Deliverables Software tools for simulation and layout of solar-hybrid gas turbine systems Two existing software tools were adapted and enhanced for layout and performance calculation of solar-hybrid gas turbine systems. The software code HFLCAL for heliostat field layout calculations was adapted to be able to economically optimise a solar tower plant with a pressurized volumetric receiver cluster. Therefore modelling algorithms for secondary concentrators and pressurized receivers were implemented into the code. The feature of "multi-aiming" (i.e. the defined distribution of the heliostats focal spots in the target plane) for circular flat apertures had to be added to the code. Additionally, the option for cost optimisation of the solar part (tower, receiver, heliostats) was implemented for minimising the levellised cost of solar thermal power. The accuracy of the HFLCAL modelling approach was validated numerically by comparison with results from a ray-tracing software for heliostat fields (MIRVAL). The HFLCAL code was further validated against measurement results from the testing campaign carried out in the scope of this project. Both validations delivered satisfying results. The HFLCAL software underlies user restrictions and is not available to the public. The basic principles of the new features added in the course of this project are described in the project report. The commercial simulation environment TRNSYS with the model library STEC for concentrating solar power plants was chosen for the annual performance calculation of commercial-size solar-hybrid gas turbine plants. Therefore, performance models for the key equipment gas turbine and combined cycle, receiver and heliostat field were developed and implemented as FORTRAN subroutines into TRNSYS. The model algorithms are based on principle thermodynamic assumptions like adiabatic compression and expansion in the gas turbine, etc.. The gas turbine and receiver models were validated against measurement results obtained with the Allison250 gas turbine at the testing campaign and showed very good results. The simulation models developed in the course of this project are added to the STEC model library and are available free of charge to the public. As a result of this project task a set of simulation tools is now available for the layout, (cost-) optimisation and performance calculation of a wide range of system configurations of solar-hybrid gas turbine power plants. These tools have been used in another task of this project to assess the technical and economical feasibility of a selection of commercial-sized solar-hybrid gas turbine power plants of different power levels at different locations. These tools will be further developed and used in follow-on R&D projects and feasibility studies with the purpose of market introduction of solarised gas turbine systems. They allow the quick analysis of the performance potential of a chosen system configuration at a specific site of interest. This is an essential information for project developers of solar thermal power plants. Demonstration of solar-hybrid system operation First, system integration and system operation strategies were defined and implemented in the control units. Appropriate emergency strategies were defined to deal with possible critical situations. After integration of the gas turbine and the receiver unit into the PSA solar test facility non-solar commissioning tests verified proper operation of the complete solar-hybrid gas turbine system. The emergency measures were checked too. After these pretests the solar energy input was increased gradually, resulting in a corresponding increase of receiver outlet temperature as input to the combustor. System operation was defined by setting the desired power to be delivered to the grid. Upon start-up, this power was delivered by burning fuel only. Then the heliostats were focused until the intended solar power input was achieved (depending on sun position and heliostat number). The fuel flow was automatically reduced by the gas turbine control according to the increased solar power input. The modified control performed well under all solar and non-solar conditions, including cloud transients. The emergency measures worked well in principle, but were not fully adapted to the final operating conditions. This resulted in a critical emergency situation, requiring changes in the set-up of a blow-off pipe. The developed system setup and the operation strategy can be transferred to other solarized gas turbine systems. The overall accumulated operation time of the gas turbine (in both test phases) was 134h, with 96h of operation with solar radiation. The estimated solar fraction of the generated electricity was approx. 5.2MWh. The aimed operation conditions with a receiver air outlet temperature of 1000°C were nearly met, the maximum average receiver outlet temperature was 959°C before the damage to the gas turbine due to the inappropriate blow-off setting occurred. The overall conclusion of the system operation was that the system is well controllable under all normal operating conditions. Performance data showed good agreement with the predicted performance figures. Emergency measures have to be adapted very carefully to avoid damage to the system, but the solution to this issue is known. However, the obtained operation time is still not sufficient to really assess long term issues like maintenance and overhaul schedules for the receiver and the gas turbine components. Modification of a gas turbine for solar operation The power-converting unit (PCU) including the solarized ORMAT Solar Turbine 3 (OST3) is based on a conventional turboshaft gas turbine that was modified for operation with external solar heating. The modifications included mainly: - Integration of a new combustor suitable for operation with air inlet temperature up to 800°C - Adaptation of the control system; - Conversion of the gas turbine into a generator set by adding a gearbox and a generator; - Replacement of the pressurized air connection tubing; - Replacement of the starter motor and batteries; - Addition of an oil cooling system. The adaption of the control system included the integration of a digital control unit with new control software. Additionally new control boxes were built and the instrumentation of the gas turbine and the PCU was renewed. The control logic was implemented with all the required functions for the interaction with the solar components and the associated additional emergency measures. The combustor was replaced by one, which was capable to operate at air inlet temperatures up to 800°C, including the appropriate tubes for connection to the receiver system. Super alloy metals were employed for these components. Special attention was paid to the sealing at these high temperatures, requiring special high temperature gaskets. A new injector was installed enabling the operation under the solar operating conditions. For the fuel flow a new metering valve was added. All modifications were made and the system was operated successfully, with gas turbine operating conditions as expected. The PCU was successfully commissioned before shipment for non-solar operation with a heat exchanger simulating the solar system airside volume (about 3m{2}) and pressure drop. An additional test of the PCU response to changes in the air temperature was performed using water-cooling. During these tests measurements of the systems vibrations and noise were carried out. The PCU was installed in the solar test facility and integrated with the receiver system. All piping and cablings were reconnected, power cables were connected to the local PSA grid, and control cables were connected to the PC in the control room. For the solar operation; the two compressor outlets were connected to the low temperature air pipe (to the receiver inlet) and the high temperature air pipe (from the receiver outlet) was connected to the combustors inlet flanges using super alloy fasteners. The control system was interfaced with the receiver control system and the emergency procedures were tested. During the solar tests the OST3 demonstrating hybrid operation using solar heated air and jet fuel simultaneously. The operating conditions ranged from idle to a maximum electric power output of 230kW. The maximum solar fraction reached about 70%. The PCU performed very well, handling all standard operating conditions without problems. Solar transient like cloud passages were easily handled by the control, i.e. the decreasing solar input was compensated by an increase of fuel flow and vice versa. The overall accumulated operation time of the gas turbine was 134h, with 96h of them using solar radiation. The estimated solar fraction of the generated electricity was approx. 5.2MWh. During one test a problem occurred during an emergency shutdown, caused by grid failure. An inappropriate adjustment of the blow-off branch was detected during this situation, causing speed-up of the turbine. Consequently, the setting of the blow-off unit was adjusted to avoid this problem. Layout for solar-hybrid power plants in 3 different power levels Three industrial gas turbines were chosen as the basis for commercial-size solar-hybrid prototype power plants in the power range between 1 and 20MWe: - Heron H1: Inter-cooled recuperated two-shaft engine with reheat. ISO rating 1400 MW, thermal efficiency 42.9%; - Solar Mercury 50: recuperated single shaft gas turbine. ISO rating 4200 MW, thermal efficiency 40.3%; - PGT 10: simple gas turbine with bottom cycle. ISO rating 11100MW (gas turbine) or 16100MW (combined cycle), thermal efficiency 31.3% (gas turbine) or 44.6% (combined cycle) For the solarization of these gas turbines the three types of pressurised solar receivers with secondary concentrators as they are used in the Solgate test system are considered: - A low temperature tubular receiver up to 600°C air temperature; - A medium temperature volumetric air receiver with metallic absorber up to 800°C; - A high temperature volumetric air receiver with ceramic absorber up to 1000°C. For the concentrating system a Spanish glass-metal heliostat with about 120m² reflective area and a beam quality of 2.4mrad is chosen. Apart from the receiver design outlet temperature, the maximum achievable solar contribution to the total gas turbine heat input is strongly dependent on the individual temperature range between the compressor outlet / recuperator outlet and the turbine inlet. The design solar contribution for the solarised prototype plants ranges from 38% for the Mercury 50 with 800°C receiver temperature to 88% for the PGT10 with 1000°C receiver temperature. To detect the geographical influence on solar-hybrid power systems two different sites were chosen for analysis of the prototype power plants: - Daggett, CA (USA) as an excellent solar potential site with annual DNI of 2790kWh/m². - Seville (Spain) as a very good European site with annual DNI of 2015kWh/m² and favourable market perspectives. Cost functions for the major solar equipment were used for least-cost optimisation of the solar part (heliostat field arrangement, tower height, receiver size): - Field sizes are in the range from 2000 - 2700 m²/MWth,sol; - Receiver aperture sizes vary from 2.9 3.5 m²/MWth,sol; - Tower heights are from 40m to 100m. The annual performance simulations based on the optimised system layout give a detailed assessment about the technical, economical and environmental potential of the prototype plants. Depending on system size and location the solar to net electric efficiency lies in the range from 14% to 19%. Levelised electricity costs for the location Daggett with 24h-operation are: - 12 Euro cent/kWh for Heron H1 1.4MW system with 18% solar share (800°C solar); - 7.4 Euro cent/kWh for Mercury50 4.2MW system with 9% solar share (800°C solar); - 5.7 Euro cent/kWh for PGT10 16MW CC system with 16% solar share (800°C solar); - 6.2 Euro cent/kWh for PGT10 16MW CC system with 28% solar share (1000°C solar); CO(2)-avoidance varies between 40 and 130kg/MWhe, leading to CO(2)-avoidance costs in the range from 1Euro/kg down to 16.7Eurocent/kg. These results present the detailed estimation of the technical, economical and environmental potential of the technology of solar-hybrid gas turbine systems under realistic site conditions and reliable up to date cost assumptions. The results are being published in a free accessible project report and various articles. This study results allow ranking of the new technology of solar-hybrid gas turbine systems among other opportunities of renewable power production. Further on, the outcomes of the analysis allow identifying key targets of further cost reduction or performance improvement. Pressurized receiver technology for solar air heating A new high temperature receiver (HT) module was developed for operation as third stage, extending the upper temperature limit of the pressurized receiver modules to 1000°C. The receiver module consists of a receiver unit and a secondary concentrator. The secondary concentrator is installed in front of the receiver unit to further concentrate the solar radiation. The entrance aperture of the secondary concentrator is hexagonal, thus allowing a honeycomb-like arrangement of multiple receiver modules to scale-up power. The receiver unit consists of a pressure vessel with an aperture, which is closed by a domed quartz window. Behind the window a ceramic absorber using multiple segments of a high porosity reticulated SiC foam, is installed. The absorber segments are integrated with a newly developed mounting structure based on thin fiber-reinforced ceramic sheets. Special attention was paid to the different thermal expansion behaviour of the components. A special absorber back layer is used to artificially increase the flow resistance through the absorber to achieve a more homogeneous mass flow distribution. The highly concentrated radiation is absorbed in the highly porous foam structure and heats it up. The air is passing through the hot absorber and is effectively heated by convection. A new window cooling technology was developed to ensure operation of the quartz window below its temperature limit. Air jets are directed towards the window and are operated in a special way to ensure good and homogeneous cooling of the window surface. The HT- module was designed for operation as third stage of a serial connection of three receiver units, resulting in an air inlet temperature of about 750°C. In the solar tests during the project period, a maximum average air outlet temperature of 960°C was achieved, with good performance of the HT receiver module. A failure of the gas turbine stopped further testing, therefore the design temperature of 1000°C could not be achieved so far. Based on the obtained operation experience it is expected that in future tests the design temperature can be achieved. A low temperature (LT) receiver module was developed for operation as first stage in the serial connection, with the goal of a significant cost reduction for the first stage. As the desired outlet temperature was not higher than 500°C, a design using multiple helically bent tubes was made. A number of 16 metallic tubes connected in parallel was bent in a way to form a cavity. The module was designed, manufactured and integrated into the system. For the advantage of low manufacturing cost a trade-off had to be made with pressure loss. For this receiver, the pressure loss is about 100mbar. The cost predictions were refined based on the manufacturing data and the expected cost reduction of about 50% was verified. The module was installed in the solar test bed, with a secondary concentrator in front of the unit. During the solar tests the receiver performed quite well, and the performance data is in good agreement with predictions. Still missing is the long term experience with the receiver modules. The test time collected so far does not enable long term predictions of eventual degradation nor the definition of maintenance schedules. Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available
