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Thermal modeling of a solar steam turbine with a focus on start-up time reduction
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Concentrated Solar Power)
Siemens Industrial Turbomachinery AB, Finspång, Sweden.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Polygeneration Systems)ORCID iD: 0000-0002-3661-7016
2012 (English)In: Proceedings of the ASME Turbo Expo 2011, Vol 3, 2012, 1021-1030 p.Conference paper (Refereed)
Abstract [en]

Steam turbines in solar thermal power plants experience a much greater number of starts than those operating in base-load plants. In order to preserve the lifetime of the turbine whilst still allowing fast starts, it is of great interest to find ways to maintain the turbine temperature during idle periods. A dynamic model of a solar steam turbine has been elaborated, simulating both the heat conduction within the body and the heat exchange with the gland steam, main steam and the environment, allowing prediction of the temperatures within the turbine during off-design operation and standby. The model has been validated against 96h of measured data from the Andasol 1 power plant, giving an average error of 1.2% for key temperature measurements. The validated model was then used to evaluate a number of modifications that can be made to maintain the turbine temperature during idle periods. Heat blankets were shown to be the most effective measure for keeping the turbine casing warm, whereas increasing the gland steam temperature was most effective in maintaining the temperature of the rotor. By applying a combination of these measures the dispatchability of the turbine can be improved significantly: electrical output can be increased by up to 9.5% after a long cool-down and up to 9.8% after a short cool-down.

Place, publisher, year, edition, pages
2012. 1021-1030 p.
Keyword [en]
Average errors, Dispatchability, Effective measures, Electrical output, Heat exchange, Solar thermal power plants, Startup time, Steam temperature, Thermal modeling, Turbine casing
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-35272DOI: 10.1115/GT2011-45686ISI: 000320967100101ScopusID: 2-s2.0-84855880509ISBN: 978-0-7918-5463-1OAI: diva2:426484
ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, GT2011; Vancouver, BC; Canada; 6 June 2011 through 10 June 2011

QC 20110628

Available from: 2011-06-28 Created: 2011-06-23 Last updated: 2014-09-01Bibliographically approved
In thesis
1. Steam Turbine Optimisation for Solar Thermal Power Plant Operation
Open this publication in new window or tab >>Steam Turbine Optimisation for Solar Thermal Power Plant Operation
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The provision of a sustainable energy supply is one of the most important issues facing humanity at the current time, given the strong dependence of social and economic prosperity on the availability of affordable energy and the growing environmental concerns about its production. Solar thermal power has established itself as a viable source of renewable power, capable of generating electricity at some of the most economically attractive rates.

Solar thermal power plants are based largely on conventional Rankine-cycle power generation equipment, reducing the technological risk involved in the initial investment. Nevertheless, due to the variable nature of the solar supply, this equipment is subjected to a greater range of operating conditions than would be the case in conventional systems.

The necessity of maintaining the operational life of the steam-turbines places limits on the speed at which they can be started once the solar supply becomes available. However, in order to harvest as much as possible of the Sun’s energy, the turbines should be started as quickly as is possible. The limiting factor in start-up speed being the temperature of the metal within the turbines before start-up, methods have been studied to keep the turbines as warm as possible during idle-periods.

A detailed model of the steam-turbines in a solar thermal power plant has been elaborated and validated against experimental data from an existing power plant. A dynamic system model of the remainder of the plant has also been developed in order to provide input to the steam-turbine model.

Three modifications that could potentially maintain the internal temperature of the steam-turbines have been analysed: installation of additional insulation, increasing the temperature of the gland steam and use of external heating blankets. A combination of heat blankets and gland steam temperature increase was shown to be the most effective, with increases in electricity production of up to 3% predicted on an annual basis through increased availability of the solar power plant.

Abstract [sv]

Hållbar energiförsörjning är för närvarande en av de viktigaste frågorna för mänskligheten. Socialt och ekonomiskt välstånd är starkt kopplat till rimliga energipriser och hållbar energiproduktion. Koncentrerad solenergi är nu etablerad som en tillförlitlig källa av förnybar energi och är också ett ekonomiskt attraktivt alternativ. Koncentrerade solenergikraftverk bygger till stor del på konventionella Rankine-cykel elgeneratorer, vilka minskar de tekniskt relaterade riskerna i den initiala investeringen. På grund av solstrålningens skiftande karaktär utsätts denna utrustning för mer varierade driftsförhållanden, jämfört med konventionella system.

Behovet av att bibehålla den operativa livslängden på ångturbiner sätter gränser för uppstartshastigheten. För att utnyttja så mycket som möjligt av solens energi bör ångturbinen startas så snabbt som möjligt när solstrålningen blir tillgänglig. Eftersom temperaturen i metalldelar hos turbinerna är den begränsande faktorn, har metoder studerats för att hålla turbinerna så varma som möjligt under tomgångsperioder.

En detaljerad modell av ångturbiner i ett solenergikraftverk har utvecklats och validerats mot experimentella data från ett befintligt kraftverk. En dynamisk systemmodell av de övriga delarna av anläggningen har också utvecklats för att ge input till ångturbinsmodellen.

Tre modifieringar som potentiellt kan bidra till att upprätthålla den inre temperaturen i ångturbiner har analyserats: montering av ytterligare isolering, ökning av temperaturen hos glänsångan och användning av elvärmefiltar. En kombination av elvärmefiltar och en temperaturökning av glänsångan visade sig vara det mest effektiva alternativet. Åtgärderna resulterade i en ökad elproduktion på upp till 3%, beräknat på årsbasis genom ökad tillgänglighet hos kraftverket.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. 100 p.
Trita-KRV, ISSN 1100-7990 ; 11/03
solar thermal power, steam-turbine, start-up, cool-down, dispatchability increase, koncentrerad solenergi, ångturbin, uppstart, nedkylning, ökad flexibilitet
urn:nbn:se:kth:diva-35386 (URN)978-91-7415-991-2 (ISBN)
2011-05-27, M3, Brinellvägen 68, KTH, Stockholm, 10:00 (English)
QC 20110629Available from: 2011-06-29 Created: 2011-06-28 Last updated: 2011-06-29Bibliographically approved

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