It is the objective of the PS10 (Planta Solar 10) project to design, construct and operate in a commercial basis a CRS demonstration plant with a design point nominal power of 10 MW, to be installed in Southern Spain and producing electricity in a grid- connected mode and based on the well known PHOEBUS volumetric air technology (Grasse, 1991; Schmitz-Goeb and Keintzel, 1997). The PS10 plant should:
The project will make use of existing and well proven technologies like glass-metal heliostats, a volumetric wire-mesh receiver, ceramic-checker storage system and steam generator developed by European companies and already tested and qualified at solar test facility scale in the Plataforma Solar de Almeria within the TSA project (Haeger, 1994).
Fig. 1.- Process flow diagram of the PS10 solar tower power plant
The PS10 plant will be located in the estate of Casa Quemada (37.2º Latitude) and nearby the town Sanlucar la Mayor, 15 km West from the city of Seville. The plant will be a solar-only system to comply with Spanish regulations. The system will make use of 981 heliostats developed by INABENSA, a 90 m high tower, a 33 MWhth heat storage system and an integrated volumetric air receiver design of 173 m2 developed by the German company Steinmüller (table 1). The basic configuration of PS10 plant consists of a heliostat field (north shape), volumetric air receiver, steam generator, solid heat storage module, EGPS, two blowers and corresponding air ducts and dampers (See fig. 1). Heliostat field layout, tower height and receiver configuration have been optimized by using the code WDELSOL. Insolation is concentrated by means of the heliostat field onto a receiver (80515 m2 mirrors). The heliostat Sanlucar-90 will be used for the PS10 plant and basically it consists of an enlarged version of the successful COLON heliostat of 70 m2 developed by INABENSA (Silva, Blanco and Ruiz, 1999).
The receiver must supply the power for feeding the steam generator and has been designed for a solar multiple of 1.15. Receiver shape is sectional cylindrical. The absorber of the volumetric receiver is made of wire mesh hexagonal modules. Design point technical specifications for the receiver are: Air mass flow: 63.1 kg/s; Air outlet temperature: 680 ºC; Air return ratio: 45%; Receiver thermal efficiency: 90%; Air missing losses: 8%. The PS10 thermal storage consists of a packed bed of ceramic 15-mm cordierite spheres embedded in an internally insulated cylindrical vessel. The main storage data are:
The steam generator is a meander-type tube bundle with natural circulation. Steam (10.73 kg/s) will be produced at 460 ºC and 65 bar. Turbine generator will produce 11 MWe gross and 10 MWe net with 30% efficiency. Heliostat field aiming strategy has been carefully analyzed with HELIOS code (Vittitoe, Biggs and Lighthill, 1978) in order to preserve flux distribution onto the absorber. Flux requirements are as follows and could be simulated with as many as 38 aiming points:
Design point thermal outlet efficiency from solar to turbine is 54% and the total conversion efficiency solar to net electric grid is 13.2%. The system is penalized by the turbine size and its corresponding efficiency (30%). At design point conditions, the solar receiver will load about 5 MW into the storage system. Annual performance as predicted by SOLERGY (Stoddard et al., 1987) should produce 22.1 GWh gross (12% efficiency) and 19.2 GWh net (10.5% efficiency), being equivalent to almost 2000 hours of equivalent nominal production (22% Capacity Factor).
Receiver thermal outlet moves between 200 MWh in wintertime and 325 MWh in summer time. Considering the power block conversions, the power production per day goes to 100 MWh.
Heat storage at PS10 has as main objective to facilitate the operability of the plant as a solar-only system. A 1-hour equivalent heat storage system has been considered enough to guarantee such operability. In wintertime or with cloud transients, about 5 to 6 hours of nominal power can be supplied to the turbine. The number of operation hours for the turbine in a typical summer sunny day may go up to 10 to 12 hours.
The PS10 project will be managed following the typical work program of most conventional thermal power plants (Falcone, 1986). Solar specificity is basically influencing the initial definition phase (already completed), like specifying a design point and a solar multiple, and selection of the site. PS10 is promoted by the ABENGOA company through the IPP Sanlucar Solar. The INABENSA company acts as single prime construction manager and as Coordinator for the EC demonstration PS10 project. The RTD project is managed by a Consortium formed by four Partners. In addition two main subcontractors are considered relevant for the success of the project. INABENSA will be responsible for supply and assembling of BOP and heliostat field and assembly of receiver system+heat storage+steam generator. In addition INABENSA will contract to external subcontractors the supply of receiver subsystem (STEINMÜLLER), master control and electric power generation system (ABENER). Detailed engineering will be jointly performed by the partners Fichtner, CIEMAT and DLR. Training operation and evaluation will be conducted by a team formed by two partners –CIEMAT and DLR- and one subcontractor –AICIA-.
| COSTS PS10 | Investment (Thousand $) |
| General Coordination | 178 |
| Civil Works | 657 |
| Heliostats | 9,678 |
| Tower | 1,876 |
| Receiver+Storage+Steam Gen. | 9,581 |
| EPGS | 4,803 |
| Control | 781 |
| TOTAL | 27,553 |
Once PS10 is completed, it will be hired to the Sanlucar Solar IPP society already registered for commercial exploitation during the operation/evaluation phase and beyond the scope of the EC project.
Project costs amount to 28 million dollar (see table) and lead to a typical LEC of $0.18/kWh. The small size of the plant and the pure solar design make necessary the existence of a public economical support through investment subsidies (both European and National) and a special tariff for the electricity produced. At present a 5 million-dollar investment subsidy has been obtained from the EC RTD ENERGIE Programme and additional subsidies are under negotiation through the Ministry of Industry and Energy in Spain. The Spanish ROYAL DECREE 2818/1998 of December 23, 1998, on the electricity production by facilities powered by renewable energy sources offers a green price between $0.11 and $0.22/kWh for the generated electricity that opens a unique opportunity to start the market introduction of solar thermal power plant technology in under commercial conditions. Eventual figures of investment subsidies and premium electricity selling price are still a matter of negotiation between PS10 promoters and the Spanish Administration.
