diy solar

diy solar

Hybrid inverters with grid tie mode

Yes and Yes.

You can either have the XW-Pro only supply power to it's output side, or command it to "sell to grid" out the input side. If it is selling to grid, you would need to add the "Watt-Node" unit to measure the grid power. I am still running without a Watt-Node. In this mode, I can tell it how much power to push back out the grid input side. I just estimate how much the house needs, and when loads turn on and off, it varies how much may go out to the grid from my home, or draw some in if needed. This is okay for me as I have a net energy metering agreement that allows me to push out up to 16 amps, or 900 KHW's per month. When you add the watt node, you get another control page. You can set it for how much you want to allow it to export. The watt node will adjust the inverter power to maintain your desired current. It could be from always taking in a little current to pushing out current. If you need true zero export, then yes, you will need the watt node.

When the grid is up, you can always take any power needed from the grid. Your main panel is fed by the grid, and if there is no inverter, it all works just fine. What happens with the inverter is that is will supply power as well as the grid. In the case of the USA version of the XW-Pro, it can be set to supply up to 6,800 watts, about 28 amps on bother legs of the 120/240 split phase output. It will even supply up to 40 amps on one leg under a large imbalance. There are models for 230 volt single phase as well, and 3 can be grouped to make 3 phase. If you have it set for grid sell with the watt node programmed for zero export, the inverter will take battery power and convert as much as is needed to zero out the grid power. If the demand in the house exceeds the power limit, 6,800 watts in my case, then any current above that will come from the grid. If the battery runs down, the inverter may shut down, and then all of the power will just come from the grid.

What do you plan to use to charge the battery bank? You still need to get the power from somewhere. To get the most out of the Schneider system, you should have DC coupled solar to charge the battery bank. The XW-Pro can chare from the grid, but you have to manually trigger it to start a charge cycle. With the DC solar, it just gets charge current whenever sun is hitting the panels.
Can I use the XW Inverter to charge the batteries in a AC couple system (enphase microInverter IQ7)?.
 
Sort of.

There is a small issue in an AC coupled only system. This is exactly what I have right now, 16 Enphase iQ7's connected to the output side of the Schneider XW-Pro inverter. This works absolutely perfect for backup power incase of a grid failure. But here is the issue. When the system is on grid, it will not automatically charge the battery bank in day to day use. This is not a problem if you only want backup power. You set the recharge volts relatively high, and if for any reason the batter does drain down, it will trigger a charge cycle, or you can just go on the configuration page and click (Force Charger State = Bulk) and that will start a full charge cycle any time you want it.

I have mine set to do "Grid Support" so it goes into invert mode and powers my home during the peak "Time of Use" rate from 4 pm to 9 pm every day. I run less than 40% of the battery capacity to cover all of my normal loads during that time. But the grid support function will stop at 0.5 volts ABOVE whatever the "Recharge Volts" are set at, so it will just sit there and not charge back to full unless something else triggers it to happen. If I do have a power failure, it will kick in and start powering, AND when the grid is out, if the solar does start producing more power than you are using, the extra power does get pushed back to charge the battery bank.

So if you are not trying to cycle the power every day to save about $1 to $2 per day taking solar power and using it during the peak rate as the sun goes down, you can just let the battery sit at 80% charge and let it take over during a power failure. But one of my main reasons was to have the time shifting of power help reduce the overall cost. I do not expect it to totally pay off, but if I can save $5,000 over the life of the batteries, it is a very good start. For the past 10 months, I have been just hitting "Force Charger State = Bulk" every morning before I go to work. If I miss a day, it is at, just a $2 loss for that day.

I am close to having a small Programmable Logic Controller send the force charge command for me. It was about $300 and a few months learning how to code it, but I think I am very close now. But this really is a function that Schneider should fix and put in the software as an option. Their suggested fix is to use a Schneider MPPT charge controller and have some of the solar array directly charge the batteries. And after doing the math, I do think I want a bit more solar anyways, so I may add about 2 KW of solar with a charge controller. The Enphase will power my home when the sun is up, and sell some extra back to So Cal Edison. The DC array will charge the batteries all day while the XW-Pro inverter just waits. When the Enphase solar output is no longer pushing power back out to the grid, the XW-Pro will go into Grid support mode and produce as much power from the battery bank as it needs to to zero the grid input to my home. To truly zero the grid, I will also need to add a Watt Node which measures the grid power and sends it to the Schneider Gateway which will then constantly adjust the grid sell current to hold the grid to zero power in or out. If the battery runs too low, it will go back to standby and I will run on grid again, until the sun starts charging the batteries. If I turn on more load than it can supply, the XW will supply the limit I set it for, and any more power needed will come from the grid.

So it is not a perfect solution, but it is actually very good. Just their software is missing some features, and it is not the most intuitive to setup, and their online tech support is kind of weak as well. But it is probably the most robust inverter out there. It can handle crazy surge current and power any normal home load without getting even warm. I have now cycled 1.2 Mega watt hours in and back out of mine in 10 months and it has been flawless, except for the lacking software that requires me a manually run the charger function.
 
I have a growatt SPH5000 and 7KW of solar and just one pylontech US2000C

before i got the battery, on a good sunny day my inveter would sit there for hours making 5300w i would be using about 800w for my house load and giving 4500w away to the grid

when i got my battery ( the Battery BMS seems to set charge / discharge to 25 amp) (25amp @50vDC) so thats 1250w @240v AC

so no on a sunny day my 5000w inverter makes 6550w (only while the battery needs charging)

800w for me to use as my load
1250w to charge the battery
4500w to give away to the grid

John
 
Hi, thanks for all your responses above. Is there any Hybrid inverters that actually measure the grid load ie when it gets to zero it backs off the battery use?
 
Hi, thanks for all your responses above. Is there any Hybrid inverters that actually measure the grid load ie when it gets to zero it backs off the battery use?
Certainly is. There is grid tie inverters that use batteries and also do not feed into the grid. There is hybrid inverters that do the same.
 
GXMnow: a bit off topic, but will the Schneiders work with optimizers such as Tigo? On-line info from Tigo says yes, but that doesn't make me confident.

I really enjoy your posts.
 
Hi, thanks for all your responses above. Is there any Hybrid inverters that actually measure the grid load ie when it gets to zero it backs off the battery use?
GXMnow: a bit off topic, but will the Schneiders work with optimizers such as Tigo? On-line info from Tigo says yes, but that doesn't make me confident.

I really enjoy your posts.
oymyakon
With the Schneider XW-Pro, you can add a WattNode energy meter on the grid input and the system can be set to adjust the inverter grid sell power to zero out the grid with no export.

SolarPrep
I can't give an absolute answer on how well they would work, but I did read up on Tigo while I was planning my DC panel addition. If (hen) I add my extra panels for the DC coupled battery charging, I will use a Schneider MPPT charge controller. I thought about using another brand, but I don't want to use yet another different monitoring system. So this is strictly to have it integrate with the XW-Pro inverter and my existing Gateway. To be fully legal where I live, I will need panel level rapid shut down. Tigo is one of the few systems that can add this at a reasonable cost. And you have the option of just RSD, or also getting panel optimizing and monitoring. From all of the paperwork I read though, it looks like the Tigo optimizers will work very well with a Schneider MPT controller, but in my use case, I just don't see a need for that added cost. Where my extra panels will be, I have minimal shading issues, and I will be able to easily measure the 3 strings to see if I have a production issue. I will just compare the total array output to what my existing Enphase panels are doing and that will give me a good idea if all of the new panels are working correctly. That being said... If I were to build a large system with all DC string connected solar panels, I think the Tigo optimizer solution is a very good arrangement. It clearly handles shading quite well compared to not having them, and in some independent tests, they performed as good or better than the Solar Edge optimizers. The fact that they will work with virtually any inverter or charge controller is a huge benefit. But the cost does come into play. You need to decide if the extra cost is warranted for your installation. In my case, it does not make sense. It will not increase my production since I don't have shade issues.
 
oymyakon
With the Schneider XW-Pro, you can add a WattNode energy meter on the grid input and the system can be set to adjust the inverter grid sell power to zero out the grid with no export.

SolarPrep
I can't give an absolute answer on how well they would work, but I did read up on Tigo while I was planning my DC panel addition. If (hen) I add my extra panels for the DC coupled battery charging, I will use a Schneider MPPT charge controller. I thought about using another brand, but I don't want to use yet another different monitoring system. So this is strictly to have it integrate with the XW-Pro inverter and my existing Gateway. To be fully legal where I live, I will need panel level rapid shut down. Tigo is one of the few systems that can add this at a reasonable cost. And you have the option of just RSD, or also getting panel optimizing and monitoring. From all of the paperwork I read though, it looks like the Tigo optimizers will work very well with a Schneider MPT controller, but in my use case, I just don't see a need for that added cost. Where my extra panels will be, I have minimal shading issues, and I will be able to easily measure the 3 strings to see if I have a production issue. I will just compare the total array output to what my existing Enphase panels are doing and that will give me a good idea if all of the new panels are working correctly. That being said... If I were to build a large system with all DC string connected solar panels, I think the Tigo optimizer solution is a very good arrangement. It clearly handles shading quite well compared to not having them, and in some independent tests, they performed as good or better than the Solar Edge optimizers. The fact that they will work with virtually any inverter or charge controller is a huge benefit. But the cost does come into play. You need to decide if the extra cost is warranted for your installation. In my case, it does not make sense. It will not increase my production since I don't have shade issues.
GXMnow; Thanks for the info. My site has many shading issues. Odd shaped house, on a complex shaped lot, with many trees, etc. I have a pretty good Eastern exposure, reasonable Southern, nearly no Western. However, in the Winter, my shading issue is better. The biggest issue for me is the low pitched roof is best for solar, but a very bad idea in snow country. So, am looking at mainly ground mounts.
We accept these limitations, and are committed to getting what we can from solar, with a serious battery backup/storage system. I'm leaning heavily towards SMA. Our local jurisdiction just adopted the 2020 Electrical code, and they now require all UL listed equipment for ANY solar produced on site that delivers 50v or higher to any device in your house. I wanted to do an off grid unit, but now will likely be forced to grid tie to meet their requirements.

We have a LOT of power outages here, and it is getting worse every year.

I like Victron equipment, but they don't get UL listing on the vast majority of their products. So I'm having to consider equipment I really don't want to consider. Like Schneider, Outback, etc. Just this week had a visit from my installer who is very big on Fronius and Solar Edge. I'm going to use him to do the racking, ground screws, etc. The "Colorist" has been fabulous to confer with, and my intent is to work with him on the inverters and BMS.

I appreciate your in-depth comments, and real world experience.
 
Optimizers aren't necessarily what's needed for shading.
Optimizers are to match varying current output of PV panels in a single string, such as for multiple orientations.

Bypass diodes work well for shading of panels in a single string, not paralleled with other strings (so long as PV panel has properly rated diodes and thermal management; some say not to have heavy shade under full sun.)
Multiple PV strings in parallel, the bypass diodes only do so much. One panel out of 10s2p shaded would be OK, 3 panels in a string shaded might cause excess loss over production.
If inverter (e.g. Sunny Boy) has multiple MPPT, one PV string per MPPT avoids that.

Probably module-level Rapid Shut Down will be required for rooftop installation (but not ground mounts.)

Two battery backup choices from SMA.
Sunny Boy Storage is 6kW, 9kW surge. Not supported for paralleling at this time; maybe that will come. Has features of export limiting and time-shifting.
Sunny Island, 5.75kW, 11kW surge, series/parallel up to 2s2p (or 4p). Doesn't implement exporting, don't think it does time shifting. Possibly other devices can talk to Sunny Boy for export limiting.

Obviously lithium would have better cycle life for daily use. You would need to address operating temperature vs. charge current. Also possibly U.L. listing requirements.

If batteries are only for backup during grid failure, the lower cycle life of lead-acid can be fine. I use AGM for that application. My SunXtender are "U.L. Recognized"
Some people use Rolls Surette FLA for greater cycle life, better price point.
 
Probably module-level Rapid Shut Down will be required for rooftop installation (but not ground mounts.)
I’m thinking about doing a high voltage array on my roof. Can you possibly explain what you mean by module level rapid shutdown and what that entails
 
I’m thinking about doing a high voltage array on my roof. Can you possibly explain what you mean by module level rapid shutdown and what that entails

Typical residential high-voltage string inverter accepts up to 600Voc. My PV strings are 480 Voc under nominal temperature conditions, and 380Vmp when operating (very cold day like -15 degrees C could approach 600Voc)

Firemen need to work on the roof in case of a fire. There are now rules requiring some walkways, especially on street side and near valleys. At the ridge, need a 3' space (maybe 18" each side) to hack vent holes.

The new requirement is that when a shutdown switch gets pulled, all wires drop to < 80V between each other. This typically means isolating between each PV panel or putting them through a buck regulator to drop to very low voltage like 1V each, still in series.

RSD Rapid Shut Down is a box per panel (typically) that panel MC cables plug into. Then all the RSD boxes wire in series. Inverter or another gizmo sends a signal to enable the PV array. Some inverters have this build in, so turning off AC to the shuts down RSD.

Looks to me like for my old "12V" panels I could connect 3 in series and connect one RSD.
What the voltage and current limits of the RSD you select; some new panels exceed their specs.
Some RSD take two panels. I previously saw models that took four.

What you need RSD, and what walkways are required, may depend on what code your location has adopted.
Some roof designs (maybe shed roof) the fire department wouldn't need to vent in this manner, so walkways might not be required.
For a while, it was 3' on two sides and the ridge. In some states, 3' inside exterior walls, so eaves don't count. This is why you see roofs with a small array in the middle.
 
Typical residential high-voltage string inverter accepts up to 600Voc. My PV strings are 480 Voc under nominal temperature conditions, and 380Vmp when operating (very cold day like -15 degrees C could approach 600Voc)

Firemen need to work on the roof in case of a fire. There are now rules requiring some walkways, especially on street side and near valleys. At the ridge, need a 3' space (maybe 18" each side) to hack vent holes.

The new requirement is that when a shutdown switch gets pulled, all wires drop to < 80V between each other. This typically means isolating between each PV panel or putting them through a buck regulator to drop to very low voltage like 1V each, still in series.

RSD Rapid Shut Down is a box per panel (typically) that panel MC cables plug into. Then all the RSD boxes wire in series. Inverter or another gizmo sends a signal to enable the PV array. Some inverters have this build in, so turning off AC to the shuts down RSD.

Looks to me like for my old "12V" panels I could connect 3 in series and connect one RSD.
What the voltage and current limits of the RSD you select; some new panels exceed their specs.
Some RSD take two panels. I previously saw models that took four.

What you need RSD, and what walkways are required, may depend on what code your location has adopted.
Some roof designs (maybe shed roof) the fire department wouldn't need to vent in this manner, so walkways might not be required.
For a while, it was 3' on two sides and the ridge. In some states, 3' inside exterior walls, so eaves don't count. This is why you see roofs with a small array in the middle.
Thanks for the explanation. I understand the reasoning for wanting the voltage to be less than 80v if there’s a fire or a short.. Although an RSD (box per panel) really makes the installation a lot more difficult. I’ve been running my array at 125v for years without a box per panel, guess this isn’t safe
 
Are the Sunny Island's low freq inverters? From their specs (weight and surge current capability) it appears so.
 
I am a bit torn on my planned DC array. I want to use 60 cell panels, but then I run 3 in series to the 150 volt MPPT controller. 2 panels in full sun just exceeds the 80 volt limit, so I need a separate RSD on all 9 panels. Might be able to use 3 of the dual panel boxes, and then 3 more single panel ones. That adds up. If I go with 72 cell panels, I would only use 6 panels, I'll be down a little on power, but I could use just 3 of the dual panel RSD boxes. The Tigo RSD only units are not crazy expensive though. The dual panel units are $47.50 USD each, and the single panel version is $32.58 each. Then I just need one signal injector and power supply to activate them. The complete kit is about $160 with a nice weather tight box. Schneider makes their own Tigo compatible RSD transmitter, but they want over $600 for it. It looks like most of these are using the "Sun Spec" signal. It seems to just be a high frequency current wave imposed on the DC cables. If it sees the signal, it closes the switch for the panel to feed the system. If the signal drop out for any reason, the panel level boxes shut off the voltage out of the panels. Most of the other systems are quite a bit more expensive.
 
Are the Sunny Island's low freq inverters? From their specs (weight and surge current capability) it appears so.

Yes, they do high-frequency switching at 48V to synthesize sine wave, then put it through a transformer to generate 120V (220V for European model.) That's what we call "low frequency".
"High frequency" uses high frequency boost converter either to create line voltage sine wave directly, or to make a high voltage rail from which line voltage sine wave is made.
I'm not sure there is anything inherent in the so-called "low frequency" design which makes it deliver more current than a "high frequency" design. If the high frequency design delivered enough current through its switchers it could, and some have such specs.

Back when inverters were MSW (or really Modified Square Wave), low-frequency would drive a rectangular pulse into transformer primary. High-frequency design used a boost converter to make 120V then switched that onto AC output.

One of these days I'm going to see how my single SI 5048 plus 120/240V transformer does at starting the central A/C. Normally the house is fed by 4x SI 6048.

Thanks for the explanation. I understand the reasoning for wanting the voltage to be less than 80v if there’s a fire or a short.. Although an RSD (box per panel) really makes the installation a lot more difficult. I’ve been running my array at 125v for years without a box per panel, guess this isn’t safe

Not that it's unsafe, just a new requirement for lower voltage within the array. Earlier regulation allowed array to have high voltage, just disconnect from wires so outside array was safe.

The installation wouldn't really be more difficult. You screw a box to PV panel frame and plug MC cables into it. But it adds $35 maybe $50 per panel, so string inverter loses much of its cost advantage over microinverters.

A rule requiring voltage under 30V or something like that was considered. Only "12V" panels are that low. 80V at least allows Voc of a single large panel.
 
I'm not sure there is anything inherent in the so-called "low frequency" design which makes it deliver more current than a "high frequency" design. If the high frequency design delivered enough current through its switchers it could, and some have such specs.
I work with several different kinds of electronics, including some high current power supplies and such. Going to high frequency switching has made it far cheaper to build a high pow device. A xenon lamp power supply used to require a 200 pound 3 phase transformer, and a huge diode bridge to handle the 150 amp DC output. With high frequency switching designs, the huge transformer assembly is not typically 6 palm sized pucks and the diodes are even pretty small with a synchronous FET across each diode to even remove the forward voltage drop. They went from 40% efficient to 96% efficient, and the whole thing is now 40 pounds. This has been a huge development for power conversion.

But when we are creating a 120/240 volt split phase of 60 Hz AC, doing it all with high frequency switching has a few drawbacks. The capacitors, transformers, and fet's are designed for the rated power. If they used stronger components, they would just rate it for more power. When use 12 KW rated pars for a 6 KW rating? The much smaller caps and coils can take a little overload, but not for long. The components will start to heat up fairly quickly. This is where the 1 to 10 second surge ratings come in. Those tiny high frequency switching transformers just can't absorb much extra heat.

When you build a 50 or 60 Hz H bridge and transformer, the caps have to hold up for the 60 Hz cycle, and the core of the transformer has to be large to keep from saturating at the low line frequency. When it is subjected to an overload, that huge heavy transformer does two things. It acts as an excellent filter to keep the sine wave pretty clean, and the large core and copper windings can absorb a lot of heat energy before the temp climbs too much. So this give us 30 to 60 second overload ratings that are much higher. The switching FETs are operating directly off the battery buss with some large capacitors, so that can also suck up a bit of overload as well. That huge transformer is needed to meet the rated power spec, so they can't really trim it down. But it's mass gives it the thermal inertia to handle the large peaks. The low frequency design is always going to be bigger, heavier, less efficient, and more expensive. The large parts needed to work at low frequency and high power are just more expensive.

I am sure someone will eventually build an inverter that fits in the middle. Use all high frequency synthesis to produce the full 120/240 volt split phase 60 Hz output, but us oversized coils that are embedded in heat sinks to handle some overload with headroom to spare. And use large enough reserve capacitors on the high voltage DC buss to power through a few cycles of the AC output. I have now worked with a few audio amplifiers that are sort of moving to this type of a design. We have several now that can punch out over 5,000 watts and surge to over 10,000 watts in a nice small lightweight package. Early Class D switch mode amplifiers had the same issues as the current small light inverters. The could do rated power, but there was no headroom, and their output was current limited when trying to drive a lower ohm load. But by beefing up the power supplies and output filter coils, they are getting close to the abilities of an old Class AB amplifier to handle a difficult reactive load. A small 2 rack unit Crown DCi 4-2400 can drive 4 channels to 2,400 watts each into 4 ohm loads. That works back to 98 volts RMS at 24.5 amps times 4 outputs. The 8 ohm rating is "only" 1,900 watts , or 15.4 amps at 123 volts RMS. So it is basically four 1,900 watt pure sine wave inverters that get their power from a DC switch mode power supply. And they have less than 0.35% distortion across the entire audio spectrum from 20 to 20,000 Hz. Using three of the channels, it could make a 3 phase 120/208 volt 15 amp variable frequency drive, with an extra channel left over.
 
You think the capacitors at battery voltage do anything to keep up with a half cycle of 60 Hz?
That's not what my math (or measurement) said. At full load, I think it comes 100% from battery. I took current measurements with scope, driving 10kW with my 23kW of inverters, saw pretty large swings.
How many uF at 48V do you think it takes to supply a half cycle of 6kW, while only drooping say 2V?

If a HF switcher boosted to say 340V (rather than just 170V peak of 120 VAC), then it could droop in half and give up 75% of its stored energy.


Big xenon flash lamps, huh? Are those for lasers? What are those used for?
 
I agree, the caps are drooping, but combined with the direct battery connection, the current is there. The HF booster making say 400 volts peak to peak to drive the PWM sine wave generator does operate at less current, but then the boost switcher needs to transfer the power, it is not just THERE in the battery voltage buss.

Actually continuous lit 2,000 to 7,000 watt xenon bulbs to light projectors for film and even digital projectors in cinemas. I also helped service an older 60 foot high Imax film screen, that used a water cooled 15,000 watt xenon bulb. That sucker runs at 400 amps at 37.5 volts. Here are the bulbs used in the common digital cinema projectors.

 
Not that it's unsafe, just a new requirement for lower voltage within the array. Earlier regulation allowed array to have high voltage, just disconnect from wires so outside array was safe.

The installation wouldn't really be more difficult. You screw a box to PV panel frame and plug MC cables into it. But it adds $35 maybe $50 per panel, so string inverter loses much of its cost advantage over microinverters.

A rule requiring voltage under 30V or something like that was considered. Only "12V" panels are that low. 80V at least allows Voc of a single large panel.
Maybe these questions are off topic. But I’m on a need to know basis.. the plan is to use a delta h6 inverter and the inverter itself says it has RSD capability. Could I use the Tigo boxes mentioned?
I am a bit torn on my planned DC array. I want to use 60 cell panels, but then I run 3 in series to the 150 volt MPPT controller. 2 panels in full sun just exceeds the 80 volt limit, so I need a separate RSD on all 9 panels. Might be able to use 3 of the dual panel boxes, and then 3 more single panel ones. That adds up. If I go with 72 cell panels, I would only use 6 panels, I'll be down a little on power, but I could use just 3 of the dual panel RSD boxes. The Tigo RSD only units are not crazy expensive though. The dual panel units are $47.50 USD each, and the single panel version is $32.58 each. Then I just need one signal injector and power supply to activate them. The complete kit is about $160 with a nice weather tight box. Schneider makes their own Tigo compatible RSD transmitter, but they want over $600 for it. It looks like most of these are using the "Sun Spec" signal. It seems to just be a high frequency current wave imposed on the DC cables. If it sees the signal, it closes the switch for the panel to feed the system. If the signal drop out for any reason, the panel level boxes shut off the voltage out of the panels. Most of the other systems are quite a bit more expensive.
 
Maybe these questions are off topic. But I’m on a need to know basis.. the plan is to use a delta h6 inverter and the inverter itself says it has RSD capability. Could I use the Tigo boxes mentioned?

SunSpec is a standard followed by many RSD and inverters. But it isn't the only way. You need to read specs for yours and see.

 
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