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Geothermal Energy Chapter 1: The Origin of Geothermal Energy Chapter 2: Geological Aspects and Geothermal Energy Chapter 1: The Origin of Geothermal Energy Chapter 2: Geological Aspects and Prerequisites Chapter 3: The Practical Application of Geothermal Energy in Everyday Life Chapter 4: Examples and Advantages

§ 1 The Origin of Geothermal Energy or how the Big Bang heats Your § 1 The Origin of Geothermal Energy or how the Big Bang heats Your Living Room

§ 1 The Origin of Geothermal Energy 99% of the Earth are hotter than § 1 The Origin of Geothermal Energy 99% of the Earth are hotter than 1, 000°C ! The mayor part of the rest is still hotter than 100°C Reasons: 1. Agglomeration of mass: gravitational energy kinetic energy thermal energy 2. Radioactive decay heat 3. Liquid metal solidifies energy contained in the movement of molecules is transformed into heat 4. Energy from the sun

§ 1 The Origin of Geothermal Energy • Agglomeration of mass and radioactive decay § 1 The Origin of Geothermal Energy • Agglomeration of mass and radioactive decay create nearly 100% of the entire heat of the earth • Radioactive decay still going on today • Although agglomeration of mass took place billions of years ago, its heat is still apparent today, since earth emits only small amounts of thermal energy • Nonetheless the aspect of the energy of the sun should not be underestimated Chapter 3 How does the heat of the inner of our planet reach the surface? 1. Convection flow of liquids (for example magma or water) 2. Conduction direct transmission of heat

§ 2 Geological Aspects and Prerequisites or where shall we drill the hole? § 2 Geological Aspects and Prerequisites or where shall we drill the hole?

§ 2 Geological Aspects and Prerequisites Denotation Depth Description Earth’s Crust 0 – 30 § 2 Geological Aspects and Prerequisites Denotation Depth Description Earth’s Crust 0 – 30 km -consisting of hard, cleft rock -tectonic plates are part of the crust - 200 -300°C in a depth of only 3 -5 km -no clear distinction between crust and core -density: 2. 5 -3. 0 g/cm 3 Earth’s Mantle 30 -2, 900 km undefined zone 30 -120 km -increasing pressure and temp. stone becomes more malleable; yet it can rest hard and cleft until a depth of ~120 km - temperature: ~2, 700°C -convection of matter which can be compared to a lava lamp - liquid matter rising to the top, cooling down and flowing down again -hot stone rises with a velocity of ~3 cm/year -motor, which is moving the surface of the earth, that is: responsible for the outbreak of volcanoes, movement of tectonic plates, earthquakes, drift of continents, creation of mountains etc. -not clearly belonging to crust or mantle Upper Mantle 120 -660 km -density: 3. 2 - 4. 5 g/cm 3 transition zone 660 -700 km -divides upper and lower mantle 700 -2, 900 km -density: 11. 2 -13. 6 g/cm 3 “D-Layer”, Wiechert. Gutenbergdiscontinuity Outer Core 2, 900 -3200 km -divides Lower Mantle and Outer Core Inner Core 5, 150 -6, 378 km -6, 300°C, 3. 5 mio bar Fe and Ni form a solid metal-ball which is rotates -radioactive decay enormous heat Lower Mantle 3, 200 -5, 150 km -mainly consisting of Fe and Ni -liquid; viscosity comparable to water -electrically conductive flowing liquid metal magnetic field!

§ 2 Geological Aspects and Prerequisites What are excellent geological conditions for the use § 2 Geological Aspects and Prerequisites What are excellent geological conditions for the use of geothermal energy? hot subterrestrial stone low depth reservoirs of hot / warm groundwater Do we find the same temperature in a certain depth all over the world? No! Although the temperature averagely rises with 30°C per km, this is only a very rough estimation. The subterrestrial temperature strongly depends on the local geophysical prerequisites (such as local thickness of the crust (influencing conduction), formation of tectonic plates, groundwater and stone (influencing convection) etc. ). Besides there might be superimpositions of convection and conduction (Soultzsous-Forêts)

§ 2 Geological Aspects and Prerequisites § 2 Geological Aspects and Prerequisites

§ 2 Geological Aspects and Prerequisites The structure of stone and its influence on § 2 Geological Aspects and Prerequisites The structure of stone and its influence on conduction and convection: pore qcond = - λ * Δϑ / Δz conduction v = ( k / η) * (Δp / Δz) convection cleft mattock / chalky qcond = conductive part of the heat flow [W/m²] λ = heat conductivity ~ 1. 0 -5. 6 W/(m K) Δϑ = difference of temp. v = velocity of flow [m/s] k = permeability [m²] (not [W/(m*K)] ) η = viscosity [Pa*s] Δp = difference of pressure [Pa] Δz = thickness of stone [m]

§ 2 Geological Aspects and Prerequisites The deposit of geothermal energy in the Crust § 2 Geological Aspects and Prerequisites The deposit of geothermal energy in the Crust of the Earth 1. Heat in the upper layers of the Crust 2. Heat in subsoil (i. e. greater depth) deposits of low enthalpy hydrothermal systems deposits of high enthalpy petrothermal systems

§ 2 Geological Aspects and Prerequisites 1. Heat in the upper layers of the § 2 Geological Aspects and Prerequisites 1. Heat in the upper layers of the Crust -strongly depending on season (until a depth of ~15 m), sun, rainfall and convection of subterrestrial water -the heat in the upper layers can usually not be used for commercial generation of electrical energy - the soil can be used as a source (in winter) and as buffer (in summer) of warmth

§ 2 Geological Aspects and Prerequisites 2. 1 Heat in subsoil deposits of high § 2 Geological Aspects and Prerequisites 2. 1 Heat in subsoil deposits of high enthalpy - usually to be found near volcanoes or borders of tectonic plates (Larderello) -water and steam of some hundred degree Celsius in low depth -purpose: mostly generation of electrical energy - having been used, the steam is usually reinjected in order to perpetuate a high subterrestrial pressure - very high pressure in the whole circulation-system (even water of some hundred degree is still liquid) - the pressure is released directly at the turbine of the power station, so that the hot water vaporized suddenly an drives it with enormous power (“flash method”) 2. 2 Heat in subsoil deposits of low enthalpy -this is a rule when there is no volcano or any other geological “abnormality” -for economic generation of electrical energy, temperatures of at least 100°C are needed necessity of deeper drills (~5, 000 m) -hydrothermal and petrothermal systems These aspects are important for the next chapter!

§ 3 The Practical Application of Geothermal Energy in Everyday Life Or why it § 3 The Practical Application of Geothermal Energy in Everyday Life Or why it is also very cool to use this hot renewable energy

§ 3 Application of Geothermal Energy in Everyday Life General distinction according to purpose: § 3 Application of Geothermal Energy in Everyday Life General distinction according to purpose: warming private households or public institutions commercial generation of electrical energy

§ 3 Application of Geothermal Energy in Everyday Life 3. 1 warming private households § 3 Application of Geothermal Energy in Everyday Life 3. 1 warming private households 1. Warming private households Open systems: -- due to pores and clefts, the pumped out of a flow to the point of Groundwater (~8 -12°C) is groundwater can fountain (“extract-hole”) withdrawal and warmth can be transferred thermal energy is gained cold water is returned via another fountain (“sink-hole”) soil may result for example in a crystallization of - an exploitation of the - problem: the pores this could seriously harm or restrictions the minerals in cannot be realized everywhere, legal even destroy entire system

§ 3 Application of Geothermal Energy in Everyday Life 3. 1 warming private households § 3 Application of Geothermal Energy in Everyday Life 3. 1 warming private households 1. Warming private households Closed systems: -The area of the ground which isvertically the warmth should have 1. 5 – 2 -Installed horizontally or used to gain times the size of the area which is warmed -System of pipes filled with transmission medium (for example -Power: 10 – 35 W/m² water with antifreeze compound) or working fluid (for example -Slinky-collector saves space! -Probes: - depth of at least 100 meters (usually deeper) ammonia or propane) - U – shape between transmission medium respectively - no direct contactor coaxial principle - material: high-density polyethylene working - power: 20 ground fluid and – 70 W/m

§ 3 Application of Geothermal Energy in Everyday Life 3. 1 warming private households § 3 Application of Geothermal Energy in Everyday Life 3. 1 warming private households Open and closed systems work according to the same principle: 1. Geothermal source of warmth provides energy 2. Heat pump makes this energy useable But how does a heat pump work? 4 steps: 1. Evaporation of a cooling liquid 2. Compression of the steam 3. Condensation of the steam 4. Relaxation of the steam

§ 3 Application of Geothermal Energy in Everyday Life 3. 1 warming private households § 3 Application of Geothermal Energy in Everyday Life 3. 1 warming private households

§ 3 Application of Geothermal Energy in Everyday Life 3. 1 warming private households § 3 Application of Geothermal Energy in Everyday Life 3. 1 warming private households Arrangement can also be used to cool your house in summer: 1. Direct cooling: water in the pipes of the heating system inside the house is pumped into the pipes in the ground 2. Indirect cooling: heat pump used as a refrigerating machine pipes of the heating system inside the house are connected to the evaporator of the heat pump; pipes under the surface outside the house are connected to the condenser of the heat pump soil used as a buffer for thermal energy instead of source

§ 3 Application of Geothermal Energy in Everyday Life 3. 2 commercial generation of § 3 Application of Geothermal Energy in Everyday Life 3. 2 commercial generation of electrical energy Commercial generation of electrical energy To work profitable, only deposits in subsoil (i. e. great depth) are considered High enthalpy Low enthalpy Excellent prerequisites (Larderello, Italy; The Geysers, California), due to extraordinary geological conditions water and steam of some hundred degrees in low depth • Hydrothermal system • Petrothermal system No geological extraordinary Thanks to new methods like “HDR” commercially usable

§ 3 Application of Geothermal Energy in Everyday Life 3. 2 commercial generation of § 3 Application of Geothermal Energy in Everyday Life 3. 2 commercial generation of electrical energy Hot – Dry – Rock: A modern and promising method -Two holes are drilled until a depth of ~ 5, 000 meters -Temperature: 200 -300°C -Water is pumped down through the first hole at very high pressure (150 bar) natural crevices in the stone are widened and / or new ones are formed (wide: up to 1 mm) -Water flows through the stone (Vol. ~ 3 -10 km³) and is heated up -Water rises to the top through the second drill -The high pressure and temperature of the water are transformed into electrical energy by a turbine on the surface Sub terrestrial stone used as a heat exchanger major parts of the arrangement hidden under the surface

§ 4 Examples and Advantages or let’s protect the Flowers and save some Money § 4 Examples and Advantages or let’s protect the Flowers and save some Money

§ 4 Examples and Advantages • Geothermal energy belongs to the generation of renewable § 4 Examples and Advantages • Geothermal energy belongs to the generation of renewable and nonpolluting sources of energy • No garbage • No emission of Carbon dioxide no greenhouse effect • Independent of seasons and weather (in contrast to most of the other renewable energies) • Available nearly everywhere • Nearly no risks • Independence of expensive fossil fuels which are often located in politically instable regions

§ 4 Examples and Advantages Examples -Larderello: -oldest geothermal power station in the world § 4 Examples and Advantages Examples -Larderello: -oldest geothermal power station in the world (1913) -Power: 400 MW -Reinjection of hot steam in order to perpetuate high subterrestrial pressure

§ 4 Examples and Advantages The Geysers, California: -Most powerful geothermal power station -Power: § 4 Examples and Advantages The Geysers, California: -Most powerful geothermal power station -Power: 700 MW -Comparison: nuclear power stations averagely got between 400 and 1, 400 MW at their disposal

§ 4 Examples and Advantages Soultz-Sous-Forêts, Alsace, France: -Pilot project (for HDR) -Power: only § 4 Examples and Advantages Soultz-Sous-Forêts, Alsace, France: -Pilot project (for HDR) -Power: only 6 MW -Depth: ~ 3, 500 meters -Temperature of steam: 170°C -Flow: 40 l/s -Expected: depth of 5, 000 m, 250°C, 50 -100 l/s

Thanks for your attention! • “Energie aus Erdwärme”, Spektrum Verlag, Kaltschmitt, Huenges, Wolff • Thanks for your attention! • “Energie aus Erdwärme”, Spektrum Verlag, Kaltschmitt, Huenges, Wolff • http: //www. planet-wissen. de • http: //de. wikipedia. org/wiki/Erdw%C 3%A 4 rme • http: //www. erdwaerme-lehrpfad. com/ • “Physik-Journal”, November 2008