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Publication Name: Description and evaluation of the new 1,000 kW Organic Rankine Cycle process integrated in the biomass CHP plant in Lienz, Austria
Original File Name Searched: Paper-Obernberger-ORCLienz-Euroheat-2002-10-01.pdf
Page Number: 001

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Published in: Euroheat & Power, Volume, 10/2002 1

Description and evaluation of the new 1,000 kW Organic Rankine Cycle process integrated in the biomass CHP plant in Lienz, Austria

Ingwald Obernberger, Peter Thonhofer, Erwin Reisenhofer

BIOS BIOENERGIESYSTEME GmbH Graz, Sandgasse 47, 8010 Graz, AUSTRIA Tel.: +43 316 481300 12; Fax: +43 316 4813004;

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1 Abstract

The ORC (Organic Rankine Cycle) process represents an economically interesting technology for decentralised biomass-fired combined heat and power plants (biomass-fired CHP plants). The ORC technology is based on the Rankine process with the difference that instead of water an organic working medium is used. A newly developed ORC technology with a nominal electric capacity of 1,000 kW was implemented in the biomass CHP plant Lienz (A) in the framework of an EU demonstration project. This plant has been in operation since February 2001.

The biomass CHP plant in Lienz supplies the town of Lienz with district heat (about 60,000 MWh/a after completion of the network of pipes) and feeds the electricity produced (about 7,200 MWh/a) into the public grid. Biomass combustion takes place in a thermal oil boiler followed by a thermal oil economiser with a nominal capacity of 6.5 MWth and in a hot water boiler with a nominal capacity of 7.0 MWth. The flue gases of both biomass-fired boilers pass through a heat recovery unit (economiser) with a nominal capacity of 1.5 MWth in order to optimise the overall efficiency of the CHP plant. Moreover, a solar collector panel with a nominal capacity of 0.35 MWth has been implemented and an oil-fired peak load boiler with a nominal capacity of 11.0 MWth has been installed.

The special advantages of the ORC technology are robustness (long service life, low maintenance costs), fully automatic and unmanned operation (personnel requirements only 3 to 5 hours per week), excellent partial load behaviour, and electric efficiency (= net electric power produced / thermal power input) of approximately 18%, which is relatively high for decentralised biomass-fired CHP plants. The ORC is a closed cycle process connected to the thermal oil boiler by a thermal oil cycle (thermal power input at nominal load 5,560 kW) and to the district heating network (thermal power output at nominal load 4,450 kW) as well as to the electric grid (net electric power at nominal load 1,000 kW). Using a new and improved coupling of the thermal oil boiler with a thermal oil economiser and an air pre-heater, the thermal efficiency of this system has been considerably improved and amounts to about 82% (= thermal power output / fuel power input [NCV]), which is about 10% higher than corresponding values from conventional biomass-fired thermal oil boilers. This increased thermal efficiency also raises the overall electric efficiency of the CHP plant to about 15% (= net electric power produced / fuel power input into the biomass-fired thermal oil boiler [NCV]). Furthermore, the overall process control system of the CHP plant will be optimised by a newly developed Fuzzy Logic control which will go into operation in autumn 2002.

Economic evaluations based on the experiences and data already gained from this project show that a biomass-fired CHP plant based on a 1,000 kWel ORC cycle can achieve specific electricity production costs between 0.09 and 0.14 EUR/kWhel depending on the specific framework conditions concerning fuel price and capacity utilisation of the ORC process. These specific electricity production costs enable an economically viable application of this


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 Supercritical Fluid Extraction Description and evaluation of the new 1,000 kW Organic Rankine Cycle process integrated in the biomass CHP plant in Lienz, Austria Page 001
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