SOLARPACES: Development of an integrated solar thermal power plant training simulator

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1 SOLARPACES: Development of an integrated solar thermal power plant training simulator Achaz von Arnim 1 and Ralf Wiesenberg 2 1 Dipl.Ing., Business Unit Energy E F IE ST BD, Business Development CSP, Siemens AG, Offenbach, Germany, Phone: , [email protected] 2 Dr. -Ing. Energy Engineering Managing Director, Sun to Market Solutions, Madrid, Spain. Phone: , [email protected] 1. Introduction There are a significant numbers of solar thermal power plants around the world which are already in operation. Spain, with more than 730MW of installed capacity in operation and 900MW under construction is nowadays the market leader for solar thermal power plants. All these p lants have one thing in common: their behaviour his highly dynamic because they have to operator under fast changing transient weather situations like passing cloud trains or morning mist with condensed water on the mirrors and receiver tubes. In contrast to conventional thermal power plants, solar thermal power plant operators have to cope with these kinds of transient situations during daily plant operation. It is obvious that operational training is crucial for safe and optimized solar thermal power pla nt operation. A full-scope control room simulator for solar thermal power plant is therefore an essential tool for training purposes. Siemens together with Sun to Market Solutions are in process of developing a full-scope integrated control room simulator for parabolic trough plants using an engineering precision dynamic plant models combined with state of the art control system interfaces. The main objective of the full-scope integrated control room simulator is to train and assess operators in general plant operation in a virtual plant, including training in plant start-up and shut-down, supervision, monitoring and control during normal, emergency situations and in safety procedures. The developed plant simulator is very flexible and can be employed in a number of diverse ways to suit the needs of the solar thermal power plant. The main objectives of the simulator, not exhaustive, are the following: Training on day-to-day operation under transient weather conditions Training on predictive, preventive and corrective maintenance Training on emergency response. Design and implementation of training plans for the CSP plant personnel Development or review of operation manuals and procedures Adjustment and validation of new operational strategies Improving the overall safe, efficient and economical operation of the solar thermal power plant The simulator has the option to work in real time or in an accelerate time mode. Furthermore, the simulator has the option to take into account price signals coming fro m an electricity spot market or PPA dispatch profile. With this price information the operator has the possibility to decide when to use the auxiliary fuel or how to operate the thermal storage system in order to increase the income from the power purchase. Several daily operation and emergency situations are generated for the simulator. These simulation situations are currently tested and evaluated by selected end user, and will be released later this year.

2 2. Types of Simulation If the topic Simulator/Simulation is raised in a discussion today the expectation of customers are quite different; especially in the CSP plant environment. Therefore it is needed to differ between at least three types of simulation to bring all parties (supplier, CSP developers, EPC, IPP/utilities) on the same level. I. Simulator for the Thermodynamics plant layout The target customers are mainly CSP developer and EPC in order to layout the plant and give the expected guarantee parameters. The focus of the emulator is mainly the thermodynamics of a CSP plant, which are quite complex especially in the technology for Parabolic trough or Tower technology. The requirements for the Thermodynamics Emulator are to simulate: annual yield calculation for guarantee purposes start-up energy consumption and times shut-down times and cool-down curves during shut-down The customer expects from the dynamic plant modeling high flexibility in component selection and configuration and reasonable calculation time (i.e. minutes not hours or days). Such a system (e.g. the ESEM or STP4 models developed by Sun to Market Solutions) would be a stand-alone tool, easily adjustable as measured data comes to hand and an interface to other dynamic systems (e.g. KRAWAL used at Siemens AG), but no interface to a DCS system is needed. II. b) Simulator for the Process Engineering The target customers are mainly CSP developers and EPCs in order to simulate their fine tune their designed CSP plant. The requirements for the Process Engineering Emulator are to simulate: Plant start-up and shut down (HTF thermal hydraulic dynamics) System response to failures: e.g. step group sequence SGS feed water pumps, black out, grid disruption Plant cool down (shut down: during night, long term) Cloud shadowing effects / variable solar heat input The customer expects from the dynamic plant modeling a time resolution in seconds/minutes and as outputs the thermal hydraulic system dynamics (including dead/lag times due to large systems dimensions). Such a system would be as well a stand-alone tool (eg. The Solver or ESOM models developed by Sun to Market Solutions), easily adjustable, but does not need an interface to the used main DCS system. III. c) Virtual commissioning of a Distributed Control System (DCS) - /Training simulator The target customers are commissioning engineers of EPC s and end user of IPP s /utilities. The focus of the emulator is mainly to shorten the commissioning time, increase the quality and train the operators of a CSP plant. The specification for this type of Simulator would be to: Interface between Simulator and a main DCS via a standard protocol like Profibus/Ethernet Simulate in real time / interactive for dynamic function test Design verification of Control Software (e.g. Open Loop Control and Closed Loop Control) Perform Customer Acceptance Test/TÜV or similar Support during pre-commissioning and system setup in factory Operator training for training DCS-System operating and CSP plant operation Simulate critical operating condition /possible load cases without destroying the real plant hardware The customer expects from this simulator to operate with a surface of their future main control system without building up the entire automation hardware again.

3 3. Training simulator for CSP plants from Siemens and Sun to Market Solutions Sun to Market Solutions and Siemens AG can offer for each of the above simulators types a solution but focus mainly on the Virtual commissioning of main control system (DCS) /Training simulator in the following. To understand the complexity of a virtual commissioning and/or training simulator it is needed to understand the layout of the control system for CSP plants and the advantage of a harmonized control system. Typically there are five process areas for a CSP plant, based on logical, vendors and long -delivery items as the Solar field, Heat Transfer Fluid HTF, Balance of Plant BOP, thermal storage, and steam turbine area (see Fig. 1). Fig. 1. Logical areas of a CSP plant (e.g. Parabolic Trough) The same applies for the control systems, where usually the Solar Developer offers the Solar field, including or excluding the storage and the HTF system from their subcontractor. Already there could be more than one automation system with an owned developed programmable logic controller PLC. The main Distributed Control System DCS, including the master control for the entire CSP plant could be from typical vendors like ABB, Emerson and Siemens AG. Since the Steam turbine is a long -delivery item, it will be ordered first and includes their own turbine control system. Most of the CSP steam turbines (non-oem/oem) are equipped with a Siemens turbine control. (see Fig. 2). Fig. 2 Process areas for a typical control system

4 The goal for each CSP plant should be in order to have highest added value (lowest CAPEX and OPEX, less training cost, less components etc.) to think already during purchasing of a DCS about an harmonized DCS. (see Fig. 3). Fig. 3 Harmonized control system SPPA-T3000 from Siemens AG 3.1. Simulator SPPA-S3000 from Siemens AG In order to build up a virtual commissioning or training simulator it is needed to emulate the existing automation hardware and the process of a real CSP plant. Therefore it is essential to know the exact control system configuration as described in the previously chapter. Before the simulator can be offered on the market it was needed to plan all needed Research and Development steps for new fe atures for a CSP plant. Additionally, some additional engineering might be needed in order to identify none yet existing emulations for special HW used in the CSP plants. In order to build a training simulator it was required to define a site and collect technical and operational data of an actual CSP plant. The reference CSP plants for the new simulators have to be chosen in accordance with the following guidelines: applicability to a wide range of customers (EPC s, IPP and utilities) availability and accessibility of technical and operational data Objectives for a CSP simulator are perfect fault handling, high product quality, reproducible workflows, optimum output through optimum operation and careful handling of the assets. All these objectives could already be improved with the SPPA-S3000 simulator in the fossil environment. In case a CSP plant has the Siemens SPPA-T3000 as the main control system, the simulator SPPA- S3000 uses a second set of the original Human Machine Interface hard- and software components. (see Fig. 4)

5 Fig. 4 SPPA-S3000= 1:1 simulation of SPPA-T3000 DCS Generally a training simulator should be always divided in three-tier concept unequal from the main DCS (see Fig 5): 1 st tier: Human Machine Interface: Second set of simulator enhanced operation and monitoring system equipment where simulator operation should be the same as the operation in the reference plant. 2 nd tier: Automation system: Emulation instead of the DCS (in case of Siemens AG: SPPA-T3000) automation server and IO modules where the emulated automation servers get the same engineering data as the physical I&C in the plant. 3 rd tier: Processes model computing The process model computer simulates the technological process of the power plant, so that the look and feel is the same like in the reference plant Fig. 5 Three tier 1:1 simulation CSP plants

6 Furthermore, for Training purposes all simulator-specific functions (e.g. start, stop, etc.) have to be implemented centrally on an Instructor Station. The SPPA-S3000 simulator environment is already in successful operation for years for the use virtual commissioning of main DCS on retrofitting projects in conventional power plants e.g. Neurath Unit D, RWE Power AG. The simulator uses a second set of the original Human Machine Interface hard - and software components. It emulates both the automation controllers and the input/output level, providing a functional 1:1 copy of the Siemens SPPA-T3000 control system used in the plant. The process model simulates the complete technological process. This concept ensures that the original engineering data from the reference plant can be used unchanged in the simulator, and vice versa. [2], [3] 3.2. Incorporation of Sun to Market Instructor Station and Process Model for the Solar field In addition to Siemens standard process model for the power block Sun to Market supplies their validated dynamic hydraulic and thermodynamic plant process model for all relevant sub-systems and components of the solar field and the optional thermal energy storage system. Sun to Market has been chosen by Siemens AG in an international selection process because of its proven track record for developing and providing sophisticated process models fo r the solar thermal power industry on international level. For the solar field Sun to Market s dynamic process model takes into account the following characteristic of the plant and its DCS system: - Geometry and slope of the solar field, - Sub-field valves control, - Automatic loop valve control (if any), - Optical geometry and loses. - HCE loses, - Loop operating status. - HTF volume, - Transient equations of each loop. - HTF pumps control, - HTF pumps curves and philosophy. - Tracking philosophy of each loop, - P&I fully reflected into the model. - Length, diameter, material and insulation of piping, - Vessel and ullage system. Furthermore, operating modes and the position of alarm and protection threshold which set status conditions in the plant (open valves, flow pumps, mechanical equipment...) are also part of the process model. The here presented process model offers the possibility to measure and control the following: Inlet and outlet flow rate, temperature and pressure of each field sector, Inlet and outlet temperature of each SCA, Solar field availability and performance, Loop status (out of order, broken mirrors, vacuum looses, ), HTF leaks produced in each loop, Valves status (% opened), Evolution of the temperature in the HCEs in the transients (Envelopes, Steel tubes and HTF). Sun to Market process model is not just a library of predefined equipment and materials. Knowing that each solar thermal power plant is unique, the process model will always tailor made and adapted to the client s needs in collaboration which each plant operator/owner.

7 Fig. 6 Example of simulation of one loop in the solar field The plant process model has been validated with real plant data of parabolic trough plants and together with SPPA-S3000 simulator environment can therefore provide a realistic virtual image of a commercially operating CSP plant. (see Fig. 6) Finally, a constructor console has to be developed in order to control and coordinate the scenarios seen by the operator under training conditions. (see Fig. 7) These scenarios could be presented to the operator as a steady state of the plant operation or under any failure of a particular system or equipment. Especially, as this kind of plants depends heavily on meteorology changes, meteorological scenario like in-coming cloud fields can be creator by the instructor, so that operators learn to handle these situations. In order to improve the operation of past situations, a data base with real meteorological situations can also be used helping to find better operating responds to it. Fig. 7 Integration and purpose of Instructor Station 4. Conclusions and results The aim of using the process model for the solar field from Sun to Market Solutions was to create a state of the arte full-scope integrated control room simulator SPPA-S3000 based on the SPPA-x3000 Siemens solution family for parabolic trough solar power plants for specific training facilities. While it is based on a Siemens SPPA-T3000 control system environment it can also be adapted to other control system architectures which widen significantly the possibility of its imp lementation in the CSP community.

8 Concluding the above presented training simulator offers for solar thermal power plants a 1:1 simulation of the reference power plant and guarantees training like real life in a safe environment even before starting commercial operation of the reference plant. References [1] M. Porras (2010). Optimization in the operation of a solar thermal power plant using the S2m Solver 1.0 tool. 16th SolarPACES conference. [2] Wüllenweber, Dr. H.-J., and Brunner, J., and Küppers, L.: Use of simulators for virtual commissioning of main DCS on retrofitting projects. Case study: Power Plant Neurath Unit D, RWE Power AG. VGB Konferenz ( ) [3] Kröck, M., and Fehse, K., and Nacke, H.: New Training Simulators for State-of-the-art Coal-fired Power Plants at KWS PowerTech Training Center. VGB PowerTech 8 (2006), S