Charging from a variable amperage 240V supply (PV Solar)

[TrojanHussar]

We're literally weeks away from purchasing an iMiev and one thing I was wondering was if the AC charging on the iMiev has any tolerances with regard to the current it expects from the AC supply. We're in the UK and have a 3.6kW solar array linked via a grid tie inverter to our 240V supply, where possible I'd like to use the iMiev to soak up solar that we'd normally be exporting to the grid.

Using something like the https://solarimmersion.co.uk/ we could divert excess PV to a 240V socket and plug the iMiev into it, this would mean we would largely be running it for free (at least during the Summer months). My question is, does the charger in the iMiev expect a specific current at 240V or will it merely use what it's given? I appreciate that at low current the charger will probably be less efficient but as the electricity is free it seems rude not to use it.

Regards,
TH

[coulomb]

Using something like the https://solarimmersion.co.uk/ we could divert excess PV to a 240V socket and plug the iMiev into it...

The web site says:
For example, resistive loads like immersion heater could be controlled by the proportional controller while inductive loads with electronic components can be controlled by the relay.

It sounds like you can't use the resistive load option (the charrger is not a resistive load), and the other option is the relay. It sounds like the charrger would be turned on and off as clouds pass. That won't be good for the charrger, and we suspect that the charrgers have a sensitivity to "pulling the plug".

However, you can use a special EVSE that varies the pilot signal to the charrger. That way, the charrger draws more or less power, depending on how much excess you have at any particular time. It might still have to stop charging altogether at times (say heavy rain), but it should be able to do that in a clean way that isn't like pulling the plug. In Australia, we would use a Zappi EVSE, but I think I heard of a similar one from a UK source on an episode of Fully Charged. It might be this one. [ Edit: Sorry, it's this one. It looks like you can get a Zappi from a supplier in the UK. ]

[Don]

The charger in the car communicates with the EVSE which powers it with regards as to the available current. If the inverter with your solar array can supply 6, or 8, or 10 amps @ 240 VAC, then set the EVSE for that number and the charger in the car will never exceed that current draw. Now, if a cloud covers your array and the available current dips BELOW the number you set on the EVSE, you may run into a problem though. I would suggest using a lower number that you know would always be available

Don

[TrojanHussar]

Thanks for the prompt replies, I've joined a few fourms recently which seem to have died and they forgot to bury them! Glad to see this one is still active.

I hadn't realised the 7kW home chargers were as 'clever' as this (albeit at a price).

I had really only factored the prevailing cost of electricity into my equations when I was selling the idea of an EV to my Wife. She however has ideas about running it entirely from solar, which whilst admirable I suspect are only realistic during the Summer months. Even banking on 100% mains power we would be looking at a 60-70% saving in the cost of much of our day-to-day travel, so every kWh of solar we can channel into the car increases that saving.

Regards,
TH.

[JoeS]

TrojanHussar, when you export electricity to the grid, does the power company use that to reduce your bill or do they pay you for it?

I like to think of the grid as a huge battery that temporarily stores the energy I've given it; in my case, the power company uses what I export to it simply to reduce my bill at the same rate, until I get energy-positive (i.e., over the course of the year I've generated more than I took), which is a separate discussion...

An alternative for you could be to have a solar-charged battery buffer feeding an inverter feeding a programmable EVSE feeding your car so you could keep the power going to the car constant at some low level. Need to do the math to see if it makes sense.

[Don]

There are people buying up used Tesla battery modules to store excess power because the power company only pays them a fraction of what they charge you when you buy that same power back from them after the sun goes down. I think the older Model S has 13 modules in it's traction battery and if you can engineer a set of those or even a partial set into your system, it will easily run your house overnight, even with a cloudy day or two factored in

As Joe suggested, charging off the battery bank instead of directly from the panels gives you greater flexibility - Maybe you haven't used enough from your battery bank over the past several nights to be able to store what you'll make tomorrow, but not use all of during the day, so recharging the car(s) at night becomes a viable option

Anything is better than selling power to the grid for 3 or 4 cents a kwh and then buying it back overnight for triple that price - You could pay for a set of batteries in only a few years if you could store all that energy instead of selling it to them, which amounts to buying it from yourself at current power company prices

Don

[coulomb]

Anything is better than selling power to the grid for 3 or 4 cents a kwh and then buying it back overnight for triple that price...

You make it sound like it's some sort of scandal. But arguably, paying only the generation cost is fair. In Australia, about a third of the electricity price is for the generated electricity. A larger proportion is for distribution; some of it is generated thousands of miles away.

BTW, I dream of paying only 9-12¢ per kWh for imported electricity (like we did ten years ago).

[Don]

No, not a scandal, per se, but close sometimes and yes, it is fair to not get back the same amount as you pay because the distribution costs are a large part of the overall price

But we do have our . . . . well, I guess maybe 'scandals' is the appropriate word built into what we pay over here in many cases. Electricity used to be 3 or 4 cents per kwh in the Pacific Northwest due to an abundance of hydroelectric power, Then the state of Washington decided to build a large nuclear power plant, not because Washington or even Oregon needed more capacity, but because they planned to sell the power to California where it was much harder to get permission to build nuclear plants. They spent billions getting the plant about 80% completed and then cancelled the project. That WHOOPS blunder doubled the cost of electricity for Washington residents almost overnight and it never went back down . . . . if the blunder is even paid for by now

We had a similar 'scandal' here in Mississippi more recently. The Southern Company which owns Mississippi Power, Alabama Power, Georgia Power and others decided to build a 'clean coal' plant which captured the CO2 so that it could then be sold for use in getting better yield from oil wells. They 'thought' they knew what they were doing . . . . the principal had been successfully tested on a smaller scale. It was a moderate sized plant (only 580 Mw) built near an almost endless supply of 'dirty' lignite coal. The plant itself burns gas and they were going to make the gas from the coal. If it had been built as a gas plant, it would have cost close to 1/10th of the eventual $6.7 Billion Dollars they spent. In the end, it didn't work and the plant now runs on natural gas. The problem? The extra capacity wasn't needed, we have other plants running at half output, but the idea was to prove the technology so they could then sell it to China!! Of course, the Southern Company didn't want to do this all on their dime, so the politicians they have in their hip pocket allowed them to raise prices on their existing customers who would never see a watt of power generated by the new plant, before the plant was built

Come to think of it, over here, your word 'scandal' pretty much does apply!!

Don

[TrojanHussar]

Our panels (3.6kW) were installed in 2012 and we got them free under a leasing deal. Essentially the company (A Shade Greener) lease the space on our roof and provided us with free panels, they collect the feed-in-tariff income to offset the cost of the panels. We get free electricity from the panels and after 25 years (2037!!) the panels are ours.

They are selling electricity as a 'small PV generator' under a deemed contract, so they get paid 21p/kWh (about 27c US) for 50% of the generated electricity regardless of how much we use. Part of the contract is that we are not permitted to install a battery to store excess energy, but we are perfectly entitled to use 100% of the energy if we can.

Over the past 6 years we've exported on average 40% of the 20MW we have generated, so I estimate that's equivalent to 4,480 miles a year (@3.5 miles/kWh) of electricity we've exported to the grid. So something like a myenergi Zappi EVSE would be ideal, even during this mild English Winter we exported 76.1kWh in the last 30 days, so that's 266 miles (@3.5 miles/kWh) for free in the middle of Winter.

Now I just have to find an iMiev/C-Zero/Ion to buy, as they're like hens teeth in the UK.

TH.

[TrojanHussar]

In the UK the government have ended the feed-in-tariff for all solar installations after the 31st March 2019. So any domestic or small scale solar installations after this date will be exporting excess generation to the grid 'for free' and energy suppliers will be selling that free energy to their customers for 14.2p/kWh (the average cost in my area).

So whilst that means that your energy will be used locally (i.e. anywhere downstream of your local substation or transformer) and will be lowering the carbon footprint of your neighbourhood it will also be lining the pockets of energy companies and increasing their profits.

No surprise that battery technology is becoming so attractive.

TH.

No, not a scandal, per se, but close sometimes and yes, it is fair to not get back the same amount as you pay because the distribution costs are a large part of the overall price

But we do have our . . . . well, I guess maybe 'scandals' is the appropriate word built into what we pay over here in many cases. Electricity used to be 3 or 4 cents per kwh in the Pacific Northwest due to an abundance of hydroelectric power, Then the state of Washington decided to build a large nuclear power plant, not because Washington or even Oregon needed more capacity, but because they planned to sell the power to California where it was much harder to get permission to build nuclear plants. They spent billions getting the plant about 80% completed and then cancelled the project. That WHOOPS blunder doubled the cost of electricity for Washington residents almost overnight and it never went back down . . . . if the blunder is even paid for by now

We had a similar 'scandal' here in Mississippi more recently. The Southern Company which owns Mississippi Power, Alabama Power, Georgia Power and others decided to build a 'clean coal' plant which captured the CO2 so that it could then be sold for use in getting better yield from oil wells. They 'thought' they knew what they were doing . . . . the principal had been successfully tested on a smaller scale. It was a moderate sized plant (only 580 Mw) built near an almost endless supply of 'dirty' lignite coal. The plant itself burns gas and they were going to make the gas from the coal. If it had been built as a gas plant, it would have cost close to 1/10th of the eventual $6.7 Billion Dollars they spent. In the end, it didn't work and the plant now runs on natural gas. The problem? The extra capacity wasn't needed, we have other plants running at half output, but the idea was to prove the technology so they could then sell it to China!! Of course, the Southern Company didn't want to do this all on their dime, so the politicians they have in their hip pocket allowed them to raise prices on their existing customers who would never see a watt of power generated by the new plant, before the plant was built

Come to think of it, over here, your word 'scandal' pretty much does apply!!

Don