1 geo thermal

7/23/2019 1 Geo thermal

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TERRESTRIAL HEAT

energy from the inside ofenergy from the inside ofthe Earththe Earth


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What does geothermal mean?

The term geothermal comes from theGreek geomeaning earthand therinemeaning heatthus geothermal energyis energy derived from the natural heatof the earth.

The heat inside the Earth core iscontinually generated by the decay of

the long lived radioactive isotopes ofuranium, thorium and potassium,hich are present in the Earth.

The heat that flos from the Earth!shot interior due to plate movements,"ones of high heat flo, may belocated close to the surface hereconvective circulation plays a

significant role in bringing the heatclose to the surface


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What happens ith the heat?

Without utili"ation, the terrestrialheat flo is lost to theatmosphere. #n this case, theisotherms run parallel to theearth$s surface and the heat flolines are perpendicular to them. #f,

instead, the heat flo can becaptured, the isotherms aredeformed and the heat flo linescan be diverted toards heatsinks.

%ue to variations of the earth$scrust thickness there ill be

different temperature profiles fromplace to place. &ome areas areknon to have hot springs and thelike and volcanic activities, suchareas ill also be ell suited forgeothermal utili"ation.


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'o does geothermal heat get up to the

surface?

&ometimes the hot magmareaches all the ay to the surface,here e kno it as lava. (utmost often the magma remainsbelo earth!s crust, heatingnearby rock and ater )rainater

that has seeped deep into theearth* + sometimes as hot as --degrees . &ome of this hotgeothermal ater travels back upthrough faults and cracks andreaches the earth!s surface as hotspringsor geysers, but most of itstays deep underground, trappedin cracks and porous rock. Thisnatural collection of hot ater iscalled a geothermal reservoir.


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(est locations

Geothermal systems can be found inregions ith a normal or slightlyabove normal geothermal gradient.

The margins of the plates correspondto eak, densely fractured "ones ofthe crust, characteri"ed by an intenseseismic activity, by a large number ofvolcanoes and, because of the ascent

of very hot materials toards thesurface, by a high terrestrial heat flo.The most important geothermal areasare located around plate margins.

World pattern of plates, oceanicridges, oceanic trenches, subduction"ones, and geothermal fields.


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/ccessing geothermal energy

#f geothermal reservoirs are closeenough to the surface, e can reachthem by drilling ells, sometimes overto miles deep. &cientists andengineers use geological, electrical,magnetic, geochemical and seismicsurveys to help locate the reservoirs.

Then, after an e0ploration ellconfirms a reservoir discovery,production ells are drilled.

Geothermal system can be describedschematically as 1convecting ater inthe upper crust of the Earth, hich, ina confined space,transfers heat from aheat source to a heat sink, usually the

free surface1. / geothermal system ismade up of three main elements2 aheat source, a reservoir and a fluid,hich is the carrier that transfers theheat.


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Generating electricity 2

Geothermal poer plants

#n geothermal poer plants,e use the natural hot aterand steam from the earth to

turn turbine generators toproduce electricity. 3nlikefossil fuel poer plants, nofuel is burned. Geothermalpoer plants give off atervapour, but have no smoky

emissions. There are several different

types of plants2 flashed steamplants, dry steam plants andbinary poer plants


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lashed &team 4lants

5ost geothermal poer plantsoperating today are 1flashedsteam1 poer plants. 'otater from production ells ispassed through one or toseparators here, releasedfrom the pressure of the deep

reservoir, part of it flashes)e0plosively boils* to steam.The force of the steam is usedto spin the turbine generator.To conserve the ater andmaintain reservoir pressure,the geothermal ater andcondensed steam are directeddon an in6ection ell backinto the periphery of thereservoir, to be reheated andrecycled.

lash steam poer plants usehot ater reservoirs. #n flashplants, as hot ater isreleased from the pressure ofthe deep reservoir in a flashtank, some if it flashes tosteam.


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%ry &team 4lants

/ fe geothermal reservoirsproduce mostly steam and verylittle ater. 'ere, the steamshoots directly through a rock+catcher and into the turbine. Thefirst geothermal poer plant asa dry steam plant, built at

7arderello in Tuscany, #taly in89-:. The poer plants at the7arderello dry steam field eredestroyed during World War ##,but have since been rebuilt ande0panded. That field is stillproducing electricity today. The

Geysers dry steam reservoir innorthern ;alifornia has beenproducing electricity since 89


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(inary 4oer 4lants

#n a binary poer plant, the geothermal

ater is passed through one side of aheat exchanger, here it!s heat istransferred to a second )binary* li=uid,called a orking fluid, in an ad6acentseparate pipe loop. The orking fluidboils to vapour hich, like steam,poers the turbine generator. #t is thencondensed back to a li=uid and used

over and over again. The geothermalater passes only through the heate0changer and is immediately recycledback into the reservoir. #n some poerplants, flash and binary processes arecombined.


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/griculture and a=uaculture

Geothermal energy is used directly inagriculture and a=uaculture2

to help gro floers, vegetables,and other crops in greenhouseshile sno+drifts pile up outside

to shorten the time needed for

groing fish, shrimp, abalone andalligators to maturity
http://geothermal.marin.org/GEOpresentation/sld081.htmhttp://geothermal.marin.org/GEOpresentation/sld087.htm


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#ndustry

The heat from geothermal ater is

used orldide for industrial

purposes. &ome of these uses

include drying fish, fruits,

vegetables and timber products,

ashing ool, dying cloth,manufacturing paper and

pasteuri"ing milk.

Geothermally heated ater can be

piped under sidealks and roads

to keep them from icing over in

free"ing eather. Thermal atersare also used to help e0tract gold

and silver from ore and even for

refrigeration and ice+making.


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'ot &pring (athing and &pas

)(alneology*

or centuries, peoples of ;hina, #celand,Aapan, Be Cealand, Borth /merica andother areas have used hot springs for cookingand bathing. The Domans used geothermalater to treat eye and skin disease and, at4ompeii, to heat buildings. 5edieval arsere even fought over lands ith hot springs.

#n Europe, natural hot springs have been very

popular health attractions.The first knon1health spa1 as established in 8@>< in

(elgium. )ne resort as named 1Espa1hich means 1fountain.1 The English ord1spa1 came from this name.* /ll over Eurasiatoday, health spas are still very popular.Dussia, for e0ample, has @,F-- spas.

Aapan is considered the orld$s leader in

balneology. The Aapanese tradition of socialbathing dates back to ancient (uddhist rituals.(eppu, Aapan, has :,--- hot springs andbathing facilities that attract 8> million touristsa year. ther countries ith ma6or spas andhot springs include Be Cealand, 5e0ico andthe 3nited &tates.


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%istrict heating

The oldest and most common use ofgeothermal ater, apart from hot spring

bathing, is to heat individual buildings, andsometimes entire commercial and residentialdistricts.

/ geothermal district heating system suppliesheat by pumping geothermal ater +usually


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Geothermal heat pumps

The heat pumps are machines that moveheat in a direction opposite to that in hichit ould tend to go naturally, i.e. from a coldspace or body to a armer one. / heatpump is effectively nothing more than arefrigeration unit. /ny refrigeration device)indo air conditioner, refrigerator, free"er,etc.* moves heat from a space )to keep itcool* and discharges that heat at highertemperatures. The only difference beteen

a heat pump and a refrigeration unit is thedesired effect, cooling for the refrigerationunit and heating for the heat pump. /second distinguishing factor of many heatpumps is that they are reversible and canprovide either heating or cooling in thespace.

Geothermal heat pumps reduce electricity

use @-+


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/dvantages of geothermal energy

DEBEW/(#7#TH /B% &3&T/#B/(#7#TH 2Earth$s heat is continuously radiated from ithin,and each year rainfall and snomelt supply ne ater to geothermal reservoirs. 4roductionfrom individual geothermal fields can be sustained for decades and perhaps centuries. The3.&. %epartment of Energy classifies geothermal energy as reneable.

;B&EDI/T#B DE&3D;E& 2 When e use reneable geothermal energy for directuse or for producing electricity, e conserve e0haustible and more polluting resources likefossil fuels and uranium. #nstalled geothermal electricity generation capacity around theorld is e=uivalent to the output of about 8- nuclear plants.

4DTE;T#B T'E EBI#DB5EBT2 Geothermal direct use facilities have minimal orno negative impacts on the environment. Geothermal poer plants are relatively easy on theenvironment.

Protection of the Air and Atmosphere.'ydrogen sulphide gas )'>&* sometimes occurs ingeothermal reservoirs. #t is sub6ect to regulatory controls for orker safety because it can beto0ic at high concentrations. E=uipment for scrubbing '>& from geothermal steam removes99 of this gas. ;arbon dio0ide ;> occurs naturally in geothermal steam but the

geothermal plants release amounts less than : of that released by fossil fuel plants. /ndthere are no emissions at all hen closed+cycle )binary* technology is used. Visual Protection./ geothermal plant sits right on top of its fuel source2 no additional land is

needed such as for mining coal or for transporting oil or gas. When geothermal poer plantsand drill rigs are located in scenic areas, mitigation measures are implemented to reduceintrusion on the visual landscape.

7W ;&T&2 the price of geothermal poer decreased ith about >F in the last >decades due to the development of the technology used and the involvement of the

government in the research regarding this domain.


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uture of geothermal energy

The outlook for geothermal energy use depends on at least three factors2 The Demandfor energy ill continue to gro. Economies are e0panding, populations are

increasing )over > billion people still do not have electricity*, and energy+intensivetechnologies are spreading. /ll mean greater demand for energy.

The Inventoryof accessible geothermal energy is si"able. 3sing current technologygeothermal energy from already+identified reservoirs can contribute as much as 8- ofthe 3nited &tates energy supply. /nd ith more e0ploration, the inventory can becomelarger. The entire orld resource base of geothermal energy has been calculated in

government surveys to be larger than the resource bases of coal, oil, gas and uraniumcombined The Competitive Positiondepends primarily on cost2 ;osts2 &horter and 7onger Term.4roduction of fossil fuels )oil, natural gas and coal* are

a relative bargain in the short term. 7ike many reneable resources, geothermalresources need relatively high initial investments to access the heat, hot ater andsteam. (ut the geothermal 1fuel1 cost is predictable and stable. Deneable geothermalenergy is a better long term investment.

;osts2 %irect and #ndirect.The monetary price e pay to our natural gas and electricitysuppliers, and at the gas pump, is our direct cost for the energy e use. Geothermalenergy is a clean, indigenous, reneable resource ithout hidden e0ternal costs.

;osts2 %omestic and #mporting.#nvestment in the use of domestic, indigenous,reneable energy resources like geothermal energy provides 6obs, e0pands the regionaland national economies, and avoids the e0port of money to import fuels.


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;onclusion2

Energy demand isincreasing rapidlyorldide. &ome energyand environmentale0perts predict that the

groth of electricityproduction and directuses of geothermalenergy ill be revitali"edby internationalcommitments to reducecarbon dio0ide emissionsto avert global climatechange and by theopening of markets tocompetition.


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1 geo thermal

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