International Geothermal Days POLAND 2004. Zakopane, September 13-17, 2004 Free contributions. 330 A. Busso, A. Georgiev, P. Roth: VERTICAL BOREHOLE HEAT EXCHANGER: REPORT ON FIRST EXPERIENCE IN SOUTH AMERICA. COOPERATIVE WORK BETWEEN CHILE AND ARGENTINA FREE CONTRIBUTIONS 331 International Geothermal Days POLAND 2004. Zakopane, September 13-17, 2004 Free contributions. 332 A. Busso, A. Georgiev, P. Roth: VERTICAL BOREHOLE HEAT EXCHANGER: REPORT ON FIRST EXPERIENCE IN SOUTH AMERICA. COOPERATIVE WORK BETWEEN CHILE AND ARGENTINA VERTICAL BOREHOLE HEAT EXCHANGER: REPORT ON FIRST EXPERIENCE IN SOUTH AMERICA. COOPERATIVE WORK BETWEEN CHILE AND ARGENTINA. A. Busso a,*, A. Georgiev b, v , P. Roth b a Department of Physics, FaCENA, UNNE, 3400 Corrientes, Argentina b Department of Mechanical Engineering, UTFSM, Valparaiso, Chile v On leave from Department of Mechanics, Technical University of Sofia, branch Plovdiv, Bulgaria • Corresponding author. Fax: +54 3783 473930, • E-mail: [email protected] Abstract Mainly eight countries (Sweden [1, 2] , Chile and Argentina are countries possessing Canada, Germany [3], Netherlands, Norway, solar energy in large amounts which can be stored Turkey [4] , United Kingdom and the U.S.A [5]) in the ground by means of UTES during the have developed the technique. summer and used 3 to 6 months later during the Some months ago (June - July 2003) an Ther- winter. The same seasonal storage could be used to mal Response Test (TRT) was performed in produce cold in the summer. A setup for testing this Valparaiso, Chile - the first one in Latin America type of storages was realized at the "Solar Energy carried out jointly between research groups of Chile Laboratory" of the Technical University Federico and Argentina. Santa Maria, Valparaiso, Chile. Research groups of Chile and Argentina performed and analyzed a 2. Test Installation charging – discharging cycle test with this instal- A shallow BHE, 16 m deep, was installed at lation. The experiments made prove the possibility the experimental grounds of the "Solar Energy La- of using underground seasonal storage for heating boratory" - Technical University Federico Santa and cooling in different regions of Chile and Latin Maria (UTFSM) in Valparaiso, Chile [6]. This BHE America (Argentina, Brazil) and to apply the BTES was used to carry out in situ determination of technology in the same region. ground thermal conductivity λ, borehole thermal resistance R and undisturbed soil temperature, Keywords: Underground Thermal Energy Storage; b Solar Collectors; Charging; Discharging. technique commonly known as Thermal Response Test (TRT). The TRT ran for 9 days (from 24th of June to 3rd of July 2003) being the first of its kind 1. Introduction in Latin America [7]. Fig. 1 presents a schematic diagram of the setup used. Long term storage of huge amounts of thermal Two main experiments were performed: TRT - energy for heating and more importantly for cool- to determine the soil and BHE thermal properties, ing, can give a significant contribution in energy and a charging / discharging cycle - to subject the saving and rational use of energy. Underground system to different heat flow conditions over a peri- thermal energy storage (UTES) is a favorable tech- od of time. This could allow deeper character- nology from both the technical and the economical ization and understanding of the shallow store. The point of view. Depending on the local geology, study was also aided by TRNSYS simulations. hydrogeology and geochemistry either aquifer For the drilling phase, the truck of the Labo- thermal energy storage (ATES) or borehole thermal ratory of Material Testing of the Department of Ci- energy storage (BTES) are applied. Because of its vil Works of the UTFSM was used. Three perfo- smaller size and less hydro-geological restrictions, rations were made along a line to a depth of about BTES has a bigger potential for application. 22 m. 333 International Geothermal Days POLAND 2004. Zakopane, September 13-17, 2004 Free contributions. installed. The perforations were subsequently replenished with the soil originally removed. The BHE is connected to the heating system on the surface by 3/4'' copper pipes. A 2 kW electric heater was mounted in the hydraulic circuit of the installation. The circulation pump is a PKM 60-1, made by Pedrollo, Italy. It has a nominal electrical power of 370 W at 2900 rpm and flow rate between 5 - 40 l/min with a maximal head of 40 m. The entire pipe length was thermally insulated to reduce heat losses to the surroundings. The entire install- lation was cover by a plastic liner to reduce direct sun influence during test. For the charging experiment three solar col- lectors were mounted and connected to the BTES (Fig. 2) providing a total active area of 4,4 m2 Figure 1. Scheme of the test installation. (collector size is 1,05 m x 1,40 m). The distance between the collectors and the storage is about 2 m. The central perforation is a borehole with 16,9 Additional by pass valves were mounted to allow m. deep and 0.15 m. in diameter Prior to refilling the system be ran in two different modes according the perforation with a 12% bentonite mixture to the type of power source in use. TRT mode - if (commercial name Max Gel, produced in Federal power is supplied purely by electric heaters; solar Summit, Houston, Texas), a U-loop BHE made of mode - if the BTES is to be charged by solar HD Polyethylene (3/4 " SDR 11), along with a energy. All connecting pipes were carefully temperature probe comprising 4 type K (Chromel / insulated. After completing conditioning works the Alumel) thermocouples at depths of 16,9 m, 10,7 pump remained running for 10 days and different m, 3,24 m and 0,25 m, were inserted into this well. variables were monitored. The temperature probes were located on the axis of To further reduce ambient influence on the the well. The other two perforations were located system 4 m2 of surface area on top of the store were 0,4 m to the left and 0,8 m to the right of the central insulated with a layer of 0.1 m of high density BHE. Into these two perforations probes polystyrene covered with aluminum foil (Fig. 2b). comprising 4 type K thermocouples at depths of 20,5 m., 13,67 m., 6,84 m. and 0,25 m. were also a) b) Figure 2.- View of the installation and components. At the end of the charging cycle a new Tap water circulated through the radiator modification was introduced to the hydraulic becoming the cold loop of the heat exchanger and system. To release the stored energy the collectors water from the BHE circulated between the radiator were replaced by one loop of a cross flow water-to- and casing walls thus becoming the warm loop. The water heat exchanger, the other loop being fed with entire heat exchanger was thermally insulated on tap water. To this purpose, an old automobile the outside to diminish ambient coupling. radiator was adapted by placing it inside a metal casing 0.24 m. height, 0.30 m. wide and 0.08 m. 3. Equipment of measurement thick. Provisions for inlet and outlet connections to With the aim of mapping the underground the radiator and casing were taken. temperature field around the BHE, 12 Chromel / 334 A. Busso, A. Georgiev, P. Roth: VERTICAL BOREHOLE HEAT EXCHANGER: REPORT ON FIRST EXPERIENCE IN SOUTH AMERICA. COOPERATIVE WORK BETWEEN CHILE AND ARGENTINA Alumel thermocouples (8 in the ground and 4 in the with a Gemini Data Logger TGP - 0017 with a bentonite) were available from the temperature case-integrated sensor. The global solar radiation probes mounted in the ground. All electrical and was measured with Gemini Data Logger TGPR - communication cables between the setup and the 1001 using Kipp & Zonen SP-LITE Silicon PC located at the laboratory were tubed in metallic Pyranometer. Fig.3 and Table 1 present a picture pipes buried in a 0.30 m. deep trench running from and main technical characteristics of the Gemini the installation to the main switch board inside the Data Loggers. The Data loggers were programmed laboratory house (some 25 m appart). by means of the software GLM v2.8. Measurements A manual rotameter "Blue White industries were recorded at 1 min. frequency in the memory 9509" with maximal flow rate of 7,5 l/min was used of the logger and downloaded to the PC using the during the charging phase. Four Gemini Data same software. The circulating pump was turned Loggers TGP-0020 with a Standard Temperature on/off by means of a differential controller STR 1 Probe PB-4724 monitored inlet and outlet borehole with safety-fuse. All the measuring equipment was temperatures and the inlet and outlet collector calibrated prior to the test. temperatures. Ambient temperature was measured Table. 1. Technical data of Gemini Data Sheet: Tinytag Plus Range G for Standard Probe TGP-0020, Tinytag Plus Temperature Range G Internal TGP-0017 and Tinytag Plus Re-ed Millivolt Input TGPR-1001. Mechanical Data Case Style : IP68 Style Case Dimensions Height : 34mm / 1.34” Width : 59mm / 2.32” Depth : 80mm / 3.15” Weight : 110g / 3.9 oz. Features Memory Size : 16k (Non-volatile) No. of Readings : 16000 (approx) Resolution : 8 bit Trigger Start : Magnetic reed switch Delayed Start : Relative / Actual up to 45 days Stop Options : When Full/ After n Readings/ Never (Wrap around) Reading Types : Actual, Min, Max. Logging Interval : 1 sec to 10 days Offload : While stopped or when logging in minute multiples Alarms : Two, fully Programmable Functional Range : - 40°C to + 85°C / -40°F to +185°F IP Rating : IP68 waterproof Battery Life : Up