[RE-wrenches] Grid tie with dump load?

[Chris Mason]

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.peltz at 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 <solman at 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
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-- 
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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