{"id":1833,"date":"2022-04-08T12:43:57","date_gmt":"2022-04-08T12:43:57","guid":{"rendered":"http:\/\/www.vicoter.it\/?p=1833"},"modified":"2022-04-08T12:59:34","modified_gmt":"2022-04-08T12:59:34","slug":"design-of-a-solar-tracker-for-wind-loads","status":"publish","type":"post","link":"https:\/\/www.vicoter.it\/index.php\/design-of-a-solar-tracker-for-wind-loads\/","title":{"rendered":"Design of a solar tracker for wind loads"},"content":{"rendered":"\n

The increasing demand of green energy brought to a request\nto improve the efficiency of solar panels and of their capability to generate\nelectricity. Among the various solutions studied and developed, the most\ndiffused one is, for sure, the solar tracker. Such device permits the\norientation of the panels towards the sun during its daily movement from east\nto west. The less the misalignment angle is, the more the effective collection\narea is and, consequently, the more the energy production is. <\/p>\n\n\n\n

Despite the various models on the market, solar tracker structural layouts are all very similar. Solar panels are connected to a long horizontal tube hinged by bearings to a certain number of vertical poles inserted into the ground. An electrical actuator, generally located in the middle of the tracker, rotates the main tube by a leverage and works as constraint, once the wanted position is reached.<\/p>\n\n\n\n

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Solar tracker layout.
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Although the geometrical and technological simplicity\ncan be misleading, solar trackers require an extensive and careful design, in\norder to be able to withstand, not only the static, but even the dynamic loads\ninduced by the wind. Due to their shape, very similar to a thin flat plate,\nsolar panels work in an air flow that generates lift and drag, according to the\nrelative angle between them and the stream velocity. Therefore, they are\nsubjected to both a forced response generated by the wind and aeroelastic\ninstabilities. The estimation of the maximum dynamic pressure encountered by\nthe structure during its life and the calculation of the induced static\nstresses become, in this way, only the first step in the development of a\nreliable device.<\/p>\n\n\n\n

The most probable dynamic effect encountered by solar\ntrackers in their life is generated by air turbulence inducing time variant\nloads, able to excite structural resonances. Due to their layout, solar\ntrackers generally have torsional modes at very low frequencies: the horizontal\ntube used to support the panels acts as the only torsional spring in the\nstructure. It is constrained on ground by the actuator and its stiffness decreases\nwhen the total span increases. A good design aims at raising the frequency of\nthe first mode to a value higher than the maximum harmonic contribution of the\nwind.  Theoretical Kaimal and von Karman\nwind power spectrum densities show that such threshold depends on the height\nfrom the ground and on the mean speed. According to the several standards such as\nthe ASCE 7, a threshold of 1 Hz can be fixed without loss of generality. <\/p>\n\n\n\n

Vicoter (www.vicoter.it<\/a>) is an Italian consulting society dealing with the structural dynamics\nmainly in the aerospace and energy sectors. Its competences integrate the\nnumerical and experimental methods to provide its clients the most suitable\nsolution in the vibration field. Due to their approach, Vicoter\u2019s engineers\nwere entrusted by RCM (www.rcm-italia.com<\/a>) to develop a validated analytical model of its new prototype of solar\ntracker, so to verify its compatibility with resonance requests and to study\nthe possibility to build wider versions. <\/p>\n\n\n\n

Three parameters must be experimentally identified to\nobtain a correlated model:<\/p>\n\n\n\n