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Steam Turbine Optimisation for Solar Thermal Power Plant Operation
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Concentrated Solar Power)
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
Keyword [en]
solar thermal power, steam-turbine, start-up, cool-down, dispatchability increase
Keyword [sv]
koncentrerad solenergi, ångturbin, uppstart, nedkylning, ökad flexibilitet
URN: urn:nbn:se:kth:diva-35386ISBN: 978-91-7415-991-2OAI: diva2:427742
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
List of papers
1. On the Significance of Concentrated Solar Power R&D in Sweden
Open this publication in new window or tab >>On the Significance of Concentrated Solar Power R&D in Sweden
2011 (English)In: Proceedings of the World Renewable Energy Congress 2011, Linköping, 2011Conference paper (Refereed)
Abstract [en]

Concentrated Solar Power (CSP) is an emerging renewable energy technology that has the potential to provide a major part of European energy needs at competitive cost levels. Swedish industry is strongly involved in CSP-based energy production either in the form of growing providers on the European energy market or as developers and producers of key components for CSP power plants. The growing industrial interest is reflected and accompanied by state of the art research in this field at the Department of Energy Technology at KTH. In the present paper the main challenges and opportunities for CSP R&D are presented and linked to the industrial environment and interests in Sweden. Related to these challenges, an overview of the latest research activities and results at the Department of Energy Technology is given with examples concerning CSP plant operation and optimisation, techno- economic cycle studies and high temperature solar receiver development.

solar thermal power, Sweden, research and development
urn:nbn:se:kth:diva-35271 (URN)
World Renewable Energy Congress
QC 20110628Available from: 2011-06-28 Created: 2011-06-23 Last updated: 2011-06-29Bibliographically approved
2. Thermal modeling of a solar steam turbine with a focus on start-up time reduction
Open this publication in new window or tab >>Thermal modeling of a solar steam turbine with a focus on start-up time reduction
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.

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:nbn:se:kth:diva-35272 (URN)10.1115/GT2011-45686 (DOI)000320967100101 ()2-s2.0-84855880509 (ScopusID)978-0-7918-5463-1 (ISBN)
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
3. Annual performance improvement for solar steam turbines through the use of temperature-maintaining modifications
Open this publication in new window or tab >>Annual performance improvement for solar steam turbines through the use of temperature-maintaining modifications
2012 (English)In: Solar Energy, ISSN 0038-092X, Vol. 86, no 1, 496-504 p.Article in journal (Refereed) Published
Abstract [en]

Steam turbines in solar thermal power plants experience a much greater number of starts than those operating in base-load plants. By maintaining higher internal temperature during idle periods, faster start-up times can be achieved, increasing the flexibility of the plant as well as increasing net electrical production. Prior work by the authors identified a number of methods for achieving this, with strong increases in daily production predicted; only two specific start-up cases were studied however. In order to obtain a more representative evaluation of the performance increase that can be achieved through increased dispatchability of the turbine, the annual improvement needs to be studied. Building on the existing results, a dynamic system model of a parabolic trough power plant has been established and used to determine the distribution of different cool-down times experienced throughout the year, with a view to evaluating the potential annual production increase. A modification of the start-up curves allows an increase in annual electrical production between 6.4% and 2.4% depending upon the operating mode (free operation versus day-time operation). Through application of a combination of heat blankets and an increase in gland steam temperature, further annual production increases between 2.2% and 3.1% are predicted.

Solar thermal power, Steam turbine, Dispatchability, Start-up
National Category
Energy Engineering
urn:nbn:se:kth:diva-35273 (URN)10.1016/j.solener.2011.10.023 (DOI)000300459600052 ()2-s2.0-84855188629 (ScopusID)
QC 20120417Available from: 2011-06-28 Created: 2011-06-23 Last updated: 2012-06-11Bibliographically approved

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