Research On Deployable Solar Concentrator System

Deployable structure has been regarded as an effective solution to build a large storage ratio andlarge aperture space solar concentrator system, due to its’ advantages of light weight, small storagevolume, and low emission cost. Therefore, it is very important to study the deployable concentratorsystem in the development of space solar high temperature utilization. In this paper, some keytechnologies of deployable solar concentrator system were investigated numerically, and theirperformances were analyzed, and then design scheme of deployable solar concentrator system wasproposed. The Optimization of deployable solar concentrator system was performed by exploring thestrategies for improving performance.Based on the cantilever beam assumption, static and modal analysis on the inflatable supportstructure was carried out by using the ANSYS software. The results show that low frequencies (first3order frequencies) are hardly affected by internal pressure; pressure has greater impact on highfrequencies (last7order frequencies); internal pressure impacts on natural frequency of structure butalso changed the vibration mode of the structure.Nonlinear dynamic mechanical control equations of inflatable structure were solved by using thefinite element method. A large size inflatable structure model which had an aperture of20m2, the focallength of8m, was simulated. The deployment dynamic simulation of one-fold and three-foldun-inflated state supporting rod and a reflecting member were carried out. Compared the pressurevariation with time during the one-fold supporting rod unfolding process to three-fold’s, the pressurein supporting rod has nothing to do with its folding number; wrinkle will be produced on theinflatable membrane material during inflatable deployment process, which will affect theconcentrating performance of the unfolded reflection unit.Based on the Monte Carlo ray tracing method and light specular reflection law, concentratingperformance of space inflatable solar concentrator was analyzed. Deployment process andconcentrating performance were optimized by adjusting the filling gas parameters, structure thicknessand modifying inflatable concentrator structure form. The results show that the focusing efficiency ofdeployed thin film reflector structure with same wall thickness is about50%; focusing efficiency canbe effectively improved up to60%by adjusting the film thickness along the radial direction; thedeployed focusing efficiency of pre-forming reflecting surface combined with inflated or mechanicalsupporting structure can reach the ideal design value. To overcome the wrinkle problem produced during the inflation processes, the wholeconcentrator structure was assembled by a plurality of groups of small size concentrating mirrorsprefabricated by inflatable membrane, which was deployed in space. Parametric3D modeling andassembly were accomplished by Pro/E software in this thesis. Unfolding and locking mechanism weredesigned, and the compressive strength, flexural properties and vibration characteristic of stretchablesupport structure were also analyzed. The results show that deployable supporting rod structure haveexcellent compression resistance and bending resistance of support structure, when applying30Naxial and radial force in the top end of the supporting rod, the safety coefficient is very reliable;maximum structure displacement which is corresponding to fifth order vibration mode, was about0.1m. Thus resonance should try to be avoided during deployment process.The expected movement process of new concentrator from folding assembly state into spaceworking state was simulated. The unfolding trajectory curve, location curve and other relevant datawere obtained. Concentrating performance was analyzed with the presence of various errors fordeployable structure. The results show that the expected unfolding process of the assembled mirrorscan be realized, and the anticipated expansion and locking effect also can be achieved; the supportingrod original length tolerances on the accuracy of the focus effects is larger than that of the supportingrod aperture parameters tolerances; when shaft clearance error existing, x coordinate position errorand y position error of the focus are moved in a circle of3mm radius. Focus position error is irregular;with the pointing error, position error and focal plane mirror surface machining error increasing, theconcentrator focal spot radius increases, and varied from circular spot into oval gradually, energy flowpeak value reduced, the total energy received by whole focal plane keep conservation. Mirror errorhas the highest affects on energy flux distribution and spot shape of focal plane, so receiving planesize and position should be set reasonably.Flow and thermal transfer characteristics of working fluid in receiver were simulated numericallyby FLUENT software. The receiver structure was optimized to balance the flow rate of working fluidin every tube. Based on the deployed concentrator’s geometric structure, the solar energy heat fluxdistribution on tubes’ wall was simulated numerically by employing Monte Carlo ray tracing methodand light specular reflection law. The results show that, helium flow rate non-uniformity is less than5%after optimization. Helium exit temperature is uniform, and the average temperature is1125K,maximum difference in temperature is50K.