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In the framework of the European Optimised Microturbine Solar Power system (OMSoP) project, a novel energy system for solar electricity production was developed, based on the integration of the solar dish technology with Micro Gas Turbines (MGT). A pilot plant with a capacity of 5-7 kW(e) was realized and installed at the ENEA Casaccia site (Rome) and went under testing to validate the feasibility of the technology and improve the current design. The present work deals with the development of a quasi-state system model, built in the Engineering Equation Solver environment, composed of different modules that correspond to the main system components. The system model was used to define the optimal system parameters, to help the elaboration on an operational strategy to maximize the overall plant efficiency, and to guide the improvement of the single components in view of their optimised design. From the analysis it emerged that the system in design conditions is able to generate, in nominal conditions, 4.5 kW(e) instead of the expected 5 kW(e) due to the limitation of the stator current to 13 A, while maximum levels of 5.6 kW could be achieved by "overcharging" the high-speed generator up to 15 A and operating the MGT at the very high speed of 150 krpm. From the transient simulation of the demo system on an annual basis, the maximum average output power is 3.58 kW(e). Regarding the cycle efficiency, the annual averaged value is about 17%, whereas the target value is 21%. The improvement of the generator only does not seem to significantly increase the power output on the annual basis (3.75 kW(e) vs. 3.58 kW(e)). Differently, the improvement of the solar dish, with the upgrade of the other system components, would significantly increase the system power output to around ~10 kW(e)., QC 20220315

The solar receiver performance has a direct impact on the CSP power plant performance and, thereby, its levelized cost of electricity. Improved receiver designs supported by new advanced numerical tools and experimental validation campaigns directly help to make CSP technology more competitive. This paper presents an experimental and numerical investigation of the influence of the cavity receiver radiative properties and the thermal power input on the Dish-Stirling performance. Three cavity coatings are experimentally investigated: the original cavity material (Fiberfrax 140), Pyromark 2500 and Pyro-paint 634-ZO. Moreover, simulations validated with the experimental measurements are utilized to define a higher performance cavity receiver for the Eurodish system. The results indicate that the absorptivity of the cavity should be as low as possible to increase the receiver efficiency whereas the optimum emissivity depends on the operating temperatures. If the cavity temperature is lower than the absorber temperature, low emissivities are recommended and vice-versa. All material/coatings analyzed for the cavity provide similar receiver efficiencies, being Fiberfrax 140 slightly more efficient. Finally, a total receiver efficiency of 91.5% is reached by the proposed Eurodish cavity receiver when operating under the most favorable external conditions., QC 20190326

This work presents the experimental evaluation of a novel pressurized high-temperature solar air receiver for the integration into a micro gas-turbine solar dish system reaching an air outlet temperature of 800°C. The experiments are conducted in the controlled environment of the KTH high-flux solar simulator with well-defined radiative boundary conditions. Special focus is placed on providing detailed information to enable the validation of numerical models. The solar receiver performance is evaluated for a range of operating points and monitored using multiple point measurements. The porous absorber front surface temperature is measured continuously as it is one of the most critical components for the receiver performance and model validation. Additionally, pyrometer line measurements of the absorber and glass window are taken for each operating point. The experiments highlight the feasibility of volumetric solar receivers for micro gas-turbine based solar dish systems and no major hurdles were found. A receiver efficiency of 84.8% was reached for an air outlet temperature of 749°C. When using a lower mass flow, an air outlet temperature of 800°C is achieved with a receiver efficiency of 69.3%. At the same time, all material temperatures remain below permissible limits and no deterioration of the porous absorber is found., QC 20180420

This paper presents the performance improvements implemented in the KTH high-flux solar simulator to deliver a total power on target closer to the working conditions of real CSP systems. Therefore, additional rectifiers were installed in the power conversion unit of the high-power lamps as well as the back reflector was coated providing more favorable spectral reflectance properties. The results of a single lamp/lens-combination show that the power on target in an aperture of 280mm in diameter was increased from 831W to 1446W while the peak flux was increased from 675kW/m² to 905kW/m²., QC 20170807

This paper presents the characterization of the first Fresnel lens-based High-Flux Solar Simulator (HFSS) showing the evaluation of the total thermal radiative power dependent on the aperture radius at the focal plane. This result can be directly applied to calculate the thermal power input into any solar receiver tested in the KTH HFSS. Three measurement setups were implemented and their results combined to assess and verify the characterization of the solar simulator: a thermopile sensor measuring radiative flux, a CMOS camera coupled with a Lambertian target to obtain flux maps, and a calorimeter to measure the total thermal power within an area of 300×300 mm. Finally, a Monte Carlo analysis was performed to calculate the total uncertainties associated to each setup and to combine them to obtain the simulator characterization. The final result shows a peak flux of 6.8 ± 0.35 MW/m2 with a thermal power of 14.7 ± 0.75 kW within an aperture of 180 mm in diameter at the focal plane, and a thermal-electrical conversion efficiency of 25.8 ± 0.3%. It was found very good repeatability and a stable energy output from the lamps during the experiments., QC 20171215

A measurement system for the experimental determination of the flux distribution at the focal plane of the KTH high-flux solar simulator was designed and implemented. It is based on a water-cooled Lambertian target and a thermopile flux sensor placed close to the focal point of the solar simulator. Correction factors to account for systematic effects were determined and an uncertainty analysis was performed. The measurement system was successfully used to evaluate the flux distribution of a single lamp/lens-arrangement with a peak flux of 675kW/m²., QC 20170807

A novel solar power plant concept is presented, based on the use of a coupled network of hybrid solar-dish micro gas-turbines, driving a centralized heat recovery steam generator and steam-cycle, thereby seeking to combine the high efficiency of the solar dish collector with a combined-cycle power block. A 150 MWe solar power plant was designed based on this concept and compared with both a conventional combined-cycle power plant and a hybrid solar-tower combined-cycle. The solar dish combined-cycle power plant could reach higher levels of solar integration than other concepts but was shown to be more expensive with current technology; solar electricity costs are double those of the hybrid solar-tower combined cycle., QC 20150622

A novel solar power plant concept is presented, based on the use of a coupled network of hybrid solar-dish micro gas-turbines, driving a centralized heat recovery steam generator and steam-cycle, thereby seeking to combine the high collector efficiency of the solar dish with the high conversion efficiency of a combined-cycle power block. To explore the potential of the concept, its performance has been compared against a more conventional solar dish farm based on recuperated micro gas-turbines. Multi-objective optimization has been used to identify Pareto-optimal designs and examine the trade-offs between minimizing capital costs and maximizing performance. The micro gas-turbine combined-cycle layout has been shown to be promising for utility-scale applications, reducing electricity costs by 5–10%, depending on the degree of solar integration; this novel power plant layout also reduces emissions through increased conversion efficiency of the power block. However, at smaller plant sizes (outputs below 18 MWe), more traditional recuperated solar dish farms remain the most viable option., QC 20160311

An integrated design concept of a 25 KWel hybrid gas turbine-receiver unit is introduced in this paper. In this design, hot section; receiver, combustor and turbine, is integrated and located in the center of the unit in order to achieve a compact structure with low heat loss and cooling requirement. A ray tracing model is developed for analyzing the focal plane of the potential parabolic dish design and predicting the radiative flux boundary conditions of the receiver. An impinging cavity receiver, with a cylindrical absorber wall and a semi-spherical bottom, is chosen as the receiver for this hybrid unit. The cooling capacities of different impinging arrangements are calculated to determine the thermal boundary conditions on the cooling side. Finally, the optimal dimensions of the receiver are chosen as well as the impingement cooling design. A ‘single ring’ impinging array was found to be optimal for cooling down the wall temperature of the peak flux region to 1200 °C and provide a receiver exit temperature of 840 °C., QC 20150302

An integrated approach for the design of a custom-tailored hybrid solar MGT with an integrated solar receiver for the use in a small-scale solar dish unit is presented in order to overcome the inherent limitations of adapting a MGT in the desired power range to solar operation. The resulting MGT-dish equipped with the ‘optimal’ MGT shows a nominal conversion efficiency of 29.6%. Then, a thermoeconomic analysis of the entire system is performed to evaluate and compare the economic and environmental performance of the MGT-dish with a Dish-Stirling system. From an economical point of view the MGT-dish outperforms the dish-Stirling with LCoEs as low as 15.3€cts/kWhel compared to 22.4€cts/kWhel., QC 20150113

Hybrid solar micro gas-turbines are a promising technology for supplying controllable low-carbon electricity in off-grid regions. A thermoeconomic model of three different hybrid micro gas-turbine power plant layouts has been developed, allowing their environmental and economic performance to be analyzed. In terms of receiver design, it was shown that the pressure drop is a key criterion. However, for recuperated layouts the combined pressure drop of the recuperator and receiver is more important. The internally-fired recuperated micro gas-turbine was shown to be the most promising solution of the three configurations evaluated, in terms of both electricity costs and carbon emissions. Compared to competing diesel generators, the electricity costs from hybrid solar units are between 10% and 43% lower, while specific CO2 emissions are reduced by 20 – 35%., QC 20140107

A systematic design procedure for a high flux solar simulator is presented in this paper. The 84 kWe solar simulator is based on an array of 12 commercially available xenon-arc lamps (each 7 kWe) coupled with silicone-on-glass Fresnel lenses as the optical concentrator. A ray-tracing model of the xenon lamp has been developed based on the real emitter shape and the Fresnel lens optics; simulations performed using a non-sequential Monte Carlo technique have been validated against experimental test data. The results show that 19.7 kW of radiative power is delivered on a 20 cm diameter target with and a peak flux of 6.73 MW/m2 and an electricity to radiative power efficiency of 23.4%. This research facility will be used as an experimental platform for high flux solar receiver and thermochemical reactor research, as well as for advanced high-temperature material testing., QC 20140916

The solar receiver is one of the key components of hybrid solar micro gas turbine systems which would seem to present a number of advantages when compared with Stirling engine systems. A solar receiver meeting the specific requirements for integration into the power conversion system of the solar laboratory of the Royal Institute of Technology - which will emulate a solar dish system and is currently under construction - was designed. The simulations that have been performed utilize a heat transfer and pressure drop model coupled with a multi-objective optimizer as well as a coupled-CFD/FEM tool, allowing determination of the ideal receiver design for the expected conditions. The analysis has shown that the use of volumetric solar receivers to provide heat input to micro gas turbine based solar dish systems appears to be a promising solution; with pressurized receiver configurations as the preferred choice due to significant lower pressure drops as compared to atmospheric configurations., QC 20121210