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Geometric Modularity in the Thermal Modeling of Solar Steam Turbines
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Concentrated Solar Power)ORCID iD: 0000-0002-8888-4474
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Concentrated Solar Power)ORCID iD: 0000-0002-3458-2112
Siemens Industrial Turbomachinery.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Concentrated Solar Power)
2014 (English)In: Proceedings of the SolarPACES 2013 International Conference, Elsevier, 2014, Vol. 49, 1737-1746 p.Conference paper, Published paper (Refereed)
Abstract [en]

To optimize the start-up schedules of steam turbines operating in concentrating solar power plants, accurate predictions of the temperatures within the turbine are required. In previous work by the authors, thermal models of steam turbines have been developed and validated for parabolic trough solar power plant applications. Building on these results, there is an interest to increase the adaptability of the models with respect to different turbine geometries due to the growing trend of having larger steam turbines in parabolic trough and solar tower power plants. In this work, a modular geometric approach has been developed and compared against both the previous modeling approach and 96h of measured data from an operational parabolic trough power plant. Results show a large degree of agreement with respect to the measured data in spite of the different detail levels. The new model allows for simple and fast prediction of the thermal behavior of different steam turbine sizes and geometries, which is expected to be of significant importance for future concentrating solar power plants.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 49, 1737-1746 p.
Keyword [en]
steam turbine, thermal stresses, start-up, finite element method
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
URN: urn:nbn:se:kth:diva-126931DOI: 10.1016/j.egypro.2014.03.184ISI: 000340733700178Scopus ID: 2-s2.0-84902271058OAI: oai:DiVA.org:kth-126931DiVA: diva2:642599
Conference
International Conference on Solar Power and Chemical Energy Systems, SolarPACES 2013, Las Vegas, NV, United States, 17 September 2013 through 20 September 2013
Funder
Swedish Energy Agency
Note

QC 20140922. QC 20160129

Available from: 2013-08-22 Created: 2013-08-22 Last updated: 2017-08-11Bibliographically approved
In thesis
1. Steam Turbine Thermal Modeling for Improved Transient Operation
Open this publication in new window or tab >>Steam Turbine Thermal Modeling for Improved Transient Operation
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The growing shares of renewable energy sources in the market and solar thermal power applications have set higher requirements on steam turbine operation.These requirements are related to flexibility during transients. A key aspect sought of such flexibility is the capability for fast starts. Due to the varying temperature gradients during start-up, the speed at which the turbine can start is constrained by thermal stresses and differential expansion. These phenomena either consume component lifetime or may result in machine failure if not carefully controlled. In order to accomplish faster starts while ensuring that lifing requirements are preserved, it is important to analyze the thermal behavior of the machine. For this, a transient thermal model was developed with a focus on adaptability to different turbine sizes and geometries. The model allows for simple and fast prediction of thermo-mechanical properties within the turbine metal, more importantly, of the temperature distribution and the associated thermal expansion. The next step of this work was to validate the assumptions and simplifications of the model. This was done through the study and comparison of two turbines against measured operational data from their respective power plants. Furthermore,validation studies also included comparisons concerning the geometric detail level of the model. Overall, comparison results showed a large degree of agreement with respect to the measured data and between the geometric detail levels. The validated model was then implemented in studies related to reducing start-up times and peak differential expansion. For this, the potential effects of turbine temperature maintaining modifications were investigated and quantified.The modifications studied included: increasing gland steam pressure, increasing back pressure and increasing barring speed. Results yielded significant improvements starting from 9.5% in the start-up times and 7% in the differential expansion.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. 63 p.
Series
TRITA-KRV, ISSN 1100-7990 ; 14:06
Keyword
steam turbines, transients, start-up, finite element model, heat transfer
National Category
Mechanical Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-156196 (URN)978-91-7595-367-0 (ISBN)
Presentation
2014-12-05, Sal Learning Theater (M235), Brinellvägen 68, KTH, Stockholm, 11:00 (English)
Opponent
Supervisors
Note

QC 20141128

Available from: 2014-11-28 Created: 2014-11-24 Last updated: 2014-11-28Bibliographically approved
2. Improving Concentrating Solar Power Plant Performance through Steam Turbine Flexibility
Open this publication in new window or tab >>Improving Concentrating Solar Power Plant Performance through Steam Turbine Flexibility
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The amount of incoming solar energy to earth is greater than any other source. Among existing technologies to harness solar energy there is concentrating solar power (CSP). One advantage of CSP is that is dispatchable, meaning that it can provide power even when the sun is not shining. However, CSP is undergoing challenges which hinder its development such as operating variabilities caused by the fluctuations of the sun or the fact that these systems are not yet cost competitive with respect to other technologies.  

One way of improving the performance of CSP plants (CSPPs) is by increasing their operational flexibility, specifically their capability for fast starts. In this way it is possible for the CSPP to harness the solar energy as soon as possible, thus producing more energy and increasing its profitability. Over 90% of CSPPs use a steam turbine to generate electricity. Steam turbines are not currently designed with the flexibility required by the CSP application. Steam turbine start-up is limited by thermal stress and differential expansion. If not carefully controlled, these phenomena either consume lifetime or even result in machine failure.

The aim of this work was to understand the improvement potential of steam turbine start-up and quantify this in terms of CSPP performance indicators. For this, a thermo-mechanical steam turbine model was developed and validated. The model was then used to analyze potential improvements and thermal constraints to steam turbine start-up operation. Furthermore, a CSP plant techno-economic model was developed including steam turbine details. This modeling approach including two levels of detail allowed for the particularities of the component to be included within the dynamics of the plant and thus be able to connect the perspectives of the equipment manufacturer with those of the plant operator. Reductions of up to 11.4% in the cost of electricity were found in the studies carried out.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. 75 p.
Series
TRITA-KRV, 17/04
Keyword
Concentrating Solar Power, Steam Turbines, Transients, Start-up
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-211780 (URN)978-91-7729-388-0 (ISBN)
Public defence
2017-09-08, M3, Brinellvägen 64, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency
Note

QC 20170814

Available from: 2017-08-14 Created: 2017-08-11 Last updated: 2017-08-15Bibliographically approved

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