Where can you get the HRSD-2C devices? What do they cost? My web search was unable to find that information.
Curious if they are meaningfully cheaper than the Tigo TS4-A-2F (~$46) since they seem to be similar if not identical in function.
Mike C.
Hoymiles HYS-7.6LV-USG1 Hybrid Inverter
- Thread starter ncsolarelectric
- Start date
Curious if they are meaningfully cheaper than the Tigo TS4-A-2F (~$46) since they seem to be similar if not identical in function.
Mike C.
ncsolarelectric
Engineering Support CEO
They're about the same price for the HRSD-2C-B devices, maybe save a buck or three if you want to buy in bulk. I prefer to sell my customers the microinverters and AC couple the battery inverter. Hoymiles has a new HAS-11.5LV-USG1 inverter that AC couples with their microinverters. It's compliant with rapid shutdown and provides individual MPPTs for every panel.
Where can you get HSRD-2C devices and what do they cost?
My issue with that is microinverter clipping and losses. It is more efficient to DC couple PV to battery which matters a lot in grid down situations. Also, microinverters tend to cost a lot to deploy since there is one pre panel.
Where to get and how much?
The DS doesn't list efficiency from PV to grid, PV to battery, etc. Makes me concerned those are not very good.
They claim under 10 ms switching from grid to battery. Have you personally tested this? If so, a video showing the system behavior on grid failure would be instructive. Ideally this is done with no PV input (night time) for a worst case.
Mike C.
zanydroid
Solar Wizard
Ncsolarelectric is one of the handful of distributors so you could frame the question as availability from him.
Those two would be addressed by a AC to battery efficiency which is not in the data sheet. I pencil in 90% when I guesstimate AC coupling; it would be better to a HV battery
Also AC coupled solutions need to be compared to other AC coupled solutions in efficiency, when used in retrofit.
You previously had a concern about clipping. Hoymiles oversizes their microinverters so they don’t clip (500W per channel). On their 4:1 microinverters they do still cost a healthy chunk above RSD. Personally I think their products are great for odd size roof planes and shading
zanydroid
Solar Wizard
I hadn’t noticed the 95% efficiency for a 48V system, that is pretty good if it can sustain it across enough power output levels. Is this rating standardized? It isn’t labeled as CEC etc in this spec sheet (not that I know what duty level CEC tests batteries at).
Do you have info on when it might be available? Do they have an easy to use website on the battery partners for 48V system (so I don’t have to go back and search your old threads for who those are).
The spec sheet feels quirky in some places, I hope it gets revised. For instance it expresses surge only in VA terms, perhaps this implies that there is a DC limit on power plus headroom for VA surges if the DC limit is respected.
They also have a weird maximum AC input power rating. Is this bypass?
They provided further details privately. The conclusion was the pricing of the Hoymiles HSRD-2C devices was not materially different than the commonly available and seemingly equivalent Tigo TS4-A-2F devices. I dislike the RSD requirements, so anything I can do to reduce the cost impact of them is worth looking into. The UL 3741 change will basically eliminate them for the most part, but timing is such that code and vendors have not caught up to that yet, sadly.
For new installs, it is fair to compare DC versus AC. From my perspective, DC coupled is going to be more efficient since PV to battery has no unnecessary mid path conversion to and from AC produced by micro inverters. So your energy in the battery gets there with much higher efficiency. The battery to load/grid will be the same for both systems, so overall PV to battery to load is better on DC coupled. This is not news.
An AC system with battery means you buy two inverters, the array of micro inverters on the panels, and then another one that is battery to load/grid. The Enphase battery system even uses plugged in micro inverters to make that explicit. A DC coupled system only has one inverter, PV and/or battery to load/grid.
Their micro inverters do seem generously rated. Hopefully this doesn't impact their efficiency at partial loads too much.
When I pencil out the systems I am considering, DC coupled string inverters win on cost and efficiency. Long term, a string inverter inside the building seems like it will last longer than the extreme temperature cycling of the micro inverters on the roof. The go from the cold of night to the baking heat of full sun under a hot solar panel and that temperature cycling wears out electronics.
Mike C.
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zanydroid
Solar Wizard
Not surprised... these things are pretty commodity, and there's only so cheap you can make semi-active electronics that supposedly can survive 25 years and need to "embody" the cost of future warranty support.
Sure, I agree with this.
I wouldn't necessarily call going from 95% (string) -> 90% (microinverter with extra conversion) "much worse". I'm personally more concerned with the increase in control complexity (especially cross vendor). Once the system reaches high SoC an off-grid DC coupled system will be able to harvest more, than an AC coupled system. Now, for a system that's primarily on-grid, this isn't really a big deal, they're probably pretty close.
If you are willing to put in the design time for a complex scenario, or know you are in a simple scenario, then there isn't that big a win for using microinverters.
If there is a small roof plane, or some part of the layout that would require going to the next level of design software/simulation to validate if used with string (to make sure no pathological case occurs in practice), then the extra $80 or so for the "redundant" microinverters power conversion (transistors, capacitors, etc) may be worth it.
Regarding serviceability of microinverters / other MLPE, IMO once you go to multi-port microinverters you might as well consider putting them in serviceable locations, since you anyway need extension jumpers for some of the panels. (Might as well put them in on all panels). On my installation with Hoymiles microinverters I have very few inverters that require pulling off more than one panel to access.
For single port microinverters and RSD this may well be a big increase in wiring complexity.
They have a different design & marketing philosophy from Enphase. Hoymiles believes in go big or go home, and adds some really chonky heat sinks/metal chassis to help with this.
Enphase tries to sell you on accepting overpaneling. And I think sometimes their spec sheet even highlights the VA vs W to make it look 5% better, LOL. Don't know if it's intentional or not.
zanydroid
Solar Wizard
(Hmm, I think RSDs can work with just transistors, basically they're SSRs with a very low output buck circuit when in shutdown mode. Since they don't need big capacitors like optimizers or microinverters maybe they really can last a lot longer like a lot of people claim. Not sure what kind of capacitors MLPEs tend to use, electrolytics would probably need special construction to avoid "boiling" off really quickly)
ncsolarelectric
Engineering Support CEO
All good information. Thank you. A few things I'd like to point out about having a single string inverter vs microinverters + AC coupled inverter.
1. You're right. Whatever efficiency the battery charger has will be 3% to 3.5% lower when switching from PV to AC to DC. However, this configuration with Hoymiles' inverters has maximum redundancy with minimum components. I like redundancy! I come from the UPS Market, where critical computer loads require 99.999% uptime, guaranteed.
2. A single-string inverter can fail ("cough" SolarEdge), and replacing it can take days, weeks, or more. If it's down for more than 10 days, then that 3% efficiency gain is lost for the whole year.
3. With these microinverters, if one fails (None have failed yet for any of my customers!), the rest keep right on working, and if the AC-coupled battery inverter fails, the micros don't care and keep right on producing.
4. Since there are no PV connections to the AC-coupled inverter, if it does fail, it's less laborious and less dangerous to replace.
5. The system does not contain HVDC, making it great for DIYers who are still learning about electricity, and is much less prone to ground faults starting fires.
6. Installing microinverters allows the cash-strapped DIYer to do the project in phases. Go grid-tied first because it costs less, and then add the AC-coupled inverter and batteries later without going back on the roof.
I used to design giant utility-scale systems, where every fraction of a percent of efficiency mattered. On residential-scale systems, IMO, the difference of a few percent is not a big deal if it means greater reliability and less downtime. Downtime due to a single central or string inverter failure is always unexpected and costly.
I don't see too many Hoymiles being sold by many vendors, so availability of those devices may not be immediate either.
If you use one of the 4 MPPT units (maybe we should call those "milli inverters"?), it does take out 4 panels.
For what I save in equipment cost, I can have a spare inverter if the criticality of the uptime is that severe. It usually isn't.
But it is on the roof, which is vastly more dangerous work environment than the wiring closet inside the building. Depending on roof pitch, it can be quite treacherous to work up there, like with steep metal roofs. And it causes roof damage to have traffic up there (like my parent's tile roof, the fewer times we have people walk on it, the better).
240 VAC can kill you. The panel connectors are good about keeping you away from the conductors.
But makes the overall system cost higher in the end.
String inverters are inexpensive, like the Growatt 11.4 KW unit for $1500. That is less than 4 of the quad micro inverters which support 16 panels. It has 4 MPPT inputs, so you can some redundancy in panel strings, and hook up a huge number of panels to it.
I wonder how many micro inverter owners have one or more out and don't know it.
Ultimately, this is a "tastes great" versus "less filling" type of thing. The two architectures have their benefits and they will continue to be choices for the foreseeable future. For a difficult install with shaping, angles, etc, micro inverters are probably a good choice since you need to optimize every panel separately. For a wide open no shade array, not so much.
When UL 3741 becomes mainstream and we no longer need per panel RSD, the micro inverters will lose that benefit (or more precisely, the string inverters will lose that penalty). One RSD per string and simplified wiring will be wonderful.
Mike C.