gschettl
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Can I divert excess solar power to my LEAF?

Sun Jul 19, 2015 3:24 pm

I just got my rooftop solar system installed and would prefer to use my excess solar power rather than return it to the grid. I have a Solar Edge inverter and a Blink residential charger, (3 years old). is there a way to absorb the EXCESS power by sending a signal to any brand of EVSE that would vary the rate of car charging between say 1.5 kW/h and 6.6 kW/h depending on how much excess power is being produced by my solar system? Of course we are always using some of the solar power due to household activities and this various moment by moment so it seems a variable control would be necessary to accomplish this.

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davewill
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Re: Can I divert excess solar power to my LEAF?

Sun Jul 19, 2015 6:33 pm

It is technically possible. If you were to build an OpenEVSE and modify your firmware to monitor your solar output, you could indeed change the output level to match your output. Monitoring your current usage would be harder, but there are ways to do that, too, if you're dedicated enough. You could even install the OpenEVSE hardware inside your Blink case, replacing the smarts that are there now.

However, there is no tangible benefit to doing so, assuming you have net metering. It makes no difference either economically or ecologically whether you use power from the grid then push power back out, or somehow carefully consume the solar generation on the spot. Now if you had a battery system that allowed you to be independent of the grid, that might make more sense, but this idea doesn't achieve that.
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downeykp
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Re: Can I divert excess solar power to my LEAF?

Sun Jul 19, 2015 8:00 pm

I have to agree with Dave what difference does it make? If you are net metering it really doesn't matter. You send them power during the day, they give you power during the night. My leaf here in Hawaii runs free of charge because I generate way more power than I use.
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gschettl
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Re: Can I divert excess solar power to my LEAF?

Sat Jul 25, 2015 7:21 am

The main reason I want to absorb my own solar energy is because the very last step, (after the solar system was installed and functional) was to sign a contract with the electric utility to allow trading electricity with a bi-directional meter. The unexpected catch is the contract specifies they will pay me less than half for each kWh exported to the utility versus what they charge me to import a kWh. I haven't gotten my 1st electric bill yet but other local solar customers have confirmed that's what I can expect.

Another reason is someday I'll have a battery storage system and would want to divert solar electricity to that too, before returning any to the grid.

So I'm surprised I'm not hearing of any turn-key system available yet designed to divert to batteries variably based upon the excess solar electricity being produced. My whole house egauge does a good job of showing how much is being returned to the grid moment by moment and it seem this information could be used wisely.

However judging from the few replies this post got, it would be more complicated than I'm willing to pursue.

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RegGuheert
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Re: Can I divert excess solar power to my LEAF?

Sun Jul 26, 2015 11:49 am

gschettl wrote:The main reason I want to absorb my own solar energy is because the very last step, (after the solar system was installed and functional) was to sign a contract with the electric utility to allow trading electricity with a bi-directional meter. The unexpected catch is the contract specifies they will pay me less than half for each kWh exported to the utility versus what they charge me to import a kWh. I haven't gotten my 1st electric bill yet but other local solar customers have confirmed that's what I can expect.
That stinks!
gschettl wrote:Another reason is someday I'll have a battery storage system and would want to divert solar electricity to that too, before returning any to the grid.

So I'm surprised I'm not hearing of any turn-key system available yet designed to divert to batteries variably based upon the excess solar electricity being produced. My whole house egauge does a good job of showing how much is being returned to the grid moment by moment and it seem this information could be used wisely.

However judging from the few replies this post got, it would be more complicated than I'm willing to pursue.
You may want to look at this thread on the Enphase Energy Management system (and their AC battery) and this thread on the Tesla PowerWall battery system, which future versions SolarEdge inverters will support. Both product families are expected around the end of this year and are designed to address the kind of issue you are facing. I expect SolarEdge will offer some sort of trade-in for older inverters if you are purchasing a battery upgrade. Whether these systems will be cost effective or not remains to be seen. Certainly in some parts of the world where electricity is very expensive, they will have value.

I agree it would be nice to do what Enphase is doing except to use the EV for the battery. Hopefully someone will engineer such a solution soon.
RegGuheert
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forummm
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Re: Can I divert excess solar power to my LEAF?

Mon Jul 27, 2015 8:27 am

In GA, I have the same issue. My utility will either pay me 40% or 13% (depending on time of day) of what they charge me. Literally using that electricity a few minutes earlier or later costs 7.5X more. It's crazy. They will be selling that electricity to my neighbors for 7.5X more than they pay me for it. AND the utility retains the REC for my solar power. AND the state allows them to charge me extra for net metering--a fee of their choice. So the risk is huge that they will do that (they asked for $27/mo but were denied--but now a law was passed to allow them to charge a fee). So I'm holding off on actually buying the panels because it's just such a bad deal.
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davewill
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Re: Can I divert excess solar power to my LEAF?

Mon Jul 27, 2015 9:18 am

Well, that sucks. Even if you don't manage to have the system automatically monitor your usage and generation, you could probably improve your bottom line just by being able to manually dial the charging rate down so that your usage is closer to your generation. If you can program at all, you could probably program in a Bell curve of charging rates to roughly match your generation curve.
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RegGuheert
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Re: Can I divert excess solar power to my LEAF?

Mon Jul 27, 2015 10:02 am

davewill wrote:If you can program at all, you could probably program in a Bell curve of charging rates to roughly match your generation curve.
It appears OP has a 2012 LEAF. As such, the maximum power draw from the wall is on the order of 3.6kW. In addition, the battery can only accept so much charge before it is full, depending on the SOC at the beginning of the day. With a 40-mile RT commute, maybe 10 kWh available each day is a ballpark figure. (But if you are commuting each day, likely the car is not even available for this purpose?) Without the ability to DISCHARGE the LEAF battery back into the grid at nighttime, the LEAF can only provide a limited amount of

With my 12.5 kW system, peak AC production is around 10 kW with the house using about 2 kW (except on hot days like today when it likely consumes around 6 kW), our 2011 LEAF would not be able to make up the power difference. And the meter can frequently roll back about 50 kWh on a "good solar day", so the LEAF would not be able to address that level of storage on those days. Taken further, we net meter over about 3 MWh (peak meter reduction) through the course of a year. Battery storage is not likely to provide for that kind of seasonal energy shifting anytime soon.

The point is that a dedicated storage solution may be better suited for the task of keeping as much of the power in-house as possible. Again, whether or not it would be cost effective is another story.

In the long run, we will need to try to move EV charging to daytime hours to match the PV peak that will occur in more-and-more locations and to simultaneously reduce the nighttime load.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

eMaS
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Re: Can I divert excess solar power to my LEAF?

Tue Jul 28, 2015 12:41 am

See if you can get your hands on the Honda HEMS system
we have a demo house here at UCDavis, CA
all the technical info is available at:
http://www.hondasmarthome.com/tagged/hems
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Marktm
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Re: Can I divert excess solar power to my LEAF?

Thu Feb 25, 2016 10:58 am

eMaS wrote:See if you can get your hands on the Honda HEMS system
we have a demo house here at UCDavis, CA
all the technical info is available at:
http://www.hondasmarthome.com/tagged/hems


Have you visited the demo? Can you set parameters such as "I don't want to drive my EV at all"? The intent of course to max out the storage of both batteries for use in the house at the optimum times. Will the HEMS communicate to you when is a good (or bad) time to use high level of loads? Thinking of all the "smarts" such a system could provide is tremendous. As an example, change the set point on your electric household heater/AC (God forbid!) within a reasonable range to minimize consumption and/or rates. Combined with some smarts put into heat retention in new construction, this could make a significant reduction in energy consumption - shifting power consumption to off-peak (essentially non-peak) can tremendously improve the grids efficiency and capacity with the (costly) installations we currently have.

HEMS seems to be more upfront (and maybe much more intuitive) approach to what the Tesla PowerWall is attempting in the long haul?
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