Realization of a supervisor system for a Combined Heat Power system based on Solid Oxide Fuel Cell

Author(s):
P. Squillari - POLITECNICO DI TORINO - DENER
M. Calì - POLITECNICO DI TORINO - DENER
F. De Benedictis - POLITECNICO DI TORINO - TURBO CARE
G. Orsello - POLITECNICO DI TORINO - TURBO CARE
G. Disegna - POLITECNICO DI TORINO -TURBO CARE

Industry:
University/Education, Energy/Power

Products:
Data Acquisition, LabVIEW, Real-Time Module

The Challenge:
Realize a primary scada for a combined heat and power Solid Oxide Fuel Cell (SOFC) system. Primary scada has to exchange data with a Siemens Simatic TI 505 (serial modbus), with a secondary scada realized using WinCC. A subset of the collected must be sent to a remote server for web publishing.

The Solution:
Industrial Automation OPC Server easily permits, using the OPC technology, to establish communication between Siemens Simatic TI 505 and LabVIEW DSC. In order to exchange data between primary SCADA (realized using LabVIEW DSC) and the secondary SCADA an ad-hoc protocol has been realized. The data transfer between primary SCADA and web server has been realized using the ftp client VIs.

Short Summary
The EOS project, started in 2004, involves: Politecnico di Torino, TurboCare S.p.a. (old name: Gas Turbine Technologies S.p.a.) - a Company of Siemens Power Generation , Pennsylvania-based Stationary Fuel Cells division of Siemens Westinghouse Power Corporation and HySyLab to collaborate on a solid oxide fuel cell project in Italy.
Using LabVIEW DSC, a SCADA has been realized with the aim to log all scientific data from the SOFC and from the cogeneration plant.

Article

Project description
The EOS project started in 2004, when the Politecnico di Torino, TurboCare S.p.a. and HySyLab signed an agreement, aiming to collaborate on a solid oxide fuel cell project in Italy. The regional government, Regione Piemonte financially supports the project.
The project foresees five years of work (2004-2009). As a first phase of the program, the Pennsylvania-based Stationary Fuel Cells division of Siemens Westinghouse Power Corporation supplied GTT with a 100 kWe, 65 kWth, combined heat and power Solid Oxide Fuel Cell (SOFC) system, fuelled by natural gas with internal reforming (CHP 100). This unit was installed in April 2005 in the GTT former gas turbines test room, which until a few years ago was used to test large Fiat gas turbines, and was converted into a SOFC test hall.
To commissioning date the generator has operated in Torino for more than 12200 hours producing more than 1.4 million kWhr of electrical energy.
The system availability of the CHP system is anticipated to be above 98%, and the electrical efficiency was demonstrated at 46%, with an overall first Law system efficiency of 70–80% when process heat is utilized.

Plant description
The 100-kWe SOFC–CHP system was designed in four major subsystems:
• Fuel cell (SOFC)
• Power Conditioning
• Main Heat Export
• Secondary Heat Export.

The Fuel Cell Subsystem is the kernel of whole plant. The desulforized gas feed to the SOFC is transformed into electricity.
The Power Conditioning Subsystem provides the interface with the utility grid, converting the DC power produced by the SOFC module to AC power required by the grid: 400 V, three-phase, 50 Hz. In case of grid interruptions or problems with the power conditioning system, a DC dissipator is also provided to permit continued system operation.
The Main Heat Export System recovers heat from the exhaust gas exiting the recuperators by heating a pressurized water flow in the primary heat exchanger.
The secondary Heat Exchanger the pressurized water flow is feed to the secondary heat exchanger for warming some offices rooms (EOS and EAST offices) in winter, while in summer it will feed to an absorption chiller producing cooling power for a system of fan-coils.

Plant supervisory
Plant control is realized (locally at the TurboCare SOFC test room) with two different controllers:
1. Siemens Simatic TI 505 for Fuel Cell, Power Conditioning and Main Heat Export subsystems
2. Siemens s7 for Secondary Heat Export Subsystem.
Each controllers has its own SCADA on a dedicate computer (the first one realized by Pennsylvania-based Stationary Fuel Cells division and the second one realized within EOS project by ELECTRO S.r.l.).
The drawbacks of this architecture are: difficult to supervisor the plant: two different HMIs are difficult to supervisor, there is no possibility to save data from the Secondary Heat Export Subsystem. Moreover there was the need to publish on the web a subset of the plant data.
In order to solve these three problems a new SCADA has been implemented using LabVIEW DSC: the Plant Supervisor SCADA.
The main requirements for PS SCADA are:
1. collect data from Fuel Cell, Power Conditioning and Main Heat Export Subsystems
2. collect data from the Secondary Heat Export Subsystem
3. store data in a data base
4. enquiry the data base
5. alarm control
6. present all data on an intuitive HMI
7. send data to the web server

The first controller (Siemens Simatic TI 505) exchange data with its own scada via a TIWAY protocol on a dedicate line, but it also has a modbus serial line that we used to read all process variable for Fuel Cell, Power Conditioning and Main Heat Exchanger subsystems. Using the Industrial Automation OPC Server in conjunction with LabVIEW DSC the retrieval of these data is made quite easy (via OPC technology).
The second controller (Siemens s7) doesn’t have an accessible bus for PS SCADA; so we realized an easy protocol between PS SCADA and the Heat Export SCADA via a file exchange. This type of data exchange isn’t a standard protocol so the implementation of this algorithm has been written directly with LabVIEW.
LabVIEW DSC, on PS SCADA, automatically logs data to a citadel database and the alarm setting (alert value) is made easy with the help of the Tag Configuration Editor.
In order to send data to a web server we implemented a second VI that periodically enquiry the citadel database in order to retrieve the subset of data we want to publish on the web. Data are formatted into a file and sent to web server using a dedicate HDSL line and the ftp protocol. On the server side a php program reads the data file and publish the data.
All software for primary SCADA and web server has been realized by GEAS S.r.l. a National Instruments Alliance Member.

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