Analysis of the employment of geothermal resources internationally with emphasis on the island of St Lucia

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(1)Electrical Engineering Faculty. Diploma’s Final Coursework Title: “Analysis of the employment of geothermal resources internationally with emphasis on the island of St. Lucia.” Author: Quincy Garner Inglis Tutor: Dr. Carlos de Leon Benitez. Santa Clara 2008 “50th Year of the Revolution”.

(2) Universidad Central “Marta Abreu” de las Villas. Electrical Engineering Faculty. Electro-energetic Department Diploma’s Final Coursework Title: “The analysis of the employment of geothermal resources internationally with emphasis on the island of St. Lucia.” Author: Quincy Garner Inglis. Tutor: Dr. Carlos de Leon Benitez Professor, Electro-energetic Department, Electrical Engineering Faculty, UCLV. E-mail: charle@uclv.edu.cu. Santa Clara 2008 th “50 Year of the Revolution”.

(3) Technical Tasks: 1. The study of the state of the art. 2. The study of the outlooks for use of the geothermal resources as renewable sources of energy. 3. Technologies for the exploitation of the geothermal resource. 4. Procedure for the prefeasibility study for the exploitation of the geothermal energy. 5. The study of perspective use of the geothermal energy in Santa Lucia. 6. Elaboration of the thesis..

(4) Table of Contents Chapter 1: Geothermal Energy; Theory and Applications. Page. 1.1 Introduction 1.2 Geothermal energy, History and General facts.. 1. 1.3 Types of Geothermal Resources. 2. 1.4 Principles and Fundamentals.. 4. 1.5 Application in Energy Generation 1.5.1 Dry Vapor Plants 1.5.2 Flash Vapor Plant 1.5.3 Binary Cycle Plants. 5. 1.6 Electricity generation. 6. 1.7 Advantages of geothermal plants 1.8 Evaluation of costs 1.9 Main benefits 1.9.1 Use for Heating 1.9.2 Geothermal Heat Pumps 1.9.3 Geopressured Resources 1.9.4 Co-Produced Geothermal Fluids 1.10 World Utilization 1.11 Current state of the use of geothermal energy 1.12 Project studies 1.12.1 Kenya. 1.12.2 Argentina 1.12.3 The Caribbean. 11 12 12. 2. 14 15 16. 1.13 Comparison with Other Energy Resources. 20. 1.14 Conclusions. 22. Chapter 2: Geothermal Energy; Research and Implementation 2.0 Introduction II.1 Stages of a Geothermal Project. 2.1 Initial Perspective Study. 2.1.1 Reconnaisance study. 2.2 Prefeasibility Study 2.3 Feasibility Study II.2 Evaluation of geothermal potential 2.2.1 Preliminary estimates of the Potential of a Geothermal Field II.3 Economic Evaluation 2.3.1 Geothermal energy Costs.. 23 24. 26 28 29.

(5) 2.3.2 Exploration costs 2.3.3 Perforation costs 2.3.4 Costs of transmission of vapor 2.3.5 Cost of a power station 2.3.6 Cost of the kWh 2.3.7 Initial cost. II.4 Environmental Impact 2.4.1 Contamination 2.4.2 Corrosion 2.4.3 Inlay 2.5 Energy situation in St. Lucia 2.5.1 Electricity Market Situation 2.6 Possible Applications in St. Lucia 2.7 Conclusions. 37 40 41 42. Conclusions and Recommendations Bibliography. 43 44. 35.

(6) Chapter 1: Geothermal Energy; Theory and Applications 1.1 Introduction Saint Lucia is a volcanic island located in the Eastern Caribbean. Its' natural beauty has made it an increasingly popular tourist destination. This, along with rapid development, has contributed to a growing demand for energy. The local utility LUCELEC has an exclusive license to generate and distribute electricity and currently supplies about 98% of the population. Electricity generation is characterized by total dependence on diesel-powered generators. At present, over 90 percent of energy used in the Caribbean is fueled by oil. There are wind energy turbines, solar panels, hydroelectric plants and geothermal plants that generate electricity, but none anywhere near the region’s potential. There are no grid connected solar energy sources, while wind, geothermal and hydro sources are grid connected in isolated cases. Geothermal energy has an enormous potential to reduce emissions into the atmosphere. Geothermal energy can be extracted in places where the flow of natural heat of the earth is located sufficiently near the surface of the earth. The water injected from the surface is heated into vapor by the geothermal source, which is used to generate electric power subsequently. The water injected can also be heated and used directly for heating methods. Geothermal energy often replaces the use of fossil fuel as a source of heat and energy for those applications, reducing emissions. Heat from the earth can be used as an energy source in many ways, from large and complex power stations to small and relatively simple pumping systems. This heat energy, known as geothermal energy, can be found almost anywhere. Tapping geothermal energy is an affordable and sustainable solution to reducing our dependence on fossil fuels, and the global warming and public health risks that result from their use. The world energy situation has been aggravated at present by high fuel prices which have propitiated the development of new projects guided towards the use of renewable resources with the employment of distributed generation systems. St. Lucia is characterized as possessing a substantial geothermal potential in comparison with the levels of domestic demand. This work has as its fundamental objective to carry out a general study of the current employment of geothermal resources at an international scale and to analyze the application field in the specify case of St. Lucia indentifying a. 1.

(7) Chapter 1: Geothermal Energy; Theory and Applications methodology for the realization of prefeasibility studies in this address, on the base of the hypothesis that it is possible to achieve high generation levels with the employment of this resource but even if one keeps in mind that the domestic socio-productive characteristics doesn't require high demand.. 1.2 Geothermal energy, History and General facts. From prehistory, the natural sources of hot water have been used to cook and to bathe. Evidence of pumping systems exists from as early as the XIV century. But the controlled exploitation of the heat of the earth really began about a hundred years ago with the first systems with pumps and pipes in Europe and USA. These were continued by the first commercial distribution of generated energy, carried out in Italy in 1904 which worked until the beginning of the Second World War. There was later a period of consolidation where the systems were developed slowly but with more solid bases due to the advancements in technical knowledge of the underground and its exploration which was really due to the advances in the exploration of hydrocarbons. Due to the petroleum crisis near 1970, geothermal plants of diverse applications began to arise around the world; there existed a much firmer knowledge of the variables to control and the geologic requirements to fill. As the years passed the rate of growth has increased, to the point that a 10% annual increase is expected in the capacity of generation of world energy, during next 5 years. The energy plants that work with geothermal energy provide worldwide near 44 billion electricity kWh and the world capacity is growing to a rate of 9% per year.. 1.3 Types of Geothermal Resources Heat constantly flows from the interior of the earth toward the surface. Most of the geothermal resources are of the concentration of the thermal energy of the earth in certain regions of the underground. (Figure 1). 2.

(8) Chapter 1: Geothermal Energy; Theory and Applications. Figure 1- Example of a Geothermal Reservoir Four types of geothermal resources exist: •. The hydrothermal resources are reservoirs of vapor or hot water, formed by water that crosses the cracks of the porous rocks that are at high temperatures and is trapped among them. These reservoirs vent through wells.. •. The resources of geo-pressurized water constitute water deeply buried to moderate temperatures that contain dissolved methane. Although available technologies exist to exploit this resource, they are not economically competitive.. •. The resources of dry hot rocks are found at a depth of between 8 and 16 km underground in all parts of the world and to lesser depths in certain areas. The access to this resource requires the injection of cold water through a pipe to circulate the water through the cracked rock heating it up and the hot water is extracted through another pipe.. •. The resource magma constitutes the melted rocks at high temperatures, this offers high geothermal potential, however there still doesn't exist technology that allows the exploitation of magma heat in a direct form.. For direct use and electricity, the geothermal reservoirs should be sufficiently near the surface to be reached by means of perforation; this is possible in places where the geologic processes has allowed for the magma to reach the surface, or where there is lava.. 3.

(9) Chapter 1: Geothermal Energy; Theory and Applications. 1.4 Principles and Fundamentals. Geothermal Energy is based on the use of the Earth's heat as an energy source. (Figure 2). Figure 2- the Earth’s Core Heat can be generated by several processes that happen inside the earth's core and their uses vary according to their origin. To be able to use that heat in some form, some means of transport should be provided, which minimizes heat dissipation. That means of transport is water, such that the underground water absorbs the heat and it transports it toward other places in the form of hot water. As under the Earth the existent pressures are much greater than those that humans are exposed to on the Earth's surface, the temperatures that the water reaches are greater than 100°C and higher still in gas state. Thanks to the technological advances and using tools of the petroleum industry, this "hot water" can be used in different forms according to the temperature it is at when extracted. Several elements are required so that a geothermal field exists: a roof made up of a covering of waterproof rocks; a deposit or aquifer, of high permeability between 300 and 2000 meters deep; fractured rocks that allow for convection of fluids, and therefore the transfer of heat from the source to the surface, and a source of magmatic heat, between 3 and 10 kilometers deep at 500-600°C.. 4.

(10) Chapter 1: Geothermal Energy; Theory and Applications 1.5 Application in Energy Generation As a basic rule it is necessary to mention that in this application and in all geothermal plants the principle task is to move a turbine that will generate electricity. This is achieved by passing water vapor or vapor of some other fluid of a low boiling point through the turbine, in a way so as to induce its movement. There exist three types of geothermal energy plants: 1. Dry Vapor Plants 2. Flash Vapor Plants 3. Binary Cycle Plants. 1.5.1 Dry Vapor Plants They are so called because they use water vapor that emanates from a well (Geysers), and they drive the turbine directly, causing the movement of the turbine with the force from the vapor. This type of plant was one of the first that was put into operation.. 1.5.2 Flash Vapor Plant. This type of plant uses water that is between 130°C and 300°C. This overheated water is driven to the surface by a machine that maintains the high pressure present underground, near the turbine, the pressure drops quickly and the water vaporizes instantly, and it moves the turbine.. 5.

(11) Chapter 1: Geothermal Energy; Theory and Applications 1.5.3 Binary Cycle Plants These plants use water that is at temperatures of between 80°C and 130°C. The underground water is led to the surface until it exchanges heat with another fluid of a much lower boiling point than the water (generally an organic compound). When exchanging heat, the organic fluid evaporates and with the force of the generated vapor the turbine is moved. In all cases, the used water condenses and is re-injected into the system to maintain the pressure and that the yields don't weaken with the passing of time.. Dry steam. Flash steam. Binary cycle. 1.6 Electricity generation Depending on the characteristics of the geothermal resource, electricity generation is carried out mainly by means of conventional vapor turbines and binary cycle plants. The conventional vapor turbines require fluids at temperatures of no less than 150°C and they are available with atmospheric discharge (back-pressure) or with de-condensation discharge. The turbines with atmospheric escape are simpler and cost less. The vapor, directly from dry vapor wells or, after separation, from humid vapor wells, is passed through the turbine and discharged to the atmosphere (Figure 3).. 6.

(12) Chapter 1: Geothermal Energy; Theory and Applications. Figure 3- Outline of an atmospheric discharge geothermoelectric plant. With this type of unit, the consumption of vapor (of the same entrance pressure) per kilowatt-hour produced is almost double that of condensation units. However, the atmospheric discharge turbines are vastly useful as pilot plants, portable plants in the case of small supplies from isolated wells, and to generate electricity with exploratory wells during the development of the field. They are useful also when the vapor has a high content of non condensable gases (> 12% in weight). The atmospheric discharge units can be built and installed very quickly and put in operation in little more than 13-14 months from the date that they are ordered. This type of machine is usually available in small sizes (2,5 - 5 MWe). The condensation units, as they have more auxiliary machines, they are more complex than atmospheric discharge units and as they are larger they require double the time for their construction and installation. The specific vapor consumption of the condensation units is however, near half of that of atmospheric discharge units. The condensation plants of 55-60 MWe capacity are very common, and recently plants of 110 Mwe have been built and installed (Figure 4).. 7.

(13) Chapter 1: Geothermal Energy; Theory and Applications. Figures 4- Outline of a condensation geothermoelectric plant.. The electricity generation from fluids of low to medium temperature or, starting from hot water coming from the separators in water dominant geothermal fields, has had significant progresses due to the improvements achieved in technology of binary fluids. The binary plants use a secondary fluid, usually of organic character that has a low boiling point and high vapor pressure at low temperatures, in comparison with the water vapor. The secondary fluid is managed according to the conventional Rankin cycle (ORC). The geothermal fluid gives heat to the secondary fluid through heat exchangers, in which this fluid is heated and vaporized; the produced vapor works a normal turbine of axial flow, later it is cooled and condensed, and the cycle begins again (Figure 5).. 8.

(14) Chapter 1: Geothermal Energy; Theory and Applications. Figure 5- Outline of a binary geothermal plant.. Selecting an appropriate secondary fluid, the binary system can be designed to use geothermal fluids with a range of temperatures between 85 and 170°C. The superior limit depends on the thermal stability of the organic binary fluid, and the inferior limit depends on technical-economic factors. At lower temperatures the size of the required heat exchangers would make the project not economically feasible. Besides the geothermal fluids at low to medium temperature, the binary systems are used also when it is preferable to avoid the "flashing" of geothermal fluids (for example, to avoid inlay of the well). In this case, pumps located inside the well can be used to capture the fluids in pressurized liquid state, and the caloric energy can be extracted from the fluid by means of binary units. The binary plants are usually built in small module units, of a few hundred KWe to a few MWe capacity. These units can be interconnected to constitute electric plants of dozens of megawatts. Their cost depends on many factors but mainly on the temperature of the geothermal fluid used that defines the size of the turbine, the heat exchangers and the cooling system. The total size of the plant is not very significant with regard to the specific cost, since it is possible to interconnect a series of standard module units to achieve greater generation capacities. The technology of binary plants is a half sure one. 9.

(15) Chapter 1: Geothermal Energy; Theory and Applications and of appropriate costs to transform into electricity the available energy of water dominant geothermal fields (lower than 170°C). A new binary system, the Kalina Cycle uses a mixture of water and ammonia like a secondary fluid, was developed in the 19 90's. The secondary fluid expands, under overheated conditions, through turbines of high pressure and later is reheated before working the low pressure turbine. After the second expansion the saturated vapor is driven toward a recuperative boiler, before being condensed in a condenser cooled by water. The Kalina cycle is more efficient than binary ORC geothermoelectric plants, but it is of a more complex design. The small portable plants, conventional or not, not only do they reduce the relative risks to the perforation of new wells, but most importantly they can help provide the energy requirements of isolated areas. The quality of life of many communities could be considerably improved by having the possibility to have local energy sources. The electricity could facilitate many seemingly menial, but extremely important activities, such as pumping of water for irrigation, freezing of fruits and vegetables for conservation. The convenience of small portable plants is even more evident for those areas that don't have access to conventional fuels and also for communities where it would be too expensive the connection to the national or regional electric system, in spite of the existence of transmission lines of high voltage in their proximities. The cost of supplying these small isolated communities is prohibitive, since the necessary transformers to obtain electricity from lines of high voltage cost more than US $675000 for each one installed and the simplest form in local distribution of electricity, to 11 kW using wooden posts, has a minimum cost of US $20000 per kilometer (US- 1998). In comparison, the capital cost (US- 1998) of an installed binary unit is between 1500 and 2500 US$/kW, without including auxiliary costs. The electricity demand per person, in places outside of the transmission systems fluctuates between 0,2 kW in less developed areas to 10 kW in more developed areas. A plant of 100 kWe can supply from 100 to 500 people. A plant of 1000 kWe can supply from 1000 to 5000 people. Hot water from geothermal resources is used directly to provide heat for buildings, crop and lumber drying, industrial process heat needs, aquaculture,. 10.

(16) Chapter 1: Geothermal Energy; Theory and Applications horticulture, ice melting on sidewalks, roads, and bridges, and district heating systems. In direct use applications, a well (or series of wells) brings hot water to the surface; a mechanical system— piping, heat exchanger, pumps, and controls—delivers the heat to the space or process. Often, direct use applications use geothermal fluids not hot enough for electricity generation. To improve efficiencies, used water from geothermal power plants can be ‘cascaded’ down for lower temperature uses, such as in greenhouses or aquaculture. Flowers, vegetables, and various fish species are examples of products from greenhouse and aquaculture systems.. 1.7 Advantages of geothermal plants. Geothermal plants are like wind or solar plants; they don't burn fuels to move the turbines. Because they don't use a combustion process, they don't emit Nitrogen Dioxide. Some emit a very low quantity of Hydrogen Sulfate around the amount that can be remove in 99,9% by means of appropriate treatment and in general they emit between 1/1000 and 1/2000 the amount of Carbon dioxide that plants that work with fossil fuels emit. In some places, the water comes with excess salts and dissolved minerals, when this occurs; the water is re-injected in the reservoir from where it came to conserve its properties and to maintain the original pressure. Rarely the plants are not operational, and they produce energy 95% of the time, this means that they produce energy 22,8 hours of the 24 hrs of the day and it has the highest capacity factor than that of any other form of energy generation. The capacity factor is the relation between the quantity of energy that is produced with regard to the quantity of energy that could be produced. There is no visual impact since the land that one needs for the plant is small in proportion to any other type of plant. Also it is not necessary to carry out great disturbance to the area to locate injection wells and extraction in comparison with that of the installation of an extraction well for petroleum or gas. There is no dangerous waste muds, nor creation of artificial lagoons, nor fuel spills, nor radio-active residue that don't disappear, nor cutting of trees.. 11.

(17) Chapter 1: Geothermal Energy; Theory and Applications 1.8 Evaluation of costs Most of the cost of the power stations is not maintenance or fuel, but rather the taxes to pay for the land used and the installation costs. In a step by step plan, the costs would go to: Exploration and analysis of information of the resource “Evaluation of the possibilities (feasibility study) “Design of the plant “Construction of the plant The initial costs in USA are approximately among USD 2000 and USD 5000 per installed Kw and the maintenance cost is from 0,015 to 0,045 cents per Dollar depending on the characteristics of the location and of the plant type. A Kw of geothermal energy is marketed at U$S 0,05 to U$S 0,08. At the moment they are trying to lower the market price. The most important aspect of this energy type is that it is not subject to international prices, but rather it can always stay at national or local prices, this way being able to export energy to other countries at low prices and generate in this way more revenues for the country. The proprietors of hothouses can reduce the costs of electricity substantially using geothermal energy as well as take advantage of it for heating or cooling. The costs of installation of the plants are redeemed faster, the greater the capacity of the plant as it can produce energy over 90% of the time.. 1.9 Main benefits. 1.9.1 Use for Heating Almost in any part of the world, the first 5 meters of the surface of the earth maintain an almost constant temperature that is between 10° and 16°C. A geothermal heating system consists of pipes buried in land under the housing, a heat exchanger, and a system of pipes in the house in question. In winter, the heat of the relatively hotter floor is driven through the heat exchanger and then inside the house. In summer, the hot air of the house is pumped through the heat exchanger to the floor that is relatively colder. The heat removed during the summer can be used to heat water.. 12.

(18) Chapter 1: Geothermal Energy; Theory and Applications Geothermal heating systems don't produce electricity, but help to use a smaller quantity of it. The electricity consumption can fall from 30% to 60% comparing it with the electricity that a conventional heating system uses. These systems have times of life of up to 30 years. The best example of this technology type is the hotel "Galt House" in Kentucky, USA. This hotel heats and cools its 750000 m2 by means of this system. The installation cost was US$1500 for each installed ton of steam, while any other system has a cost between U$S 2000 to U$S 3000 for each ton. As a second economic benefit, the system saves the hotel U$S 25000 per month in electricity costs and it also leaves 25000 m2 of free pipes that can be taken advantage of for any other venture on land that would have been occupied if opting for another heating system. Lastly, it must be mentioned that the hotel has been working for 15 years without any problem with the facilities.. 1.9.2 Geothermal Heat Pumps Geothermal heat pumps (GHPs) use the Earth’s huge energy storage capability to heat and cool buildings, and to provide hot water. GHPs use conventional vapor compression (refrigerant-based) heat pumps to extract the low-grade heat from the Earth for space heating. In summer, the process reverses and the Earth becomes a heat sink while providing space cooling.. Figure 6 - Geothermal heat pump (GHP) illustration for a commercial application.. 13.

(19) Chapter 1: Geothermal Energy; Theory and Applications 1.9.3 Geopressured Resources The geopressured resource consists of deeply buried reservoirs of hot brine, under abnormally high pressure, that contain dissolved methane. The resource contains three forms of energy: methane, heat, and hydraulic pressure.. 1.9.4 Co-Produced Geothermal Fluids Sometimes referred to as the ‘produced water cut’ or ‘produced water’ from oil and gas wells, co-produced geothermal fluids are hot and are often found in water flood fields in a number of U.S oil and gas production regions (See Table 1). This water is typically considered a nuisance to the oil and gas industry (and industry is accountable for proper disposal), but could be used to produce electricity for internal use or sale to the grid. Like geopressured resources, co-produced geothermal resources can deliver nearterm energy savings, diminish greenhouse gas emissions, and extend the economical use of an oil or gas field. New low-temperature electric generation technology may greatly expand the geothermal resources that can be developed economically today. 1.10 World Utilization Geothermoelectric plants at the moment produce around 8.000 megawatts of electricity, which satisfies the residential electric necessities of 60 million people. Every year, the construction of new geothermal plants increases the generation capacity by approximately eight percent. Besides the electric generation, the direct" uses" (non electric) of the heat in the geothermal fluids is equal to approximately twenty million barrels of petroleum each year.. Figure 7- World Geothermoelectric Capacity. 14.

(20) Chapter 1: Geothermal Energy; Theory and Applications In the Americas, geothermoelectric plants have capacities of approximately 2.800 megawatts (MW) in the United States, 750 MW in Mexico, 105 MW in El Salvador, 70 MW in Costa Rica, 70 MW in Nicaragua, and 4 MW in Guadeloupe.1. 1.11 Current state of the use of geothermal energy After the Second World War many countries were attracted by the geothermal energy, considering it economically competitive regarding other energy sources. [2] It doesn't require importation and, in some cases, it is the only source of locally accessible energy. The countries that use geothermal energy to generate electricity appear in table 1.1, which includes the electric capacity installed in 1995 (6.833 MWe), in 2.000 (7.974 MWe), and the increment between 1995 and the year 2000 (Huttrer, 2001). The same table also reports the total capacity installed at the beginning of 2003 (9.028MWe). The capacity installed in countries with respect to development in 1995 and 2000 represents a 38 and 47% of the world total respectively. The use of geothermal energy in countries with respect to development shows an interesting tendency through the years. In the 5 years between 1975 and 1979 the geothermoelectric capacity installed in such countries increased from 75 to 462 MWe); at the end of the following 5 year period (1984), 1.495 MWe had been reached, showing a rate of increase during these 2 periods of 500% and 223% (Dickson and Fanelli, 1988). In the following 16 years, from 1984 to the 2000, there was an increment of almost 150%. Geothermoelectric power plays quite a significant role in the energy balance of some areas; for example, in 2001 the electric power produced by means of geothermal resources represented 27% of the total electricity generated in the Philippines, 12,4% in Kenya, 11,4% in Costa Rica and 4,3% in El Salvador. The most common non electric use in the world (in terms of installed capacity) corresponds to heat pumps (34,80%), followed by bathrooms (26,20%), heating (21,62%), hothouses (8,22%), aquiculture (3,93%) and industrial processes (3,13%) (Lund and Freeston, 2001).. 1. LA GEOTERMIA: ENERGIA CONFIABLE Y LIMPIA PARA LAS AMERICAS, pagina 2 www.ubp.edu.ar/todoambiente/monografias/Energia_geometrica.pdf. 15.

(21) Chapter 1: Geothermal Energy; Theory and Applications. Table 1.1 Geothermal generation capacity installed in the world from 1995 to 2000, and the beginning of the 2003 (Huttrer, 2001) 1.12 Project studies. 1.12.1 Kenya. Between 1979 and 1996 The World Bank carried out five projects in support of the program for the use of geothermal energy resources in Kenya, the first of its type in Africa. In the appraisal report of the five projects prepared the DEO reached the conclusion that their results had been satisfactory, but noticing that it was not very probable that the last two were sustainable without greater support from the government. The five projects were executed between 1979 and 1996 and they helped the Kenya Power Company (KPC) to install the first power stations of geothermal energy in Africa. The first three projects were completed practically on time and without surpassing the estimated costs, although the results of the perforations didn't fill the expectations. All. 16.

(22) Chapter 1: Geothermal Energy; Theory and Applications the generation units worked to the limit of their capacity or above during several years, and now they work at their installed capacity without any serious problems. The power station in Olkaria had difficulties to maintain sufficient vapor levels with which to feed its turbines. After working above their specified capacity up to 1985, that power station began to have production problems due to insufficient investments in new wells that were necessary to compensate the constant decrease, of 3% to 5% a year, in the vapor produced by the existent wells. The production of vapor and electric power decreased gradually from 45MW in 1989 at 30MW in 1995. The five projects achieved satisfactory results. The levels of first perforation of the first three (1979-86) were unacceptable, but production increased a lot in 1987 and it remained high during the rest of the operations. The KPC has increased its own capacity up to the point of being able to assist its geothermal energy program entirely with its own personnel, without appealing to external consultants. Now, the equipment used is old and it will need to be replaced for operations to continue efficiently. The KPC should reexamine its commitments in exploration material and perforation for the use of geothermal energy, and to identify the resources that are needed to carry out its program with efficiency. The exploitation of that energy should become the responsibility of a self-sufficient utilities center in conjunction with the activities of generation of electric power of the KPC, with the necessary resources to support its maintenance and its expansion. The KPC has to enlarge the training in the sphere of design of surface facilities for the systems of gathering of vapor.2. 1.12.2 Argentina Until today, the geothermal resources corresponding to an approximate surface area of 300000 km2 in the northwest, central-west and south of the country were evaluated. Based on the derivative recommendations of the recognition studies, the studies were furthered in eight geothermal areas with favorable characteristics, in those that were continued with the prefeasibility studies. The same ones were developed, for high enthalpy projects. In the volcanic areas of Tuzgle (Jump-Jujuy), Domuyo 2. Article “Precis; Departamento de Evaluación de Operaciones del Banco Mundial- Verano de 1998; Numero 162”. 17.

(23) Chapter 1: Geothermal Energy; Theory and Applications (Neuquén), Copahue (Neuquén) and Valle del Cura(San Juan) and, for the low enthalpy projects, in the area of Bahia Blanca (Buenos Aires),. Figure 7; Map of the areas studied. Caimancito, La Quinta and El Palmar (Jujuy) and Río Valdéz (Tierra del Fuego). Of the group in the realized studies, the state-of-the-art projects correspond to the geothermal fields of Copahue (Neuquén), Rio Valdéz (Tierra del Fuego) and Bahia Blanca (Buenos Aires). The project Copahue was in the developmental stage. In April of 1988 pilot geothermal power plant using Binary Cycle with a capacity of 670 Kw was put into operation. In Domuyo, direct use was made of the hot water for heating and bathrooms in the tourist complex Villa Aguas Calintes. 3. 1.12.3 The Caribbean At present, over 90 per cent of energy used in the Caribbean is fueled by oil. There are wind energy turbines, solar panels, hydroelectric plants and geothermal plants that generate electricity, but none anywhere near the region’s potential. There are no grid connected solar energy sources, while wind, geothermal and hydro sources are grid. 3. Energías Alternativas, paginas 10, 11; http://www.ingenieroambiental.com. 18.

(24) Chapter 1: Geothermal Energy; Theory and Applications connected in isolated cases. The following table shows the amount and sources of energy used in selected Caribbean countries. Table 1.2 Breakdown of electricity generation and demand by individual countries in 1992. A study conducted in 1992 showed that at least six of the Caribbean islands had good potential for geothermal energy. Preliminary studies show that Nevis, Dominica and Saint Lucia have the most potential for the generation of electricity from geothermal sources. Geothermal energy, like wind energy, is capable of grid connection, as relatively large amounts of energy can be generated from a single plant. A French company is successfully operating a plant in Guadeloupe producing about 3 megawatts of electricity to power a village. An attempt to develop a geothermal plant in Saint Lucia was not successful, due mainly to inadequate feasibility studies. However, after a review of the available data, the French company has expressed an interest in revisiting the project. The. 19.

(25) Chapter 1: Geothermal Energy; Theory and Applications cost of geothermal energy is approximately 4-7 cents per kilowatt, making it very competitive with fossil fuel-based energy.4. 1.13 Comparison with Other Energy Resources Table 1.3 Energy Equivalents by Resource Category Resource Category. Shallow. Estimated. Estimated. Accessible. Developable Resource. Resource. – 2050. Hydrothermal1(Identified) 0.81. >90˚C/194˚F. Quads135 0.81 Quads135 million. million BOE. Shallow Hydrothermal1(Unidentified) 3.2. Quads540 –. >150˚C/302˚F. million BOE. Co-Produced & Geopressured2. 2.7. Quads450 2.7 Quads450 million. million BOE Deep Geothermal4. 35.1. BOE. to. BOE 351 3.5 tp 35 Quads0.58 to. Quads5.8 to 58.5 5.8 BBOE BBOE Direct Use5. 0.88. Quads150 15 Quads112.5 million. million BOE Geothermal Heat Pumps (GHP)6. BOE. 15 Quads2.5 billion 15 Quads2.5 BBOE BOE. GHP6 Avoided Power. 1.8. Quads300 1.8 Quads300 million. million BOE. BOE. 4. CARIBBEAN COUNCIL FOR SCIENCE AND TECHNOLOGY; GENERAL LC/CAR/G.565CCST/99/14 June 1999; RENEWABLE ENERGY IN THE CARIBBEAN WHERE WE ARE; WHERE WE SHOULD BE. 20.

(26) Chapter 1: Geothermal Energy; Theory and Applications. Energy Comparison Information U.S annual energy consumption equals about 100 quads (EIA, 2004). U.S annual electricity production equals about 40 quads (EIA, 2004). U.S. petroleum demand equals about 21 million bbl/day, 7.67 billion bbl/yr (EIA, 2004). World petroleum demand equals about 84 million bbl/day, 30 billion bbl/yr (EIA, 2004).. Energy Equivalents 1 Quad = 0.170 billion barrels of oil, 170 million barrels of oil 1 Quad = 45 million short tons of coal 1 Quad = 1 trillion cubic feet of dry natural gas 1000 KWh = 0.59 barrels of crude oil 1000 KWh = 0.15 short tons (300 pounds) of coal 1000 KWh = 3,300 cubic feet of dry natural gas 1 barrel of crude oil = 1,700 kWh 1 barrel of crude oil = 5,600 cubic feet of dry natural gas 1 barrel of crude oil = 0.26 short tons (520 pounds) of coal.5. How Energy Equivalent Calculations Were Made Electricity as the equivalent energy content of the produced electricity: Barrels (bbls) of oil equivalent (BOE) [(electricity production potential/MWe) (1000 kW/MW) (8760 hrs/yr.) (0.9 capacity factor) (3413 BTU/kW-hr)] 1 bbl oil equivalent/6 x 106 BTU = BOE/yr. for a minimum of 30 years. Quads (Q) [ (electricity production potential/MWe) (1000 kW/MW) (8760 hrs/yr.) (0.9 capacity factor) (3413 BTU/kW-hr) ] 1/1015 BTU/Q Thermal calculations assumed a duty cycle of 50% – 5. Bruce D. Green and R. Gerald Nix, National Renewable Energy Laboratory; “Geothermal—The Energy Under Our Feet”; page12 ; www1.eere.energy.gov/geothermal/pdfs/40665.pdf. 21.

(27) Chapter 1: Geothermal Energy; Theory and Applications BOE [ (MWt) (1000 kW/MW) (8760 hrs/yr.) (0.5 duty cycle) (3413 BTU/kW-hr) ] (1 bbl oil equivalent/6 x 106 BTU) Quads (Q) [ (MWt) (1000 kW/MW) (8760 hrs/yr.) (0.5 duty cycle) (3413 BTU/kW-hr) ] 1/1015 BTU/Q. 1.14 Conclusions: 1. Geothermal energy is a vastly underutilized resource. The rising cost of fossil fuels will soon force countries to exploit alternative forms of energy. It will soon be necessary for countries to aid their economies by incorporating renewable energy into their consumption. 2. Some countries have already incorporated wind, solar and geothermal energy into their systems, with less taking advantage of biomass and fuel cells. From the research done in this thesis it can be concluded that on an international scale there is a move towards the use of hybrid systems which incorporates in the use of more than one energy form. 3. It can also be concluded that geothermal energy is one of the most feasible forms of energy to ease off the dependency on fossil fuels. The cost of installation of geothermal energy is low compared to fossil fuels and does not have a major environmental impact. 4. Another conclusion which can be made is that the most common immediate use of the geothermal resource apart from the production of electricity is for climate control of buildings. It is a cheap and effective method of heating or cooling buildings.. 22.

(28) Chapter 2: Geothermal Energy; Research and Implementation Introduction The current geothermal industry is based on the exploitation of resources called geothermal hydrothermal resources; however, the long term viability of this energy resource will depend on the technology development that allows for the use of all types of geothermal resources. Some of the necessary technologies to exploit this renewable source are costly. However, with technological development the tendency is toward a decrease in the costs, which will allow for an increase in the employment of renewable energy. This chapter includes the detailed insight into the necessary stages for the research of a possibly exploitable geothermal resource and the installation and implementation of a geothermal plant. In particular, the case of St. Lucia will be examined. The following aspects will be studied in this chapter: II.1 Stages of a geothermal project. 2.1 initial perspective study. 2.2 Prefeasibility study. 2.3 Feasibility study. II.2 Geothermal resource evaluation. II.3 Economic Evaluation •. Costs of geothermal energy.. •. Exploration costs.. •. Perforation costs.. •. Costs of transmission of the vapor.. •. Cost of a power station. .. •. Cost of the kWh.. II.4 Situation in St. Lucia. 23.

(29) Chapter 2: Geothermal Energy; Research and Implementation II.1 Stages of a Geothermal Project.. 2.1 Initial Perspective Study. There are several methods of exploration, geologic, geochemical and geophysical which are used for the location and characterization of a geothermal field. By virtue of the great extension of the initially subjected areas to study and of the costs of the exploration it is necessary for the planning of the study in stages, identifying the areas of more interest progressively. It is determined this way the convenience or not of following the investigation with more and more precise and more expensive methods. The phases of a complete geothermal project proposed by the OLADE (Organización Latinoamericana de Energía) include: •. reconnaissance study- Area: 10000-100000 km2. •. Prefeasibility study- Area: 500-2000 km2. •. Feasibility study- Area: 10-100 km2. •. Development.. •. Exploitation.. 2.1.1 Reconnaisance study. This is carried out in an area whose extension can vary between 10000 and 100000 km2, with the objective of evaluating the geothermal possibilities at a regional level, to select smaller areas of more interest and to plan the following stages of exploration. In this stage the following is carried out: •. The summary and evaluation of all existent information, that is, regional geology, geologic and topographical maps, aerial photographs and satellite images, geophysical, meteorological, hydrological data and information about thermal manifestations.. •. Field reconnaissance that includes the taking of samples, as much of rocks as of water, for their future analysis.. The objectives of geothermal exploration are (Lumb, 1981): 1. To identify the geothermal phenomenon. 2. To discover if a usable geothermal field exists.. 24.

(30) Chapter 2: Geothermal Energy; Research and Implementation 3. To estimate the size of the resource. 4. To determine the type of geothermal field. 5. To locate the productive areas. 6. To determine the caloric content of the fluids that will be irrigated from the wells in the geothermal field. 7. To compile a group of basic records with which the future controls can be confronted. 8. To determine those environmentally sensitive parameters, before the exploitation of the resource. 9. To acquire knowledge about some characteristics that can cause problems during the development of the field.. The relative importance of each objective depends on numerous factors, most of which are bound to the same resource. These include the foreseen use, the available technology, the economic aspects, as well as the situation, localization and weather, all of which influence the exploration program. For example the preliminary recognition of the geothermal manifestations has much greater importance in a remote and unexplored area than in a very well-known area; the estimate of the magnitude of the resource can be less important if it is to be used on a small scale, which uses much less heat than that which discharges naturally; if the energy is going to be used for heating or for some other application that requires a low grade of heat, then it is not an objective of great importance to find fluids of high temperature (Lumb, 1981). Numerous methodologies and technologies are available to reach these objectives. Many of these methods are commonly used and they have been broadly proven in other areas of investigation. The techniques and methodologies that have been proven successful in the exploration of minerals and in petroleum and gas will not necessarily be the best solution in geothermal exploration. On the other hand, techniques of little use in the exploration of petroleum could be ideal tools in the search of natural heat. 25.

(31) Chapter 2: Geothermal Energy; Research and Implementation 2.2 Prefeasibility Study. The prefeasibility study embraces an area between 500 and 2000 km2. In this phase it is sought to achieve a preliminary evaluation of the resource and, possibly, to locate the places for the perforation of deep exploratory wells. The geologic, hydro-geologic and geochemical studies are guided to the determination of the presence and origin of the thermal anomaly, the characteristics of the reservoir and of the superior rocky formation.. 2.3 Feasibility Study. The objective of the feasibility study is the delimitation of the geothermal field, the estimation of the exploitable reserves, the study of the geothermal fluids and its possible uses. In this stage the first exploratory wells are dug, studies of the reservoir, economic studies and design of the pilot plant. The extension of the study area is between 10 and 100 km2.. II.2 Evaluation of geothermal potential. The geothermal reservoir in a first approach, can be considered to be like a" closed" box, in which a mass of water enters (m0), called Recharge, a quantity of heat (Q0), contributed by the Heat source, and from which come out: a mass (m1) and a quantity of heat (Q1) transported by the superficial manifestations, as well as a quantity of heat (Q') irradiated by the surface.. Figure2.1- Reservoir Model The incognitive is what capacity the reservoir has. To respond to this, a "Reservoir Model" is built in order to know the volume, heat flow, recharge, porosity, permeability,. 26.

(32) Chapter 2: Geothermal Energy; Research and Implementation deep temperature, physical state of the fluid (vapor or hot water), direction of circulation, quantity and quality of the contained gases, etc. The system schematized above can be approximated to a system in balance for relatively short lapses; this is industrial times, not geologic. It is also easy to demonstrate that to a system like the one proposed, if a quantity of such fluid is extracted that the heat lost by the reservoir is twice as much that the natural flow of heat (Q1+Q'), important changes won't be introduced. Exploited in this way, one can then say that this is a renewable resource. But if a great quantity of wells are perforated the reservoir can leak heat in a short time, the resource would then be nonrenewable. The tendency is to exploit the geothermal field among these two extremes, trying not to drain it prematurely, but with such intensity that allows it to be a profitable activity. In the development of the field it proceeds step by step, the most promissory area is taken first, the superficial exploration is done and then the more in depth one. With the information from the perforated wells during the deep exploration, the production wells are programmed to supply to the first module (usually smaller or similar to 35 MW), then expanding the deep exploration to other areas, new production wells are perforated and new modules are installed, interconnected to each other by means of electricity lines. This process has some advantages: •. The investments are staged, that is to say, it is not necessary to make a great initial investment in order to begin to produce energy. (For example a hydroelectric power station should be built, then to fill the reservoir and finally it begins to work).. •. The installation of the first module allows for generation while the tests for Engineering of the Reservoir are carried out, without necessity of venting vapor.. •. Materials are tested and technology developed, since the repairs or corrections are always less expensive in small plants.. •. Maintenance can be programmed in a more comfortable form, as it requires only taking out of service small modules whereas in the case of a great power station a stop in generation can cause major problems in the electric system.. •. Finally if similar machines are adopted, it diminishes the lot of necessary reserves for maintenance.. 27.

(33) Chapter 2: Geothermal Energy; Research and Implementation As disadvantages it should be pointed out that: •. The yield of the small machines is smaller.. •. The investment is greater.. 2.2.1 Preliminary estimates of the Potential of a Geothermal Field. For the determination of the capacity of the reservoir, diverse methods exist, among them: 1. Superficial Heat Flow Method. It is based on the determination of the heat loss of the field on the surface (Qt) by conduction (Qc) and the transported heat by the thermal efluentes (Qm). The total energy (Qt = Qc+Qm) is assumed that it dissipates during the lifetime of the field, 104 - 105 years. The product of these two values allows for the total energy present in the field to be estimated. A factor of recovery (always less than 25%) is estimated and the quantity of heat that can be used is obtained. The method lacks precision, but it is very useful as a first approach. 2. Volume Method. The field is divided in homogeneous parts of similar temperature, porosity, etc., the energy contained in each one of the parts is calculated, a factor of recovery (Rg) is estimated and with it the energy that can be extracted. The precision of the method increases if more accurate data of the geometric, physical, and chemical parameters of the field is available. When the field is in the exploration phase its potential is determined with considerable uncertainty, which diminishing with more detailed exploration and then the exploitation. In practice, these calculations begin with the first exploration phases and they conclude with the exploitation. 3. Method of the Magmatic Chamber. Developed by Noguchi (1970), it bases its idea more or less on the presence of magmatic chambers near the surface. It calculates every so many years a volcanic event is produced with, an average size chamber and an average cooling time; with this the energy involved in the volcanic activity of an extensive area is calculated. It allows for an estimate at a regional scale, but with a considerably high margin of error.. 28.

(34) Chapter 2: Geothermal Energy; Research and Implementation. II.3 Economic Evaluation. 2.3.1 Geothermal energy Costs. The geothermal energy cost of production is determined, by the costs in exploration, perforation, lines of transmission of the fluid and of construction of the power station.. 2.3.2 Exploration costs. The exploration of geothermal resources implies, from the economic point of view, a risk that can be limited developing it in successive stages, with gradual investments and according to the results obtained in each stage. A study of this type, in a preset area of 2030 km2 costs approximately 1 to 1,5 million dollars.. 2.3.3 Perforation costs. These costs depend on the depth of the reservoir, rock type to perforate, diameter, cementation method, accessibility of the area, etc. These values are very dissimilar, according to the existent bibliography vary in a range from 547500 to 2250000 dollars per well in different places in the world.. 2.3.4 Costs of transmission of vapor. The amounts, according to different authors, vary between 30000 to 240000 dollars per MW, according to the pressure and temperature of the fluid to transport, the distances between wells and the plant, number of separators, steel type to be used, etc.. 2.3.5 Cost of a power station. The variations that are observed in the published costs depend on the power of the group, yield, location and domestic industrial development of the country. As an indicative value it can be estimated the value proposed by Larderello of 480 USD/kW, it includes machinery, civil works, transformers, etc.. 29.

(35) Chapter 2: Geothermal Energy; Research and Implementation Goldsmith calculates a value of 562,5 USD/kW for a composed power station of 100 MW for two groups of 50 MW. 7 Baldo estimates a cost for mobile units of small dimensions of 400 USD/kW, while a condensation unit, of high-performance, with a unitary power of 30-50 MW would have a cost of 1200-1400 USD/kW including civil works, machinery, works for elimination of waste waters, and also the investigation cost and in production of the field.. 2.3.6 Cost of the kWh. Great differences exist in the bibliography on the exploration costs, perforation and facilities that compose a geothermal power station. In order to calculate this cost, the impossible task of estimating a half flow of the well, also the number of wells that will be sterile, makes it difficult to determine the number of wells that must be perforated to obtain a certain quantity of fluid. For example Armstead calculates an average production per well of 45 tn/h, with a probability of 66% that the perforated well is productive (two productive wells out of every three perforated). Goldsmith estimates for his calculations a production of 56 tn/h per well. Any forecast that is made will have an error margin that will be directly tied with the data available on the geothermal field that is analyzed; the more that is known about the field, the less the error made in evaluating the costs. As for the period of paying-off of the power station, in general they take 25-30 years and to the wells a useful life of 10 years is assigned. As for fully automated or not plants, or according to the adopted operation mode, it can have a remarkable variation in the required manpower, but this won't introduce great errors, because this is 10-15% of the operating cost. Since geothermal plants almost always produce base energy and their maintenance is simple, the load factor is high (7500-8000 h/year).. 7. (*) Source: Fundamentos sobre la Energía Geotérmica - J.L. Sierra, G. Pedro, O. Levi. 1987. Energía Geotérmica -J.L. SIERRA, G. PEDRO. 30.

(36) Chapter 2: Geothermal Energy; Research and Implementation 2.3.7 Initial cost. Feasibility. It includes the perforation of 5 exploratory wells, reservoir engineering and corresponding interests. perforation cost oscillates between 17357340 - 21563160 USD. Perforation. It includes the perforation of 8 wells, necessary to maintain production. It is considered that 40% of the wells will be sterile its cost oscillates between 12526210 - 13454330USD. Production, plants and miscellaneous costs. The reception and transport costs of the vapor to the plant are near 300000 USD/well and the cost of the plant is 650 USD/kW. Taking into account the miscellaneous expenses and the corresponding interests one has 46807870 - 50736230 USD Total investment Feasibility....................................... 17.357.340 - 21.563.160 USD Perforation....................................... 12.526.210 - 13.454.330 USD Production, plants and miscellaneous.... 46.807.870 - 50.736.230 USD TOTAL....................................... 76.691.420 - 85.753.720 USD Dividing the initial total cost by the installed capacity a value is obtained for each installed kW of; USD/kW 1523,83 - 1715,07. Generation cost. Operation and maintenance. It is considered to be 1% of the initial cost plus the corresponding interests.... mills USD/kW 2,03 - 2,29. Maintenance of the production. It includes the necessary perforation costs to maintain the production after commencing generation...................................................................... mills USD/kWh 1,56. Capital cost. Keeping in mind a factor of use of 85% and an annual paying-off of 812%.............................................. mills USD/kWh 16,25 - 27,44.. 31.

(37) Chapter 2: Geothermal Energy; Research and Implementation Total cost of generation. Operation and maintenance............ mills USD/kWh 2,03 - 2,29. Maintenance of production..... mills USD/kW 1,56. Capital cost............................. mills USD/kWh 16,25 - 27,44. TOTAL......................................... mills USD/kWh 19,96 - 31,48.. Comparative costs of energy. The values that are considered in this section are international values, those that have appreciable differences with the current internal costs of electric power, originated starting from the transformation of the sector that began starting from 1991. The efficiencies and costs for the geothermal energy generation and other forms of generation (conventional and non conventional) they are indicated in the Table 2.1. In order to make a more precise comparison they are grouped in the Table 2.2 the plants that are characterized to produce base energy. For these the ranges of variation of the capital costs are pointed out as likewise the average value. The widest ranges appear for the hydroelectric plants (of great capacity, as of small and medium capacity). The geothermal plants have a width in their cost range similar to those of vapor and diesel plants, although their average cost is greater by virtue of the cost for development of the field. As for the generation costs, these are indicated in the Table 2.3. For the non conventional forms, the average values vary between 0,0400-0,0465 USD/kWh, which are lower than those corresponding to the conventional plants that oscillate between 0,0650-0,0780 USD/kWh. For the geothermal plants the average generation cost is 0,0400 USD/kWh.. 32.

(38) Chapter 2: Geothermal Energy; Research and Implementation. Table 2.1 Efficiencies and costs for the geothermal energy generation and other forms of generation.. 33.

(39) Chapter 2: Geothermal Energy; Research and Implementation. Table 2.2 Capital Costs for diverse types of plants.. Table 2.3 Generation Costs.. 34.

(40) Chapter 2: Geothermal Energy; Research and Implementation II.4 Environmental Impact.. 2.4.1 Contamination. The geothermal wells can produce vapor or pressurized hot water. It depends on the field type in which the well is perforated," vapor-dominant" or" water-dominant" and the forms in which it being exploited. If the well produces vapor, the only possible contamination is atmospheric and taking into account that the quantity of associate gases is greater in this case, one can affirm that the wells producing vapor contaminate more the atmosphere than those producing hot water. When the product is hot water, by means of a separator the vapor is extracted. The residual water which is of the order of 2/3 of the total production, would be the most serious contamination problem, but is usually re-injected in the reservoir taking advantage of sterile wells or of those of low capacity, diminishing the environmental impact notably. The reinjection, not only minimizes the pollution, but it also contributes to the feedback of the field, pressurizing it. Although the reinjection is a habitual practice, this operation is made with supreme care for not cooling the production area prematurely. As for the sulfur dioxide (SO2) levels, these are calculated starting from the concentration of hydrogen sulphide (H2S) of geothermal origin. These values are very possibly overestimated because the calculation gives the maximum possible concentration, but in our opinion their concentrations will be inferior, and according to the following reactions: 1. Geothermal gas plus oxygen in the air:. 2. Product and reagent to each other:. This last one will be favored if it is carried out in presence of a catalyst, with that which the reaction would be totally displaced to the right. From this it concludes that contamination produced by the electric power generation starting from endogenous gases is very low and the level of contamination can be further reduced using the appropriate facilities.. 35.

(41) Chapter 2: Geothermal Energy; Research and Implementation 2.4.2 Corrosion. Impurities in Geothermal Vapor. In the “liquid-dominant" reservoirs, the hot water that flows through an experimental well, experiences as a consequence a reduction of pressure, there is a separation of vapor. This vapor contains such impurities as: silica (SiO2), calcium carbonate (CaCO3), iron (He), chlorides (Cl), etc. from the brine and solids that crawls up from the reservoir. The high corrosiveness of the brine is the result of the high temperatures, its high content of salts, the presence of dissolved carbonic anhydride (CO2) and hydrogen sulfide (H2S) and its high content of calcium sulfate(CaSO4), calcium carbonate (CaCO3) and silica (SiO2).. 2.4.3 Inlay. It is one of the main problems in the exploitation of geothermal resources. The main types are: a) Silica and silicates; b) Carbonates; c) Sulfates and sulfides. Three main mechanisms of formation are recognized: 1. Deposition from a fluid in a phase (injection lines). The nucleation and kinetics of the deposition depends on the level of oversaturation, pressure, temperature and catalytic effects or inhibitors produced by the presence of lesser elements, etc. 2. Deposition by separation of fluid, (flash), in wells, separators and two phase lines. The separation or ¨flash¨ of the fluid takes place by the decrease of pressure, in turbulent flow, originating by the oversaturation by loss of vapor, with increase of the concentration of solutes in the non-volatile liquid. Temperature drop, associated with the expansion process by loss of stable gases as carbonic anhydride (CO2) and hydrogen sulfate (H2S), with increase of the pH. 3. Deposition from the vapor (separators, turbines, vapor lines). It originates from the leakage of drops of water from the vapor that then evaporate on the substrata. Since the evaporation is complete, the inlays can also contain some soluble minerals.. 36.

(42) Chapter 2: Geothermal Energy; Research and Implementation 2.5 Energy situation in St. Lucia St. Lucia has developed a plan to decrease the dependence on fossil fuel energy production. As mentioned earlier, the local utility LUCELEC has an exclusive license to generate and distribute electricity and supplies about 98% of the population with a total dependence on diesel-powered generators. Much research has already been undertaken into Saint Lucia's geothermal resource but an additional assessment of the island's market potential for renewable energy is needed. Potential energy sources include biomass, wind, solar and geothermal. These energy sources can provide energy services with almost zero emissions whilst improving local technology and providing job opportunities. The plan aspires to produce an electricity generation mix by introducing a Renewable Energy Portfolio Standard that will ensure that a specific percentage of electricity is generated via renewable-energy systems. This will ultimately result in 30% of installed capacity being delivered from renewable sources by 2010. 8 Records of the geothermal project in St. Lucia The first geothermal works were carried out with the attendance of United Nations, by means of the use of a consultant who considered interesting from the geologic point of view the geothermal area of “Sulphur Springs”, near the town of Soufrière, to the Southwest of the island. The first systematic investigations, were developed in the same area, starting from 1974, when the island was a British territory, and they undertook the perforation of seven exploratory wells with depths between 116 m and 725 m, the works were completed in 1976; the most important result in this effort was the identification of brines of high temperature in the underground. New investigation works began in Soufriere in 1982, after the independence of St. Lucia, with the financial support of the European Investment Bank (EIB). In 1983 the National Laboratory of The Poplars with the financial aid of the USAID, carried out similar works in the same place. Again between 1986 and 1989 the international cooperation became present through the Revolvente Fund of the United Nations (UNRFNRE) and US-AID. The actual works correspond to the stage of feasibility according to the evaluation methodology adopted by the present study. Two 8. “Saint Lucia to develop a sustainable energy plan”- Ministry of Planning, Development, Environment and Housing – St. Lucia; www.oas.org/reia/GSEII/Saint%20Lucia/Energy%20Policy%20Outline3.doc. 37.

(43) Chapter 2: Geothermal Energy; Research and Implementation deep wells of commercial diameter were perforated and one had forecasts for the installation of a small generating plant. However, the obtained results were not satisfactory, for lack of supervision and the cost of the perforations were exceptionally high. These factors were what impeded the conclusion of the feasibility study. The conclusion of the project was summarized to, that fluids of high temperature exist in economically exploitable depths and that the geothermal objective that offers better perspective of temperature and permeability is the dome of Terre Blanche. In 1990 production rehearsals with funds of the European Development Bank begun on one of the perforated wells (SL-2), which were not completed due to bad conditions of the well. In 1992 UN-DTCD integrated the evaluation of the geothermal activities carried out in Saint Lucia inside the context of a regional project that undertook other islands with geothermal potential. For the case of St. Lucia it was recommended to complete the previously initiated feasibility stage. The Government carried out an economic evaluation for the installation of two units of 5.2 MWe in the vicinities of the geothermal area of Sulphur Springs, as alternative to diesel plants. The results favor the geothermal option. However for the production lack in the perforated wells, the project was stagnant. In 1997, a mission of experts of the project Cepal/CE (Phase I) visited the island in order to: a). To verify the domestic general situation, in what refers to an eventual geothermal. development; b). To analyze the advances in connection with the project “Sulphur Spring”. The opinion expressed by the expert of the project, was clearly reflected in the Final Report of the Phase I: “……….. The geothermal prospect of greatest perspective in the Caribbean area is that of Sulphur Springs, Saint Lucia, was the conclusion of the feasibility stage of the resource. The potential to install - either 10 or 20 Mwe - it represents a good size from the technical and economic point of view. The project Sulphur Springs represent, therefore, the viable opportunity for the industry and European investors in the region...……..” In August of 1999-based on an official order of the Ministry of Planning and Finance the responsible technician of the project Cepal/CE, Mr. Coviello, carried out a new visit to the island jointly with the official of the CEPAL/Port-of-Spain, Mr. St.Aimee. On that. 38.

(44) Chapter 2: Geothermal Energy; Research and Implementation occasion a meeting took place with the Office of Sustainable Development of this ministry, Mr. Bisnhu Tulsie, and with the then Permanent Secretary of the island, Mr. Bernard La Corbiniere. Both reiterated the local government's strong interest in receiving technical support on the part of the project CEPAL/CE as regards: c) Promotion, regulation and development of the national geothermal resources; d) Regulation and implementation of energy measures of efficiency. They took advantage of their presence in the island to carry out jointly with officials of the local government - a visit to the geothermal field of “Sulphur Springs”. The area confirmed the interesting geothermal potential once again already identified previously by other experts also confirming the eligibility of the site in terms of: Industrial (the presence of an interesting electric market in the area and proximity with a central interconnection system); Technical (evidence of resources of very high enthalpy, those that would allow to feed a plant of medium size); Environmental (low visual and sound impact of an eventual geothermoelectric plant); The personnel informed that in January of 1999 the Government of the island had signed a technical agreement with a private European firm (Compagnie Francaise Geotermique, France), in connection with the development of some additional studies and with a revision of the existent data on the project Sulphur Springs. This agreement, however, didn't represent (neither does it represent at the present time) a commitment between the governments and the private company for the development and exploitation of the field. The Sulphur Springs are located in what is known as the Qualibou Caldera. This depression, which is 6 km in diameter, is believed to have been formed following the collapse of a large volcanic cone. The island of St. Lucia lies within the north-east Trade Wind belt and is normally under an easterly flow of moist warm air. Its location in the Atlantic Ocean/ Caribbean Sea means that ambient sea surface temperatures vary little from 26.7oC at any time. The island receives an almost constant amount of surface solar radiation from month to month. Wind speeds are highest, on average, during the months of January to July, corresponding roughly with the dry season. Wind speeds average 15 mph during January to July and 10 mph during August to December. Higher gusts are occasionally experienced with the passage of tropical disturbances and cyclones.. 39.

(45) Chapter 2: Geothermal Energy; Research and Implementation. 2.5.1 Electricity Market Situation. St. Lucia Electricity Services Limited is the sole commercial generator, transmitter, distributor and seller of electrical energy in St. Lucia. The customer base as of December 31st 2002 was 48,633, consisting of residential, commercial and industrial customers. Lucelec operates three power stations, with a standby facility at Soufriere on the western coast of Saint Lucia and three sub-stations integrated to form one power system. The Company uses diesel fuel as its exclusive energy source and has a fuel supply contract with Hess Oil St. Lucia Limited (HOSL).. 1. Generation In 2002, generation operations recorded 239 million units of electricity for sale. Demand peaked at 43,400 kilowatts. Fuel cost represented approximately 30% of total cost and over 40% of operating cost. Cul de Sac power station is the mainstay of operations, though the aging Union Power Station is held in availability in case of need. Cul de Sac remains a state of the art station, where the facilities and sophistication can compare with any in the world. The performance and reliability of the new Wartsila diesel generators is superlative, and problems experienced in earlier years with other equipment have been completely resolved. The Company now serves its customers with one of the finest generating systems in the region. At present the Cul de Sac Plant houses seven generators with an available capacity of 55.6MW. An eighth generator is currently being installed at that facility. This additional unit will bring the available capacity to 65.8MW. 2. Transmission & Distribution System The critical transmission and distribution systems are responsible for providing the power supply to all domestic and business customers. The Company has built a 66 kV line to the north, extending to Reduit Substation in the north of the island, to Dennery on the East Coast. The System Control department coordinates the various facets of system operation, and in particular manages the unified transmission and generating systems introduced in 1990. The department currently coordinates the operations of Cul de Sac. 40.

(46) Chapter 2: Geothermal Energy; Research and Implementation and Union power stations, with a transmission and distribution system serving six 66 kV sub-stations and over 1,000 miles of overhead lines. An enhanced computerized SCADA (System Control and Data Acquisition) system was installed in 2000.. Table 2.4; Operating capacity in St. Lucia (1997-2002). 2.6 Possible Applications in St. Lucia. In a first approach to the possible use of the geothermal resource, there are three types of potential uses with possibilities of success. The first use would be as direct heating, or through a heat pump, from the drying process at low temperatures, the heating of hothouses or of water to be used in diverse processes. Among the drying processes that could be mentioned: the process of drying herbs, tea and tobacco. A second potential application is refrigeration. In this case it is suggested to analyze the use of systems of absorption. It stands out that these systems they can present values of low function factor and low capacities for temperatures inferior to 80ºC, that which would show the necessity of an appropriate design for such systems. On the other hand, the use of the geothermal resource seems feasible being used in a vapor cycle that can be used as a refrigerator.. 41.

(47) Chapter 2: Geothermal Energy; Research and Implementation 2.7 Conclusions: 1. In the case of St. Lucia, it can be concluded that there is present a viable geothermal energy resource which can supply a substantial area. 2. In spite of the high investment costs that accompanies the employment of geothermal systems, the situation of current fuel prices make it that this type of project is feasible in great measure. 3. The studies carried out in the case of St. Lucia show that it is possible to obtain generation levels that surpass 40% of the current demand of the system. 4. The application of these systems on a small scale turns out to be viable given the characteristics of the loads that make up the system.. 42.

(48) Conclusions and Recommendations General Conclusion •. The methodology of the proposed evaluation allows for one to make assertive decisions in the study of projects of this nature.. Recommendations •. Greater exploitation of renewable resources in order to lessen the environmental impact on the planet. A move towards clean energy by first incorporating hybrid systems which combines fossil fuel generation with other renewable energy sources which will help with the transition into clean energy.. •. Research uses of renewable energy source in the manufacturing industries. Many factories use energy for heating materials which requires large amounts of energy. The use of renewable resources in particular geothermal energy can contribute in the reduction in the cost of production of many of the goods.. •. In the case of St. Lucia, more detailed research needs to be done on the potential of the geothermal resource. From the research already done on the area in question, it is obvious that St. Lucia has an exploitable geothermal resource but lacks the necessary information on the area to maximize its exploitation.. •. It is also recommended that research be done into the implementation of other forms of renewable energy such as solar, wind, hydroelectric and biomass. There is the possibility for the exploitation of all these forms of energy on the island.. 43.

(49) Bibliography Bibliography 1. Agencia de Cooperación Internacional del Japón (JICA). Proyecto de Desarrollo Geotérmico en la Zona Norte de la Provincia del Neuquén (Informe Final). 1984. 2. Centro Regional de Energía Geotérmica del Neuquén. Pozo Geotérmico Copahue II.1986. 3. ARMSTEAD, H.C.H., 1983. Geothermal Energy. E. & F. N. Spon, London, 404 pp. 4. BARBIER, E. and FANELLI, M., 1977. Non-electrical uses of geothermal energy. Prog. Energy Combustion Sci., 3, 73-103. 5. BEALL, S. E, and SAMUELS, G., 1971. The use of warm water for heating and cooling plant and animal enclosures. Oak Ridge National Laboratory, ORNLTM-3381, 56 pp. 6. BENDERITTER, Y. and CORMY, G., 1990. Possible approach to geothermal research and relative costs. In: Dickson, M.H. and Fanelli, M., eds., Small Geothermal Resources: A Guide to Development and Utilization, UNITAR, New York, pp. 59—69. 7. BROWN, K. L., 2000. Impacts on the physical environment. In: Brown, K.L., ed., Environmental Safety and Health Issues in Geothermal Development, WGC 2000 Short Courses, Japan, 43—56. 8. Bruce D. Green and R. Gerald Nix, National Renewable Energy Laboratory; “Geothermal—The Energy Under Our Feet”; page12 ; www1.eere.energy.gov/geothermal/pdfs/40665.pdf 9. CARIBBEAN COUNCIL FOR SCIENCE AND TECHNOLOGY; GENERAL LC/CAR/G.565CCST/99/14 June 1999; RENEWABLE ENERGY IN THE CARIBBEAN WHERE WE ARE; WHERE WE SHOULD BE 10. COMBS, J. and MUFFLER, L.P.J., 1973. Exploration for geothermal resources. In Kruger, P. and Otte, C., eds., Geothermal Energy, Stanford University Press, Stanford, pp.95—128. 11. ENTINGH, D. J., EASWARAN, E. and McLARTY, L., 1994. Small geothermal electric systems for remote powering. U.S. DoE, Geothermal Division, Washington, D.C., 12 pp.. 44.