We have a solar array on the roof. It’s great. But the dc->ac converter needs the grid to be active to do its conversion, so when the power goes out no solar. (I suspect it syncs with the grids 60hz...)
If you include a battery backup in your system, you can run without grid power.
When I worked at a power monitoring start up we had a demo house that was charging an electric rav4, so it’s possible.
Yeah, that's the actual reason. I've seen someone use a small Honda generator to generate the frequency required to trick the solar generator into going... it's a weird setup because you basically tie in your generator using a breaker, so both generator and solar can be enabled at the same time.
Most home solar installs are grid-tied. No utility power, no solar power.
It simplifies the system a lot, because the grid provides "instantaneous" load matching for your house. If the inverter is sourcing more current than your house is sinking, the grid will sink it. If the house is sinking more current than your inverter is sourcing, the grid will source it.
When there's a utility outage, you need something else to provide the load matching. Either a local generator, or a battery is common; but either way, it's a lot more expensive.
It is a more complex and expensive inverter that can operate both isolated from the grid and in sync with it I think because it has to know when to do which and if it is outputting power how can it tell if the system is live because it is grid tied or because it is keeping the system energized itself.
I think they need external signals to tell them which mode to operate in.
Maybe the external system sees the frequency and voltage dropping or lower than normal range and decides to disconnect the load from the grid and opens a breaker and tells the inverter to operate in isolated mode.
When the external system sees the utility power is good again it could tell the inverter to shut off, close the breaker to connect the load to the utility, and then the inverter can go back to grid tie. The outage can be very short unless the load is large motors they don’t like the instantaneous change in phase when switching between different sources that are out of sync.
It's a safety reason. If the company disconnect the grid upstream to work on it, and your house is still powering it, they have a problem. You need extra equipment to automatically disconnect the house from the grid too.
I understand why grid-tied systems are built this way, but from an engineering standpoint this is really inefficient. Converting from DC to AC and back to DC, for no reason. In fact, most solar controllers are already designed to use and charge batteries.
It doesn't help that most car manufacturers use locked battery charging protocols that don't allow you to easily change this process.
AFAIK other car makers in the US use either CCS or ChaDeMo.
In Europe, all car makers (including Tesla) support CCS.
CCS allows DC charging and has support for load balancing, so I assume it could be feasible to create a home CCS charger that directly charges an EV with DC from solar panels.
However, considering how expensive power electronics are, and how difficult it would be to integrate such a charger into an existing solar installation, I have doubts that many people would buy such a charger. Also, I don't really know how CCS works in detail, so I may be totally wrong about this.
solar panels are the wrong dc voltage, so some sort of conversion is needed. I'm no EE, but my understanding is you go through AC and a transformer anyway in most cases.
Virtually all off-grid solar installations use some kind of an MPPT controller with a battery setup. The controller is always charging the battery (when there is power output from the panels), and the consumer power output is supplied by the batteries. This way you get much higher peak current output than the panels could provide, you also ensure stability.
In fact, many cabin installations don't even use inverters to convert into AC. They instead use DC appliances. So no, going through AC makes no sense in this scenario.
As for DC voltage levels, that of course is dependent on solar panel configuration and battery cells configurations/packing. Virtually all electric cars have a built in charger with a switching power supply that's already doing the DC voltage conversion. What I was remarking was that there is a lot of duplicate electronics that perform the same function and that a lot of intermediary steps can be eliminated.
Off grid is going to be designed to fit and probably cheap. Not always best. If you panels are near the batteries and near the load what you say can make sense (though I wouldn't be surprised if the charger had a AC step internally, that is clearly optional)
That isn't what you would do for anything tied to the grid. This is far more common (economies of scale mean the parts are cheaper). There you would take advantage of AC's ability to change voltage easily to allow the panels to be farther from the rest of the system. You would also want to use the grid as a backup for any system failures in the solar setup.
With a charger that goes down to 750w you can charge your ev off grid with an inverter.
I currently do it with 12 100w panels. I run ac/dc converters to supplement additional dc from the grid to charge at 1500w, but have a 750w charger for emergencies that will charge directly from the sun with no grid. It does require a small buffer battery to work reliably.
at 750W, even with perfectly efficient energy transfer, you're looking at adding ~2.75 miles of range to your car every hour it's charging. That means during winter, if it's sunny, you might be able to charge your car all day and get 25 miles from it.
You'd be a lot better off with a jerry can and a $500 gasoline generator....
The article is citing needing 6-8 panels between 320-330 watts to charge a Tesla Model S; 8 if you live in the northeast United States (it's not backyard orientation, it's about where you live geographically), 6 if you live in the southwest United States. The "small" Tesla panel arrays that I mentioned are 4.08 kilowatts [1], which is more than enough even in the northeast to charge a Model S, or any EV. They take up 240sqft, which would fit in most backyards, although a roof mount would of course be preferable both because it'll get less shade and because it won't take up backyard space, unless you have a lot of open backyard space away from any existing structures.
Really. There's a reason Tesla sells solar panels, and it's because they can charge the cars Tesla makes. They can also lower your electric bills (or drop them to zero, or make you money depending on the region you live in), since even the smallest panel array they sell produces more electricity than an average American driver needs per year for an EV.
Do you own Tesla solar panels? I've heard mixed reports about them. I live in Northern California where there is a big solar presence but most of the solar people I've spoken to (installers and owners) say Tesla is too expensive and not particularly great.
I'll be doing solar panels on our roof when the battery storage tech becomes viable and PG&E start being sensible about individual electricity production.
I don't own Tesla solar panels! I'm just going off publicly available info. I'm willing to believe that Tesla is not competitive on price, although I would be surprised if their wattage numbers were fake.
If you include a battery backup in your system, you can run without grid power.
When I worked at a power monitoring start up we had a demo house that was charging an electric rav4, so it’s possible.