongoing commitment to maintenance of these wells and abandonment where necessary (Koorey, 1999). A few of the exploration wells were drilled into fields which are now classified as protected for their scientific, cultural, heritage or tourism values (Luketina, 1999). However, most of the effort was placed in fields recognised early on as good candidates for development (see Table 1). The existence of these wells has been a boon to developers. Several of the highest producing wells ever drilled in New Zealand have since been sold to developers at a low price. Wells drilled by the Crown have been sold to developers at Mokai, Ngawha, Tikitere, Tauhara, and Rotokawa. WHERE TO FROM HERE? Geothermal energy in New Zealand continues to face stiff competition from natural gas, which has been chosen as the fuel source in a number of new power plants. The low price of natural gas in New Zealand is expected to continue for some years to come, as it results from historical take or pay contracts inherited by Contact Energy during its formation. The impact of targeted CO 2 reductions, which New Zealand has committed to in the international Kyoto protocol agreement, may yet have an effect on the price of competing fuels. Although all New Zealand geothermal stations emit CO 2 they do so at a much lower rate than natural gas stations, which are their main competition. This issue remains open, since the mechanism by which New Zealand will set out to achieve CO 2 emission reductions has not yet been decided. Although the New Zealand Government no longer provides money for new geothermal exploration programs the benefits of the earlier work will continue to flow for some time. Several as yet undeveloped fields have proven potential. As electricity demand rises new geothermal power plants will be built in New Zealand. In the short-to-medium term, the most likely scenario is small incremental developments and expansions in the recently developed fields. Efficiency improvements planned for long established fields like Wairakei are also expected to result in some new construction. ACKNOWLEDGEMENT Thanks to Kevin Brown, Andy Cass, K.C. Lee and Arnold Watson for providing information and photographs of the power plants described. Table 1. Government funded wells drilled into systems now classified as Development Systems. Field Production Injection Shut-in Abandoned Horohoro Kawerau Mokai Ngawha Rotokawa Tauhara Source: Koorey (1999) 11

14 REFERENCES Bloomer, A., Rotokawa Geothermal Power Station: Resource and RMA issues. Proc. 16 th New Zealand Geothermal Workshop, pp Bloomer, A., Kawerau Geothermal Development: A case study. Geo Heat Center Quarterly Bulletin, Vol.19 No.3, pp Hotson, G. W., The long term use of geothermal resources at the Tasman Pulp and Paper Co. Ltd mill, Kawerau, New Zealand. Proc. 16 th New Zealand Geothermal Workshop, pp Hunt, T. M., Geothermal resources in New Zealand. An overview. Geo Heat Center Quarterly Bulletin, Vol.19 No.3, pp Koorey, K., Investigation drilling: History and Issues. Proc. NZGA Seminar - Geothermal Energy: Adding Value, June 1999, Taupo New Zealand. 4pp. Luketina, K., The Waikato Regional Plan: How it affects small-scale users of geothermal resources.. Proc. NZGA Seminar - Geothermal Energy: Adding Value, June 1999, Taupo New Zealand. 4pp. 12

15 GEOTHERMAL HEAT PUMPS FOUR PLUS DECADES OF EXPERIENCE R. Gordon Bloomquist, Ph.D. Washington State University Energy Program P.O. Box Olympia, WA INTRODUCTION Despite the fact that commercial geothermal heat pump (often called ground-source heat pump or geoexchange) systems first gained moderate popularity as early as the late 1940s and early 1950s, widespread acceptance of the technology by architectural and engineering firms, mechanical design teams, developers, and building owner/operators has been extremely slow. And although there was a momentary increase in the installation of geothermal heat pump systems following the oil crises of the 1970s, it has not been until the past few years that interest in commercial geothermal heat pump systems has once again been on the rise. However, uncertainty over first cost, life cycle cost, operation and maintenance questions, and system long-term reliability have continued to plague the industry and prevent greater adoption of the technology. In order to meet this need, a number of studies have been completed to document maintenance and operation histories, equipment replacement requirements, actual cost of service, and long-term system reliability. The number of such studies has, however, been fairly limited and good data has not always been readily available as few building owners maintain good records and often ownership has changed, some times several times, since the system was first installed. In order to improve and strengthen the operation and maintenance data base Washington State University (WSU) has completed a series of case studies of commercial geothermal heat pump systems. The United States, and especially the state of Washington, has long been a leader in geothermal heat pump installation and use following the first successful demonstration of the technology at the Commonwealth Building in Portland, Oregon, in Most of these early systems are still providing a high level of service to building owners, and include systems in Tacoma (Tacoma City Light Building, 1954), Vancouver (Clark County PUD, 1956) Walla Walla (Whitman College 1964), Ephrata (Grant County PUD, 1955). Data obtained through the course of the current study indicates that geothermal heat pump technology is energy efficient with total building electrical energy use for those buildings where data was available ranging from 9.40 to 24.7 kwh/sq.ft./year while HVAC-related energy use ranged from 8.43 to kwh/sq.ft./year. Maintenance costs were also found to be very attractive and averaged $0.17/sq.ft./year (Table 1). The most interesting findings of this work, however, were the high level of reliability that most systems had provided over periods exceeding 25 to 30 years if routine maintenance procedures were followed and the very high level of owner satisfaction that was witnessed during the course of the interviews that were conducted. PRESENT STUDY The present study was conducted in two phases. The first began with a look at a number of installations in Washington State with an emphasis on obtaining information on building size and use, type and size of geothermal heat pump system, reasons for selecting geothermal heat pump technology, and owner/operator satisfaction with the system. The second phase of the study expanded the geographic area to include systems in several additional parts of the country and the scope to include much more concentration on operational, maintenance, and reliability issues. Systems were first identified through conversations with equipment sales representatives, architectural and engineering firms, well drillers, ground loop installers, HVAC contractors, and utilities. Once a substantial number of systems had been identified, the owner/operator of each system was contacted by phone and an interview conducted to determine whether or not the system should or could be further considered. The prime criteria for selection was willingness on the part of the owner/operator to participate in the study, availability of data, and age of the system. Every effort was made to include as many systems as possible with 20+ years of operating history, and as few as possible with five years or less of operating history. Once the systems had been selected, detailed interviews were conducted with the owner/operator, maintenance staff, and, when possible, the system designer. The interviews were conducted by phone and often required discussions with several individuals. Once the interviews were completed, all of the systems were visited, additional interviews conducted, and each system gone through in as much detail as possible. Table 1 summarizes the important building and ground source heat pump (GSHP) system characteristics of the 22 buildings that serve as the basis for this paper. As a baseline for a comparison of the results of this study, ASHRAE operation and maintenance estimates were reviewed. The ASHRAE Handbook (ASHRAE, 1995) provides a standard method for calculating maintenance cost for commercial-size HVAC systems. Based on calculations using the ASHRAE method, geothermal heat pump system maintenance can cost from $0.11 to $0.22/m 2 /year in

16 TABLE 1. BUILDING AND GSHP DESCRIPTIONS Site Location Beaver Lake Issaquah, WA Middle New School Bryant College Clark County PUD Admin. Exchange Building Grant County Courthouse Haverhill Public Library Heritage College Library Inn of the Seventh Mountain Kittitas Middle School Lane Community College LDS Office Tower North Bonneville City Hall Parkview Apartments Smithfield, RI Retrofit Vancouver, WA 1957(a)- New Farmington, CT New Ephrata, WA Retrofit Haverhill, MA Retrofit Wapato, WA New Bend, OR Retrofit Kittitas, WA New Eugene, OR Retrofit Salt Lake City, UT New North Bonneville, WA Retrofit Winchester, MA New Building Type Square Footage System Type Middle School 109,000 Ground loop - loop under athletic field - 45,062 meters in loop kw e electric boiler 2 College 38,000 Ground loop 138 Dormitories meters deep vertical bores - 9,963 meters total Administration Offices Office & Commercial Complex Courthouse & Courthouse Annex Library 44,000 including 27, addition 32,000 Open loop heat exchanger well meters deep 12 ºC, 19 L/s possible 275,000 Open loop four wells - 84 meters deep 13 ºC total flow 32 L/s 52,000 Open loop connected to 31 ºC municipal water supply system Open loop four wells - standing column 14 ºC 4-5 L/s per well isolated with heat exchanger College Library 18,000 Open loop 10+ºC isolated with plate and frame heat exchanger Condominium, Hotel Complex, Convention Center, Spa, and Pools 280, units and convention center Open loop 1 well - 73 L/s Middle School 39,000 Ground loop vertical bores 70 bores, 61 meters deep Total 8,534 meters Downtown Comm.College - Converted Montgomery Ward Store Offices & Public Rooms - 30-story tower plus 2 Wings City Hall Administration and Offices Condominium Complex 318 apts. 58,000 Open loop 3 wells 16 ºC Total flow 16 L/s 680,000 Open loop 4 wells - total flow 513 L/s. two wells at 119 meters deep. two wells at 192 meters deep, 19-24ºC 4,600 Ground loop horizontal 1,829 linear meters 207,400 Open loop 2 wells 11 to 15 ºC 95 L/s total flow Number of HP Units Heat Pump Capacity, kw t kwh Square Foot/Year kwh/square Meter/Year Maintenance Cost $0.00US/Square Foot/Year (a) (a) (a) (a) ,848 kw t plus an 879 kw t chiller to provide heat to loop x 2 1,055 (a) (a) (a) (a) 0.64 (g) 2 1, (e) 2.27 (e) (18 H 2 O-to-air) (12 H 2 O -to- H 2 O) 1 3 compressors 295 (a) (a) ,913 (a) (a) 0.12 (h) Compressor/ units 1, (F) 1.43 (f)

17 Site Location Squaw Valley Day Care Sundown M Ranch Tacoma City Light Tower Building Walla Walla Community College Walla Walla Corps of Engineers Whitman College Science Building Whitman College Administration Building Yakima County Correctional Facility Squaw Valley, CA New Yakima, WA New New New New Tacoma, WA 1954(b)- New Yakima, WA Retrofit Walla Walla, WA New Walla Walla, WA New Walla Walla, WA New Walla Walla, WA Retrofit Yakima, WA New Building Type Day Care Center with Snow Melt Drug & Alcohol Rehab Complex 61,800 20,650 39,736 7,500 Administration & Office Building Offices with first floor Commercial Administration office, classrooms, student lounge, and cafeteria Administration Office and Printing Shop Square Footage System Type 15,000 sqm Closed loop horizontal bld. 9,000 ground loop - 2,880 meters sqm snow melt Open loop 2 wells -61 meters deep - total flow 35 L/s 10+ºC 130,000 Open loop 2 wells - 14ºC 27 meters deep 50 L/s 12ºC 65 meters deep 79 L/s - shallow well winter; deep well summer - separated by heat exchanger 133,000 Open loop connected to two wells via heat exchanger 37 meters and 74 meters deep 16-18ºC 100,000 Open loop one production well ºC, meters. 63 L/s - water rejected to city water system prior to treatment 91,432 Open loop connected to municipal water system via heat exchanger ºC Science Building 88,000 Open loop pumped well 23ºC with intermediate heat exchanger 47 L/s Administration Building Correction Facility 30,000 Open loop pumped well 23ºF with intermediate heat exchanger - 47 L/s 120,000 (1983) 60,000 (1991) Total 180,000 Open loop 274 meters well 21ºC connection via heat exchanger Number of HP Units (a) Not separately metered. (b) Originally 2 centrifugal chillers were used; however, in 1988 one was replaced with a twin screen Dunham Bush chiller. (c) Sized to provide conditioning to Law and Justice Center but never connected. (d) Average daily winter HCAC system usage, facility not occupied or used year round. (e) 1.43 kwh/m 2 /yr. equals total consumption. HVAC consumption equals 0.78 kwh/m 2 /yr. (f) 2.27 kwh/m 2 /yr equals total consumption; however, HVAC consumption equals 0.94 kwh/m 2 /yr. (g) Maintenance contract. (h) Includes $0.0023/square meter/year for chemical treatment. Heat Pump Capacity, kw kwh Square Foot/Year kwh/square Meter/Year Maintenance Cost $0.00US/Square Foot/Year (d) (d) ,231 (528 kw t ) (703 kw t )?????? total square footage ,055 (a) (a) ,110 (a) (a) (a) 422 (a) (a) > (a) (a) ,

18 dollars U.S. compared to $0.38 (medium) to $0.05/sq.ft./ year (mean) for an average conventional HVAC system. As a comparison, the Fort Polk, Louisiana, (Pratsch, 1999) project is budgeted at $0.018/sq.ft./year while the 4,000 kw t Galt House East Hotel in Louisville, Kentucky, has a cost of $0.12/sq.ft./year. (Geothermal Heat Pump Consortium, 1996). GEOTHERMAL HEAT PUMP INSTALLATIONS Selection Criteria A number of the GSHP systems that date back to the 1950s were installed as a result of the building owners wish to adopt a unique, quality design that would create a positive impression in the community. This was also at a time when air conditioning was becoming more and more of an issue, and a driving force in selection of many of the geothermal systems. In the mid to late 1970s and early 1980s, a number of systems were built as a direct result of the oil crises of the early 1970s. Many of those interviewed who had responsibility for the construction of these systems indicated that the availability of a secure, locally available, indigenous resource was extremely important in the decision-making process, especially in a time of rapidly escalating energy costs and concerns over fossil fuel availability. Many owners of the more recently-developed systems contributed their decisions to go with geothermal heat pumps to past experience with such systems, very high quality of the installation, energy efficiency, and cost savings. Other reasons given included: environmental considerations compatibility with building design or retrofit requirements utility incentives reputation of engineering design firm need for individual temperature control reduced space for mechanical equipment life cycle cost savings. In truth, the publicity that many of the early systems received played a major role in replication of the technology in nearby areas. This can be clearly seen with the success of the Commonwealth Building in Portland, and the press that is was afforded. To a large extent, many of the systems that were built in that era were a desire on the part of building developers to capitalize on the positive publicity that the Commonwealth Building generated. DEVELOPMENT TRENDS Development trends can be divided into several distinct designs, including pumped wells with central or distributed heat pumps and loop systems, horizontal or vertical, relying primarily on a distributed heat pump system layout. Fortunately for the industry, all of the above seem to offer unique solutions to meet building design or retrofit requirements. Unfortunately, the industry has not yet matured to the point where all engineering design teams feel comfortable with all available technical alternatives, and thus design is often as much a factor of prior experience as it is a conscious decision to select the most appropriate technology for a given application. 16 Most early systems were based on pumped wells with either injection or disposal to nearby surface water. Other systems used surface water sources such as lakes, but were of essentially the same design. The heat pumps were water-towater and two- or four-pipe systems were used to circulate water to fan coil units situated throughout the building. By the early 1970s, pumped systems were still dominating the geothermal heat pump scene, but distributed systems were becoming a major player. With the availability of polybutelene pipe in the late 1979s, the trend seems to be moving more and more toward horizontal or vertical closed loop systems, although for many large commercial applications, the open loop water source system does seem to provide some economic advantage and continues to capture a significant market share where constraints on ground or surface water use have not been adopted. On the building side, decentralized or distributed heat pump systems seem to increasingly dominate the field primarily because of the ease of operation and localized temperature control that they provide. This seems to be an extremely attractive configuration in schools where the individual needs of each classroom can be easily met, and each teacher has total control over the system. Large, centralized systems, however, continue to play a major role and are ideally suited to many retrofit situations, especially where, because of the historical nature of buildings, major changes are very difficult or impossible. Centralized systems are also an extremely attractive choice for office parks or where low-temperature hydronic heating can be provided. Because of the wide range of water sources and ground loop configurations that can now be used and the number of in-building systems that are possible, geothermal heat pump systems can now be tailored to fit almost any possible need. The only challenge for the design engineer is to determine the best combination of water or ground source and in-building configuration to best serve the client s needs in the most efficient, reliable, and cost-effective manner possible. BUILDING AND GSHP SYSTEM CHARACTERISTICS Table 1 presents information on in-building system design and energy performance. Unfortunately, because of the age of many of the installations, no actual capital cost data was available for most systems and, therefore, no attempt has been made to cover capital cost information in any detail. For the 22 systems that are covered in this paper, the installed heat pump capacity varies from a low of 1.36 tons/sq.ft. per 1,000 square feet to a high of 6.00 tons/sq.ft. (the system was designed to meet future growth at the college) per 1,000 square feet. For the water source systems, flows range from 1.30 gpm per ton of installed capacity with an average of 3.43 gpm per ton. Required flow is, of course, very dependent upon water temperature and heating and cooling requirements. For closed loop systems, the heat exchanger circuit pipe length ranged from 236 feet per ton to 600 feet per ton, with an average of 454 feet per ton. Of those with vertical bores, the range is 166 feet of bore per ton to 204 feet.

19 Building electrical energy use ranges from 9.40 kwh per square foot per year to kwh per square foot per year, with an average of 18.7 kwh per square foot per year. For those systems where it was possible to determine electrical load for the mechanical system, the range was 8.43 kwh per square foot per year to kwh per square foot per year. Electrical rates and demand charges are so utility-specific that no meaningful trend could be discerned from an analysis of available data. EQUIPMENT AND DESIGN PROBLEMS Due to the fairly unique differences between open and closed geothermal heat pump systems, the equipment and design problems will be treated separately as will maintenance issues and costs. Open-Loop System As was mentioned earlier, open systems dominated the geothermal heat pump market from 1946 until approximately 1980 when horizontal and vertical closed loop systems became readily available. A majority of open loop systems rely on one or more wells. Water is withdrawn from the well or other source and disposed of through the use of injection wells, through surface discharge, or, in the case of standing column wells, the water is returned to the outer annulus of the production well. There is little doubt that well problems dominate when it comes to open loop systems. The two most often encountered problems are inadequate flow in the production well and plugging that causes pressure build-up in the injection well. Production problems are most often a result of excessive draw down of the acquifer due to over use or severe drought. It can also be a result of sedimentation in the bottom of the well. In many cases, the wells are simply not drilled deep enough or completed correctly. Many such problems can be corrected by deepening the production well or by reworking. In those cases where sedimentation is a problem, correct screening can provide a relative straightforward solution. However, the vast majority of problems associated with open loop systems are caused by the injection well. The principal cause appears to be iron bacteria and, where a mature colony is established, extremely difficult to eliminate. The problem can, however, be minimized by regular maintenance including chlorination (once every 3-6 months) and back pumping of the well. In some cases, the pressure build up problem is caused by scaling (often calcium carbonate, CaCO 3 ). Again, the problem can be minimized through the use of chemical treatment, although in some severe cases, some reworking of the well on a regular basis may be required. Of course, excessive injection pressure may also be the result of poor well completion or an inadequate injection horizon. The next most common problem associated with open loop systems is pump failure. Both open shaft, vertical downhole pumps; and submersible pumps are regularly employed and, at least for those cases where high volume is desired, the down-hole shaft system appears to dominate. Principal problems seem to be with bearings and seals, often resulting in the need for major maintenance and, in a worse case scenario, resulting in a broken shaft. Major pump problems seem to be avoided through proper sand screening and by ensuring adequate lubrication. Finally, the lack of a heat exchanger (shell and tube or plate and frame) to isolate the production flow from the inbuilding equipment can result in major system problems including excessive corrosion in the heat pump tube bundle. Most systems are now moving from shell and tube to plate and frame exchangers due to the closer approach temperature, the ease of maintenance and the flexibility they offer in terms of ease of expansion. Closed-Loop System Closed-loop systems began to challenge the dominance of the open-loop systems in the late 1970s/early 1980s. However, unlike open-loop systems where required flow can easily be determined based on load, source temperature, and equipment performance, loop length is much more difficult to calculate and is highly dependent upon soil characteristics including temperature, moisture content, particle size and shape, and heat transfer coefficients. Correct sizing of the ground loop continues to be a cause for continued design problems and special attention should be placed on minimizing inference between loops, whether they be horizontal or vertical. Other problems associated with loop design and installation include improper header design, inadequate system purging, leaks associated with corrosion of fittings, or poor workmanship. All of the above problems can be minimized through proper system analysis and design, and the use of well-trained and experienced installation personnel. One of the most often encountered problems is related to the circulated heat transfer fluid. Methanol and Environol seem to be the least problematic and best heat transfer fluid choices. Central vs Distributed Heat Pump Systems There seems to be very few problems associated with either the choice to employ a centralized or decentralized heat pump arrangement. Both afford the capability to provide supplemental heating or cooling through the use of boilers or cooling towers. The only major design problems that seem to be somewhat common in many centralized heat pump systems is the use of a two-pipe system to circulate hot or chilled water. Because the two-pipe system does not allow for the simultaneous supply of both heating and cooling, the building owner/system operator must choose which service will be provided at any given time. Because most such systems are difficult to reverse once the decision is made to go from, for example, heating to cooling, the system can not readily be changed back should a late spring cold spell come unexpectedly. Because the provision of heating is almost always more critical than cooling, operators most often chooses to error on the side of having heat available. 17

20 OPERATION AND MAINTENANCE Open-Loop System Most maintenance problems associated with openloop systems are well related. The problems include problems with pumps, including bearings and seals. Other maintenance issues include the need to clean or even rework production and injection wells and the need for chemical treatment of injected water to control scaling or bacterial growth that plugs the injection wells. Another potentially major maintenance issue is removal of sand from the heat exchanger(s) if adequate filters and/or sand traps are not used. Closed-Loop System Maintenance of closed-loop systems appears to be extremely minimal and restricted to circulating pumps unless the heat transfer fluid results in corrosion of fittings and other system components. Central and Decentralized Heat Pump Systems Central heat pump systems seem to require very limited maintenance, and because all major pieces of equipment are located in a central location, most maintenance chores can be carried out easily. Decentralized systems, on the other hand, do require considerably more routine maintenance including changing filters every three to six months. For example, when the Tower Building in Yakima, Washington, was purchased by the present owner, approximately one compressor per week required replacement; however, once a routine preventative maintenance program was put into place, only one compressor failure occurred over the entire following year. Care should be taken when installing a decentralized system to ensure that maintenance personnel have adequate access to each unit for routine maintenance and also for repairs when they become necessary. Despite the maintenance issues mentioned, maintenance costs are relatively low in all but a few cases, averaging $0.016 per square meter per year (see Table 1). In only three of the cases evaluated was maintenance considered a major concern. In one of these, the equipment was in definite need of replacement after nearly 35 years of service, and with the others, problems with the heat transfer fluid had resulted in serious corrosion problem and leaks as well as control problems due to the leaks. Anonymously high maintenance costs were a result of, in one case, a poorly structured maintenance contract; in another, lack of local maintenance providers; and in two cases, to relatively high inhouse personnel costs assigned to the HVAC system. CONCLUSION Geothermal heat pump systems are an increasingly attractive option for commercial buildings. Based on over 50 years of operating experience, it is safe to say that earlier concerns over long-term reliability, operation, and maintenance costs were, to a large extent, unfounded. Although some systems have had to be replaced due to problems related to production and/or injection well problems, a majority of the systems have proven to be extremely reliable, with many having been in service over 25 years, and maintenance problems and costs have been acceptably low. Advancements in equipment, installation techniques, and control systems as well as knowledge of heat transfer continues to reduce equipment and design problems. Increasing knowledge and use of a wide variety of water sources as well as ground loop designs and configurations, together with the number of in-building systems that are now possible allow that geothermal heat pump technology can be tailored to fit almost any possible building need. REFERENCES ASHRAE, Handbook: HVAC, American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc., Atlanta, GA. Geothermal Heat Pump Consortium, Earth Comfort Update--The Geothermal Change, National Information Resource Center Newsletter, Washington, DC. Pratsch, Lew, Personal communication, U.S. Department of Energy, Washington, DC. 18

21 CURING BLOCKS AND DRYING FRUIT IN GUATEMALA Luis Merida, Designer and Manager Eco-Fruit and Bloteca Guatemala INTRODUCTION In Guatemala, there are six geothermal fields recognized as potential sources of exploitation and only two have already been utilized. The first two successful uses of geothermal energy in Guatemala have been direct-use applications at the Amatitlan Geothermal site. Figure 1. Geothermal areas of Guatemala. The first one is Bloteca, a construction block factory established about 20 years ago and that recently started using geothermal steam in the curing process of concrete products. The other one is Agroindustrias La Laguna, a fruit dehydration plant, that was setup as an experimental and demonstration project. While developing this second project the owners decided to bring a product, Eco-Fruit, to the local market using the plant. The product was so successful that it has been in all supermarket chains for the past two and a half years. BLOTECA In the 1976 Guatemala earthquake, poor construction materials caused most of the destruction. Most of the houses where built with adobe bricks, and casualties where not really from falling objects, but from collapse and suffocation. From this experience the goverment implemented new building regulations mainly for house construction. Because of these regulations, a group of investors decided to setup a construction block factory since few existed in the market. Since Amatitlan was just 30 km away from the city it offered a good spot, not only because it reduced transportation costs, but due to the fact that it was located in a volcanic zone where suitable materials are located close by. The materials used are pumice, gravel, limestone, etc., which are very abundant in a volcanic zone; however, it never occurred to use geothermal steam to supply the factory for the curing process of the plant. Figure 3. Bloteca loading area. Figure 2. Detailed map of the Amatitlau region. By 1993, the demand on the products from Bloteca was so high that the production could not keep up with the demand and new factories started to come into the market. The need to set up a new production line was obvious. Since the steam supply was one of the biggest problems and having to buy a new boiler, the project was put on hold for some time. 19

22 Figure 4. Well and supply line. The answer came up while drilling a well to obtain a water supply. The drilling had to stop because the water was too hot. The well actually started flowing steam and water and the geothermal resource was discovered. A few geophysical studies where conducted, like electrical resistivity and electric potential. This showed the most favorable site to drill a production well. In May 1994, a second well, B-2, was drilled to a depth of 700 feet (213 m) and with a downhole temperature of 185 C. This wells produces enough steam to supply the needs of the plant. The system consists of two different lines that control the flow of the well, one that goes into a silencer and then into a weir to measure the water before injection, and the other line that goes into a cyclone separator. Since the steam is not needed all the time, it is controlled by regulating the flow that goes into the cyclone separator and then to the distribution lines. how much steam they do not have to produce by burning fuel. A plant with this capacity needs to consume around 16,000 gal (57 tonnes) of diesel fuel a month. The price on Guatemala of diesel fuel in Guatemala is about US$ 1.50/gal ($0.40/liter); so, this come up to a savings of US$ 24,000 a month. All of the installation including the drilling of the well, cyclone separator and distribution lines came up to around US$ 200,000. So the investment was paid of in less than one year and if we multiply the next three years of operation, we come up to a benefit of US$ 864,000. This is a benefit not just economically for the plant but for Guatemala not having to depend on the import of fuel. It also qualifies Bloteca as a plant with a environmental friendly process. Figure 6. Bloteca process line 2. At present, Bloteca produces 1.5 million units a month and it offers 24 types of blocks and 4 grades of fire resistance blocks. Figure 5. Cyclone separator. Although in Bloteca they are concerned on how much steam this well can produce, they are concerned more on 20 ECO-FRUIT Agroindustrias La Laguna was originally just a experimental and demostration project on which it was intended to prove in Guatemala that geothermal energy could be applied in a agroindustrial project. In this case, dehydration was the process selected. The pilot plant was setup and proven and while the investors decided to find a way to make it economically attractive they decided to dry fruit.

23 Fruit is abundant in Guatemala and a lot of the harvest does not go into export since it does not comply with international standards of shape, color and form. All of the reject fruit stays in the country and goes to waste, which is available in the market at a very low price. The intention of the project was to give the exporters a service on which they could give an added value to the fruit they do not export and make it attractive to the export market. This project was undertaken in order to start making some profit by extending the market of a local product and selling it in small stores as a natural product with a environmental friendly process. The product was so successful that it has been in all the supermarket chains for more than two years. The products produced are: pineapple, mango, banana, apple and pears. Figure 8. Setting up the DHE. Figure 7. Samples of the dried fruit. The project started with the idea to use a downhole heat exchanger to extract the heat. A well was drilled with a 12" diameter all the way down. A downhole heat exchanger was installed and tested. The performance decreased after a few hours of operation so some tests where conducted. A temperature profile was taken and it did not give very good result. (see Fig no enhancer). To increase the performance of the downhole heat exchanger an enhancer tube was used. This is a 4-in. diameter pipe with perforation at the two bottom tube segment, solid in the middle and perforated again at two tube lengths at almost the top of the pipe. This creates a convention cell that causes the temperature profile to be almost linear all the way down (see Fig enhancer installed). After setting up the enhancer, the performance of the downhole heat exchanger increased more than enough to supply the heat load of the dehydration plant. The concept of the system is very simple. The resource is only used as a heat source and does not supply the system with any amount of fluid. Water is pumped from a process water tank through the heat exchanger where it gains temperature. This water is then pumped through a finned tube heat exchanger (radiator coil, three step) where the airstream, that dries the fruit, is heated. The air dries the fruit that is set Figure 9. Setting up the enhancer. up in trays and tray-trucks inside a tunnel drier. The fruit stays inside the tunnel drier until its water content is reduced to 4%. 21

24 Figure 10. Temperature profile of well L-2. At the moment, the capacity of the plant varies depending on the fruit it handles and the way the fruit is set up. Either slices or cubes yield a different capacity for the plant, the average is: Fruit Banana Mango Pineapple Pear Apple Capacity Pounds (kg) 1800 (816) 1600 (726) 1800 (816) 1500 (680) 1500 (680) Drying Time (hours) CONCLUSIONS I believe that, although direct-use projects are generally smaller in scale that power generation, they have a greater economical benefit in countries like Guatemala. You have to build something around the use of the geothermal energy use. You keep more people involved at all times so in the long run they will create a larger development in a country like Guatemala. REFERENCES Lienau, P., Industrial Applications, Geothermal Direct-Use Engineering and Design Guidebook. Geo-Heat Center, Klamath Falls, OR. Merida, L., Fruit Dehydration Thesis. Geothermal Institute, University of Auckland, New Zealand. Popovski, K., Direct Application in Agriculture. Geothermal Institute, University of Auckland, New Zealand. Rafferty, K. and G. Culver, Heat Exchangers, Geothermal Direct-Use Engineering and Design Guidebook. Geo-Heat Center, Klamath Falls, OR. A. Weighing the fruit. B. Slicing. C. Setting up in trays. D. Tray trucks. Figure 11. Steps in processing the fruit. 22

25 ITALIAN GEOTHERMAL DISTRICT HEATING SYSTEMS Roberto Carella Milano, Italy SUMMARY Italy has large geothermal resources, both high and low temperature. It is the most important producer of geothermal electricity in Europe, but it also uses its lower enthalpy fluids in spas, agriculture, industry and district heating. The main plants for this last application are briefly described. ITALY S GEOTHERMAL SETTING AND DIRECT USE STATISTICS The Italian territory is characterized geologically by two mountain ranges: the Alps and the Apennines. The latter constitutes the backbone of the peninsula and separates an outer foredeep to the east, with basins which can be defined as cold if compared with the average temperature of the earth, from an inner hot Tyrrhenian belt, with back-arc basins. The Alps limit to the north, the cold Po basin (Fig. 1). Figure 1. Italy geothermal scheme and space heating plants. 23

26 The hot Tyrrhenian belt is associated with young mainly intrusive magmatism in Tuscany and volcanism in Latium and Campania. Geothermal gradient may reach 5-20 o C/100 m; maximum temperature in some wells exceed 400 o C. Geothermal targets in the area are mainly highenthalpy resources used for electricity production, but lowenthalpy prospects are also important at the edge of the main thermal anomalies or as cascaded use from geo-power plants. The outer cold foredeep induces a number of sedimentary basins from the most important Po basin in the north to the Adriatic coastal belt and to central Sicily. These basins are filled with a thick sedimentary sequence consisting of Quaternary and Tertiary clastics overlying a Mesozoic carbonate section. Geothermal gradients (2-3 o C/100 m) are typical of subsident basins and commercial prospects are lowand medium-enthalpy fluid applications. Concerning Italian direct uses, projects for the equivalent of 240,000 TOE/y are operational, of which 125,000 are for therapeutically-related uses in spas; 60,000 for greenhouses and fish farming; 40,000 for residential heating, and about 15,000 for industrial purposes. A large portion of civil space heating uses is concentrated in the Abano spa resort area, in northeast Italy. As regards district heating, the most important plants are those of Ferrara and Vicenza in the eastern Po Valley which started operation in Smaller DH systems are installed in the Tuscany geothermal steam fields area and in the lesser spa towns of Bagno di Romagna (northeast Apennines) and Acqui Terme (Piedmont). The main plants are briefly described below (locations in Fig. 1). ABANO AREA (Po Valley, Veneto) This area concentrates the largest consumption of geothermal energy for building heating, and is the most important example of integrated use of this energy for health, recreation and residential heating purposes in Europe. The spa area for Abano, extending for about 23 km 2, is located on the Euganea volcanic district, mostly at its eastern edge; several small towns with many hotels and resorts dedicated to the health and relax business are concentrated in the area, famous since ancient times for its hot springs. Most hotels in Abano and Montegrotto have their own wells (2 or 3) and are equipped with spa facilities (Fig. 2). Some 230 wells produce by pumping 3,600 m 3 /h of 65 to 87 o C low salinity water during the five months of the main tourist season (yearly average yearly production 2,500 m 3 /h). Average well depth is m, with some reaching 700 m. Completion is open-hole in fractured Upper Mesozoic limestone. Geothermal water is used for curative treatments, in swimming pools and to heat buildings and provide domestic hot water. Heat for these last two purposes is transferred through plate or shell-and-tube heat exchangers to a fresh water network. Back-up conventional boilers are seldom installed and emergency needs are generally taken care of by connecting to nearby wells. To regulate the flow, hot and cold water storage tanks are commonly set up. The exhaust water, at a temperature of about o C, is discharged at surface. In total about 120 hotels in the Abano area are fitted with geothermal spa facilities. Total heated volume is around 2.5 million m 3, equivalent to 12,500 standard flats, in addition to 200 swimming pools. Figure 2. Wells in the Abano Terme area. 24

27 Substituted energy is estimated about 25,000 TOE/y for building heating and sanitary water, and 90,000 TOE/y for therapeutical and recreational uses. FERRARA (Po Valley, Emilia) The Ferrara geothermal field was discovered in 1956, as a result of oil and gas exploration by AGIP, the then national oil company. Well Casaglia 1 drilled to the depth of 3,379 m without finding hydrocarbons evidenced the presence of 100 o C salt (65 g/l) water starting at about 1,100 m in fractured Mesozoic carbonates within a vary large structural high. In 1981, after reentering and testing successfully the well, it was completed for geothermal production under a joint venture with the national utility ENEL. In the same year, a new well (Casaglia 2, about 1 km from Casaglia 1, and 1,960 m deep) was drilled and tested up to 400 m 3 /h of fluid on pump. After signing a preliminary heat sale contract in 1983 with the Ferrara Municipality, which undertook to gradually build the downstream heating plant and DH network, the first geothermal heat delivery took place in The initial production facilities consisted of Casaglia 2 used as producer (at the rate of 200 m 3 /h on pump) and well Casaglia 1 acting as reinjector, both with open-hole completion. In 1995, a second producer (Casaglia 3) was drilled, parallel and few meters from Casaglia 2 to 2,000 m, doubling the field s flow rate. The surface equipment works in a closed circuit at 18 bar pressure. Anti-corrosion additives are injected in the producing wells; while, bactericides are mixed with the reinjected fluid. After a filtering unit, a set of titanium plate heat exchangers pass the available heat to a freshwater circuit belonging to the municipality feeding the DH system. A pre-insulated steel double line, 2 km long, conveys the heated 95 o C freshwater to the municipal heat plant, halfway between the production wells and the town, then carries the fluid back, cooled to an average of 60 o C to the AGIP- ENEL heat exchangers. The heat plant (Fig. 3) is composed of the geo-system terminal, peak-load and back-up gas boilers, hot and cold water regulating storage tanks, a 150-ton/day solid waste incinerator and an inter-connecting pump station. A co-generation unit was added in The DH network covers an extensive area along the central axis of Ferrara town, starting from its northwest outskirts. A 30-km grid of double preinsulated steel pipes connects 270 large users for a total of 2.7 million m 3 of heated space. Optimization of the return temperature is being investigated and the network is being expanded. Geothermal energy currently provides 5,000 TOE/y of the energy needed, corresponding to almost 60% of the total, as compared to about 20% each originating from the incinerator and the gas boilers. Figure 4. Ferrara hot reservoir with solid waste incinerator in the background. Figure 5. Ferrara pumping plant. Figure 3. Ferrara heat plant. VICENZA (Po Valley, Veneto) Hot freshwater in Mesozoic limestones was discovered by AGIP in 1977 in an oil and gas well (Villaverla 1) located 14 km north of the town of Vicenza. A detailed technical evaluation indicated that the resource should extend to Vicenza and, after signing a preliminary sale agreement with the local municipal company, AIM, AGIP and ENEL in a joint-venture drilled a well in 1983 located within the town limits. Vicenza 1 was successfully completed open-holed in Mesozoic limestone at 2,150 m, producing by pumping up to 125 m 3 /h of 67 o C freshwater with a limited amount of H 2 S. 25

28 After the granting of an exploitation lease and signing in 1985 a contract for the purchase of the hot water, AIM built the heat plant and the DH network between 1988 and Geothermal heating began in winter The heat plant is quite complex and included, after plate heat exchangers to isolate the geothermal fluid, dual-power (gas or electricity) heat pumps with heat recovery components, cooling towers, peak and back-up gas boilers, and a pumping system. The DH network consists in a 7.4 km double preinsulated steel pipeline and a parallel one-way sanitary hotwater line fed by 20 m 3 /h of geothermal fluid. Inlet-outlet DH temperatures are o C. The geothermal fluid was discharged in the town drain works at o C. The DH system services 74 main users, heating 1.33 million m 3 of space. Geothermal energy use with gas heat pumps amounts to about 2,700 TOE/y. Because of technical problems with the heat pumps and a dispute over the geothermal water sale price, use of the geo-heat is suspended after a few years and the DH system operates with co-generating units installed in Solution of the controversy is imminent and could lead to resumption of the geothermal operations. BAGNO DI ROMAGNA (Northeastern Apennine, Emilia- Romagna) The municipality of this small spa town with 45 o C springs, which has exclusive rights on the use of the resource, decided in the 80s to develop a geothermal DH system. The availability of sufficient amount of resources was verified by drilling some very shallow wells which evidenced a potential of over 200 m 3 /h of o C nearly freshwater in fractured sandstones of Miocene age. Well No. 3, 50 m deep, completed with slotted liner for a production by pumping of 90 m 3 /h of 37 o C water, was selected to feed the DH system. The well is located only 400 m from the main spring; however, no interference occurs. The heat plant consists of gas-electric heat pumps with heat recuperator, co-generation units, and gas-gasoil back-up boilers. A network of 9-km two-way preinsulated steel pipelines connects several hotels and houses with about 190 substations for a heated space of 220,000 m 3. HE inlet temperature is 80 o C and return 60 o C. Spent geothermal water is rejected at 20 o C in a nearby river. The system was built in and went on stream in Geothermal energy output is about 500 TOE/y. Ongoing expansion of the grid will double the connected heated space by the end of Figure 6. Figure 7. Overview of the city of Vicenza. Vicenza heat pumps. ACQUI TERME (Northwest Italy, Piedmont) Acqui is a spa town with a quite hot spring (La Bollente) with a temperature of 70 o C and a free-flow rate of 33 m 3 /h. A private operator uses the resource for therapeutical purposes. During , the municipality developed a DH plant and grid to utilize the Bollente spring water in periods when the spa facilities are closed (spring, autumn and part of winter). The heat station consists of a steel plate heat exchanger, gas-fed heat pumps with heat recuperator and gas-fueled boilers for peaking and backup. The DH network is a 2.2 km two-way preinsulated steel line, with input temperature of the water 80 o C and outlet 60 o C. It connects public buildings with 11 substations for a total of 130,000 m 3 of heat space. Design temperature of the spent geothermal fluid is 35 o C with an expected energy output of around 300 TOE/y. Heat delivery started in 1988, but because authorization for the energy use of the spring water has not yet been granted, the DH network is fed provisionally by conventional boilers. TUSCANY In several west Tuscany towns, ENEL utilizes part of the steam available from power generation or, more often, steam unsuitable for electricity production because of low pressure or temperature, for direct uses (mainly space heating). Geothermal energy supplied to several centralized and district heating plants in the ENEL area amounts to about 7,000 TOE/year. The largest share (70%) is utilized in the Pomarance Municipality where DH systems are installed in four suburbs (Larderello, Montecerboli, Serrazzano and Lustignano). In Larderello, offices and living quarters of ENEL are served directly; while, the other heat systems are owned and operated 26

29 by the municipality. The main fluid used is power-plant grade steam at o C tapped from the steam lines; while, in Lustignano, 170 o C steam from a dedicated well is employed. Heat is transferred to the DH water circuits via shell-and-tube heat exchangers. Return temperature is 70 to 95 o C. A small DH system serves the town of Monterotondo Marittimo using 95 o C steam with a return temperature of 70 o C. Other small geothermal DH networks are developed in the Castelnuovo V.C. Municipality, downtown and in the Sasso Pisano suburb. The downtown heat plant was completed in 1987, being fed with high-grade steam tapped from the pipeline to the Castelnuovo power station. The plant was recently refitted to use low-pressure 105 o C steam from shallow wells and a separate distribution line for domestic hot water was laid down. Steam from the power station network will be used for peaking.. The Sasso heat plant owned by ENEL (while the DH network belongs to the municipality) was completed in It serves 150 dwellings for a total of 50,000 m 3. Low pressure 105 o C steam from refitted shallow wells is fed into a shell-and-tube heat exchanger to cover base load needs of the DH system. Peak demand is met by steam tapped from the Sasso Pisano power station feeder line, through as second shell-and-tube heat exchanger. The plant has a gas disposal unit and the spent geothermal fluid is reinjected at 70 o C (Fig. 8). GROUND-SOURCE HEAT PUMPS Contrary to several central and northern European countries (including Switzerland), Italy has very few systems of this type. POSSIBLE NEW DEVELOPMENTS Most of the action is concentrated in Tuscany, where installation of geothermal DH units in the town center of Pomarance and in the S. Dalmazio suburb started in ENEL will also provide geothermal heat for the Santa Fiora Municipality DH system (for a total of 2,400 TOE/y) and has proposed a similar arrangement for the town of Piancastagnaio. Use would be made of hot water effluents from power plants and of steam not suited for electricity production. Outside Tuscany, the Grado Municipality, on the Veneto coast (northeast Italy) is interested in a DH project involving also some spa use. The system would be fed by o C water from a well to be drilled to the depth of 1,000 m, in the town center, tapping a Mesozoic limestone reservoir. Figure 8. Sasso heat plant scheme: 1) to/from DH grid, 2) power steam line, 3) heat meter, 4) heat exchanger, 5) shallow production wells, 6) gas disposal, 7) pond and 8) to reinjection wells. 27

30 Available Now! GRC Publications Stories from a Heated Earth Exciting New Publication Details Our Geothermal Heritage Through the Ages and Around the World new and exciting book is hot off the press with a fresh but timeless topic the history of mankind living Aon a geothermal planet. Published by the Geothermal Resources Council and the International Geothermal Association, Stories from a Heated Earth, Our Geothermal Heritage, is neither a science text nor a technical treatise. Instead, its focus is on people, and how geothermal phenomena have affected cultures around the world. Stories from a Heated Earth was painstakingly compiled and edited by Raffaele Cataldi (geothermal consultant-italy), Susan Hodgson (California Division of Oil, Gas & Geothermal Resources) and John Lund (Oregon Institute of Technology Geo- Heat Center). Created to collect, preserve, interpret and distribute global geothermal history prior to the Industrial Revolution, the 588-page volume with 215 photographs and illustrations is a unique amalgamation of both fact and fiction true and imaginary accounts of our geothermal heritage unlike anything ever published before. Covering more than 25 countries, this beautifully crafted paperback book is written in an easy, nontechnical style designed for broad appeal. The 47 international authors of Stories from a Heated Earth found the historical information presented by this superb volume in the works of archaeologists, historians, geographers, anthropologists, scientists and engineers. Inspiration flowed from artists, photographers, poets, philosophers, and literary figures with geothermal quotations from Chinese and Japanese poets, Homer, Shakespeare, Pushkin, Herman Melville, Mark Twain and Edgar Allan Poe. In addition, Stories from a Heated Earth derives interesting tales and practices from ancient manuscripts and the oral tradition, never before recorded. And antique quotations in over 30 languages were extracted for the book from pottery, drawings, maps, votive statues, shrines, stelae, myths and legends. All contribute to the fascinating reading offered within the covers of this engrossing, must have addition to both geothermal and historical libraries. From the dawn of history, people have been entranced by the wonder and benefits of geothermal manifestations. Prehistoric tribes and civilizations in antiquity considered the Fire of the Earth as a gift bestowed by the gods for the benefit of mankind. Hot springs and fumaroles were described as Wakan Tanka ( Great Mystery ) by the American Dakota Sioux, and as tapu ( sacred ) by the Maori. These beliefs, expressed in popular customs, traditions, religious feelings and rituals, were handed down through hundreds of generations and still influence our customs and though today. With their awe-inspiring beauty and sometimes destructive power forever commanding our attention, volcanoes have inspired religious practises, provided fertile