Deliver power only when generating

[JimLudden]

I would like to control an outlet (to charge my EV) and a circuit (hot water heater) so that they are only energized when my solar panels are producing power.
I have a grid-connected Enphase Combiner 4 with ten panels in sunny New Mexico. The outlet and Combiner panel are in the garage.

I can get relays to control the outlet and circuit, but how do I get a signal to run the relays? And the water heater is 70' from the Enphase Combiner panel, so may need to use Power-line communication (PLC).

Thanks for your suggestions.

[solardreamer]

The simplest way is probably to use an AC current sensing switch on the PV output to activate contactors when the PV current is above certain threshold.

[JimLudden]

Thanks for the education?

[PNPmacnab]

I think that is over simplistic. If I understand correctly, you are wanting to create zero export. A current relay would sense that you are generating and it is being used. So, better than consuming energy when there is no sun at all. What current do you set it at? Suppose it could produce energy and you are consuming very little at the time, it won't turn on. For water heating you would want proportional control to use just extra is being produced. This can be just a timer for normally peak times or a very elaborate system. I'm a controls guy and all the problems of solar can be solved with just some junk from my garage and an hours time. Not that easy to do with off the shelf products. Without spending tons of money on diversion products like My Eddi for the water heater, I'd use a little solar panel loaded down with a resistor and a voltage relay, a makeshift sun intensity diversion. Then, I live in a place with lots of clouds and days can be anything. You probably don't need more than a timer.

Talking about hot water, this is my hot water diverter I built which diverts only excess power not used. This is off grid right from the panels. This works amazing. I can't believe China isn't cranking these out by the thousands.
GWH22828.jpg

[scrambler]

EMporia has a solution for that with their Vue monitoring and EMporia EVSE

[Ampster]

I have an Emporia Vue and EVSE and it facilitates charging my EVs from excess solar.

[JimLudden]

I'm currently simply using the schedule on my plug-in hybrid car so it only charges mid-day. Since our electric coop is 100% daytime solar, anything I generate is surplus. So driving around on my own solar power is a real bonus.
I'll probably use a simple timer for the electric water heater, too. But the idea of using a small solar panel, with electronics in my mechanical room (which is on the flat roof) to control the water heater seems feasible.

[Rade]

Yes, something that my be a bit lower-tech and more of an intermediate solution would be to use the EV's ability to program when you want to charge. I recently bought a Rivian, and I can program the charge times to use mid-day power and level of amps I want to pull from my architecture. We are entering the depths of winter here in Rhode Island. I am getting about 3 hours a day where my solar panels are generating above 8kWh. When I set the charge limit on the truck to pull no more than 12amps, according to my solar app, the EV is only pulling about 6kW of power during that time. Since I am not driving every day, it can sit on that cycle for a few days to recover the battery range. Just a thought...