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CCAT MEOW

5 bytes added, 13:31, 8 November 2012
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Image:Not So Hideous MEOWCCAT_MEOW_hardware.jpg|Fig 2: The MEOW V2 after a fresh coat of paint.Image:CCAT_MEOW_hardware.jpg|Fig 2a: The previous hardware panel (2005).Image:MEOW New Hardware Construction.jpg|Fig 2b2a: The CCAT Crew mounting the new components.Image:MEOW New Panel.jpg|Fig 2c2b: New batteries, inverter, and charge controller successfully mounted (2012).
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The PV rack turned out to be one of the most difficult components to rebuild. Although the bandits did not take the PV rack, in their mad dash efforts to remove and steal our valuable PV panels, they did manage to leave the rack system horribly mangled and more-or-less useless to us. Due to a lack of mechanical and structural expertise, our preliminary designs for the new rack weren’t fully functional (each panel weighs roughly 40 lbs. and must be able to safely travel down the highway at speeds of 65 mph; headwinds encountered on the highway must also be considered). In the name of safety and a long lasting system, we decided to work with local professional John Davis at Solar Racks to build the new PV rack. For John’s efforts, we traded him a couple of 60 W monocrystaline PV panels that had been lying around the CCAT house and had not been put to use in some years; because we are a worthy NGO, John also gave us a good deal on materials. By working with John we were able to give several students the opportunity to work in a metal working shop and receive hands-on experience with building solar racks.
 
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Image:MEOW Rack Jerome.jpg|Fig 3: Jerome (HSU student) filing one of the beams in John's shop.
Image:MEOW Rack Dustin.jpg|Fig 3a: Dustin (HSU student) doing some precision metal cutting.
Image:MEOW Rack Jess.jpg|Fig 3b: Jess (HSU student) making sure it will all fit together.
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===Wiring the System===
Because CCAT is mainly a teaching and demonstration facility, we decided to take the reconstruction process as an opportunity to give a free PV system wiring workshop to HSU students and community members. The workshop was led by the Arcata based solar company Roger and His Band of Merry Solar Installers. Held over two separate weekends, the workshop series was very successful where over 20 participants learned the basics of PV wiring and left with the satisfaction of contributing to a fully functional solar system! [[File<gallery>Image:MEOW Panel Up.jpg|Fig 4: HSU students hoisting up the PV panelsImage:MEOW Wiring Workshop.jpg|thumb|Fig 44a: HSU students being instructed on how to wire the PV system.]]</gallery>
The four panels of the array were all wired in series (i.e. four series with one parallel string). This configuration simplified the wiring process and made the system safer by allowing less DC current to pass through the lines. Initially, we had some concern that the 150 V limit of the charge controller would be surpassed in an all series configuration. If all four panels were to be simultaneously open-circuited the system voltage would total 147 V (36.8 V x 4 panels); if one considers a safety factor of 1.25 (representing a cold morning with full sun) the system voltage could spike to 184 V and possibly fry the charge controller. However, after consulting with Roger and his professional team, they informed us that this situation is highly unlikely due to the flat (0°) tilt of the array, the local solar resource, and shading profile at the CCAT house.
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