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INTRODUCTION

ENERGY. CONVERSION SYSTEMS

THROUGHOUT THE WORLD.

John W. Lund*

Geo-Heat Center

Oregon Institute of. Technology

'203.9-4-

Equipment for the direct utilization of geothermal energy, for the .most 'part,

utilizes known technology. Basically, h6t water is hot water whether .from a

boiler or from the earth. The utilization. of geothermal · energy requires only

straightforward engineering design and the use.of currently available ."off-

the-shelf" equipment. The technology, reliability, economics, and environ-

mental' acceptability of geothermal energy have been demonstrated throughout

the world. ' :'•'

However, it i.must be : remembered tthat each , resource is · different, and the

systems must be.designed accordingly. Problems with corrosion and scaling are

generally confined to the higher-temperature resources, as most of the ;low-

temperature· resources are rela�254ivdlybenign with low dissolved· solids.

Chemistry-related.problems. can ·.be solved by proper material ,selection and

engineering design. For some resources, standard .engineering materials can be

used if particuldr attenti6n is . given to the exclusion and/or removal of

. atmospheric and· geothermally generated gases. For others, econ6mical designs .

are possible which lidit geothermal .water to a small portion of the overall

system by, utilizing highly -efficient heat exchangers and corrosion-resistant

materials,in the primary side.of the system,

Today·, over 5,000 megawatts thermal are utilized in,the world for space condi-

tioning ( heating and cooling), agribusiness ( agriculture and. aquaculture), and

' industrial processes ( GRC/Lund, 1979). The agribusiness-related uses utilize

temperatures ·.from'800 - 180'F, the majority of which is f6r greenhouse space

heating. Space conditioning (mainly heating ) utilizes temperatures .from :

1500 - '200'F, . with heat pumps extending the useable range. down to 50'F.

Industrial. processing uses'both..steam .and -hot·water,,thus:temperatutes. up to

300'F are' 6ften necessary; however, many - drying processes require temperatures

of only 1500 -:200'F.. A.visual representation of the.required temperature for

various direct-tliermal useshis shown in Figure. 1 (Lienau/Lindal., 1974 ) on.the •

following page.

EXAMPLES OFKCURRENT UTILIZATION

Traditionallf; . direct use of geothermal ener•y has been on· a small scale by

individuals.' Surface hot springs were utilized, and shallow wells' could be

*Mr. Lund is currently a professor · of Civil Engineering Technology, Associate

Dean and Head of Engineering Technologies, and Associate-Director'of.the Geo

Heat.Center.at the Oregbn Institute .of Technology, Klamath. Falls; Oregon..

Mr. Lund has a Ph.D. in ,Civil Engineering from the University of Colorado

and is a· registered professi6nal engineer in California and Oregon.

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justified'with on-the-spot use or short transmission distances ·in uninsulated,

pipes or channels. H6wever, at today's prices.for development and hardware;

the cost savings of these individual uses are often marginal. Large-scale use

demands require more ptoduction and can thus justify deeper .wells, longer

transmission distances, ' more sophisticated 'utilization, and lower

temperatures.

Most of .present-day developments involve large-scale projects, such as dir

trict heating ' ( Iceland), greenhoukie complexes'' (Hungary), or major industrial

use. ( New Zealand ) . Heat, exchangers are. also becoming more, 'efficient. and •

better adapted to geothermal 'use, -allowing the ·use of 16wer-temperature waters

and highly saline fluids. Heat pumps are extending, geothermal development�036

into traditionally' nongeothermal countries, such as France, Austria, and

Denmark, as'well as the eastern United States.

' Space Conditioning

The mos t famous s'pace-heating' project in the world is the .Reykj•vik municipal

heating project, serving about 97 'percent of the 113,000. people 'in the 'capital

city of Iceland. .At.present; .a total of 1.0 x 1019.gallons:'of geothermal

fluid are used annually to supply 16,000 homes with space heating. ' One field

supplies water through two 14-inch and one 28-inch diameter pipelines over a

I2-mile'aistance. ·' 'Insulated stotage '·tanks '(6.9 x ].06 gallons )•'are used· to

meet peak flows and provide an emergency supply in the event of breakdown in ,· ,

the system. A.fbssil fuel-fired ,peaking station is' used: to boost the 176:F

water to 230 °F during 15 to 20 of the . coldest days/of the .year. The city is

served by 9 pumping stations, distributing fluid •• through,200 miles of pipe-

lines. .The entire system provides 1,840 GWh pet -year or 420 MWt.(including• - ,

the· peaking station, Lienau/Zoega, 1974 ).

An example of individual,home- space· heating is in Klamath Falls, 9regon, where

.over 400 wdlls, are used for space heating, using· waters from 100°.- 230'F.

The principal heaE-extraction system ,is'l the.-'closed-loop - d6wnhole h9at

•exchanger utilizing city 'water in'.: the. 100p ( Lund et al:, 1974 ). 'Larger :

examples of space heating in Klamath Falls ,include'the Oregon Institute of

, Technology'campds, where,three wells up to. 1,800'feet deep' each- produce up to

450 gpm'of'192'F water and heat approximately 600,000 ft; of floor space. The

geothermal water is pumped from the.well using ·deep-well turbine' pumps and, in

most cases, is,/used directly in the 1 heating, system for each building. The

annual operating cost of the campus syste• i's· approximately.'$30,000, a''savings

of almost $400,000 per year when compared witE the cost of heating with'con-

ventional fuel. .A,district heating'project -is currently under construction in,

the city, designed to'provide heat to 14.government buildirigs. This initial

phase (approximately.4.MW6) will. provide: 220'F geothermal water through an

8-inch 'diameter insulated steel linei placed in a, concrete tunnel to a central

heat exchange facility. Plate-type heat ' exchangers will transfer heat ..to ' a

secondary clos.ed-loop, FRP ·(fiberglass reinforced plastic ) 'pipeline at 180'F.

Proposed expansion of the system' will heat 11 commercial city blocks (10"MWt)

and eventually 57 downtown blocks of Ehe central business district ( 40·MWt).

The cities of Boise, Idaho,'and Susanville, California, · are also constructing

similar district heating projects.

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A geothermal district heating. system will generally.have the same basic compo-

nents as a conventional system.• .The production field, which includes wells,

pumps and collection .mains, replaces the b6iler in a conventional system. All'

other, components, such·as piping, valves, controls and metering, etc., wouldf

be similar to'a conventional.system.

District heating 'metering systems for the purpose of ·billing consumers can be

based on quantity of water .used ( volume metering), quantity · of. heat used

..(energy metering•, or 'specified apportioriment factors ( nonmeter billing). ,

Geothermal energy can be.used as a preheater in,the case of a low-temperature

resource. The geothermal fluid can be boosted to a higher temperature by ;

fohsil fuel, such.as. in the Reykjavik.s•istem, or to preheat a secondary: fluid

which is in turn peaked by fossil fuel. Capital costs are ·generally, reduced • •

by introducing an auxiliary boiler into large district heating .systems.

Designed to' meet the : peak heat load a few days out of the year by increasing

fluid temperature, this results in smaller pipes,· pumps, heat .exchangers, and •

.fewer wells..

Another possibility in the case of a lowltemperature·•(140' - 160'F) geothermal

res6urce is to include heat pumps in. addition to ·the'auxiliary boilers. A

, system . of :tliis type installed in . the Paris basin supplies heat to 10,000.

apartments and .is claimed to be ec6nomical . (GRC/Ryback, 1979). Low-

temperature cooling can be provided by geothermal lithium bromide absorption

chillers. Temperatures as low as, 180'F can be used; h6wever, ,higher tempera-

tures are more efficient. Examples are chillers in Rotorua, New. Zealand, and

on the Oregon Institute of • Technology campus.

Agribusiness

Agricultural applications'•are. particularly attractive because they'require

heating at the lower'end· of the' temperature spectrum where there is' an

abundance of.geothermal resources.

All commonly marketed vegetables, flowers, .house. plants, and many tree

seedlings 4re suitable 'for greenhousing. ,Greenhouse . temperatures are a

function of the crop; typical:.highest:maintained temperatures trange. approxiT-

mately from.65' '- 80 ° F. Greenhouse'heating can,be accomplished by'(1 ) circu-

lation 6f air·over 'finned-coil heat•.exchangers carrying hot water,· (2) hot

water circulating pipes or ducts located in ( or ' on). the floor, (3) finned

units located along the walls and under benches, or (4) a combinationt of these .

methods.• · The heating fluid in these units can be as low as about,90'F. ' The ''

air circulation method is more common and utilizes' forced-air fincoil units.

The heated air · is often passed through • perforated plastic tubes .running the

l�254ingthof.the greenhouse in order to maintain uniform ·heat distribution. .

Excellent examples of greenhouse operations exist in the United States, the.

largest being, the Honey Lake Hydroponic farms compl ex near Susanville,

California. Cucumbers and tomatoes are grown in a hydroponic system. · Heat is.

provided 'to the greenhouses by 'geothermal fluid using forced-air heaters. At

present, 60 greenhouses have been constructed, with expansion planned to over

200,units. Sduth of, Klamath Falls, at the Liskey ·Ranch, greenhouses are used

for raising tree seedlings arid, more re6ently, cacti. Heat is provided' by

under-bench finned-tube piping.

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In Hungary, ,geotherinally heated greenhouses amount to over. 13 million ft2.

Many of . these ireenhouses are built on rdllers, so they Call·be: .spulled,·from

their location by tractors, ,the ground cultivated with large equipment; and

then· the greenhousd returned to 'its locatioil: : In additi6n, to minimize c6st,

much of the building-structure pipe-supporting,system also acts as the, supply

and radiation :system for ' the geothermal fluid. Somes experimental work is

being peitformed.with grain, hay, tobacco, and paprika drying. .In these cases,

hot witer supplies heat. to'forced-airtheat •xchangers and 1209 - 140'F Air is

blown over the ptoduct to be dried (Lienau/Boldizar, 1974):, I ..

Environmentally .c'ontroiled livestock raising .provldes M'significant advantages

as compared' to th6 typical practice 9f outdoor expohure to the elemdnts: • , The

lefel of thdfmal environniental .control cufrently practicdd ranges . frod fldor,

heating f6r mosily-open .cattle finifh-feed lots to tothlly enclosed raising, 6f

hogd,add. dhickeds: ' Tlie totally • enclosed systems. utilizd bbth dpace heating

and·floor-slab heating ( at about: 900F ). to maintain about 70•F.

'. Fish•'faroiing. .is that•por£idn, Ff·aquaculture which in<rolve § the. rearin• And

harvestin• 'of aquatic animals. , .Among farmable spdcies ,are cgmmon carp,

•Chinese carp, Indian' carpiebdffdlo'fish,., paddle fiAh, catfioh, pikes, perches,

bldck 6#ss, su'nfish; tilapia, frogs,.'mullet, :milkfish, 'edls, salmons,

salmobids, smelt; sturgeon, .shad, ;stripped bass,lshridp',' lobdtir, .crayfish;

crabs, oysters, clams, scallops, mussels, and abalone.

Heating can.Ge acdomplished using 'hot water ( 900 - 110"F ) bearing pipas in·the

gfowth pondA or 69 direct'•additidn of suitablelquality hot watet. (70' - 90•F )

• in Order to maintain.pond''teinlieritures near 80'F.. The. main' caution-is.tes'tidg

th6 compatibility Ofithe aqdatic an'imal: and the chemistry of the· water When

it is used directly in,ponds ahd racewdys.

One of the best: agribu'siness ·examples' is in Japan. .Here, greenhousds cover

about 157.,000 .ft2'...wherea•variety of vdgetables.add f16wers are gr6wn. Many·

large greenhouses' ard ·opetated as -tropical: gardens for' sightseeing ,purposes.'*

Ra'ising poultry· through,the use of.geothermal energy has'been a«.very succeds-

ful · enterprise, · .Here, under-the-floor - heating is · utilized in she'ds where

40,000 chickens are rais�254dannually. Another successful business is :breeding

I and raising. carp add eels. Eels ard the most profitable'and are raised in 10-

. inch diameter ' by 20-foot. long earthenware' •ipd4. Water in the pipes is held '

at, 73'F by mixing hot' spking.'witer. 'with river watur. .. The adult. eels wdigh

frbm 3-1/2,t6 :5-1/4'6unced, with..a t6tal ,dnnudl proiluction 6f 8,400 lbs:

Alligators-and':crotodiles'are also'faised in geothermal water. . These rebtilds

iare'bding bred-purely for 'sightsdeing p'urposes.' ..In combination with green-

,houies 6ffering tropical flora, alligator,farms are 6ffering increasingly

lar*e indocements to the local growth of the 'tourist industry .(Japan

:Geothermiil Energy Assocf, 1974).'I, ' .

Industrial. Processes

, Th«ugh there are rdlatively few 6xamples of industrial processing use of geo-,.

-thermal energy, they reprdsent a· 'wide'. •range of I applications, frbm drying , of •

agricultural ; products, wool,' fish, ' earth, -and .lumber to pulp, and paper

processing and, chemical extraction.'' The two largest indubtrial uses ard the

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. diatomaceous earth drying plant in Iceland' and the paper and :wood processing,

:plant in New Zealand. Thermal energy up to 300'F,can be . used for a'range of

-Ibasic processes such . as preheating, washing, cooking, evaporating,

sterilizing, distilling, drying, and refrigeration. -

-An example of industrial processing is the use of geothermal steam for the

• ,-Tasman Pulp, and , Paper Compa'ny in New .Zealand.' . Here, /100 - 125 MW.(180

tons/hr steam) of -thermal energy areused for the lumber drying, black· liquor

evaporation, and pulp and paper drying. The total investment cost for geo-

thermal is $6.8 million,•the-majority of which· is for well development.· This

amounts to approximately $70 per kWt and will reduce the price of energy to 70

percent of conventional fuels f6r an annual savings of $1.3 million. The"'

annual daintenance c6sts are.. 2 percent .of the 6apital .cost (Lienau/Wilson,

1974).

In Northern Iceland, a.diatomaceous'slurry is dredged.from Lake Myvatn., This

slurry, is transported through' a pipeline and held in storage ponds. The 80.

percent moisture.is. then removed.:in large rotary-drum driers using high.

temperature geothermal steam. . The plant produces 27,000 tons of. diatomite

filteraids·'per yeari most of which are used'.in beer' processing•. in,Germany

( Lienau/Lindal, 1974).

Two 'industrial processing uses of geothermal energy are of' note .in .the United

States: Medo-Bel Creamery in Klamath Falls, where low-temperature fluid id

used for pasteurizing milk, and Geothermal Food Processors at Brady Hot

Springs, Nevada, where high-temperature fluid is used for dehydration of

onions and other vegetables.

CONCLUSION

4At present-day prices, 'the ge6thermal application will cost about the same or

less than' the corresponding annual fossil-fuel' cost. Dub ·to the expected

escalation' of. fossil-fuel. prices, the costs of the geothermal system will

decline. ·. Most geothermal direct-use systems will pay for themselves in 5 to

10 years from savings in conventional fuel.

The ec6nomics are. greitly enhancea where cascading (multi-stage use) . is con-

sidered. The Japanese· optimize cascading where geothermal fluids are first

used for electrical power production, then space·heating, cooking, and bathing

( Otake). .Here, an attempt is made':tq "squeeze" the "last drop of energy" from

the fluid. Lower-temperature cascading could consider space heating, agricul-

ture, bhthing ( swimming pools ), and snow melting.: Low- and intermediate-·

temperature geothermal resources' can also be used to meet.the:'base load of an

energy demand.• Heat pumps and fossil fuel can then be used to meet the peak

demands,: thus conserving .the resource and minimizing capital investments:

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REFERENCES

Anderson, David N., and John W. Lund. Direct Utilization of. Geothermal

Energy: A Technical Handbook. Geothermal' .Resources .Council Special

Report No. 7. Davis, California, 1979.

Geothermal Resourcds Council·. A Symposium of Geothermal Energy and Its Direct

Use in the Eastern United States (Roanoke, VA ) · '. GRC Special''Report No:

5. Davis, California, 1979.

/ \

- Ryback, Ladislaus. Urban Heating from Geothermal Aquifers in the

Paris.Basin.

Lund, John W. Worldwide Direct Application Review.

Japan Geothermal Energy·Association.

1974.

Geothermal' Energy Utilization in Japan,

Lienau, Paul J., 'and John W. Lund. "Multipurpose Use. of·Geothermal ·

Energy, " Proceedings 'of the·•International Conference.on Geothermal Energy

for Industrial,.'Agricultural, and Commercial-Residential Uses. Oregon •

Institute ·of' Technology,·'Klamath Fallsi 1974. ,

Wahl, Edward F. Geothermal Energy· Utilization. New York: John Wiley and

Sons, 1977.

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