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11670Re: [hreg] TXSES report

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  • mkewert
    Jul 17, 2013


      Thanks for the clarification. Maybe they can find something to do with the excess solar, like produce hydrogen.


      From: "Andrew McCalla" <andrew@...>
      To: hreg@yahoogroups.com
      Sent: Friday, July 12, 2013 12:25:08 PM
      Subject: RE: [hreg] TXSES report




      Seeing the third item on Mikes report, I feel the need to offer some clarification:


      I think that the description that “too much solar going back to the grid is a problem with the current design” omits some important details and might give the impression that the problem at this location is simply with the amount of PV generation.


      This (Palmer Events) facility sits on a network distribution system, the likes of which you will find in many communities, typically in downtown areas, and which exist to provide added power reliability to the “higher priority” ratepayers which it serves. This system can be contrasted to the radial distribution system, the likes of which likely feeds your house, for example.


      Without getting into the details of each, the bottom line for this topic is that radial systems can be supplied power in reverse (back-fed) by distributed renewable generation as it occurs, and network systems can’t, since this condition will most certainly open the network protection devices (leaving that portion of the network without power), and perhaps causing other damage.


      At this time, and until network protection devices get “smarter”, any solar going back onto network distribution systems is a problem. 


      Ideally, PV systems on networks are designed such that they rarely, if ever, generate more than facility demand, because that surplus is going to get curtailed.  The device that most utilities require to preclude generation in excess of electrical load, or reverse power flow, is a Minimum Import Relay (MIR).   Unfortunately, the location in question is an intermittent use facility, with a fairly large array, so the on-site generation regularly eclipses facility demand.  To compound matters, Austin Energy not only requires an MIR, but they also require that the ratio to which this MIR is calibrated (the ratio of allowable distributed renewable generation on site relative to facility load) is such that a PV system can not only never generate power in excess of facility power requirements, but that PV generation be further limited to never produce more than 25% of facility power requirements at any given time. 




      Andrew McCalla



      From: hreg@yahoogroups.com [mailto:hreg@yahoogroups.com] On Behalf Of mkewert@...
      Sent: Wednesday, July 10, 2013 10:41 PM
      To: HREG
      Subject: [hreg] TXSES report



      The Texas Solar Energy Society (TXSES) board of directors met last night for a quarterly meeting. Here is a quick report.
      Austin's Cool House tour had lower attendance this year, but still made money.
      TXSES has been helping a charity in the Colonias along the Mexico border apply for Green Mountain's Big Texas Sun Club grant to get solar panels on their building.
      Austin Energy has noticed a problem with breakers tripping in the grid when the solar panels on their convention center are producing and there is no event going on. In other words, too much solar going back to the grid is a problem with the current design.
      July 20-30 is the Solar Challenge car race for high schools from Texas Motor Speedway all the way to Los Angeles.
      TXSES will be donating $500 toward the HREG Solar Tour this fall!
      Do you have an article you would like to submit f or the Texas Solar Reflector? If so, please let me or
      lucy@... know.
      If you are not already a member of TXSES, please join today and help promote solar at the state level.

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