Can I divert excess solar power to my LEAF?

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gschettl

Active member
Joined
Jun 6, 2012
Messages
35
Location
jordan minnesota 55352 (Minneapolis suburb)
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.
 
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.
 
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.
 
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.
 
gschettl said:
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 said:
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.
 
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.
 
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.
 
davewill said:
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.
 
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
 
eMaS said:
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?
 
After seeing how my utility treats solar user I've been thinking of taking my solar system off grid. Its not practical food me to go totally off the grid but I'm wondering if I could use the Powerwall or something like that to act as a buffer and a regulated voltage system for new circuits that are separate and isolated from the grid. The idea is to run a separate circuit from the Powerwall to my garage to plugin my EV. By doing this my solar system will be available when the grid is down.
 
davewill said:
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.

I was wondering about this. Has it been confirmed that the Leaf will react to a change in the EVSE's max current signal during a charge cycle?
 
miscrms said:
I was wondering about this. Has it been confirmed that the Leaf will react to a change in the EVSE's max current signal during a charge cycle?
Yes, quite some time ago.
 
davewill said:
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. .

I have the deluxe 30 amp model that I built from a kit and will be attempting to monitor a battery pack voltage to adjust the amp setting on the level 2 charger for my Leaf. This is purely experimental in nature to learn more about "programming" the OpenEsve with the hopes I can eventually charge my Leaf off-grid with a 48 volt DC/208 volt AC inverter that I have (re-purposed UPS). Would this be a major undertaking for someone not that familiar with arduino hardware/software development? I'm certainly up for the learning experience.

BTW, the solar off grid based system is already in place at a rural location where the Leaf will eventually reside. As a new Leaf owner, I've been posting about making this "100 mile trip" on this forum and feel confident at this point.
 
There are only two ways to use the actual electricity from your solar PV panels in your Leaf is to:

1) charge the Leaf while the sun is shining

2) get a home battery storage system, like the Tesla Powerwall.
 
NeilBlanchard said:
There are only two ways to use the actual electricity from your solar PV panels in your Leaf is to:

1) charge the Leaf while the sun is shining

2) get a home battery storage system, like the Tesla Powerwall.


Yes, my hope is to "opportunity" charge and get the max energy during a typical sunny day cycle from the panels. Since no one (that I can find) makes a high voltage MPPT charger that accomodates the EV type batteries, it is looking more like some type of HEMSx (Honda) or PowerWall will be required to fill the gap. The issue is grid-tied. My goal is off-grid emergency use of the EV, which presents another set of problems essentially requires DC/DC MPPT charging to get reasonable efficiencies.
 
My feeling is that the electric vehicle doesn't make a good off-grid storage device...for a couple of reasons. First we usually like to drive around in the daytime more than we do at night. Kinda hard to charge it and drive it at the same time. Second, if you run the car's battery down at night, how will you drive anywhere? It's best, I think to get your off grid system going, but include enough renewable generation to keep the car topped up, too.

Besides, EV batteries degrade badly enough without putting them through extra cycles using them as daily storage. Now if you're talking about being grid tied, but being able to use the energy in the car if you get snowed in with no power, then it could work fine. Just get a good inverter and use it to keep your fridge and a couple of essentials going.
 
davewill said:
Now if you're talking about being grid tied, but being able to use the energy in the car if you get snowed in with no power, then it could work fine. Just get a good inverter and use it to keep your fridge and a couple of essentials going.

Use of the Leaf's battery in emergency off-grid mode has a major missing link - the inverter. I don't know of any reasonably priced, efficient, high VDC to 240 VAC (split phase) inverter designed for off-grid use. Some of the UPSs operate in the range of 400 VDC, but require a center DC tap (which is accessible from the Leaf in the emergency plug). However the UPS "0" VDC appears to NOT be isolated from the AC neutral. Not being an electrical engineer, I'm not sure, but I believe that could be a real problem when connected to the Leaf's battery.
 
Marktm said:
davewill said:
Now if you're talking about being grid tied, but being able to use the energy in the car if you get snowed in with no power, then it could work fine. Just get a good inverter and use it to keep your fridge and a couple of essentials going.

Use of the Leaf's battery in emergency off-grid mode has a major missing link - the inverter. I don't know of any reasonably priced, efficient, high VDC to 240 VAC (split phase) inverter designed for off-grid use. Some of the UPSs operate in the range of 400 VDC, but require a center DC tap (which is accessible from the Leaf in the emergency plug). However the UPS "0" VDC appears to NOT be isolated from the AC neutral. Not being an electrical engineer, I'm not sure, but I believe that could be a real problem when connected to the Leaf's battery.
Nissan sold one in Japan that plugged into the CHAdeMO port, but that wasn't what I was suggesting. Most people who have done this use the 12v bus to feed the inverter. You have to leave the car on so that the DC to DC converter will operate. Only good for emergencies.
 
If the goal to avoid sending extra power to the utility company because they are offering such terrible return rates, you could set a charge timer on the Leaf to just charge when the sun is brightest from the solar. I am not sure how it would work into your drive schedule though if you need to use it at the same time.

The best you could do with the Leaf as an extra power source is use the 12 volt system to power an inverter that runs under 2kW of power as either emergency power in an outage or custom systems in the home to draw and use the power. I use my Leaf to power a separate AC/Heat in my home for example. It won't run a stove or hot water heater, but it can keep the home warm/cool and power some outlets for TV, Microwave, Fridge, etc.
 
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