Energy Procedia 47 ( 2014 ) 71 – 75

1876-6102 © 2014 The Authors. Published by Elsevier Ltd. Open access under CC BY-NC-ND license. Selection and peer-review under responsibility of the Scientific Committee of Indonesia EBTKE Conex 2013doi: 10.1016/j.egypro.2014.01.198

ScienceDirect

Conference and Exhibition Indonesia Renewable Energy & Energy Conservation [Indonesia EBTKE CONEX 2013]

Finding Geothermal Energy Based on Radioisotopes Technology Doddy Dirgantara Putraa,*, Irma Lelawatia

aDepartment of Engineering Physics, Faculty of Engineering, Universitas Gadjah Mada, Jalan Grafika No. 2, D.I Yogyakarta, Indonesia

Abstract

Increasing energy consumption in Indonesia won’t fulfilled if only rely on availability of available energy nowadays. There are many natural resources that can be used as renewable energy. One of them is geothermal energy. Nowadays, Geothermal known only on the surface of earth with observation from geysers and hot springs. With the sophistication of modern technology, geothermal energy can be found by observing radioisotope to find content silicate and carbonate potential more accurately in groundwater. So it’s expected geothermal energy more stronger to turn on a turbine at the power plant on a large scale.

© 2014 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Scientific Committee of Indonesia EBTKE Conex 2013.

Keywords: energy; natural resources; geothermal; radioisotopes; power plant .

1. Introduction

Increasing energy needs and oil prices, especially in 1973 and 1979, have triggered countries in world to decrease dependence oil. We need to accelerate development of new and renewable resources. Nowadays, geothermal energy has utilized to power plants in twenty four countries, including Indonesia.

Indonesia's geographical location on the Pacific Ring of Fire has endowed this country with geothermal potential are not paralleled [1].

Geothermal energy is not only clean and renewable, but also requires less space than other renewable energies such as solar energy and wind energy. Geothermal also provides supplies predictable and constant, not affected by weather conditions and time. Geothermal energy is the energy contained as heat in the Earth's interior from inside of earth which has transferred to surface earth by heat conduction from sources occurs through the rock and convection

* Corresponding author. Tel.: +6285645675809. E-mail address: doddydirgantaraputra@yahoo.com

Available online at www.sciencedirect.com

© 2014 The Authors. Published by Elsevier Ltd. Open access under CC BY-NC-ND license. Selection and peer-review under responsibility of the Scientific Committee of Indonesia EBTKE Conex 2013

72 Doddy Dirgantara Putra and Irma Lelawati / Energy Procedia 47 ( 2014 ) 71 – 75

occurs due to contact between the water with a heat source which can be used continuously for heating and electricity generation [2].

The origin of this energy is linked with the internal structure of our planet and the physical processes occurring there. This heat is brought to the near-surface by thermal conduction and by intrusion into the Earth's crust originating from great depths [3]. Geothermal surface manifestation characterized by hot springs, hot mud, geysers and other geothermal manifestations. Geothermal potential is great, that is approximately 30 40% of world geothermal potential. Potential of Indonesian geothermal resources are estimated to generate 27,000 megawatts of electricity if fully exploited. Indonesia is currently only using 1,200 megawatts of electricity from geothermal energy shows Indonesian away from taking advantage of the natural condition of Indonesia as shown by figure 1 Indonesia geothermal potential.

Fig. 1. Indonesia geothermal potential. There are 256 potential geothermal areas, 84 located in Sumatra, 76 located in Java, 51 located in Sulawesi, 21

located in Nusa Tenggara, 3 located in Papua, 15 located in Maluku, and 5 located in Kalimantan. Nowadays, there are 7 geothermal working areas have been developed with a total capacity of 1,196 MW which located in Darajat (260 MW), Dieng (60 MW), Kamojang (200 MW), Mount Salak (377 MW), Sibayak (12 MW), Lahendong (60 MW), and Wayang Windu (227 MW). Between 1974 to 2009, 430 wells have been drilled [4].

As various initiatives aimed at developing renewable energy sources, geothermal exploitation activities are also affected by the lack of supportive government framework in the field of research on geothermal development in Indonesia. The aim of this paper discusses the potential for discovery of new blocks exploration of geothermal research development collaborating study of nuclear, especially radioisotopes technology. One application of the use of radioisotopes as tracer in hydrological studies. Tracer technique is one of techniques used to gain insight into the character of a system by marking systems with certain materials, such as radioisotopes. By using radioisotope tracer, various problems in the fields of hydrology will be solved by direct way which much faster than conventional way. Radioactive tracers have been used to study the movement of water in several geothermal fields, including Wairakei and Broadlands, in New Zealand.

2. Material and method

Nowadays, Geothermal known only on the surface of the earth with observation geysers and hot springs. With the sophistication of modern technology, geothermal energy can be found by observing radioisotope through groundwater seepage cycle. Radioisotopes are made in a nuclear reactor that has a density (flux) of neutrons by the reaction between the high specific atomic nuclei with neutrons. Radioisotopes are used radioisotope compounds are soluble in water and can detect the presence of gases, such as Cobalt60 [5, 6].

Composition of high-temperature hydrothermal fluids is controlled primarily by the pressure-temperature conditions, reaction kinetics and rock composition in the high-temperature reaction zone [7].

Science geohidrology be key in detecting flow of groundwater. Water seeped into the ground to form a stream which the water is contaminated with material in the ground. The ground water trapped between two impermeable layers. The ground water contains substances that can be detected by cobalt60.

Doddy Dirgantara Putra and Irma Lelawati / Energy Procedia 47 ( 2014 ) 71 – 75 73

Fluid containing cobalt60 injected into existing soil and water catchment areas are expected to be passed by the frozen magma. The selected area is an area that has been frozen or magma towards the freezing process. Cobalt60 who has been injected will flow according to the flow of groundwater [8]. The flow of goroundwater it is possible to have many ramifications.

Hydrothermal fluids commonly pass through two-phase conditions in their subseafloor reaction path [9]. It can be explained that the water that has been heated by the magma contains higher levels of cobalt60. Surface of earth in the form of detection equipment has been installed underground water flow which the tool also detects the presence cobalt60 have injected along with the groundwater flow.

Tracer test provide information on the nature and properties of connections or flow paths, between reinjection and production wells, connections that control the danger and rate of cooling of the production wels during long term reinjection of colder fluid [10, 11] and for technologies in many industrial sectors. Tracer tests were first used in the early 1900s in hydrology [12]. Tracer tests provide a better understanding of the studied reservoir including inter well connections [13]. Radioisotope tracer technical helps in detecting the presence of water flow in soil which contain cobalt60.

2.1. Research stage diagram

As case the other mineral searches, to get to the production stage should be done survey. To obtain geothermal resources exploration by conducting exploration into several stages as follows:

Preliminary survey with interpretation and analysis of aerial photos and satellite images. Volcanologist study. Mapping and geological structure. Geochemical survey is very important because it can determine type of rock which will being sampled, type

of rock which beneath the surface of the earth, the water samples to see the level of acidity and the substances contained within it, and the gas content of around manifestations, and its temperature.

Geophysical survey can be known the recording subsurface structure (fracture location, the types of rocks under the surface, the thickness of the soil layer, and the layer of permeable and impermeable) to be drilled.

Exploration drilling. In the field of hydrology, technical Tracking was done by monitoring the radiation emitted by the

radioisotope tracer, or better known as the radiotracer. In hydrological studies, which used radiotracer is released directly into the environment. The tracer selected needs to meet a few basic criteria [10] : it should (a) not be present in the reservoir (or at a concecration much lower than the expected tracer concentration), (b) not react with or absorb to reservoir rocks, (c) be thermally stable at reservoir conditions, (d) be relatively inexpensive, (e) be easy (fast/inexpensive) to analyse and (f) be environtmentally benign.

Radioisotopes not be absorbed by soil, plants and other organisms. Research phase diagram as shown reinjection scheme radioisotopes in this below.

74 Doddy Dirgantara Putra and Irma Lelawati / Energy Procedia 47 ( 2014 ) 71 – 75

Fig. 2. Research phase diagram.

Tracer techniques is used to obtaining information on the behavior of objects by marking the object with a given material. Object here is a dynamic system which changes as a function of space and time. Dynamic system of this paper is future population of fluid flow. While certain materials are materials tracer of this paper is one of radioisotope such as tritium and cobalt. In a dynamic system tracer material mixed with fluid flow past populations. Information which want to know from obtained such systems by detecting tracer that has been mixed with a homogeneous population of past fluid flow of the system investigated.

In addition, there are several requirements for the application of tracer techniques to be perfect: Tracer material which is used must have same characteristic with material of the future population of fluid

flow which are investigated. Tracer material should have a special identity that can be detected with a detection tool.

Basic application of the radioisotope tracer technique is exposure to the activity of each of the elements used. Instrument that can be used to measure of exposure to the activity is Liquid Scintillation Counter (LSC), Gamma Counter, HPGe, and others.

3. Result and discussion

The phenomenon of emergence steam in a geothermal field derived from meteoric precipitation water which seeped deep into the earth met with magma so as to create steam with high temperature and pressure. Geothermal caused by hot magma induces a porous layer of groundwater permeation in between layers of impermeable rock. This vapor tends to return to the earth’s surface as geothermal manifestations in the region indicate that there are sources of geothermal energy. Therefore location of recharge area of the geothermal fluid is a very important factor to known in an effort to preserve sustainability of geothermal energy production.

In some places, hot water naturally comes up to or close to earth’s surface. Naturally heated hot water that comes to the surface is called a hot spring. Naturally heated underground reservoirs are called geothermal reservoirs.

To determine the movement of ground water wells used many methods (multi well technique). Radioisotope tracer is injected into a center of well and on the other drill holes around it, further monitoring was conducted with radioactive detector. Direction of groundwater movement can be determined by knowing the presence of radioactive wells drilled on these [14]. Utilization of geothermal resources to electricity demand in Indonesia has begun to be developed, examples injection of tracer tritium (H-3) on the field Kamojang, West Java in 1992 and 2003, injection of tracer tritium (H-3) on the field in 2004 Lahendong, North Sulawesi, and injection of tracer tritium (H-3) and Cobalt60 in the field of petroleum SOPA, Sumbagsel in 2004. Use of nuclear technology particularly radioisotope tracer technical have helped to determine the temperature of the heat source and heat reserves through identifying natural isotopic composition was conceived by the heat source.

Injected Into The Potential Ground

Recording Radiation Received

Radiation Detectors To Track

Radioisotop Emits Radiation

Radioisotop

Doddy Dirgantara Putra and Irma Lelawati / Energy Procedia 47 ( 2014 ) 71 – 75 75

Cobalt60 and Tritium radioisotopes are useful for detecting flow groundwater and gasses have injected into a porous layer of water permeation which save groundwater. Cobal60 and Tritium which flow with groundwater give sampling an overview of geothermal prospect area that includes potential area, depth of reservoir, fluid characteristics and estimates of potential reserves and its natural heat to find the location and exploration drilling targets.

Geothermal exploration can produce steam for a long enough period of about 25 until 30 years [15]. On the other hand, to keep stability of groundwater cycle environment should be held reforestation surrounding geothermal wells so that the tree can absorb water and save it in the soil. If not held reforestation, occur in the soil is drying and consequently there isn’t groundwater to evaporated and geothermal wells become dry. It takes decades to replenish the water supply in the soil for geothermal purposes

4. Conclussion

The potential for discovery of new blocks exploration of geothermal research development collaborating study of nuclear, especially radioisotopes technology is accurate to be implemented further in the entire search geothermal in Indonesia. It is evidenced New Zealand have used radioisotope tracer technology. With radioisotope technology is expected to be explored geothermal more power to turn on a turbine at a power plant on a large scale. And radioisotop tracers methods developed faster than conventional methods. Moreover, radioisotope tracers give more information about an overview of geothermal prospect area that includes potential area, depth of reservoir, fluid characteristics and estimates of potential reserves and its natural heat to find the location and exploration drilling targets. If the project is successful, fulfilment of electricity in the area and even other areas can be spread evenly.

Acknowledgements

Firstly, We give our best honour to Allah SWT. Secondly, We give our best thanks to Our Parents.

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