low enthalpy power generation with orc- turbogenerator the ...€¦ · the total electrical...

Gerhard Pernecker and Stephan Uhlig: THE ALTHEIM PROJECT___________________________________________________________________________________

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Under the auspice of:Division of Earth Sciences

Chapter 3.5

Low enthalpy power generation with ORC-Turbogenerator

The Altheim Project, Upper AustriaThermie contract number GE-0070-96/A-I-F-D

Gerhard Pernecker, Marktgemeindeamt A-4950 Altheim, Upper Austria

Stephan Uhlig, Geotec Consult, D- 85570 Markt Schwaben, Bavaria

Abstract

In Altheim project a district heatingsystem is fed by the 106 °C geothermalfluid flowing from an aqifer ca. 2300 mdeep. Since 1989 efforts were undertakenby the municipality to supply 10 MWthermal heat to a district heating network.In order to keep the water balance in theMalm aquifer a reinjection drill hole wasrequired. The new idea was to use theincome of a power production to financethe injection drill hole. A binary cycleturbogenerater should be installed.

The main contractor and operator forthe installation is the Marktgemeinde Alt-heim. The Altheim project is challengingfrom the ORC point of view, both becauseof the low temperature of the heat sourceand the fact that the well head and theturbogenerator are placed within thetown, near the town hall. Hence, veryefficient silencing is required and the useof a flammable working fluid was excludedfor safety reasons. As a working fluid aharm-less fluorocarbon was selected. Atotal power of 1000 KW was generatedduring the test run.

The ORC is cooled by the water froma nearby works canal.

After the use, geothermal water ispumped back at a temperature of 65°C tothe geothermal deep Malm-aquifer, allow-ing a lasting exploitation of the systemitself. The balance of the water in theMalm reservoir remains maintained.

Introduction

Altheim is a municipality in the UpperAustrian „Inn-region“ with 5000 inhabi-tants and encloses an area of about 22 km2.The budget on a yearly base is about6.300.000 Euro. The decision to constructa geothermal heat supply, for environ-mental reasons, was made by the muni-cipal council in january 1989.

Heat supply / Production drillhole /Supply network

a) The production borehole was drilled in1989. After two months the water bearingMalm was drilled at 2300 m depth. Theartesian flowrate was finally 46 l/s, at atemperature of 104 °C. Thus the aimedheat distribution of 2500 kW was possible.The expenses for the first drillholeamounted to 1.450.000 Euro.

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b) Presently about 650 consumers areconnected to the heat supply, the thermalpower is 10.000 kW. About 40 % of theinhabitants of Altheim live in buildingsthat are connected to the heat supply. Thesupply network has a length of about 14,5km. The biggest single consumer aremunicipal facilities with about 1000 kWthermal power (school, gymnasium). Themajority of the supplied objects are one-and two-family houses.

The fee for the heat supply is 39,39Euro per MWh. To create an impulse forthe consumer to be connected to the heatsupply, the contract conditions in 1989were made consumer friendly: almostexclusively a fix temperature difference of

30 °C was charged. The real temperaturedifference is greater, thus the consumerspay less per MWh. Meanwhile the com-munity is in a better position: the increa-sing demand made it possible to createmore favourable conditions for them (thenew consumers are charged for the actualsupplied energy). The calculated 1500operating hours per year in 1989 could’ntbe realised. The actual number is about1200.c) The use of geothermal energy for heatsupply lead to a significant reduction of airpollution and hothouse gas in the commu-nity area as well as to immense saving offossil fuels.

Comparison of 1989 and present state:1989 present state reduction

CO2 11,150.000 kg 3,094.000 kg 72 %NO2 8.000 kg 2.600 kg 67 %SO2 32.200 kg 11.200 kg 65 %CO 411.000 kg 173.000 kg 58 %

Fossil fuels 2.500 t / year

Reinjection Drill Hole / Construction ofthe Power Plant

In order to keep the water balance inthe water bearing limestone of the Malmauthorities ordered to reinject the thermalwater. The question was how to financethis second drill hole. Incomes for thedistrict heating were not sufficient. Newpossibilities had to be found.

Then in 1994 a project of geothermalpower generation was developed. Thepower output from a very first design ofthe project was calculated to 240 kW – notenough for the financing of a drill hole. Anew concept had to be developed.

At least a production rate of 100 l/shad to be achieved to produce an electricalpower of 1 MW.

As the costs per MWh withoutfundings were calculated to 140 Euro, aproposal for additional financial supportby the Commission of the EuropeanCommunities was compiled together withthree other project partners.

A 35 % fFunding was granted by theCommission. With additional funds from

the local government of Upper Austria andthe federal governmernt of Austria theproject was totally financed. Negotiationswith the local energy supplier "EnergieAG - Oberösterreich" followed. Liberali-sation of the energy market leads to adecreasing reimbursement of the genera-ting costs - but nevertheless an appropriatefinancal contribution of the energy utilityhelped also in this case. With that aneconomic operation of the power plant bythe municipality than was ensured. In1998 the drill bit went downward oncemore - 40 m away from the first drill hole.

In order to reach the thermal waterbearing layer at a horizantal distance of1700 m the drill hole had to be deviatedfrom the vertical. At a depth of 460 m thistechnical ticklish operation starts. The drillbit had to be guided several times into theright direction.

The deviation operation was perfor-med by Becfield Drilling Services.

After 8 months of drilling the finaldepth was reached. By a total length ofalmost 3100 m the drill hole reached thetarget at 2200 m depth - the white treasure


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in the Malm karst of the molasse bassin.The horizontal distance between startingand landing point of the drill hole is 1700m.

Hydraulic tests showed that hot waterwith 100 l/s at a temperature of 93 °Ccould be produced. The same rate can alsobe injected.

According to the planning the firstwell was used for production and thesecond drill hole as reinjection well. Thethermal water is produced by a hightemperature downhole pump which isinstalled at a depth of 290 m.

A Rankine turbogenerator has beenconstructed by Turboden in Brescia, Italy.To obtain a high efficiency of the binarycycle the working parameter of theturbogenerator are very well adapted to the

rate and temperature of the producedwater. The working fluid had to be nontoxic, there must be no danger ofexplosion and it should also not affect theOzone layer in any way. A suitable fluidwas found by Turboden. A harmless“Fluorocarbon” was selected. In a heatexchanger the thermal water heats up theworking fluid. The fluid evaporates atrelatively low temperatures of 28-30°C.As steam it drives the turbine. The vapo-rised medium is cooled down, condensedand then be once again continues its waythrough the closed turbine cycle.

After using the heat of the thermalwater it is reinjected into the undergroundagain still at a temperature of 70°C. Bythis measures the balance of water in theMalm reservoir remains maintained.


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In December 2000 the test run began.The total electrical capacity of the powerplant is 1MW. The cooling water for theturbine is taken from a nearby workscanal. The cooling system requires a flowrate of 340 l/s.

The floor space required is very low.The heating plant with a thermal capacityof 10 MW needs only 70m3. Both wellheads of the two drillholes require 50 m_each. The power house requires some 230m3.

The general planning of the integ-

ration of the turbogenerator system intothe district heating grid was carried out byGeotec Consult from Markt Schwaben inBavaria. The staff of Geotec Consult wasalso responsible for the design andsupervision of the drillhole.

The first geothermal power generationfrom low enthalpy resources in MiddleEurope was performed. Only geothermalenergy is the single one which isindependent from climate and can be usedall over the year and is capable for a baseload energy.

Geothermal water inlet temperature: 106 °CGeothermal water outlet temperature 70 °CGeothermal water flow rate: 81.7 kg/sCooling water flow rate (about): 340 kg/sCooling water inlet temperature: 10 °CCooling water outlet temperature: 18 °CElectric generator: synchronous.low voltageNet electric power output (*): 1000 kW

TABLE 1: Altheim ORC turbogenerator performance data sheet

Electricity power plant 1.580.000 EUROReinject. drillh. / Completion prod. drillh. 2.117.000 EUROUnderwater product.- / Inject.- installation 378.000 EUROFurther expenses 436.000 EUROTotal expenses 4.511.000 EURO

TABLE 2: Expenses for the project

Due to the funding of the EuropeanCommission the continuous expenses

could be reduced to following numbers:

Yearly costs 349.861 EUROProduction costs per MWh 91,47 EURO

TABLE 3: Yearly / production costs

ATS EUROWinter - High rate 0,72 0,0523Winter - Low rate 0,607 0,0441Summer - High rate 0,473 0,0344Summer- Low rate 0,421 0,0306

TABLE 4: Input tarif per kWh (fixed price guaranteed for 15 years)

With this contract and tarif concept it willbe possible to run the geothermal station

for heat and power in the municipality ofAltheim economically.


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ORC Turbo Generator without housing nearby the townhall of Altheim


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Geological Cross Section with production andreinjection well


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low enthalpy power generation with orc- turbogenerator the ...€¦ · the total electrical...

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