Anyone Home Solar Charging?

[Fullerene]

Anyone charging from Solar? Just looking at 'solar compatible' chargers.

I've got 4kW PV Solar and an immersun - which I believe bears some relation to eddi - myenergi from a previous life, it does a great job of diverting excess solar into the hot water cylinder.

I work from home so the car would generally be plugged in all day, I'd likely expand my solar panels as 4kW peak gives about 20 something kWh on a blue sky day this time of year.

I believe the home charger options that would let me scrape the surplus from my solar: zappi, Andersen, TWC (if hacked) From my perspective the Pros+ and Cons-

Zappi
+ incorporates the DC breaker
+ looks neat
- needs hub to operate
- cloudbased UI

Andersen
+ appears to incorporate the DC breaker
+ looks neat
- cloudbased UI

TWC
+ multiple TWCs allowed with load balancing
+ can be hacked along the lines of cdragon/TWCManager for solar
+ 3 phase included as standard
+ only one to activate the socket cover on car?
- not OLEV eligible
- cable may end up looking a bit messy when stowed

(As much as it's hard to avoid in life, I'd prefer not to be locked into a cloud based proprietary data harvesting scheme. Fingers charred with the owl intuition becoming subscription (Owl Intuition is becoming a paid service ) fortunately I have put some scripts together to listen to the data directly and output to influxdb and graph with grafana, I also firewalled my Owl so it can't reach the open internet with fear of non-subscribed devices being remotely disabled..)

Tempted to go with the TWC despite the DC RCD requirement.

Also really tempted to get the Zappi to see if I can pry apart the comms on either the RF or the network from the hub..

Thanks baldrick for the excellent EVSE Options - Google Sheets and Args for the definitive guide to RCDs: Tesla Wall Connector - Type B / Type A-EV RCD

 

[PB.Brown]

Hi, I have Zappi version 1. For it to charge your car there needs to be an excess 1.5 kw from your PV. I also have a Sonnen battery. My experience shows the benefit of having two electric cars. So that one can be charging over the week whilst you use the other one. I currently have a Zoe 40kw which can do 180 miles. I have sold my ice main car and placed an order for a M3 LR AWD. Gulp, totally electric motering!

 

[MrBadger]

Seriously look out of the window and put it on charge when you think it will give you some decent excess. Then set the charge rate to roughly match what your excess might be.

4kWp is not going to charge your car any better with a solar tracker charger than sticking your head out of the window and making the judgement call yourself.

Charging an electric car is a very big difference to heating hot water - hot water is easily doable from excess, most of the time charging a car is not. So set it to charge manually using experience of what you think your PV may yield and take any contribution from solar as a bonus. If you under estimate the rest of the country benefits from your export, if you over estimate you pay a couple of pence for getting it wrong.

I recon I could get within 70% (so a few £/year) of what a Zappi can achieve using my eyes and the standard Tesla functionality - say limit charge to 4a on day like today. The only thing that would be nice is to auto start/stop charge based upon insulation curve. And you can do that via the api if you wanted.

 

[ewoodrick]

There's a difference from taking the surplus and charging the car. When you plug the car in, and it's needing to charge, it's going to take all the current available through the plug that you have plugged in. If it's a 120V 15A plug, then that's 120V@12A or 1440 watts of power. If solar isn't giving that much, then it's coming from the grid. If a cloud passes over, it comes from the grid.

To use solar to charge the car, you'd really need a storage system that's bigger than the car's capacity. That way solar can charge the storage as power is available and then the car can pull what it wants.

 

[MidhurstNigel]

I've got a Zappi 2 on order. I decided in the end it was probably not worth the extra cost if you can get a really good EV night tarriff, but who knows how long they will be available? If full price electricity is the only option for charging then the Zappi (or something similar) makes a lot more sense. So I thought the extra cost was worth it as an insurance policy. Also, to the extent that I can use my own generated power it is a really green way of driving. Also boosts my street cred with my children!

 

[squarepeg77]

Seriously look out of the window and put it on charge when you think it will give you some decent excess. Then set the charge rate to roughly match what your excess might be.

So set it to charge manually using experience of what you think your PV may yield and take any contribution from solar as a bonus.

I have 4kW solar and get a good amount of free charging for my Model S (in the UK), basically using the approach described.

I have an “Eco Eye PV Smart PV energy monitor” which is hooked up to a Raspberry Pi to monitor the PV generation and household usage and pushes the data up to pvoutput.org every 5 minutes. I can see import/export data on the website or app.

As VanillaAir_UK says, you get pretty good at judging the solar generation from the weather forecast and seasons.

Here is my charging profile from Monday:

Green is solar, red is total usage. Big lump is car charging at 6 amps (240v). Other spikes are kettle, shower, oven etc.

If you want to say under the generation curve, you tend to charge at lower power/current 5 or 6 amps (~1250-1500W) On a crystal clear day you can get maybe 6 hours of 8 amps/2000W charging completely free. It would be great if the charge current was controllable via Tesla app or API and then you could follow the insolation curve through the day...

If the clouds roll over, you can stop charging via the app - or pay the few pence it costs if you get it wrong. And t really is not much... I know, I’ve been tracking it in a spreadsheet.

Obviously you don’t get much free charging in winter. In December we only get 60-100kWh solar generation for the month and a lot of it is at very low power, so that’s not much use for car charging.

I didn’t know about hacking the Tesla Wall Charger to vary the charging current, so will have to look into that, thanks. The manual monitoring solution works, but I’d quite like an automated one anyway

 

[MrBadger]

I have an “Eco Eye PV Smart PV energy monitor” which is hooked up to a Raspberry Pi to monitor the PV generation and household usage and pushes the data up to pvoutput.org every 5 minutes. I can see import/export data on the website or app.

I wonder if you are using my PVS2PVO software for Pi that I wrote many years ago? Some chap modified it further with graphs etc, but basic logging was started by me. I'm a bit loathed to shut it down as its been running continuously since 04/11/2017. I've got a few more things to add and will probably link it to Tesla Api to start/stop charging automatically, if/when car ever comes.

 

[gangzoom]

Also really tempted to get the Zappi to see if I can pry apart the comms on either the RF or the network from the hub..

Would it not make almost as much sense to look at a PowerWall for all the trouble of having to work out when/how to charge on direct solar PV?

We are on E7, and 99.99% of car charging is done at night, even with an inefficient X 'fuel' costs are really laughable. We coverd 1200 miles in the bill period, so work out as 2.6p per mile in fule costs, even taking into account charging losses and also we run all our other domestic appliances at night.

We also have a Solar PV setup with linked heater in the house, it was installed by the previous owners some time in 2015, what I don't get is the massive difference between total amount generated by solar PV and amount 'saved' by the heater over what I persume is a simlar time period - 12000kWh generated on solar versus just 2700kWh saved??

Anyways we are lucky enough to have a referral prize PowerWall coming soon, engineer has already been so just waiting on approval by WesterPower for install to go ahead. So hopefully soon I can push over day time time electricity use down to zero even in winter - PowerWall can charge using off peak, might even be able to make the crazy tidal traiffs that have time limited 5p per kWh eletrcity work. Though been honest saving 3p per kWh from 8p per kWh might be penny pinching gone too far!!!

 

[squarepeg77]

I wonder if you are using my PVS2PVO software for Pi that I wrote many years ago? Some chap modified it further with graphs etc, but basic logging was started by me. I'm a bit loathed to shut it down as its been running continuously since 04/11/2017. I've got a few more things to add and will probably link it to Tesla Api to start/stop charging automatically, if/when car ever comes.

I am using PVS2PVO! Awesome, what a small world!

Thanks very much for that script. I've had so much enjoyment (weird?) from this solution, over the past few years... watching the graphs "ooh... that's the refrigerator, that's the oven..."

Took me a while to find the link where I originally got the script from:
Python 3 code (RaspberryPi) for logging to pvoutput.org from EcoEye serial port

Is that the prime location for it, or have you got it on github now?

 

[MrBadger]

Powerwall does not make financial sense if you have to pay for it. About 3 years ago, I did an analysis on payback period and my actual solar generation/usage and export over a year. The payback period was significantly more than the lifetime of the Powerwall and that was even before the price of the Powerwall going up. It didn't include current tarrifs, but I don't think it will be much better even now. I've done some schoolboy maths on some of the new tarrifs and don't think they will save more than a coffee or two/month using occasional overnight reduced rate - they make up for this with their standing charge which is 24/7/365.

Apart from the Powerwall price rising in last few years, which is a bit of an anomaly to Powerwall, you actually save more money waiting for home battery storage than installing it, by virtue that (apart from Powerwall), prices are reducing year on year by more than the savings. Others have come to this same conclusion too.

Unfortunately, quite a few installers are hoodwinking people on the costs of these batteries by including the savings from EV in the same calculation. Had they separated the two out, they would find that payback period of PV would be a fraction of combined PV/battery and payback period on a Powerwall would be never.

Regarding immersion heater diverters, you can typically run an immersion mostly from PV for 4-6 months of the year. Apart from cost saving, which for us is around £10/month based upon our actual summer gas usage (can't remember if that included obligatory standing charge, don't think it did), you do save on wear and tear on boiler which if you don't use it much for 6 months of the year is actually quite significant. I actually still run the boiler, but with 40C thermostat setting in summer. So shoulder months, we get partial heating, summer months, usually 0 gas used month on month. I actually turn off diverter late Oct through mid Feb as tbh, we have so little excess, its not worth bothering about and we just export a bit more.

Same goes with charging car from solar. Oct through Feb, its not even worth thinking about letting Solar do its thing so we will charge as and when needed and any free solar is a bonus. We generate a little less than many on winter months as we have lots of trees at bottom of garden but tbh, its negligible difference as f-all of f-all is still f-all. April is when things really start to wake up.

 

[squarepeg77]

Would it not make almost as much sense to look at a PowerWall for all the trouble of having to work out when/how to charge on direct solar PV?

I've done the maths on a Powerwall, assuming an installed cost of at least £7500.
Payback in 25 years maybe? (Unless there's an apocalypse.)

I know Tesla owners might all be in the more-money-than-sense bracket, but I couldn't justify the Powerwall.
My solar PV will pay for itself in about 8 years, 4.5 years from now.

I reckon I put 86kWh into my car with home charging in July and 83kWh came from solar.
That's about 286 miles of driving (86kWh at 300wh/mile) for about 48 pence (3kWh import at 16p per unit), so less than 0.2p per mile.

 

[MrBadger]

I am using PVS2PVO! Awesome, what a small world!

Thanks very much for that script. I've had so much enjoyment (weird?) from this solution, over the past few years... watching the graphs "ooh... that's the refrigerator, that's the oven..."

Took me a while to find the link where I originally got the script from:
Python 3 code (RaspberryPi) for logging to pvoutput.org from EcoEye serial port

Is that the prime location for it, or have you got it on github now?

Yes, that was me. One day I will make it more accessible. Needs a bit of a rewrite as the original was a few hours work just to interface my monitor to some online graphs, but since writing, I've come up with a few more uses that I would like to use it for, like turning Tesla charging on and off.

Ian

 

[MrBadger]

Here is my charging profile from Monday:
View attachment 437156

Green is solar, red is total usage. Big lump is car charging at 6 amps (240v). Other spikes are kettle, shower, oven etc.

Same day, same 4kWp worth of panels, different location.

More than happy to keep to a single charge rate rather than chasing penny's tracking the highs and lows and not knowing what sort of level of charge I will have at the end. Hot water fully to temperature by 10am, but not every day. State of charge determined by other household usage patterns - I just want to know I have enough charge for my needs. I know Zappi has some mode to do this, but I prefer to keep things simple - car is complex enough already and that is coming from a former 'techie' (hate that term) - which is probably why I am cautious as I spent much of my time mitigating against problems, probably more than many people spend now in todays throwaway society.

 

[Alset2go]

Not yet but very interested in all the comments.Thank you.

 

[Fullerene]

Hi, I have Zappi version 1. For it to charge your car there needs to be an excess 1.5 kw from your PV. I also have a Sonnen battery. My experience shows the benefit of having two electric cars. So that one can be charging over the week whilst you use the other one. I currently have a Zoe 40kw which can do 180 miles. I have sold my ice main car and placed an order for a M3 LR AWD. Gulp, totally electric motering!

great stuff! I am hoping to ditch the ICEs this year or early next - assuming M3 arrives.

I've done the maths on a Powerwall, assuming an installed cost of at least £7500.
Payback in 25 years maybe? (Unless there's an apocalypse.)

Would love to be self sufficient for power, house and car.. assuming no apocalypse, not so much bothered about the survivalists off-grid aspect, but export only would be great.

Powerwall does not make financial sense if you have to pay for it. About 3 years ago, I did an analysis on payback period and my actual solar generation/usage and export over a year. The payback period was significantly more than the lifetime of the Powerwall and that was even before the price of the Powerwall going up. It didn't include current tarrifs, but I don't think it will be much better even now. I've done some schoolboy maths on some of the new tarrifs and don't think they will save more than a coffee or two/month using occasional overnight reduced rate - they make up for this with their standing charge which is 24/7/365.

Apart from the Powerwall price rising in last few years, which is a bit of an anomaly to Powerwall, you actually save more money waiting for home battery storage than installing it, by virtue that (apart from Powerwall), prices are reducing year on year by more than the savings. Others have come to this same conclusion too.

PowerWall stacks up even less with the EV tariffs (I've only really spotted the one from EDF) blowing E7 out of the water. 8p/kWh all weekend feels like free dialup for the weekend circa 1999.. Tempted to switch - will these tariffs last? I've spent way too much time following various homebrew power walls, the economics with homebrew is better, particularly for Australians with high kWh costs and huge blue skies.. fire risk on the other hand is a worry.

With my overnight base load averaging ~300W, a few kWh of batteries would save the overnight import and a blue sky over summer would make it plausible to avoid importing. Add a car into the equation and that goes out of the window unless I install a lot more panels. The divert to hot water works fine for 6-8 months a year, gas boiler remains off for about 6 months of the year, with an occasional half hour or so from the boiler on gloomy days . I was watching the clouds / feeling the tank to avoid no hot water and the wrath of the family. Got sick of the grief and fixed 5 sensors onto the tank earlier this year so I have an indication as to how much hot water is left.

Enjoying the comments on this subject, still sitting on the fence for charger choice, worst case it will be 10A from a 3 pin plug: low cost & Model 3 Reservers/Owners/Orderers will be renowned for their patience.

 

[MrBadger]

Try leaving boiler on normal times for heating hot water, but set thermostat to 40C April through to Oct - assuming thermostat around 2/3 from top of tank. It will prevent cold water being dispensed (not hot but warm enough for a shower) but will prevent boiler from firing except after a few very gloomy or high use days.

Sounds like you have done your homework so assume that you know that a Powerwall will not work off grid - or at least couldn't last time I looked. 30kWh+ worth of second hand forklift batteries seems to be weapon of choice of off gridders. Far cheaper than a Powerwall but very much hands on. Certainly a second (or more) power source is needed for off grid.

For others contemplating home charging, typical seasonal variances are below. I have winter shading end Oct through to end Feb so those with direct view to horizon will produce a little more during these months, maybe 50-70% more. Not a huge absolute amount more and certainly nowhere near enough to think that charging an EV is a viability unless ~2-4 miles/day range is all you need and you can keep connected to charger 7 days a week.

Annual monthly generation

Dec 2018 daily generation - peak generation approx. 1kW on a couple of days. So not enough to trigger a Zappi to charge by sounds of it.

Happy to provide more real world figures for anyone considering PV. I have nearly 6 years usage and generation data at 5 minute intervals. Or pick a site on PV Output close to where you live.

 

[Fullerene]

Try leaving boiler on normal times for heating hot water, but set thermostat to 40C April

Nice Graphs. Thanks for this suggestion will give it a go. Here's April 1st this year for me. Exporting jumps up when Hot Water is heated. I'd be lucky to have 3hours at above 1.5kW spare, so that's 4.5kWh and I believe approx 18 miles 'in the tank' once the standby losses are taken into account that's the school run and something like 70p saved - early retirement is so much closer

i, I have Zappi version 1. For it to charge your car there needs to be an excess 1.5 kw from your PV

From what I understand ( Definition and implementation of a global EV ... - Park & Charge ) SAE J1772 signalling standard controls the charge rate for home chargers. The minimum allowed PWM duty cycle is 10% which equates to 6A "offer current" from the charger hence the minimum spare solar input being about 1.5 kW The TWC has a rotary switch that selects the allowed current or enables slave mode. It's a shame Tesla doesn't (afaik, haven't looked at the API at all - if I went down that rabbit hole I would probably spend hours fiddling with it) allow the car to cap charge current, then I could control it connected to a 3pin plug at home... though my guess is the average person will want max charging current.

I can see myself getting the TWC and spend ages fiddling with it....

 

[Akikiki]

I just this week completed an upgrade of my existing PV system to 12K. And moved from Enphase microinverters to a single Solaredge EV Inverter. I am on a Net Energy Metering Agreement with my utility. So, my production rolls to the grid and I use it as I need it. Now, I am producing far more than I need, so I won't get credit, but can use all I wish. The Solaredge EV inverter just intercepts the power going back to the grid and I can use it. Really no big deal compared to some other charger. But it was available, so I added it. We'll see how it helps besides allowing for a second EV to charge using its J1772.

 

[gangzoom]

Sounds like you have done your homework so assume that you know that a Powerwall will not work off grid - or at least couldn't last time I looked.

New gateway allows it to run totally off grid, but adds another £1200 to the price.

I'll be getting original gateway as its the 'free' option, but installed told me Tesla are phasing out the old gateway so I may end up with a gateway 2 anyways.

Total all in costs would have been £8k+ I think with old gateway and close to €10k with the new gateway. Financially paying it for your self makes no sense.

 

[gangzoom]

I just this week completed an upgrade of my existing PV system to 12K. And moved from Enphase microinverters to a single Solaredge EV Inverter.

How much did that cost could I ask?