The project objective is the development of a solar-hybrid power system with direct solar heating of a gas turbine's pressurized air. In combination with highly efficient combined cycle systems or recuperated gas turbines significant cost reductions for solar electric power generation can be achieved (predicted LEC of 0.069 EUR/kWh at 50% solar share, specific investment cost of 1410 EUR/kW). The project will prove the technological feasibility, performance and cost reduction potential of such power plants. Description of the work: The project is based on recent developments on solar receivers and new highly efficient gas turbines. It is the consequent continuation of the proof-of-concept receiver test towards a marketable solar hybrid power system. An aero derivative 280 kW gas turbine (shaft power) will be procured and modified for external solar air heating. A new combustor and fuel injection system will be installed, ducts and the control system will be adapted. Auxiliary units will be integrated to build the complete grid-connected power conversion unit (GT, generator, synchronizing board etc.). A pressurized receiver module for 1000°C will be developed and built. The high temperatures will be achieved using ceramic absorbers in combination with active cooling measures on the receiver window. To reduce receiver cost a low temperature tubular receiver module (as first stage in series with the high temperature module) will be designed and built, with emphasis on low-pressure drop. The components will be integrated to a complete solar-hybrid power system and installed in the PSA solar tower facility in Almeria, Spain. The tests will cover all relevant operating conditions to demonstrate the performance of the components and the system: solar-only, solar-hybrid and fossil modes. Solar testing will be carried out for approximately 8 month to obtain reliable information about component durability and maintenance issues. Software tools will be developed to allow simulation of the component and system performance. The tools will be verified by comparing performance predictions with measured data. Then the tools will be extended to allow the cost-optimised layout of commercial solar-hybrid gas turbine power plants. The tools will be used for the conceptual layout of prototype systems, based on 3 industrial gas turbines ranging from 1.4 to 17 MWe. Combined cycle and recuperated gas turbine configurations will be assessed. The required modifications to these gas turbines will be assessed with respect to cost and influence on performance. Cost figures for the receiver system and the components for integration will be determined. The system performance is analysed and the electricity cost evaluated. The European and worldwide market potential will be assessed to define a marketing strategy. A plan for a specific demonstration plant will be developed. Expected Results and Exploitation Plans: The project will provide a sound database for the required modifications of gas turbine as well as for the high temperature receiver technology and the system integration aspects. Solar testing will prove the predicted component and system performance. From the design for 3 solar-hybrid gas turbine systems (1 to 17 MWe) a plan for a specific demonstration plant will be developed. The initial and long-term market potential will be determined, and a plan for market introduction prepared.
The main goal to built and operate a solar-hybrid test system was met. The achievements of the project were in detail:
1) a helicopter turboshaft gas turbine was modified for operation with externally preheated air. The power shaft of the gas turbine was coupled to a gear box connected to a generator. A combustor suitable for air inlet temperatures up to 800 C was developed. The compressor discharge and the combustor inlet ducts were modified to enable coupling to the solar receiver system. A new control system was developed to allow for the special operating conditions of solar-hybrid systems. The nominal power rating of the modified gas turbine system was 240 kWe;
2) a low-cost receiver module was developed and tested. This module is operates as first stage in the serial connection of three receiver modules. It consists of 16 bent metallic tubes connected in parallel. The module was designed, manufactured and integrated into the test system. The cost predictions were refined based on the manufacturing data and the expected cost reduction of about 50% was verified;
3) a high temperature receiver module for up to 1000 C was developed and tested. This module uses the pressurized volumetric receiver technology with a newly developed silicon carbide absorber structure and absorber mounting insert;
4) the components were integrated to a solar-hybrid test system. The modified gas turbine was connected with the newly developed receiver modules using special connection tubing. The complete unit was installed into the PSA test bed. The appropriate fuel supply and electric connections were made. Non-solar commissioning tests verified proper functioning of all components;
5) solar-hybrid system operation: the gas turbine system was operated for 135 h, about 96 h of that time were with solar radiation. The estimated solar fraction of the generated electricity was approx. 5.2 MWh. The maximum achieved receiver outlet temperature was 960 C within the test period, and the design temperature of 1000 C seems feasible;
6) the performance for the system and the components was evaluated from the measured performance data (power level, component and system efficiencies). Problems occurred with the accurate measurement of the receiver air mass flow;
7) the cost estimates for the solarised gas turbine and the receiver system were assessed, and the modified cost assumptions were used for the system layout study;
8) software tools were developed to simulate and optimize solar-hybrid systems; the subcomponents (modified gas turbine, receiver components and solar field, auxiliary units) were modelled and the tools were verified using the performance measurements from the test system;
9) optimised system configurations in three power levels from 1 to 17 MWe were obtained. Depending on the configuration, the avoided CO2 emissions can reach up to 0.15 ton/MWh (CC configuration, 16 MWe, 1000 C max. receiver temperature). The average levelized electricity cost can be as low as 0.06 €/kWh, (CC configuration, 16 MWe, 800 C max. receiver temperature, solar share: 16%, 24 operation hours/day). For this case, the solar incremental LEC, i.e. the incremental cost for the solar contribution related to the solar power fraction, goes down to about 0.118 €/kWh. For operation during sun hours and increased receiver temperature, the solar share increases significantly. For the 16 MW CC system with 1000 C maximum receiver temperature, the solar fraction reaches about 53%. Due to the reduced operation hours the LEC goes up to about 0.09€/kWh. Specific plant investment cost were 1440 €/kWe and 1860 €/kWe for 800 C and 1000 C, respectively;
10) the solar market potential was assessed for the Mediterranean region. It was concluded that a potential for solar power plants clearly exists. Still missing is the long term experience with the receiver modules and the modified gas turbine components. The test time collected so far does not enable long term predictions of eventual degradation nor the definition of maintenance schedules.
Funding SchemeCSC - Cost-sharing contracts