GEOTHERMAL ENERGY AND ITS APPLICATION IN CENTRAL SYSTEM OF HEAT SUPPLY

Transcription

1 GEOTHERMAL ENERGY AND ITS APPLICATION IN CENTRAL SYSTEM OF HEAT SUPPLY Ján Takács Katedra TZB Stavebná fakulta STU Bratislava Radlinského Bratislava Slovak Republic Phone: takacs@svf.stuba.sk 1. PREFACE Slovakia has good conditions for utilization of geothermal energy (GE). Results of the research proved increased geothermal activity with average value of thermal flow 64,5 mw.m -2 and higher substantiality (120 mw.m -2 Košice valley), where the thermal flow is higher than the world average value 60 mw.m -2. The average value of geothermal gradient for Slovakia is 33 K.km -1 (in the world it is 30 K.km -1 ), in some localities it is as much as 50 K.km -1. O on the territory of Slovakia there were selected (chose) 30 perspective localities with occurrence of geothermal water (GTW) with the temperature from 25 o C to 150 o C. Preponderance of perspective localities has GTW temperature suitable for heating of buildings. Total useful energy potential is approximately MW [1]. Preponderance of geothermal energy (GE) supply (approximately 90%) depends on GTW supplies where the economical utilization is dependent on returning or exactly on re-grouting of utilized GTW. 2. PRESENT STATE ( CONDITION ) OF UTILIZATION OF GEOTHERMAL ENERGY In the geothermal systems the geothermal energy is used in 14 localities for agricultural purposes to supply the heat to greenhouses and foil-houses and to temper agricultural land. In 6 localities GE is used to supply the heat for housing estates, flats, farm buildings, sports halls and restaurants. In 3 localities GE is used

2 to prepare the technological water for breeding the fish. In 30 localities GE is used in recreation sphere in thermal swimming-pools. Total quantity of GE used in 36 localities represents heat power 132,3 MW at GTW substantial 846,4 l.s -1. Total greenhouses and foil-houses area heated by GE is approximately 27,6 ha. Data about utilization of GE-supplies for individual purposes are in the table 1 [2]. UTILIZATION OF GEOTHERMAL ENERGY BY TABLE No. 1 Place of utilization Installed power output Annual consumption (MW) (%) of energy (TJ.year 1 ) Building heating 15,2 11,5 277,5 Greenhouses heating 22,5 17,0 355,4 Fish breeding industry 2,3 1,7 36,2 Recreation purpose 90,9 68,7 1437,1 Thermal pumps 1,4 1,1 12,1 Sum (total) 132,3 100,0 2118,3 In Slovakia GE is utilized especially for recreation purpose 90,9 MW (68,7 %), then for heating of greenhouses and foil-houses 22,5 MW (17,0 %) and for heating of buildings 15,2 MW (11,5 %). GE is also used in fish breeding industry - 2,3 MW (1,7 %) and for thermal pumps (TP) 1,4 MW (1,1 %). Their applications mean a big perspective (operation improvement) in the whole energy system. 3. THE METHODS OF UTILIZATION OF GEOTHERMAL ENERGY Utilization of geothermal energy in take-off place for the needs of centralized heating supply can be realized as follows: Directly GTW has a favourable chemical-physical qualities, it does not cause (induce) incrustation, does not cause distribution pipelines corrosion and technological equipment corrosion. Direct GE utilization is shown on the picture 1. GTW is transported from a bore directly to the take-off place to heating radiators.

3 Picture 1 - Principle of direct utilization of geothermal energy 1 bore, 2 bore head, 3 GTW supply pipeline, 4 cooled GTW, 5 heating radiators, 6 making GTW neutralization, 7 recipient Indirectly GTW has an unfavourable chemical-physical qualities (creates incrust, causes corrosion of distribution pipelines and so on). GTW is used as primary heat spreading water through heat exchanger while conditioned secondary working substance circulates in heating system. Scheme of indirect GE utilization is on the picture 2. GTW is transported from bore as primary heat spreading water to the heat exchanger, where GTW transmits its energy and secondary heating substance flows to the take-off place of heating system. Picture 2 Principle of indirect utilization of geothermal energy 1 bore, 2 bore head, 3 heat exchanger I, 4 heating system I, 5 pump, 6 heat exchanger II, 7 heating system II, 8 pump, 9 recipient

4 According to the GTW flow method through take-off place of centralized heating system we distinguish two geothermal systems: Opened geothermal system. GTW is exploited by mining bore and utilized GTW is discharged to recipient, or to the public sewerage. According to the picture 1 and 2 GTW rises from the bore by its own pressure and is transported to the takeoff place. If a source does not dispose of adequate over pressure a pump is put into the system. This pump transports GTW to the heat exchanger. GTW is discharged to recipient after cooling Closed geothermal energy system. Utilized GTW is returned through reinjection bore to the original water-bearing collectors and spout-pipes. The example of a closed system is on the picture 3. GTW is transported from the bore to the heat exchanger by its own overpressure. There the GTW transmits its energy and the re-injection pump forces GTW back into original water-bearing collectors and spout-pipes. [3]. Picture 3 Principle of closed indirect utilization of geothermal energy 1 bore, 2 bore head, 3 heat exchanger, 4 take-off place No.1, 5 water pump, 6 heat exchanger, 7 take-off place No.2, 8 water pump, 9 re-injection pump, 10 re-injection bore head, 11 re-injection bore 5. EXAMPLE OF SUCCESSFUL UTILIZATION OF GEOTHERMAL ENERGY In the town of Galanta (Trnava region) there are two geothermal bores with substantiality m 0 = 50 l.s -1 and with GTW temperature on the bore head t 0 = 78 C. These bores supply flats, the public service rooms (third sphere) in the housing

5 estates Sever (The North) and the hospital in the town of Galanta with heat. In the year 1996 the first geothermal headquarters in Slovakia with 8 MW t of power were put into. GTW is used to supply the heat and warm household water. The peak source of heat is used for heating up, if the day temperature is lower than t e = - 2 C. The peak source is usually a boiler room which burns natural gas [3]. There are in the headquarters prepared these sorts of heat spreading substances: Heating with temperature gradient 77/52 C (the flats housing estate Sever ), Heating with temperature gradient 90/70 C (heating system the hospital), Heating with temperature gradient 52/42 C (low-temperature ceiling heating the hospital), Warm household water (the flats and the hospital). The whole geothermal energy system is controlled by computer and all important source parameters of GTW bores, and also the take-off places parameters are longterm recorded. Construction of energy-centre on the base of GE brought in Galanta these results in Galanta: The working boiler room for the hospital, which burnt low-calorific brown coal, was put out of operation. This boiler room consumed t low-calorific brown coal per year and produced 330 t SO 2, 36 t NO x, 159 t CO 2, 600 t of cinder. The boiler room - Sever consumed approximately 3 mil.m 3 nature gas per year. Operation of the geothermal station reduces consumption of nature gas to 1,2 mil. m 3 per year. This also reduces emission about 60 % against an original level. The most important geothermal installation is closed geothermal energy system Podhájska in Nitra region: For the first time in Slovakia there is successfully operating re-injection station, which was put into operation in GTW is exploited from the bore Po-1 (m 0 = 53 l.s -1, t 0 = 82 C) and are forced back into earth by reinjection bore GRP-1 Podhájska (m 1 = 28 l.s -1, t 1 = 39,5 C). GE is used for heating of the hotel with 86 beds, administration building and greenhouse agriculture with area 3,2 ha. GTW supplies recreation swimming-pool and hipbaths all the year round. The location Bešeňová in Liptov valley uses GE also complexly. The bore ZGL-1 in Bešeňová has substantiality m 0 = 28 l.s -1 and water temperature

6 t 0 = 61,0 C. This recreational-rehabilitation complex, which used GE in a rapid way, was put into operation in Nowadays GE are used all the year round for filling 5 swimming pools (for swimmers, for children, for recreation), to heat recreational facilities (cloak room, showers, restaurant, hotel, massage room). It altogether presents power about 1,3 MW. Greenhouses for cultivating vegetable with total area 2,5 ha (3,8 MW) are heated with the help of GE. In Bešeňová GE is complexly used and this means significant contribution to the protection of environment in polluted surroundings and more attractive all recreational and tourist services in this region. 6. LITERATURE 1. Franko, J. - Franko, O.: The trends of utilization of GEW. Scientific conference with international part The trend of economical development of Slovakia in 1998, Trenčianske Teplice, July Fendek, M. a Franko, J.: Country update of the Slovak Republic. Proceedings of the World Geothermal Congress Kyoshu Tohoku, Japan. 3. Petráš, D. a col.: Low-temperature heating and renewable energy sources. Jaga 2001, Bratislava, page 271