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Improving Concentrating Solar Power Plant Performance by Increasing Steam Turbine Flexibility at Start-up
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Concentrating Solar Power)
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Concentrating Solar Power)
2017 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257Article in journal (Refereed) Submitted
Abstract [en]

Among concentrating solar power technologies, solar tower power plants currentlyrepresent one of the most promising ones. Direct steam generationsystems, in particular, eliminate the usage of heat transfer uids allowing forthe power block to be run at greater operating temperatures and thereforefurther increasing the thermal eciency of the power cycle. On the otherhand, the current state of the art of these systems does not comprise thermalenergy storage. The lack of storage adds to the already existing variability ofoperating conditions that all concentrating power plants endure due to theuctuating nature of the solar supply. One way of improving this situationis increasing the operating exibility of power block components to betteradapt to the varying levels of solar irradiance.In particular, it is desirable for the plant to achieve fast start-up times inorder to be available to harness as much solar energy as possible. However,the start-up speed of the whole plant is limited by the thermal inertia ofcertain key components, one of which is the steam turbine. This paperstudies the potential for power plant performance improvement through theincrease of steam turbine exibility at the time of start-up. This has beenquantied by carrying out power plant techno-economic studies in connectionwith steam turbine thermo-mechanic behavior analysis. Dierent turbineexibility investigations involving the use of retrotting measures to keep theturbine warmer during oine periods or changing the operating map of the turbine have been tested through multi-objective optimization consideringannual power performance and operating costs. Results show that reductionsof up to 11% on the levelized cost of electricity are possible through theimplementation of these measures, which in turn has a favorable impact onpower plant protability.

Place, publisher, year, edition, pages
Elsevier, 2017.
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-211779OAI: oai:DiVA.org:kth-211779DiVA: diva2:1131018
Funder
Swedish Energy Agency
Note

QC 20170814

Available from: 2017-08-11 Created: 2017-08-11 Last updated: 2017-08-14Bibliographically approved
In thesis
1. 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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