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Zawartość zarchiwizowana w dniu 2022-12-27

MODULAR ORGANIC RANKINE CYCLE TURBOGENERATOR FOR GEOTHERMAL WATER (1-1 5 MEGAWATT RANGE)

Cel

Scope of the activity has been the design, construction, testing and operation of a binary geothermal plant, realised according to the Organic Rankine Cycle (ORC) concept, with the general aim of verifying the technical and economical viability of such machines in the 1 MW power range with heat source temperatures in the range 90 to 114 deg. C.
Following the design criteria specified in the early stages of the project, the machine is modular (two main skids superimposed, plus one auxiliary box), transportable on normal trucks, factory pre-assembled. It includes a heat exchange surface as large as possible given the skid limits, and features high corrosion resistance materials for all the parts exposed to the geothermal fluid (AISI 316 stainless steel and grade 2 titanium).
The hot and cold water supply system was completed by Enel in June 1992. Contemporarly the ORC modules and the auxiliary boxes, pre-assembled at the factory, were mounted on site and connected.
The machine was first put in parallel to the grid at the beginning of July 1992.
Some infancy problems had to be solved during about six months of operation (concerning the air compressor, electric generator, uninterruptible power supply). Also some adaptation of the control software and parameters was required. The program has been delayed also due to a large increase of the design phase, delays from suppliers and pressure vessel verificators.
A complete series of tests was performed to evaluate the off-design performance of the plant. The obtained results are extensively reported in the final report to EEC, for a power output exceeding 1.3 MW (1).
The performance tests indicated a very good overall performance of the machine, which in fact produced more than 1.3 MW electric power at lessthan nominal hot water temperature. The turbine efficiency at design point is better than 80%.
The project as a whole is an encouraging success, having reached the main goal, a good performance of the machine in terms of electric power generated.
In particular the turbine did not require any set-up or modification to reach the predicted performance thus confirming the level of the know-how reached by Turboden in the design of Organic working fluid expanders.
From a more general point of view too, the project has to be considered a success also for the operational aspects, once a number of modifications (to non-fundamental items) have been performed during the start-up of the plant.
For the binary geothermal module a power output of 1-1.4 MW was adopted. The 1 MW size can be considered an optimised solution for the following reasons :
- the power is large enough to yield an acceptable cost per installed kW;
- the assembled machine is small enough to be easily transportable;
- a large power can be obtained by coupling a number of standard modules.
ENEL, the National Electric Utility of Italy, was very interested in the demonstration of the 1 MW module and indicated as a size for the machine installation the Castelnuovo Power Plant, near Larderello (PI).
The power conversion module realises a "binary" cycle, which means that a suitable working fluid is used to generate power in a Rankine cycle, while the geothermal fluid provides only the thermal power. Hence the geothermal fluid does not flow through the turbine.
The binary cycle solution allows a better control of the potential pollution of the environment by the gases dissolved in the geothermal water, in particular carbon dioxide and hydrogen sulphide. In the design stage, a thorough optimisation of the components was performed utilising CAD and Finite Element Analysis in particular for the turboexpander.
The main design features are here summarised :
. titanium was used for the hot water heat exchange tubing (the tubesheets were titanium-clad) . stainless steel was used for the cooling water tubes and tubesheets.
- both hot and cold section tubes are finned on the working fluid side, the fins being obtained by cold rolling, according to a technique widely used in the refrigeration technique.
In this way the size of the heat exchanger can be significantly reduced and the water path can be abbreviated.
The turbine realizing the expansion of the organic working fluid is single-stage, full admission, reaction turbine, rotating at 300 rpm.
The machine is controlled by a C-programme microprocessor (housed on the skid), interfaced with a host computer, which is used as friendly interfacefor the operator and as accumulator for the Data Acquisition. A large number of signals are recorded and can be automatically compared or elaborated off line.
Throughout the design and construction of the machine care has been dedicated to the quality, with strict adhesion to quality plans and procedures.

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SOWIT SRL
Wkład UE
Brak danych
Adres
VIA PIO LA TORRE 14/B
20090 VIMODRONE (MI)
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