Hi Kelly - Sounds like a fun project. We've got a few 10+ kW grid tied Sunny Island projects and although they are not with Enphase inverters I thought I'd pass on how we've been wiring them up with good results.
We tie the solar inverters into the critical loads panel and then put a transfer switch (either auto or manual depending on the client's choice) between the main and critical loads panel. The Sunny Island(s) output circuit (AC1) is also tied into the critical loads panel and the AC2 connection is tied into the main. During normal on-grid operation the PV is tied directly to the main through the critical loads panel and transfer switch so there are no losses through the Sunny Island. The Sunny Island at that point is simply keeping the batteries charged though the AC2 connection and monitoring the grid. When the grid goes down the transfer switch disconnects the critical loads panel from the main and the Sunny Island kicks in. The PV inverters shut off immediately during the switch but then kick into waiting mode once receiving the signal from the Sunny Island. The PV stays on during the grid outage until the batteries are fully charged then the voltage increases until the PV turns off, goes back into waiting mode and the whole process repeats - this is assuming that we're getting more PV than load. I've tested both scenarios and if the load is larger than the PV then the inverters will stay on indefinitely. What was your reasoning for tying the PV into the main and using a relay to switch to the critical loads panel during a power outage? Best, August August Goers Luminalt Energy Corporation 1320 Potrero Avenue San Francisco, CA 94110 m: 415.559.1525 o: 415.641.4000 aug...@luminalt.com -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Kelly Keilwitz, Whidbey Sun & Wind Sent: Thursday, January 13, 2011 7:33 PM To: RE Wrenches listserve Subject: [RE-wrenches] AC coupled, grid-tied Sunny Island - contactor & bypass Wrenches, We are including 2 Sunny Island inverters into a previously battery- less grid tied design utilizing 20 kW of PV on Enphase micro inverters and 2 SMA Windy Boy 6000 inverters (10 kW XZERES 442 turbine). Our customer wishes to run his fuel generator as little as possible when the grid goes down. Nothing is in the power room yet, the house is under construction. Only the wind turbine is installed. With a pass-through limit of 56A, the two Sunny Islands cannot conduct the combined RE production to the grid. There is not enough critical load demand to justify two more SI's, nor is there space for them. Our plan is to connect the micro-inverters (84A, peak) directly to the main service (grid) in normal mode, switching to the critical load panel (SI AC output) when the grid goes down. The Windy Boys (56A) would remain connected to the critical load panel. I'm hoping that the frequency shifting control of the Windy Boys from the SI's will allow the PV micro inverters to connect and stay connected to the SI's while there is demand on the critical loads and the batteries are charging. When there is more PV output than load demand we expect that the SI frequency will rise to the point where the micros will go out of spec and disconnect, maybe in a nicely staggered pattern. Questions: 1. Has anyone experience with this much grid-direct RE capacity and/or micro-inverters AC coupled to Sunny Islands? I'm a little scared by a previous post from Darryl wherein he found that the RE capacity from the GD inverters should be 1/2 that of the battery-based inverters in an AC coupled system. Please let me know if you are certain that this is not going to work! 2. Any experience with specifying a contactor/relay to switch the PV output? The contactor will be controlled by one of the SI relays. Switching from the main panel (grid) to the critical load panel will be during a grid outage, so doesn't need to be load-rated, but switching back after the grid comes back up could be load-break. Our current solution is to use two 80A contactors from Schneider (#LC1D80G7) with an intertie kit. 3. Any suggestions for an inverter bypass (service disconnect) for the two SI's? We're considering either a monster 2P2T 200A switch (100 A would do), or using a gen-transfer type panel for the critical loads. Comments and informed opinions quite welcome. Thanks, -Kelly Kelly Keilwitz, P.E. Principal Whidbey Sun & Wind Renewable Energy Systems ke...@whidbeysunwind.com PH & FAX: 360.678.7131 NABCEP Certified PV Installer WA Electrical Administrator _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
