Csilla Tonkó, GyörgyPátzayBME KKFT&MTET

6. May. 2011RENEXPO 2011

ENVIRONMENTAL ASPECTS OF GEOTHERMAL ENERGY USE IN HUNGARY

•Geothermal energy is one of the cleanest, partially renewable energy.

•Conventional geothermal energy (100-2500m depth) can be used directly for heating, drying stc. or indirectly for electric energy production.

•Geothermal fluids are multicomponent, multiphase fluids or steam, containing dissolved solid, gas, organic materials and suspended solid particles. These components concentrations vary in a broad scale.

•Concentration of the dissolved components are usually increasing with temperature. Some components (toxic etc.) should be removed before or after the energetic use.•Potentially the components with high risk (Hg, B, As, and Cl) could be separated, and the used fluid should be recharged into the reservoir.

Geothermal energy

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Some geothermal wells are potentially suitable for electric energy production (ORC) in Hungary

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NSz-3 high entalphy well

parameters values unit

Depth of well 3165.0 m

Water flowrate 1313.4 dm3/min

Water temperature 171.0 oC

TDS 24855.0 mg/dm3

Gas flowrate 6986.1.0 dm3/min

Gas temperature 171.0 oC

Wellhead pressure 45.0 Bar

Separated GWR 1700.0CO2 16.270 vol%, CH4 79.440 vol%N2 4.290 vol%

Ndm3/m3

Dissolved GWR 3400.0CO2 35.250 vol%, CH4 61.910 vol%N2 2.840 vol%

Ndm3/m3

Water analysis Ca2+ 1.335.10-3

Mg2+ 3.350.10-4

Na2+ 3.453.10-1

SO42- 2.380.10-4

Cl- 3.179.10-1

ATOT 2.600.10-2

mol/kgmol/kgmol/kgmol/kgmol/kgmol/kg

High TDS and chloride, less calcium- and magnesium bicarbonate and sodium sulfate. There is no calcium-sulfate and chloride present.

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Parameter value unit Depth of well 4239.0 mWater flowrate 3750.7 dm3/minWater temperature 180.0 oCTDS 27200.0 mg/dm3

Gas flowrate 46500.0 dm3/minGas temperature 180.0 oCWellhead pressure 40.0 BarSeparated GWR 4400.0

CO2 76.714 vol%, CH4 20.899 vol%N2 2.566 vol%

Ndm3/m3

Dissolved GWR 8000.0CO2 89.300 vol%, CH4 7.824 vol%N2 3.876 vol%

Ndm3/m3

Water analysis Ca2+ 3.081.10-3

Mg2+ 4.540.10-4

Na2+ 4.284.10-1

SO42- 2.380.10-4

Cl- 4.684.10-1

ATOT 1.009.10-2

mol/kgmol/kgmol/kgmol/kgmol/kgmol/kg

Fab-4 high entalphy well

High TDS and chloride, less calcium- and magnesium bicarbonate and sodium sulfate. There is no calcium-sulfate and chloride present.

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Other possibilities:

Heat pump heating using geothermal heat.Example: Szeged city . The building of the Environmental authority is heated. 15 drilled 120 m deep heat exchanger used.

District heating with geothermal wells using recharging wells into Upper-Pannonian sandstone in Hódmezővásárhely. Since 1998 the system is in service.

The GeoGas Energia-hasznosító és Szolgáltató Co. developed a project to use the separated methane content of 32 geothermal wells in gas engines to produce electricity. The mathane content of these wells are between 65-95%. The project contains future use of 27 gas engines (7 with 201 kWe, 10 with 150 kWe and 10 with 105 kWe capacity.)

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Geothermal energy direct use has advantages:

• Low- and medium-enthalpy fluids could be used (<150oC)• Theese fluids are the most of the fluids (80 countries)• In direct use no convection- high efficiency• Conventional drilling technology can be used• Conventional, not too expensive devices are needed (fitted on the

temperature and chemistry of the fluids)• Construction time is short• Small scale use is possible:

– households– greenhouses– Fish-farming, algal growth etc.

• Large scale is possibel too:– District heating, heating of buildings etc.– Drying of foods, wood, ores etc.

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Environmental aspects of geothermal energy useAir quality

All geothermal fluids contain more or less carbeonates, hydrogen-carbonates and dissolved carbondioxide in equilibrium below the bubble point depth. Above the bubble point depth boiling is started, and non condensable gases (most often carbon dioxide, methane and nitrogen) are segregated, forming a separated gas. Bertani et al (2002) investigeted 85 geothermal power plants and determined an average 122 g/kWh carbon-dioxide emission value.

In most hydrothermal systems the oxigen concentration is very low, and in theese systems the reduced form of sulfur, nitrogen and carbon (H2S, NH3, and CH4), are in the gas-steam phase. In most geothermal system the ratio of the steam-non condensable gas phase is less then 5% by mass. In binary cycle geothermal power plant ther is not separated stem-gas phase, and gas content of the fluid is recharged into reservoir.

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In direct-use systems the gas-steam phase is separated, methane could be fired in a gas-motor, ammonia and hydrogen sulfide separated, while carbon-dioxide is emitted into environment.

In some cases the steam-gas phase could contain volatile Hg, Rn, B, N2 and He components. The most important air pollutatnts are: CO2, H2S, NH3, Hg, As and H3BO3. (H2S is the most irritating).

Air pollution is higher at high-enthalpy, mostly liquid phase fluids.

Air pollution is happening mainly during the energy pruduction.

Recgarging and/or waste heat multistep use diminishes the air pollution.

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Some air pollution examples at geothermal power plants (mg/kg) (Hg mg/kg) Brown, Ellis

CO2 and H2S emission in Icelandic power plants (Armannsson)

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Typical steam-gas phase compositions (g/kg) (Barbier 1997)

 Components (g/kg)

The Geysers USA

Larderello Italy

Matsukawa Japan

Wairakei N.Z.

Cerro Prieto Mexico

H2O 995.9 953.2 986.3 997.5 984.3

CO2 3.3 45.2 12.4 2.3 14.1

H2S 0.2 0.8 1.2 0.1 1.5

NH3 0.2 0.2     0.1

CH4 + H2 0.2 0.3      

Others 0.2 0.3 0.1 0.1

 

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Surface and subsurface water pollution

Dissolved salts: Na, K, Ca, Sr, Ba, Ra, Li, Mg, Fe, NH4+, Cl-, SO4

2-, HCO3-, CO3

2-, F-, NO3

-, HPO42-, HS-, Br-, I-, SiO2

Dissolved toxic components: Li, B, As, H2S, Hg, Cu, Pb, Cd, Fe, Zn, Mn, Al

Liquid wastes are generated during drilling and production too. Most danerous are the hot, toxis, alkaline or acidic, high salt content fluids. Toxicity depends on the temperature of the fluid and on the type of the reservoir rocks.

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Pollutants and toxic components concentrations in geothermalwaste waters (mg/kg) mercury (mg/kg) ( Ellis & Mahon 1977, Ellis 1978, Brown, 2000)

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Waste heat

Waste heat is generally high for geothermal plants compared to other energy types. According to DiPippo (1991), a liquid dominated geothermal field releases 8 times more liquid heat per year than conventional fossil fuel fired power plants, while a vapor dominated field releases nearly 4 times as much heat.

In case all waste liquid is reinjected into the deep reservoir this impact is zero, otherwise hot waste liquid can rise the temperature locally so that animals and vegetation are killed.

The impact of the disposal of hot waste liquid depends on many factors, such as the amount and temperature of the waste stream, but also on climatic and seasonal conditions and on the flow characteristics and temperature of a river or lake.

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The used thermal waters of high temperature and organic matter content conducted upon the ground surface into the rivers or lakes are increasing the heat and pollution load of surface waters and that of the geological formations.

They are damaging the natural ecosystem through increasing the pollution and temperature of the recipient. Even a 2-3-oC-increase in the temperature of water as a result of discharging wastewater can damage the ecosystem. Hydrobiological processes increases and dangerous changes in the biological equilibrium can be expected. The solubility of oxygen decreases.

The plant and animal organisms that are most sensitive to temperature variations can gradually disappear.

In many cases the thermal water utilisation and drain systems are constructed with the insertion of a cooling pool to make possible the cooling of water below 40 oC in such situations as well.

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Waste heat of different power generation technologies

1.1

3.0

1.6

1.7

2.0

2.3

4.4

4.8

5.3

9.0

0 1 2 3 4 5 6 7 8 9 10

Gas

Oil

Coal

Nuclear

Solar Thermal

Geothermal

Thermal power (MWe) / electric power (MWe)

Waste heat emissions of power plant types

Direct steamDouble flash

Single flashBinary

Gas (combined cycle)

Gas (single cycle)

Rybach 2005

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Subsidence

oSubsidence of the ground is an irreversible process as a result of fluid withdrawal due to geothermal exploitation. When fluid withdrawal exceeds natural inflow, the pressure in pore spaces reduces.

oThe amount of subsidence in an area depends both on the production rateand on physical-mechanical properties of the reservoir such as lithostatic pressure, enthalpy of the reservoir fluid, elastic moduli of the rock and can possibly be accompanied by (undetectable) effects of compaction of the caprock and reservoir thermo-elastic contraction (Ciulli et al., 2005).

Change in thermal features

This is due to a decline in reservoir pressure because of mass withdrawal during production. Pressure reduction can cause a drawdown of the groundwater table through permeable paths in the bedrock and results in a reduced amount of geothermal fluids reaching the surface.

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Land use

The land that is occupied by the exploitation equipment and a large part around this area can not beused for other purposes either for mankind or to serve as habitat for living species.

Might cause loss of valuable cultural sites or recreational area for example and might result in some social effects and might have an impact on the biodiversity of the area under exploitation.

The amount of land occupied by geothermal exploitation is much smaller than for other renewable energy sources.

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Land requirement for power plants

66.0

40.0

28.0

10.0

2.7

1.2

0 10 20 30 40 50 60 70

Solar PV

Coal

Solar Thermal

Nuclear

Geothermal

specific land requirement [103 m2/MWe]

Flash cycle

Binary cycle

Rybach 2005

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Noise oPeriodic blasting noise could occur during construction of well pads, sumps and the power plant site, which can be reduced with the help of noise shields around drilling rigs and residential grade mufflers.

oDuring operation noise could increase above ambient levels, but these effects would not contain any perceptible high frequency tones and would produce a neutral, indistinguishable sound. Noise above ambient level could have adverse impacts, especially on noise sensitive wildlife species.

Sound levels

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Impact Probability of occurring

Severity of consequences

Air pollution L M

Surface water pollution M M

Underground pollution L M

Land subsidence L L to M

High noise levels H L to M

Well blowouts L L to M

Conflicts with cultural and archeological features

L to M M to H

Socioeconomic problems L L

Solid waste disposal M M to H

Pollution can be chemical and/or thermalL = low, M = medium, H = high

Potential environmental impacts of direct use geothermal projects: probability and severity (from Lunis 1989).

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Geotermia

NaturalGas

Oil

Coal

Source: EIA 1998; Bloomfield and Moore 1999

CO2 emission(Ton/MWh)

0,1000

0,500

0,250

0,750

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Typical exploitation of a geothermal field

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Dissolved materials, such as sodium chloride (NaCl), boron (B), in some cases traces of arsenic (As) and mercury (Hg) – whose concentrations usually increase with temperature – is a source of pollution if discharged directly into the environment. There may be a need for monitoring in case their concentrations exceed permitted pollution limits.Thermal waters cooled in the course of utilisation are usually released to public sewers, drainage canals, sometimes at lakes or storage reservoirs or occassionall used for irrigation. But in many cases the total dissolved salt content of thermal waters or equivalent % of Na is exceeding the limit value below which used waters may be disposed in public sewers without pollution fee or used for irrigation without spoiling soil quality.

Dissolved materials

Some environmental aspects of the Hungarian geothermal energy production

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In some geothermal direct use systems the used warm water is collected in a surface lake, and after cooling is partially discharged.The total dissolved solid (TDS) content or the sodium content of this water is often above the limiting values. cooling. These waters can be discharged only with dilution.

Na %: ratio of sodium between cations

If in the water HCO3- is dominating, max Na % is 35%.

If in the water Cl- is dominating, max Na % is 45%.

100)()()2()2(

%

KNaMgCa

NaNa

For discharge important characteristics are:

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SAR (sodium adsorption ratio)

Na cause alkalization in soil!!

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MgCa

NaSAR

27Specific conductivity measures the total dissolved solid content!

Total salt content in Hungarian thermal waters

Specific conductivity

Wells Surface water

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Salt content of some Hungarian Thermal Water

Szentes ~2000 mg/l

97 %

Mezőkövesd ~4200 mg/l

39 %

Zalakaros ~11600 mg/l

91 %

Hévíz, Bogács, Eger< 1000 mg/l

14%, 20 %, 11 %

Bükfürdő~10000 mg/l

89 %

Kistelek~1500 mg/l

94%

Na eq % = Na eq / (Na eg + K eq + Ca eq + Mg eq) * 100MSZ 1484-3 (6. point) standard

Na eq = Na mg/l /23 Ca eq = Ca mg/l /20

K eq = K mg/l /39,1 Mg eq = Mg mg/l /12

- TDS- Na eq%

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•Radioactive isotopes (226Ra, 228Ra, 222Rn)

Mined thermal water contain mor or less 238U and 235U isotopes and their decay products, among other radioactive 226Ra, 228Ra, 222Rn in dissolved form or as scale.

Radon gas bubbles out very easily from thermal water and diluted with air is less dangerous.

Isotopes of radium, like calcium, magnesium and barium precipitate as sulfate type scale. High energy gamma-ray of 226Ra maydanegerous and such type os separated scale should be stored in a closed separated place. Radium could be separated from water by adding barium-chloride.

•Organic compounds (humic acids, phenols etc.)

Environmentally dangerous aromatic and polyaromatic compounds may be present in high concentration only at higher temperatures. In some Hungarian thermal water there are detectable amounts of phenolic and alky-benzene types of organic compounds. COD~20-70 mg O2/l .

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•Boron compounds

Boron compounds are present in some Hungarian thermal waters with several hundreds of ppm concentration. They are potential pollutants for the environment. Boron dissolved in water is an essential element for the plants, but above 1 ppm it is toxic. Boron compounds can be removed by adsorption, ion exchange or memnrane separation.

•Arsenic compounds

Some Hungarian thermal waters contain considerable (~10 mg/l) amount of arsenic compounds. The cooled water should not recharged into surface waters without arsenic removal. Water containing arsenites and arsenates, the former forms are more toxic. Human consumption is possible below 50 mg/l, for watering this limit is 200 mg/l. Arzenic compounds could be removed from thermal water by adsorption, ion exchange and membrane separation.

wellBmg/l

CSERKESZŐLŐ 203519HAJDÚSZOBOSZLÓ 185017SÁRVÁR 128278ZALAKOMÁR 106076CSERKESZŐLŐ 88487ZALAKAROS 88310ZALAKAROS 83874ZALAKAROS 76054BÜKKSZÉK 74130ZALAKAROS 74007BÜKKSZÉK 72477BÜKKSZÉK 70923ZALAKAROS 69073BÜKKSZÉK 67839ZALAKAROS 67839BÜKKSZÉK 66606NYÍREGYHÁZA 62905SÁRVÁR 61672ZALAKAROS 61672ZALAKAROS 61672NYÍREGYHÁZA 60439ZALAKAROS 60300

well NoAsmg/l

MEZŐCSÁT 46 930

MEZŐKÖVESD 48 620

MEZŐKÖVESD 48 620

CSERKESZŐLŐ 1 584

MEZŐKÖVESD 48 570

BÉKÉS 27 500

POROSZLÓ 34 480

GÁLOSFA 4 400

BÉKÉS 46 360

BÉKÉS 29 339.64

NAGYSZÉNÁS 13 300

ABÁDSZALÓK 40 290

POROSZLÓ 34 280

NAGYSZÉNÁS 13 270

FÜZESGYARMAT 34 230

KÖRÖSÚJFALU 4 201

GÁLOSFA 4 200

KISVÁRDA 154 200

CSORNA 47 200

BÉKÉSCSABA 1019 200

FÜZESGYARMAT 41 200

well No fenol ind.mg/l

SZEGED 376 100SZEGED 650 13.8BÉKÉSCSABA 953 8.59SZEGED 474 8.25GYULA 453 6.872SZEGED 602 5.895SZARVAS 61 5.87SZARVAS 87 5.59SZÉKKUTAS 271 5.55SZARVAS 80 5.3DESZK 40 4.527SZARVAS 110 4.36DOMASZÉK 25 3.691VÉGEGYHÁZA 19 3.17MEZŐTÚR 140 3.1SZEGED 476 3.092TÚRKEVE 26 3.02ÖCSÖD 46 2.98TÓTKOMLÓS 145 2.92OROSHÁZA 481 2.917HÓDMEZŐVÁSÁRHELY 1077 2.9MAKÓ 230 2.6MAKÓ 189 2.1BÉKÉSCSABA 282 1.94SZARVAS 81 1.9BÉKÉSCSABA 282 1.8KISKUNMAJSA 49 1.44CSERKESZŐLŐ 1 1.4SZENTES 658 1.34SZARVAS 88 1.25SZEGED 453 1.022

As, B content and phenol index in some Hungarian geothermal water

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well No K+ Na+

SÁRVÁR 23 26544.5SÁRVÁR 36 1100 17500SÁRVÁR 36 1280 17000SÁRVÁR 36 16916SÁRVÁR 23 680 16600SÁRVÁR 23 16292.7SÁRVÁR 23 16211.5SÁRVÁR 36 16128.6SÁRVÁR 36 570 16000SÁRVÁR 36 900 15500SÁRVÁR 36 770 14800SÁRVÁR 36 1020 14800GÖDÖLLŐ 74 146 14000SÁRVÁR 36 13684.5GÖDÖLLŐ 74 13279.7GÖDÖLLŐ 74 13067.4

BALATONSZABADI 49 150 10600CSERKESZŐLŐ 1 10376KAPUVÁR 84 127 9800CSERKESZŐLŐ 1 99.8 8884.9BÜKKSZÉK 1 7850.3BÜKKSZÉK 1 93.2 7797BÜKKSZÉK 1 96.72 7784.3BÜKKSZÉK 1 7452BÜKKSZÉK 1 7254.89BÜKKSZÉK 1 6800.91BÜKKSZÉK 8 6796BÜKKSZÉK 8 6796BÜKKSZÉK 9 100 6750BÜKKSZÉK 1 6607.4BÜKKSZÉK 1 6533.4

SÁRRÉTUDVARI 19 6323.62BÜKKSZÉK 9 178.4 6200BÜKKSZÉK 9 72.6 6140BÜKKSZÉK 9 95 6100KAPUVÁR 61 120 6000

well hardnessBÜK 8721BÜK 7226BÜK 7168BÜK 5152BÜK 5152SZOMBATHELY 4750BALATONSZABADI 4652SZOMBATHELY 4450BÜK 4379SÁRRÉTUDVARI 3448.52BÜK 3048PÉCSVÁRAD 2960BÜK 2280GÖDÖLLŐ 2260.05GÖDÖLLŐ 2250GÖDÖLLŐ 2200KISKŐRÖS 1912KISKŐRÖS 1880HEVES 1520KAPOSSZEKCSŐ 1460BÜK 1331DÉVAVÁNYA 1320HEVES 1180BUDAPEST-XIV.KER. 1092VAJTA 1072TÁPIÓGYÖRGYE 920ZALACSÁNY 900SÁRVÁR 858KEHIDAKUSTÁNY 844BÜK 841.39MEZŐKÖVESD 827.39BÜK 820ZALACSÁNY 820SÁRVÁR 817.13SZEGED 812SÁRVÁR 803.34SÁRVÁR 802.13

K, Na content and water hardness (mg/l) in some Hungarian geothermal water

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Parameter Unit Energeticaluse

Balneologicaluse

Thermal bath

Chemical Oxigen Demand (COD)

mg/l - 150 -

TDS mg/l 3000 5000 2000

Sodium-equivalent % 45 95 45

Ammonia-ammonium-nitrogen

mg/l - 10 -

Sulfids mg/l - 2 -

Phenolindex mg/l 1.0 - -

Total barium mg/l - 0.5 -

Heat discharge oC 30 30 30

28/2004. (XII. 25.) KvVM Governmental Decree Emission limits

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Variations of the wellhead pressures in Szeged ,Székelysor well (By Dr Török, J.)

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Thank you!