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Concept Global d'une nouvelle centrale solaire à cycle combiné Dual-Fuel.
... Les centrales combin~es solaires int~gr~es offrent la possibilit6 de r6duire la consommation de combustible fossile, donc de limiter la production de gaz ~ effet de serre, tout en offrant une garantie de disponibilit6 de production 61ectrique [1,2]. Pour am~liorer les performances d ' u n e telle centrale une approche nfixte, eonjuguant technique du pineement et optimisation pour la ddtermination des paliers d'6vaporation de la partie cycle ~ vapeur, a ~t6 nfise en ~vidence dans l'artiele pr~cSdent [3]. ...
... L'int6r6t d'une telle approche m6thodologique a est que 3 L'6tude compldmentaire envisag6e comprendra trois Stapes essentielles : a) couplage entre la m6thode du pineement global ~tendu 5, l'enveloppe du c6ne des d6bits et line mod~lisation permettant une optimisation thermodynamique par algorithme d6terministe (premi~ere partie [31) ; b) m4thode de d6termination complete des diff6rents diagrammes de flux %els d6taill~s par l'interm6diaire d'une th~orie ,~d'interaetion de flux de ehaleur-compl6t6e par des solutions de configurations de centrales issues de %seaux d'dchangeurs exerg6tiquement optimaux (cette publication) ; c) optimisation thermo6conomique et environomique sur la base d'une superstructure de composants g~n~r6e g la phase b). The previous paper [3] described a mixed approach based on the concept of composites of pinch technology coupled with an optimization algorithm to deternfine the evaporation pressure levels of the Rankine cycle of an Integrated Solar Combined Cycle System (ISCCS) [1,2]. This paper extends the analysis to define the actual streams (mass flows) and design the heat exchanger network to achieve maximum energy efficiency for the various operational modes typical of this type of plant. ...
Steam production units (HRSG and HSSG) of ISCCS include several heat exchangers (economizers, evaporator, superheater, reheaters, etc.). The knowledge of the extended composites as a function of the solar input, allows the determination of the most critical zones for heat transfer but does not allow, in itself, the full knowledge of the real streams needed to be able to design an optimum heat exchanger network. The procedure proposed in this paper permits, from so called interaction factors which characterize the interdependancy between streams, the determination of the massflows in each stream. The choice of the best heat exchanger network must respected, for each set of operational conditions, the optimum evaporation levels (including pressures and temperatures) determined in part I, as well as the particular practical operational factors (independence or not between the various heat recovery units, etc.). The network design is performed using the standard guidelines of pinch technology (respect of the minimum pinch ΔTmin for each heat exchanger close to the pinch temperature, separate design of the zone above and below the pinch temperature, etc). The respect of the ΔTmin in the critical zones of heat transfer requires the use of stream splitting and the network includes heat exchanger tubes which are interlaced at the same level of the stack. One example of the best performing power plant designed on the basis of this approach is given.
... Les centrales combin~es solaires int~gr~es offrent la possibilit6 de r6duire la consommation de combustible fossile, donc de limiter la production de gaz ~ effet de serre, tout en offrant une garantie de disponibilit6 de production 61ectrique [1,2]. Pour am~liorer les performances d ' u n e telle centrale une approche nfixte, eonjuguant technique du pineement et optimisation pour la ddtermination des paliers d'6vaporation de la partie cycle ~ vapeur, a ~t6 nfise en ~vidence dans l'artiele pr~cSdent [3]. ...
... L'int6r6t d'une telle approche m6thodologique a est que 3 L'6tude compldmentaire envisag6e comprendra trois Stapes essentielles : a) couplage entre la m6thode du pineement global ~tendu 5, l'enveloppe du c6ne des d6bits et line mod~lisation permettant une optimisation thermodynamique par algorithme d6terministe (premi~ere partie [31) ; b) m4thode de d6termination complete des diff6rents diagrammes de flux %els d6taill~s par l'interm6diaire d'une th~orie ,~d'interaetion de flux de ehaleur-compl6t6e par des solutions de configurations de centrales issues de %seaux d'dchangeurs exerg6tiquement optimaux (cette publication) ; c) optimisation thermo6conomique et environomique sur la base d'une superstructure de composants g~n~r6e g la phase b). The previous paper [3] described a mixed approach based on the concept of composites of pinch technology coupled with an optimization algorithm to deternfine the evaporation pressure levels of the Rankine cycle of an Integrated Solar Combined Cycle System (ISCCS) [1,2]. This paper extends the analysis to define the actual streams (mass flows) and design the heat exchanger network to achieve maximum energy efficiency for the various operational modes typical of this type of plant. ...
Integrated solar combined cycle systems (ISCCS) represent, both economically and energetically, a promising alternative for the conversion of solar energy while offering a guarantee of a minimum power supply independant of the level of solar radiation. Their performances are however strongly dependant on the intensity of the solar input. The approach proposed in this paper allows, from the characteristics of the turbines (gas turbines and steam turbines) and of the solar field, to rationalize the choice of the pressure levels and of the massflows of a steam cycle with multiple pressure levels. It is based on the coupling of a pinch technology approach with a thermodynamic modeling allowing an optimisation with deterministic algorithms. Results are applied to a dual pressure steam cycle and accounts for the respect of the "cone law" for the steam turbines. It is shown that an increase of the exergetic losses linked to heat transfer in the steam generators is inevitable at certain operational regimes and depends directly on the level of solar supply. The variations of the main steam cycle parameters as a function of the thermal supply (combustion gases + solar thermal oil) are shown for an 80 to 120 MWel power plant equipped with two gas turbine and one steam turbine train.
... ț the SEGS power plants in California [4] with electric powers between 30 and 80 MWe, which are based on cylindro-parabolic concentrators with additional fossil fuel burners or natural gas boilers to supply a steam cycle, ț the Integrated Solar Combined Cycle Power System (ISCCS), such as PAESI [5][6][7] or ISSCS-Nevada, USA [8,9] based on efficient combined cycles with a better fuel conversion efficiency and reduced electricity production costs (by as much as 42%) compared to the present SEGS plants [4], and ț concepts using high efficiency parabolic solar concentrators, delivering solar heat at an exergy level sufficient to preheat or to fully heat the compressed air of the gas turbine of a combined cycle or to supply heat for endothermic fuel reforming [10]. ...
This paper introduces a novel concept of mini-hybrid solar power plant integrating a field of solar concentrators, two superposed Organic Rankine Cycles (ORC) and a (bio-)Diesel engine. The Organic Rankine Cycles include hermetic scroll expander-generators1 and the sun tracking solar collectors are composed of rows of flat mirror bands (CEP) arranged in a plane, that focus the solar energy onto a collector tube similar to those used in SEGS plants in California. Waste heat from both the exhaust gases and the block cooling of the thermal engine are also heat sources for the ORCs. Such units meet electricity, cooling and pumping needs of remote settlements. The thermal engine guarantees a minimum level of both power and heat availability at night or during cloudy periods. Laboratory tests, made with the superposed ORCs only, confirmed adequate operational characteristics with good performances over a broad range of conditions. A few preliminary tests on the site of the solar power plant when coupled with the engine confirmed a reasonable behavior and the interest of the concept even at part load or during sharp variations of the thermal supply.
... Integrated Solar-Fossil Power Plants (ISFPP) represent, both economically and energetically , a promising alternative for the conversion of solar energy while offering a guarantee of a minimum power supply independent of the level of solar radiation (Favrat, 1995; Allani and Favrat, 1991; Allani et. al., 1996 ). ...
p>Hybrid solar thermal power plants (with parabolic trough type of solar collectors) featuring gas burners and Rankine steam cycles have been successfully demonstrated by California's Solar Electric Generating System (SEGS). This system has been proven to be one of the most efficient and economical schemes to convert solar energy into electricity. Recent technological progress opens interesting prospects for advanced cycle concepts: a) the ISCCS (Integrated Solar Combined Cycle System) that integrates the parabolic trough into a fossil fired combined cycle, which allows a larger exergy potential of the fuel to be converted. b) the HSTS (Hybrid Solar Tower System) which uses high concentration optics (via a power tower generator) and high temperature air receivers to drive the combined cycle power plant. In the latter case, solar energy is used at a higher exergy level as a heat source of the topping cycle. This paper presents the results of a thermoeconomic investigation of an ISCCS envisaged in Tunisia. The study is realized in two phases. In the first phase, a mixed approach, based on pinch technology principles coupled with a mathematical optimization algorithm, is used to minimize the heat transfer exergy losses in the steam generators, respecting the off design operating conditions of the steam turbine (cone law). In the second phase, an economic analysis based on the Levelized Electricity Cost (LEC) approach was carried out for the configurations, which provided the best concepts during the first phase. A comparison of ISCCS with pure fossil fueled plants (CC+GT) is reported for the same electrical power load. A sensitivity analysis based on the relative size of the solar field is presented.
This paper was presented at the ECOS'00 Conference in Enschede, July 5-7, 2000 </ul
This paper presents the analysis of an original design of small hybrid solar plant using Organic Rankine Cycles with hermetic scroll expander- generators. The hot supply is provided from vacuumed collector tubes along the focal line of solar concentrators made of mirror bands fixed on a plane surface (CEP). The plant is integrated with a cogeneration Diesel engine unit to ensure power availability independently from the variations of solar radiation. It is primarily intended for isolated sites in developing countries. Measurements on the power unit of 13 kWel show an excellent behavior over a broad range of parameters with an efficiency of the order of 18% (50% exergetic efficiency), which is very promising, particularly when considering that the concept of superposed cycles will allow operations at higher supply temperatures with further technological developments.
The integration of a solar collector field generating steam into a conventional combined cycle in order to partially replace the fossil fuel required by the latter results in a substantial reduction in greenhouse gases, in an increase in the return on investments associated with the solar field and in an almost complete elimination of the need for solar energy storage. This paper discusses the design of such an integrated hybrid solar-fossil combined cycle with maximum daily and nightly power outputs of 88 MWe and 58 MWe, respectively. This cycle is currently being evaluated from a technical and economic risk feasibility standpoint for possible implementation as a pilot plant in Tunisia. This paper outlines pertinent design considerations utilized in the thermoeconomic optimization approach employed for developing the hybrid combined cycle proposed here. The approach shows that there are several advantages to this type of design when compared with a purely solar steam cycle or any of the several other hybrid solar concepts which exist today. In addition to these advantages, the design presented revolves around the definition of a number of degrees of freedom which allow the solar energy part of the cycle to be highly integrated into the conventional part. A discussion of them is given. Finally, from an environmental standpoint, the obvious advantage of this type of cycle is that due to the substitution of fossil fuel, there is a marked mitigation in CO2 and NOx emissions when compared to a conventional cycle and to other hybrid concepts. Pertinent results for these reductions are presented.
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