Benn, I have a little experience from about a decade ago. Don't know how useful it will be though.
AEE and DC Power used to team up to supply power for a three-day outdoor music festival in Mendocino Co, CA in the mid 90's and early 2000's. Music from 5-8PM on Friday, and from 11AM-10PM on Sat and Sun. I don't know how big the crowd was - 5-6000 I would guess. We would bring a rack-mounted 12kW Exeltech MX inverter set-up (24V and not even N+1 redundant) and 5-6kW of PV (a lot of 120W modules). DC Power would bring two big tractor-trailer loads of industrial wet-cell batteries (I have no idea what the total amp-hours were, but a hell of a lot). The sound crew would show up each year with a bigger set-up, even though we warned them that the power supply was limited. Stage lighting was left on generators running biodiesel. The last year that we did it, the sound guys showed up with a sound system rated at 14kW. It drew 6kW just being on with no sound. Not even a hint of buzz or hum from the inverter power. The MX is good stuff. I nervously watched that Exeltech all weekend as the bar graphs on each power module stayed in the red over-load range for most of each band's set. When the drummers or bass players would go nuts it was all red lights. We were measuring up to 600A of current flowing through the four pairs of 4/0 cables coming from the batteries, and a good bit of voltage drop as the cables were at least 30' long. The inverter was seeing less than 24VDC most of the time. The cooling fans on the MX modules would run for 20-30 seconds, and shut off for a minute or two and then come on again. This is with temps in the upper 90's, and the inverter sitting on the ground under the stage. Even with all this torture, the Exeltech never even hiccupped, which was quite impressive. The sound engineer was hollering at us that the inverter was clipping off the high notes, but neither I, nor the audience ever noticed. All I could do was shrug and tell him that he was warned about limited power availability. The music was great. By the end of the weekend, those batteries were pretty drained, so it's hard to actually say that the show was "solar powered". Sitting around with a few beers afterwards, we all agreed that the ranch owners could install a 2kW grid-tie system on a tracker at the concert site and that system would produce all the energy needed for the show in a year's time, likely including the energy use for the lighting and by the vendors. This would have required that utility power be brought to the site, which would have been a rather expensive deal, but would have made more sense, and would have made it a more truly solar-powered event. Brian Teitelbaum AEE Solar From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of benn kilburn Sent: Wednesday, April 27, 2011 3:51 PM To: Wrenches Subject: [RE-wrenches] PV powered music festival Wrenches, I have been asked about sizing PV systems for a couple different music festivals that have been run solely off of generators in the past. The problem i'm having is determining the energy consumption of music/stage (amps, speakers, lights, etc...?) loads as well as concession. The organizers have never considered the kwh of electricity used and it has never been metered. I believe the attendance of one festival is expected to be in the range of 5000 and the other closer to 15000 over the course of a weekend. Do any of you have any experiences in this area? How were the loads determined? No doubt that generator back-up will still be needed, to what extent, will be determined. So what we're looking at would be a temporary off-grid PV system with generator back-up... Any suggestions on how to proceed with this one? benn DayStar Renewable Energy Inc. b...@daystarsolar.ca 780-906-7807 HAVE A SUNNY DAY
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