I can weigh in here, having done this. The reason we do this is the utility puts in a meter that charges you for export (not everyone lives in the US).
We have built a contactor based system that centers around a Raspberry Pi and an Egauge. We read the egauge over ethernet (JSON), determine the power consumption/export, and switch loads on and off. The loads can be water heaters, air conditioners, or any large load that does not have to be on continuously. In the one case I did this successfully, we had two 30KW systems, so we would switch one off when there was too much production, using a large contactor. We had to have the contactor anyway as there was a big generator that powered the facility in the event of a power outage. If the inverters had the ability to be ramped, I would have used that. Our next stage was to be Modbus control of the inverters, but we then moved to a Solar-Log based system, and here is the press release about that. The Solar-Log controls the inverters by Modbus and monitors the exported power, so you can achieve a near zero export, and I believe also can control dump loads if you can find anything useful to do with the excess power. http://www.prnewswire.com/news-releases/solar-log-power-management-delivers-zero-grid-export-300096381.html It's easy to do with a Raspberry Pi, the hard part is to find a dump load large enough and flexible enough. On Wed, Sep 7, 2016 at 8:48 PM, jay <jay.pe...@gmail.com> wrote: > Hi Kris, > > yes I think you need to help us with greater information about what the > reasons are, and the specific requirements. > > 1. instantaneous or monthly? > 2. does it have to be listed and approved? > 3. is this utility requirement or customers fancy? > 4. anything else? > > thanks > jay > peltz power > > On Sep 7, 2016, at 11:31 AM, Kristopher Schmid <sol...@legacysolar.com> > wrote: > > REWs, > > I have a client that asked me if i can install a battery free grid tied > system and have a dump load activate when it is overproducing. I am at a > loss, here. Anyone have ideas? A CT on the line side that would activate > a relay while current is flowing to the utility? > > Thanks, > Kris > > -- > Shine On! > > Kris Schmid > Legacy Solar, LLC > 864 Clam Falls Trail > Frederic, WI 54837 > www.legacysolar.com > 715-653-4295 > NABCEP Certified PV Installer > Licensed Wisconsin Master Electrician > BSEE > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches. > org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches. > org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > > -- Chris Mason NABCEP Certified Solar PV Installer™ Solar Design Engineer Generac Generators Industrial technician www.cometsolar.com <http://www.cometenergysystems.com> 264.235.5670 869.662.5670 Skype: netconcepts
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