EV: off grid solar charger without batteries?

Is an arrangement of this type feasible? Would work daytime only, obviously, but would the variation of available power be a serious problem? Google finds a few articles, nothing definitive.


Background: we have a 56 panel grid tied system built on two 40ft wide steel frames. We can widen these to accommodate 16 more panels and plan to do so this year or next. The connections are in place for this expansion. It still won't supply all the power we use (feeds two houses) but close.



We built a third frame at the start of the project and don't plan to use it. The utility does not currently permit signification expansion of a grid-tied system once built.


One possible use of the spare frame would be a car port with a charger station. Fixed batteries would make it completely uneconomical but if it could work without it might just be worthwhile. Thoughts?


I don't yet have an EV so no particular hurry. WV ID Buzz is the first EV on the horizon that looks seriously interesting - by the time it's in production, there may be a hint of charger infrastructure in this region

da.hs said:

We built a third frame at the start of the project and don't plan to use it. The utility does not currently permit signification expansion of a grid-tied system once built.

One possible use of the spare frame would be a car port with a charger station. Fixed batteries would make it completely uneconomical but if it could work without it might just be worthwhile. Thoughts?

Click to expand...

What you suggest is certainly possible. This "spare frame", if populated with panels would generate how much power? You did not mention how many KW your system generates. The 2 big questions would be the KW output of your panels and the size (capacity) of the car's battery. You might want to calculate whether or not a full day's sunlight can generate enough power to fully charge the car's battery. This might be what would make your idea worthwhile - your electric car will be your "fixed battery". Of course you would need to make sure that you give the car's charging system a voltage it can use. The easiest way to do this would probably be a 115 or 220 VAC inverter. I believe that most electric cars can use standard AC power. Some car's may also have DC charging ability (I'm not sure). In either case you will need some kind of "interface" between the panels and the car.



Have Fun!


Don

I think a good option for you would be SPS from SMA. The new SMA grid-tie inverters have a 'Secure Power Supply' option. You flip a switch and the inverter disconnects from the grid and energizes a 120v outlet up to 2kW or the energy available from the solar array which ever is less.

https://www.youtube.com/watch?v=8cbIwvDzNjo

I would think you'd want/need some amount of additional batteries as a buffer for a completely off-grid charging stall.

The panels are 320W max - 28 or 36 per frame => 9KW or 11.8KW
That's max.. we don't quite have Nevada strength sunshine though. Yes, I would assume inverters needed. The existing grid-tied system uses one micro-inverter per two panels.

The question is a good one, and the inverter maker needs to answer. an added benefit would be your ability to use solar for power in the case of a grid interruption. (say a really bad ice storm that takes out a good chunk of the distribution system for an extended period)


and then the problem is how to make sure the use will stay under the capacity. under varying conditions.



I am not aware of a charging voltage vehicle interface that responds to varying current capacity. the vehicle interface is designed to communicate the capacity, and the vehicle charger limits how much current it uses to stay under this.


if you were to set this up, and have loads close to capacity, then a cloud comes along, the output would drop, and likely the inverters drop off line due to output voltage drop. (would want to verify this protection)

It can be running without batteries, energy share from utility and solar to loads alternatively.
Without batteries, it can help to reduce the whole solar system cost and more importantly it can save electricity fee.
It combines a high PV input MPPT controller, it can convert solar energy form PV to loads directly and the same time the remaining solar energy converted to batteries.
When PV output is reduces by clouds or at night, resulting in no surplus PV power available, loads powered by utility and batteries is charged, when utility outage, batteries discharged.
Off grid solar system running without battery can help to reduce the cost and save electricity fee, energy share from utility and solar to loads alternatively.

you would need a 22vac inverter that would output enough for the car. an ev will not charge during winter on 110v. i think tavarash proved that. the battery heaters take about all the incoming 110 power to stay warm. i say this because.... canada.

An interesting point - do you have more numbers? My garage (insulated but not normally heated) is generally around -5C most of the winter, ie 5 months or so. Outside would be anywhere from 0 to -40C. There's been a lot of -25C this year. If an EV would be using 1.5KW or so just maintaining battery temperature it would much reduce the economics of owning one. Stick to diesel...

I've no comparative figures. Our panels are HES-320-72P-MC, inverters AP Systems YC500I. Running for 2.5 years without failure. Snow: needs a long handled snow rake with cloth to prevent scratches to get some or most of the snow off quickly. Once a bit of each panel is exposed, the next sunshine will melt the rest off

if you are Grid tied and your meter spins both directions throughout the day/night, you already have a large battery. its called the Grid.

the rest is just hooking up your car charger to your existing ac/dc power system at your house/property to charge your car.