Alain Ferriere

Development Steps for Parabolic Trough Solar Power Technologies With Maximum Impact on Cost Reduction

Besides continuous implementation of concentrating solar power plants (CSP) in Europe, which stipulate cost reduction by mass production effects, further R&D activities are necessary to achieve the cost competitiveness to fossil power generation. The European Concentrated Solar Thermal Roadmap (ECOSTAR) study that was conducted by European research institutes in the field of CSP intends to stipulate the direction for R&D activities in the context of cost reduction. This paper gives an overview about the methodology and the results for one of the seven different CSP system concepts that are currently under promotion worldwide and considered within ECOSTAR. The technology presented here is the parabolic trough with direct steam generation (DSG), which may be considered as an evolution of the existing parabolic systems with thermal oil as heat transfer fluid. The methodology is explained using this exemplary system, and the technical improvements are evaluated according to their cost-reduction potential using a common approach, based on an annual performance model. Research priorities are given based on the results. The simultaneous implementation of three measures is required in order to achieve the cost-reduction target: Technical improvement by R&D, upscaling of the unit size, and mass production of the equipment.

SOLAR PROCESSING OF MATERIALS: OPPORTUNITIES AND NEW FRONTIERS

Abstract Synthesis of materials with unique properties or with a high chemical selectivity is presented as a competitive application domain for concentrated solar energy with respect to laser or plasma systems. To illustrate the general arguments recent experimental data are presented in three domains (1) surface hardening of steel, super hardness of 1000 Hv is obtained without tensile peak at the interface between treated and non treated material (2) oxides nanopowder processing, pure oxide powders and composites are obtained by vapo-condensation with typical size in the range 10–100 nm (3) fullerenes and nanotubes synthesis, a selectivity of 20% for fullerenes is achieved (ratio of fullerenes to soot mass), more recently single wall nanotubes are processed at pressure 450hPa. These results obtained with 2 kW solar furnaces are commented in the view of solar process scalingup.

Detailed Performance Analysis of a 10kW Dish∕Stirling System

The CNRS-Promes dish/Stirling system was erected in Jun. 2004 as the last of three country reference units built in the “Envirodish” project. It represents the latest development step of the EuroDish system with many improved components. With a measured peak of 11 kW electrical output power, it is also the best performing system so far. The measurement campaign to determine the optical and thermodynamic efficiency of the system is presented. The optical quality of the concentrator and the energy input to the power conversion unit was measured with a classical flux-mapping system using a Lambertian target and a charge coupled device camera system. An efficiency of the concentrator including the intercept losses of 74.4% could be defined for this particular system. For the thermodynamic analysis all the data necessary for a complete energy balance around the Stirling engine were measured or approximated by calculations. For the given ambient conditions during the tests, a Stirling engine efficiency of 39.4% could be measured. The overall efficiency for the conversion of solar to electric energy was 22.5%.

Solar Field Efficiency and Electricity Generation Estimations for a Hybrid Solar Gas Turbine Project in France

The production of electricity with gas turbine and solar energy project aims to install at the Themis site (Targasonne, France) a prototype of hybrid solar/fossil gas-turbine system for electricity generation. The system features a 3800 kW th pressurized air solar receiver combined with a fossil backup feeding a recuperated 1400 kW e Turbomeca gas turbine with an external combustion chamber.

An instrument for measuring concentrated solar-radiation: a photo-sensor interfaced with an integrating sphere

The expression of the intensity of light reflected by the internal surface of an integrating sphere with an input power provided by a concentrated solar beam is established using a model of multiple reflection of photons. This intensity appears to be proportional to the input power, and thus makes viable the utilization of a photo-sensor interfaced with an integrating sphere to build a solar fluxmeter. The major parameters of the design of the fluxmeter are then identified, and an optimized design is proposed. An example of a practical instrument is given, and its performance is measured and discussed. The sensitivity of the fluxmeter to the spectral distribution of the solar radiation requires a careful calibration of the gauge in order to achieve a measurement error less than ±5% of reading.

Solar Processing for the Glazing of ZrO2-Y2O3 Thermal Barrier Coatings: Reduction of Crack Initiation

The glazing of thermal barrier coatings using concentrated solar energy has already been demonstrated, but crack initiation appeared as a major drawback of this processing. In this paper, the thermo-mechanical effects resulting from the fast heating at high temperature were modeled. Crack initiation was found to result from high temperature gradients in the ceramic coating. Experiments performed on plasma-sprayed ZrO 2 -Y 2 O 3 layer showed that a significant reduction of crack initiation was achieved when the specimen was preheated at temperatures in the range 500°C-800°C. The potential of the solar processing was improved and this technique becomes competitive with conventional laser processes.

Optimal Sensor Strategy for Parametric Identification of a Thermal System

Abstract Recent investigations on the solar hardening and on the induced stresses in solar-irradiated metallic materials have shown encouraging results and provide an alternative to more conventional processes (laser or plasma sources). In this paper, heat transfers in a specimen submitted to short flashes of concentrated solar energy are investigated. Estimation of model parameters is a crucial step for the control of solar systems regarding some industrial requirements such as the control of the products and the reproducibility of the results. Thus the unknown influent parameters have to be carefully estimated. An optimal sensor strategy is also proposed based on the sensitivity analysis in order to minimize the measurement noise.

Numerical simulation of the cooling of a hot disk rapidly subjected to combined convective and radiant heat losses

The development of a transient method for measuring the spectral directional emissivity of solid materials at high temperature is currently being completed by the analysis of the influence of various sources of error. A hot disk is subjected to mixed convective and radiant heat losses on one face after the rapid withdrawal of a shutter. The cooling is investigated during a short period of observation through numerical simulations of the transient temperature. The thermal problem is simulated using 3D and axisymmetric 2D codes. The progressive withdrawal of the shutter results in a delay for the transient temperature in comparison with the instantaneous withdrawal. For an insulating material, the influence of the side wall boundary conditions remains negligible at the center of the front face. The strong influence of the convective heat transfer is demonstrated.

Development Steps for Concentrating Solar Power Technologies With Maximum Impact on Cost Reduction: Results of the European ECOSTAR Study

Beside continuous implementation of concentrating solar power plants (CSP) in Europe, which stipulate cost reduction by mass production effects, further R&D activities are necessary to achieve the cost competitiveness to fossil power generation. Therefore the cost range of 15–20 cents€/kWh for the currently planned CSP systems in Europe has to be decreased by a factor of 2–4. The European Concentrated Solar Thermal Roadmap (ECOSTAR) study that is conducted by leading CSP research institutes in Europe intends to stipulate the direction for R&D activities in the context of cost reduction. It uses a common methodology approach, based on an annual performance model to identify the most essential technical innovations that will reduce the cost of seven different CSP system concepts, which are currently under promotion world wide. The potential of innovative concepts for solar light weight concentrators, low-cost thermal energy storage concepts, solar receivers/absorbers and power cycles are in the main focus of interest. The results of the study include a description of the value of CSP power, the sensitivity of the electricity cost information, a list of innovations that have been investigated and recommendations for the focus of further R&D work.Copyright

Solar absorptivity of metallic layers subject to a short-flash of concentrated solar energy. Theoretical-experimental calculation

The paper develops a procedure for the theoretical-experimental calculation of the solar absorption coefficient of metallic layers under the action of a short flash of concentrated solar energy. The knowledge of this coefficient is relevant when the solar thermal processing is used to make a quench in a thin superficial layer of metallic slabs. The experimental data of temperature of the sample are obtained using the SURFSOL experimental device at SOLFACE (High Flux Solar Facilities for Europe), France. In particular, the sensors of temperature are located on its back side as the solar radiation impinges the front irradiated one. The theoretical data are obtained solving the nonlinear inverse transient heat conduction problem using the IHCP1D software based on the well-known function specification method (FSM). It gives transient surface heat fluxes as well as temperatures on the irradiated side of the sample using internal temperature histories. Then a transient radial fin model accounts for the heat diffusion in the radial direction and re-calculates the heat fluxes. Once temperatures and heat flows are known, an estimate of the solar absorption coefficient of the metallic layer (during the flash solar heating process) may be obtained as a function of temperature (AISI 316L steel).