Hybrid inverter with grid-tie backup, no battery charger

[2milehi]

Hello all, first time poster with a question. I have searched through the forums and I am not finding an answer to my question. I am wanting to DIY install of a 2 - 3 kw solar power system. I'll be charging a Chevy Volt with 120 ac (1 kw), power a small heater (1.5 kw) and maybe run a fridge (700 w).

- Power said devices with solar when available
- Inverter switches to grid when solar can't keep up
- Inverter will not send power back to grid
- No battery backup

My thought is when the sun shines, power the loads. When the sun doesn't shine, use grid power. This system would be used predominately for charging the Chevy Volt. I'm looking for an inverter that has all these features. I am finding battery backup hybrid inverters, but not inverters with no battery backup.

 

[newbostonconst]

Hybrid invertor with batteries is your best option...

If you have a smart meter then the power company will likely know immediately when you back feed the grid....Mine cam out within an hour when I first turned on my solar but I already had my contract with them approved. The meter guys thought I had flipped my meter to try and steal power.

You likely will need a contract with your power company to back feed the grid. But most Hybrid inverters can be set up to not back feed and instead power as much as possible and keep usage at zero with a battery(many call this grid zero).

 

[GXMnow]

My solar power is using Enphase microinverters. They can be setup with zero export mode. You will only get power when the sun is up, it will just add it's power to your home breaker panel. It uses power consumption current transformers, and when set in the HECO Hawaii grid code mode, it will produce as much power as it can, up until it sees power go out. Within a second, it can adjust the power production down to stop it from sending any power out to the grid. For this to work, you just need the Enphase iQ combiner box with the consumption CT's. That is also their system monitoring unit. And then a microinverter on each solar panel. You can get the system running on just one and add as many as you like at any time. I have been very happy with all of my Enphase gear. There are other units that can do this. Basically look for anythign that can meet Hawaii HECO requirements as they are all zero export.

 

[fafrd]

My solar power is using Enphase microinverters. They can be setup with zero export mode. You will only get power when the sun is up, it will just add it's power to your home breaker panel. It uses power consumption current transformers, and when set in the HECO Hawaii grid code mode, it will produce as much power as it can, up until it sees power go out. Within a second, it can adjust the power production down to stop it from sending any power out to the grid. For this to work, you just need the Enphase iQ combiner box with the consumption CT's. That is also their system monitoring unit. And then a microinverter on each solar panel.

Where is the ‘smarts’ in this Enphase solution? Are consumption CTs clamp sensors monitoring consumption/export and if so, which box/smarts are they connected to, the Enphase IQ combiner box or their ‘monitoring unit’?

And wherever the smarts reside, how is the control unit / smarts communicating with the microinverters? Is it using power line communication or monkeying with the grid signal (amplitude or frequency)?

You can get the system running on just one and add as many as you like at any time. I have been very happy with all of my Enphase gear. There are other units that can do this. Basically look for anythign that can meet Hawaii HECO requirements as they are all zero export.

Thanks for the pointer - I’ll do some research...

 

[GXMnow]

Here is the data sheet for the Enphase iQ combiner 3. This is the unit I have. It is rated for outdoor use if that helps for your install. For my system, it is mounted next to my main breaker panel.

https://enphase.com/sites/default/files/downloads/support/IQ-Combiner3-DS-EN-US.pdf

All that is needed from the microinverters on the solar panels is a 2 conductor cable that carries the current. The control and monitoring data is carried by powerline communication over the same cable. The combiner will take up to four 20 amp strings. This unit also needs to connect to the internet. It has an RJ45 ethernet port, and WiFi built in. Mine is pretty far from my router, and it would occasionally drop offline, so I installed a WiFi extender in my garage. I may run an ethernet cable later. It also has an option for a cell phone modem, but then there is a monthly charge for that. To be able to do the consumption measurement and zero export, you do need to add another pair CT's that install at the main feed and wire to the board inside of the iQ combiner. They are clamp on style and should fit around 200 amp feed cables. The setup is done with an app on a iOS or Android device. You can monitor the live operation with the setup app, but to get the nice history graphs and total production and consumption data, you use their cloud app Enlighten. If the system does not have an internet connection, it will still produce power without a problem.

The Envoy is the "smarts" of the system, and it is available as a separate unit, but the Envoy board and functions are built inside the iQ Combiner 3 unit. So there is not another device needed. Some people just choose to use a standard sub panel and the Envoy instead of the iQ Combiner. I like the combined unit, it makes for a simple clean install.

When running in the Zero Export mode, the Envoy board is monitoring the power consumption CT's and it sends data to the inverters to adjust the output to match your demand. Here is a paper on how that works.

https://enphase.com/sites/default/files/downloads/support/TechBrief-Export-Limiting-HEI-Self-Supply-EN-US.pdf

This is all about Hawaii, because they have strict rules of no export due to a small power grid being overwhelmed with a lot of solar power systems.

I am not a dealer, and I get nothing for promoting Enphase. I own a system that I paid full price for, and I am very happy with the system. They are not the cheapest up front, but they are not much more expensive than even basic systems, once you figure in the rapid shut down and the system efficiency and reliability. My system has been up and running for 19 months, and it has produced 11.6 Mega watt hours. In my system, I have 16 inverters. None have had any issue yet, but if one did fail, I still have 15 others still making power. Check out their web site, and fee free to ask any questions.

 

[fafrd]

Here is the data sheet for the Enphase iQ combiner 3. This is the unit I have. It is rated for outdoor use if that helps for your install. For my system, it is mounted next to my main breaker panel.

https://enphase.com/sites/default/files/downloads/support/IQ-Combiner3-DS-EN-US.pdf

All that is needed from the microinverters on the solar panels is a 2 conductor cable that carries the current. The control and monitoring data is carried by powerline communication over the same cable. The combiner will take up to four 20 amp strings. This unit also needs to connect to the internet. It has an RJ45 ethernet port, and WiFi built in. Mine is pretty far from my router, and it would occasionally drop offline, so I installed a WiFi extender in my garage. I may run an ethernet cable later. It also has an option for a cell phone modem, but then there is a monthly charge for that. To be able to do the consumption measurement and zero export, you do need to add another pair CT's that install at the main feed and wire to the board inside of the iQ combiner. They are clamp on style and should fit around 200 amp feed cables. The setup is done with an app on a iOS or Android device. You can monitor the live operation with the setup app, but to get the nice history graphs and total production and consumption data, you use their cloud app Enlighten. If the system does not have an internet connection, it will still produce power without a problem.

The Envoy is the "smarts" of the system, and it is available as a separate unit, but the Envoy board and functions are built inside the iQ Combiner 3 unit. So there is not another device needed. Some people just choose to use a standard sub panel and the Envoy instead of the iQ Combiner. I like the combined unit, it makes for a simple clean install.

When running in the Zero Export mode, the Envoy board is monitoring the power consumption CT's and it sends data to the inverters to adjust the output to match your demand. Here is a paper on how that works.

https://enphase.com/sites/default/files/downloads/support/TechBrief-Export-Limiting-HEI-Self-Supply-EN-US.pdf

This is all about Hawaii, because they have strict rules of no export due to a small power grid being overwhelmed with a lot of solar power systems.

I am not a dealer, and I get nothing for promoting Enphase. I own a system that I paid full price for, and I am very happy with the system. They are not the cheapest up front, but they are not much more expensive than even basic systems, once you figure in the rapid shut down and the system efficiency and reliability. My system has been up and running for 19 months, and it has produced 11.6 Mega watt hours. In my system, I have 16 inverters. None have had any issue yet, but if one did fail, I still have 15 others still making power. Check out their web site, and fee free to ask any questions.

That’s a nice architecture. So the ‘combiner’ monitors export and uses PLC to choke-back the Microinverters as needed.

Pricey, but not outrageously so.

I think this may be my fall-back solution in case the Sunpower GTIL-based solution I purchased proves unequal to the task.

All I really need the envoy to do in addition is activate an AC battery charger when there is export to avoid and I’d be all set

 

[svetz]

Welcome to the Forums!

Enphase, no grid=no power
I have Enphase and love them, but without IQ8s (not out yet) or Ensemble you won't get power when the grid is down.

Why Zero Export?
On the upside, no reason for zero export in most locations. I had $0 charges to get hooked up to the grid and get my PTO. I believe Colorado has laws limiting solar permitting fees, so might not be too bad. If you're thinking about 1741, that only controls what the inverter exports to the grid.

Pricey?
As to "pricey", the Envoy and microinverters do add up. But a String inverter system has other components too: for example a roof mounted system would need a Rapid Shutdown (RSD) device, an Automatic Transfer Switch (ATS), additional wiring, a critical circuits panel, and you'd probably also want a small battery for AC in-rush so would also need a Low Voltage Cutoff (LVC). Warranty on the Enphase microinverters is 25 years (usually ~5 years for a string inverter) and fewer components means less to go wrong and easier to diagnose (oh, Enphase provides panel level diagnostics you can't get on a string inverter).

A rough comparison of a string based system Vs. Enphase:

​

​

​

Critical Circuits & Lost Power
When you're not grid tied (zero export), your investment throttles back - that power is lost and not trying to recoup your investment.

Same thing with a critical circuits panel. As the power from Enphase microinverters terminates at the load center (aka circuit breaker panel), everything in the house can benefit from the power. With a critical circuits panel, only the devices connected to it can make use of the solar, so potentially more wasted energy.

The big upside to a critical circuits panel is you're not powering stuff you don't want powered when the grid is down (e.g., the hot water tank).

Hybrid
A hybrid inverter is a sub-type of "string" inverter, it allows power when the grid is down and you can export unused energy for credit (or some have a zero export feature), but typically the ATS and LVC are built in. Not positive, but believe the Skybox doesn't need a battery.

 

[GXMnow]

The discussion in this thread has moved around a bit.
What is the most important feature for the system being designed?
Is the grid reliable, or are power failures a problem?
Why is zero export needed? Is there a NEM agreement, or is this "off the books"?
What is more important? Keeping the cost low, spending more to ensure zero export, or having backup power during a grid outage?

At first, I was sure I wanted the NEM agreement, but with what they did with the rates, it is tempting to stay back on tiered power and zero export when it was $0.17 per KWH for the first tier. But as always happens, they even cranked up the tiered rates now. The lowest tier is up to $0.23 now, the same as my off peak rate on the Time of Use NEM. So, no going back now. It's still better to get some credit for the extra production than to just throw it away with throttling the inverters. But it is also telling me I want more panels and more battery.

If I was building a system from scratch right now, this is the route I would take.
My upper roof would be DC coupled to an OutBack SkyBox. 8 x 330 watt panels.
My lower roof array would have 2 more panels for 10 x 330 watt, all with Enphase micros.
I would also have 6 more 330 watt panels on Enphase micros on my garage roof.

That gives me a little more Enphase power than I have now. Still 16 panels, but the sweet spot on cost now is 330 instead 300 watt. And the 8 panels of DC on the high roof has no shading issues, so good battery charging no matter what. All of the micros can be AC coupled on the OutBack as well. It can accept up to 7,000 watts of AC solar, so even if I used the better iQ7-A inverters, I am still under the limit. With my limited 100 amp main panel, I would change out the main breaker to an 80 amp. That would allow a 40 amp breaker for the solar power. My backup loads panel would be larger. At least a 12 full size slot panel. My 6 slot is full. I used 2 tandem breaker to make it 8, and I still want 2 more.

I would run a 20 KWH LFP battery bank. That is about 400 amp hour at 16S. Two strings with separate BMS units to share the load current.

With careful programming, it would be very close to zero export, as it would store up most of the power when the sun is up, and be able to run the house all night off battery. The only grid power needed would be the air conditioner in the summer. 80% of my loads could easily run on the solar from 24 x 330 watt panels. This setup makes 45 KWH a day. 30 KWH on the micros, and 15 KWH DC battery charging. But it's not cheap.

 

[solar8484]

Hello all, first time poster with a question. I have searched through the forums and I am not finding an answer to my question. I am wanting to DIY install of a 2 - 3 kw solar power system. I'll be charging a Chevy Volt with 120 ac (1 kw), power a small heater (1.5 kw) and maybe run a fridge (700 w).

- Power said devices with solar when available
- Inverter switches to grid when solar can't keep up
- Inverter will not send power back to grid
- No battery backup

My thought is when the sun shines, power the loads. When the sun doesn't shine, use grid power. This system would be used predominately for charging the Chevy Volt. I'm looking for an inverter that has all these features. I am finding battery backup hybrid inverters, but not inverters with no battery backup.

From your description, it looks like the grid is available but you just want to consume solar power for your loads without exporting to grid. If so, what you described is the normal operation of a system of grid-tied inverters with export limiter and no battery. Solar power from grid-tied inverters will always get consumed by any loads (e.g. fridge) you have then any excess solar power will be exported to the grid if you don't have export limiter. When there is no enough solar power for your loads the grid will make up the gap without any extra switches.

 

[Larryblaikie]

I live in Cornwall Ontario Canada and this little part of Ontario is run by Cornwall Electric and that is owned by FORTIS Ontario basically a private company. bottom line is as of today Feb. 23rd 2022, I was informed that I am not allowed to backfeed power into the Grid. I am just looking into installing Solar but have an electronic background and the excuse they provide does not make any sense and i am waiting for a more complete answer. The answer they give is "they buy their power from Quebec Hydro (province next door) and we are not permitted to backfeed" The answer does not make any sense to me but I am looking at all options and one of them is Net Zero metering so I appreciate the information as i am just learning about this possibility. I was trying to figure out how i could install a 6kw system but not backfeed. I was not planning on installing batteries but must say am now looking at all options. Excited to learn that some systems comply with Hawaii HECO requirements - The research will continue.

 

[GXMnow]

The setup I am running could certainly be dialed in to zero export now, but it is not totally straight forward.

How much power do you need? Have you done even a rough energy audit for how much energy you want to produce? Have you looked up what kind of "Sun Hours" you can expect up there in the north? I am in So Cal, so I am cheating right off the bat. My 4,800 watts of solar panels pumped out a crazy 24 KWH today. And that was even with a late start due to morning cloud cover. That is a solid 5 sun hours in late February. I am very happy with that.

What kind of budge for equipment? Are you looking at UL listed safe and warrantied gear, or are we looking at Ali Express? The best way to do zero export is going to need batteries. There are solar inverters that will do zero export, but what that means is that any energy they could produce beyond your needs is just lost. And then you would need to buy all of your energy for the evening when the sun is down. Batteries will be the biggest investment. My bank is now 36 KWHs and I can run my home (without the A/C running) for more than a full day on the bateries. I have it shut down the inverter when there is still about 50% left though. It is easier on the batteries, so they last longer, AND, it will give my the power I need to fire up the system if we have a few days of lousy sun. The "Dark Start" issue is a problem with my AC coupled system. If you go with DC coupled charging, it is not a problem.

If I was building from scratch for a zero export system, I would certainly go with DC charging to a battery bank, and use a stiff low frequency inverter like the Schneider XW-Pro inverter that I am using now. And with the WattNode power meter setup, it can be programmed for true zero export. The software is already setup to do HECO legal zero export as well as other grid codes. If the solar makes enough, and you have enough battery, you just run essentially off grid until the battery voltage runs too low. At that point, the inverter will go into standby pass through mode and let the grid power the loads. It won't charge from the grid input without being commanded to do so. And you have to intentionally set it to back feed the grid, in normal setup it won't.

I am running my XW-Pro with AC coupled solar from Enphase microinverters. I finally having it working the way I want it, but it was a bit of a pain to build and program an external controller to make it time shift power from day time solar input to evening peak rate time output. But when you pair it with a Schneider MPPT charge controller, it goes from dumb to brilliant. As long as the grid is there, it will sync to it, yet still provide all of your power. So if you do run out of battery, it just keeps you running from the grid input. My system does that often as I was not soring enough each day to cover to the next morning. But since I have my charge control working now, the batter should make it to sun up on most days.

There are other inverters that can work like this, but I actually have hands on experience, so I know how it will respond now. Other hybrid systems like a Sol-Ark or Growatt should also be able to work in a similar manner, but I don't know what it would take to dial it in and what kind of adjustments you can make to get it to true net zero.