The House of Representatives: “Grand Depository of the Democratic Principle”?

The solar simulator is the key facility for indoor research of solar PV cells, solar heat collectors, space craft and CSP systems. This paper classifies the four types of solar simulators based on their characteristics and their design objects: space solar simulator, standard PV cell testing solar simulator, collector testing solar simulator and high-flux solar simulator. The review of solar simulator developments is mainly based on the developments of light sources and optical concentrators. The light source is the most important component for a solar simulator design; carbon arc lamp, metal halide arc lamp, quartz tungsten halogen lamp, xenon arc lamp, mercury xenon lamp, argon arc lamp and light-emitting diode lamp (LED) are used to be chosen as the light sources to meet the various requirements for the design objects. The optical concentrator is another key component; ellipsoidal reflector, compound parabolic concentrator (CPC), light cone, hyperboloid concentrator, parabolic dish concentrator and Fresnel lens are also reviewed in this paper. Finally, the near future developments of these four type solar simulators are discussed based on the requirements of research and the available technology of light sources and optical concentrators.QC 20141017</p

Techno-economic performance evaluation of solar tower plants with integrated multilayered PCM thermocline thermal energy storage: a comparative study to conventional two-tank storage systems

Copyright 2016 AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.Solar Tower Power Plants with thermal energy storage are a promising technology for dispatchable renewable energy in the near future. Storage integration makes possible to shift the electricity production to more profitable peak hours. Usually two tanks are used to store cold and hot fluids, but this means both higher investment costs and difficulties during the operation of the variable volume tanks. Instead, another solution can be a single tank thermocline storage in a multi-layered configuration. In such tank both latent and sensible fillers are employed to decrease the related cost up to 30% and maintain high efficiencies. This paper analyses a multi-layered solid PCM storage tank concept for solar tower applications, and describes a comprehensive methodology to determine under which market structures such devices can outperform the more conventional two tank storage systems. A detail model of the tank has been developed and introduced in an existing techno-economic tool developed by the authors (DYESOPT). The results show that under current cost estimates and technical limitations the multi-layered solid PCM storage concept is a better solution when peaking operating strategies are desired, as it is the case for the two-tier South African tariff scheme.Peer ReviewedPostprint (published version

Exergy analysis and thermo-economic optimization of a district heating network with solar- photovoltaic and heat pumps

International audienceElectrification of district heating networks, especially using heat pumps, is widely recommended in literature. Installing heat pumps affects both electricity and heating networks. Due to lack of suitable modelling tools, size optimization of heat pumps in the heating network with the full consideration of the electric distribution network is not well addressed in literature. This paper presents an optimization of a district heating network consisting of solar photovoltaic and heat pumps with the consideration of the detail parameters of heating and electric distribution networks. An extended energy hub approach is used to model the energy system. Exergy and energy analyses are applied to identify and isolate lossy branches in a meshed heating network. Both methods resulted into the same reduced topology. Particle swarm optimization is then applied on the reduced topology in order to find out the most economical temperature profiles and size of distributed heat pumps. The thermo-economic results are found to be highly influenced by the heat demand distribution, the power loss in both electric and heat distribution network, the cost of generation, the temperature limits and the coupling effect of the heat pumps

Techno-Economic Analysis of a Solar Hybrid Combined Cycle Power Plant Integrated with a Packed Bed Storage at Gas Turbine Exhaust

[EN]The present work performs a techno-economic analysis of an innovative solar-hybrid combined cycle composed of a topping gas turbine coupled to a bottoming packed bed thermal energy storage at the gas turbine exhaust, which runs in parallel to a bottoming steam cycle. Plant performances have been evaluated in terms of the capacity factor, the specific CO2 emissions, the capital expenditure, and the Levelised Cost of Electricity. The influence of the combustion chamber outlet temperature, solar multiple and energy storage capacity has been assessed by means of a sensitivity analysis. The present study also compares the previously listed performance against that of conventional molten salt tower Concentrating Solar Power plants and traditional combined cycle gas turbine power plants with equivalent installed capacities and load factors. The results show that it is worth hybridizing the system, particularly at high combustion chamber outlet temperature, large storage size and solar multiple. Furthermore, plant configurations leading to a Levelised Cost of Electricity lower than 110 $/MWh can be achieved for a capacity factor of about 60%. Under these working conditions, the proposed configuration would be only 1.66 times more costly than an equivalent size CCGT. At the same time, it would yield less than half of the emissions of the latter. Simultaneously, the proposed layout is considerably cheaper than an equivalent molten salt Concentrating Solar Power plant

Numerical Investigation of Aerodynamic Blade Excitation Mechanisms in Transonic Turbine Stages

With the present drive in turbomachine engine developmenttowards thinner and lighter bladings, closer spaced blade rowsand higher aerodynamic loads per blade row and blade, advanceddesign criteria and accurate prediction methods for vibrationalproblems such as forced response become increasingly importantin order to be able to address and avoid fatigue failures ofthe machine early in the design process. The present worksupports both the search for applicable design criteria and thedevelopment of advanced prediction methods for forced responsein transonic turbine stages. It is aimed at a betterunderstanding of the unsteady aerodynamic mechanisms thatgovern forced response in transonic turbine stages and furtherdevelopment of numerical methods for rotor stator interactionpredictions. The investigation of the unsteady aerodynamic excitationmechanisms is based on numerical predictions of thethree-dimensional unsteady flow field in representative testturbine stages. It is conducted in three successive steps. Thefirst step is a documentation of the pressure perturbations onthe blade surface and the distortion sources in the bladepassage. This is performed in a phenomenological manner so thatthe observed pressure perturbations are related to thedistortion phenomena that are present in the blade passage. Thesecond step is the definition of applicable measures toquantify the pressure perturbation strength on the bladesurface. In the third step, the pressure perturbations areintegrated along the blade arc to obtain the dynamic bladeforce. The study comprises an investigation of operationvariations and addresses radial forcing variations. With thehelp of this bottom-up approach the basic forcing mechanisms oftransonic turbine stages are established and potential routesto control the aerodynamic forcing are presented. For the computation of rotor stator interaction aerodynamicsfor stages with arbitrary pitch ratios a new numerical methodhas been developed, validated and demonstrated on a transonicturbine test stage. The method, which solves the unsteadythree-dimensional Euler equations, is formulated in thefour-dimensional time-space domain and the derivation of themethod is general such that both phase lagged boundaryconditions and moving grids are considered. Time-inclination isutilised to account for unequal pitchwise periodicity bydistributing time co-ordinates at grid nodes such that thephase lagged boundary conditions can be employed. The method isdemonstrated in a comparative study on a transonic turbinestage with a nominal non integer blade count ratio and anadjusted blade count ratio with a scaled rotor geometry. Thepredictions show significant differences in the blade pressureperturbation signal of the second vane passing frequency, whichwould motivate the application of the new method for rotorstator predictions with non-integer blade count ratios.NR 2014080

Simulate a ‘Sun’ for Solar Research : A Literature Review of Solar Simulator Technology

The solar simulator is the key facility for indoor research of solar PV cells, solar heat collectors, space craft and CSP systems. This paper classifies the four types of solar simulators based on their characteristics and their design objects: space solar simulator, standard PV cell testing solar simulator, collector testing solar simulator and high-flux solar simulator. The review of solar simulator developments is mainly based on the developments of light sources and optical concentrators. The light source is the most important component for a solar simulator design; carbon arc lamp, metal halide arc lamp, quartz tungsten halogen lamp, xenon arc lamp, mercury xenon lamp, argon arc lamp and light-emitting diode lamp (LED) are used to be chosen as the light sources to meet the various requirements for the design objects. The optical concentrator is another key component; ellipsoidal reflector, compound parabolic concentrator (CPC), light cone, hyperboloid concentrator, parabolic dish concentrator and Fresnel lens are also reviewed in this paper. Finally, the near future developments of these four type solar simulators are discussed based on the requirements of research and the available technology of light sources and optical concentrators.QC 20141017</p

Supercritical CO2 Brayton Power Cycle for CSP With Packed Bed TES Integration and Cost Benchmark Evaluation

The present work introduces an indirect supercritical CO2 - air driven concentrated solar plant with a packed bed thermal energy storage. The proposed plant design enables a supercritical CO2 turbine inlet temperature of 800 degrees C, overcoming the temperature limits imposed by the use of solar molten salts as primary heat transfer fluid. Furthermore, the packed bed thermal energy storage permits the decoupling between thermal power collection from the sun and electricity generation. Besides, the thermal energy storage unit grants operational flexibility and enlarges the plant capacity factor, making it as available as a conventional coal facility. A transient thermodynamic model of the integrated concentrating solar plant, including receiver, thermal energy storage, intermediate heat exchangers and supercritical CO2 power cycle has been developed. This same model has been used to evaluate the thermodynamic performance of the proposed plant design over a complete year. A similar model has been implemented to simulate a supercritical CO2 plant driven by a more traditional solar molten salt loop. A comparison of the thermodynamic performance of the two plant designs has been performed. A complete economic model has been developed in order to evaluate the economic viability of the proposed plant. Furthermore, a multi-objective optimization have been executed in order to assess the influence of the thermal energy storage size, supercritical CO2 turbine inlet temperature and plant solar multiple on the key performance indicators. Results show that the proposed indirect supercritical CO2 air driven with a packed bed thermal energy storage concentrated solar plant leads to improved thermo-economic performance with respect to the molten salts driven design. Enhancements in the power cycle efficiency and in the overall electricity production can be achieved, with a consequent reduction in the levelized cost of electricity. Particularly, for a design net electrical power production of 10MWe a minimum levelized cost of electricity has been calculated at 89.4 $/MWh for a thermal energy storage capacity of 13.9 hours at full load and a plant solar multiple of 2.47 corresponding to a capital investment of about 73.4 M$.QC 20200322</p

Thermo-mechanical solar receiver design and validation for a micro gas-turbine based solar dish system

This work presents the comprehensive development of a solar receiver for the integration into a micro gas-turbine solar dish system. Special focus is placed on the thermo-mechanical design to ensure the structural integrity of all receiver components for a wide range of operating conditions. For the development, a 3-dimensional coupled multi-physics model is established and is validated using experimental data. Contrary to previous studies, the temperature of the irradiated front surface of the absorber is included in the comprehensive validation process which results in a high level of confidence in the receiver design. Finally, a full-scale solar receiver for the integration into the OMSoP solar dish system is designed and its performance determined for a wide operating range to define its safe operating envelope using the validated model. It is shown that the receiver is capable of operating at 803_C with an efficiency of 82.1% and a pressure drop of 0.3% at the nominal operating point, while at the same time functioning effectively   for a wide range of off-design conditions without compromising its structural integrity. At the nominal operating point, the maximum comparison stress of the porous absorber is 5.6 MPa compared to a permissible limit of 7.4 MPa.QC 20200427</p