Energy from the deep subsurface potentials of geothermal

Energy from the deep subsurface, potentials of geothermal for a sustainable supply of increasing energy demands Annamária Nádor Geological and Geophysical Institute of Hungary 3 rd European Energy Conference, October 27 -30, 2013, Budapest

Current energy consumption is unsustainable - actions are urgently needed! Ø growing energy demand Ø restricted and uneven distribution of fossil fuels → supply security Ø climate change debate: enhanced use of fossil fuels → increased atmospheric CO 2 concentration → global warming, extreme events Kyoto Protocol 20/20/20 by 2020 COM(2006)848 Ø cut energy consumption (fossil fuels) and CO 2 emisssions Ø increase energy efficiency Ø increase renewable energy sources (RES) increase of renewables in the energy mix: integrated economic development ü innovative and competitive technologies ü structural changes in the industry and agriculture ü new working places ü decentralized → rural development

New Energy Strategy of Hungary 2011 -2030 National characters Ø Import dependency: ~ 83% of hydrocarbons Ø Security supply, focus on own resources Russian import 20 billion m 3/y European market 4, 5 billion m 3/y Main aim: ensure the longterm sustainability, security, and economic competitiveness of energy supply in Hungary Total consumption: 12 billion m 3/y Own production: 1, 8 -2, 0 billion m 3/y 4, 5 bn m 3/yr 6, 5 bn m 3/yr 4, 1 bn m 3/yr Increasing the share of renewables RES Directive (2009/28/EC): 13% RES for Hungary: not an obligation but a POSSIBILITY for economic growth: 14, 65% RES by 2020 (120, 57 PJ)

Contribution of geothermal energy 2010 9% of total RES 2020 17% of total RES Direct heat (PJ) 4, 23 14, 95 Electricity production (MW) 0 57 2010 2020 Distribution of RES in the Electricity and Heating-Cooling sectors

Geothermal energy: definition and basic concepts Geothermal energy is energy stored in the form of heat below the surface of the solid earth (shallow – stored solar and deep) Origin of heat: decay of radioactive isotopes: U 238, U 235, Th 232, K 40 Heat content of the Earth: 12, 6∙ 1024 MJ Takes over 109 years to exhaust via global terrestrial heat flow Total volume of the Earth Heat flow Crust (rich in radioactive isotopes) 2% 8 x 1012 W mantle 82% 32. 3 x 1012 W Core (no radioactive isotopes) 16% 1. 7 x 1012 W 1000°C 4300°C 3700°C

Main geothermal provinces of Europe high enthalpy (el. power) high temp. basins (el. power, district heating) medium temp. basins (district heating) everywhere shallow geothermal EGEC

Hydrogeothermal (convectional) systems heating → thermal expansion of stored groundwater → lower density, rise and replaced by colder meteoric water of high density coming from the margins of the system Enhanced Geothermal Systems artificially enlarged fractures as „heat exchangers” in deep lying hot rock bodies

Lindal diagram Cascade utilization of geothermal energy >150°C: high enthalpy electricity generation < 150°C: low-medium enthalpy - heatingcooling + many others

1904: the world’s first geothermal power station with a 10 k. W generator at the Larderello dry steam field, Italy, Tuscany Thermal bath of Caracalla, Thermae Antoninianae

Geothermal potential of Hungary Favorable conditions due to Miocene basin formation (10 -12 My ago) Average terrestrial heat-flow: 100 m. W/m 2 Geothermal gradient: 45 °C/km Thickness of the lithosphere

Subsurface temperature distributions (°C) -1500 m -2500 m Zilahi Sebess et al. 2012

Pannonian basin - hot sedimentary aquifer (convectional flow system): utilization of geothermal energy ≈ thermal groundwater / fluid abstraction Ø high heat flux Ø thermal „insolation” of basin fill sediments Ø regional groundwater flows driven by hydraulic potential between 1 recharge and discharge areas Main geothermal reservoirs Paleo-Mesozoic fractured, karstified basement rocks Mio-Pliocene porous basin fill: multi-layered sandstones, shales depth (top) >2 -3000 m 600 -1500 m temperature >100 -150 °C 50 -100 °C prospect direct heat, balneology power, CHP

Current utilization schemes in Hungary 595 thermal wells (outflow T > 30 °C) Annual production: 68, 44 million m 3 (2011) Nádor et al. 2013

Current utilization schemes Nádor et al. 2013

Renewability vs. sustainability Renewability – attribute of the energy source The energy extracted from a renewable energy source is always replaced in a natural way by an additional amount of energy and the replacement takes place on a similar time scale as that of the extraction” (Axelsson et al. , 2001) Geothermal energy: replacement of heat and fluid Sustainability – how we use it? „. . . for each geothermal system and for each mode of production there is a certain level of maximum energy production, below which it will be possible to maintain a constant energy production for a very long time (100 - 300 years)” (Axelsson et al. , 2004)

Balanced heat-fluid production Balanced fluid/heat production (not producing more than the natural recharge re-supplies) is fully sustainable. These rates are limited and often not economical for use High production rates exceeding long-term rate of recharge can lead to depletion of the reservoir, which can be avoided by reinjection of used fluids.

Hydrogeological models: different scanarios TRANSENERGY project: transboundary hydrogeothermal systems only SK only HU csak SK SK, HU, SLO present SK, HU, SLO 5 X Tóth, 2012

TRANSENERGY project, Danube basin pilot area (SK-HU) Hydraulic heads field in Upper Pannonian geothermal aquifer, doublets scenario Hydraulic heads field in Upper Pannonian geothermal aquifer, pumpig wells scenario Svasta, 2013

Concluding remarks Ø Geothermal energy is an important RES and has huge potentials for growth Ø Geothermal energy is renewable on time-scales of technological /societal systems, though it is an exhaustible energy source Ø Production should be limited to sustainable levels which secures the longevity of the resource (not exceeding natural re-charge and/or re-injection) Ø Due to the favorable geological setting, the geothermal potential of Hungary is very good Ø In the current utilization balneology is overwhlemming, direct use in agriculture is significant, but much beyond the potentials in district heating Ø Ambitious NREAP numbers forecast a 3, 5 times growth in direct heat and establishment of power production by 2020

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Thank you for your attention! nador. annamaria@mfgi. hu tel: +36 -30 -924 -6823