Combining MicroInverters and String Inverters

[Siwastaja]

open modbus protocol on the inverter to read out data

To be fair, this seems to be standard feature on every random Chinese inverter these days. Sometimes with a bit of trouble finding the correct document with Google - e.g. Sofarsolar has at least three different interface specifications with no documentation to which model numbers they apply -, but you can always do it.

[nctnico]

I spend more money than necessary in other areas of life and derive pleasure from the extra expense so if people want to pay too much for DC optimisers or microinverters and feel good about it then so be it.

Of course but people should have access to the information and know what they are doing. Pay premium for premium features that actually do what is promised. We (as a player on the smart energy business) have seen aggressive microinverter sales companies who sell FUD (false claims about others) and false promises of their own systems.

I would like to see microinverter systems evolve and gain real traction on the market through real advantages but currently it seems they are falling behind in the competition, i.e. quality is going down (e.g., they have no resources to update their product lines for new higher-power panels -> hence they clip power, totally unacceptable!), while competion is going forward (string inverters having more and more MPPT inputs, smaller start/minimum voltages, battery option for very little extra cost, better efficiency...

I hate to see it when the underdogs don't get their shit together but instead start to play dirty. FUD and lying in marketing are reasons alone I will not recommend microinverters to anyone. If a fresh new player who does something new on the field pops up I'm super happy to change my mind.

I don't see microinverters ever becoming a viable option from a financial standpoint. Having a single unit (=string inverter) doing the job of 20 seperate units is always going to be cheaper due to manufacturing, maintenance and handling costs alone.

From what I've read from Enphase, getting a system running requires a lot of fiddling with software, registering online, etc, etc. They should drop all that crap and make their system work out of the box. Plug & play. That alone would save a lot on installation and maintenance costs. Nobody cares about monitoring.

[Siwastaja]

I don't see microinverters ever becoming a viable option from a financial standpoint.

I believe it could be possible but it requires a different mindset. I.e., they should be solving problems, not adding them. They concentrate on a few made-up/exaggerated problems and forget all the rest.

But there is room for improvements. E.g. DC cabling between panel and inverter. DC connector mess with MC4 and compatibles. Microinverters do not even try to do aynthing about this. You still wire the panels to the inverters. Shorter wires, yes. Still wires. Still connectors. Still authorities saying you must match the connector brands. How the fuck you are supposed to do that, buy Enphase branded MC4 connectors, strip off the existing connectors from panel stubs and re-crimp the Enphase MC4 connectors? At least on a string inverter you have much fewer connectors to crimp.

No, microinverters would need to integrate into the panel itself, to create an AC panel. Then it needs a well designed weather sealed AC plug system. Just like MC4, but single plug for L,N,PE. Then add a reliable and problem-free power line communication or wireless system. Engineer it all top-notch reliability, but also engineer it for low cost (increasing NRE to decrease unit cost), and then apply economy of scales to bring the final product price down. Which is chicken-and-egg, you need money upfront for all that work.

And do all of the above really well, there is not much room for error because competition from normal string inverters is harsh, and optimizers cater pretty well for those who want to improve trackability of panels + partial shaded production.

[nctnico]

That sounds like integrated solar panels to me 
It could be worthwhile but the major problem is that it will take time for the technology to mature and builders & architects to embrace this technology. IMHO even the retrofitted solar panels aren't mature technology at this point. The whole issue with non-compatible MC4 connectors blew my mind. I also think the panels are too big too handle safely and make a system harder to install than it should be. Needing to bolt the panels down is also not convenient. Especially when you need to take a single panel out. Some kind of click / lock system would be much better for maintenance but it would have to be an industry standard.

[tszaboo]

That sounds like integrated solar panels to me 
It could be worthwhile but the major problem is that it will take time for the technology to mature and builders & architects to embrace this technology. IMHO even the retrofitted solar panels aren't mature technology at this point. The whole issue with non-compatible MC4 connectors blew my mind. I also think the panels are too big too handle safely and make a system harder to install than it should be. Needing to bolt the panels down is also not convenient. Especially when you need to take a single panel out. Some kind of click / lock system would be much better for maintenance but it would have to be an industry standard.

If you had a professional installer, two guys can place an entire installation in like 3 hours.
Its really not big of a deal.

[nctnico]

That sounds like integrated solar panels to me 
It could be worthwhile but the major problem is that it will take time for the technology to mature and builders & architects to embrace this technology. IMHO even the retrofitted solar panels aren't mature technology at this point. The whole issue with non-compatible MC4 connectors blew my mind. I also think the panels are too big too handle safely and make a system harder to install than it should be. Needing to bolt the panels down is also not convenient. Especially when you need to take a single panel out. Some kind of click / lock system would be much better for maintenance but it would have to be an industry standard.

If you had a professional installer, two guys can place an entire installation in like 3 hours.
Its really not big of a deal.

Have you ever seen those 'professional' installers use any kind of safety gear? Most (if not all) don't because handling a big panel while being strapped in a safety harness doesn't go together so well. And wait until the wind picks up... I'm very sure professional installers would like smaller panels instead of larger. Keep in mind roof tiles are typically about 35x35cm; that is not some random coincidence. If it where more practical to make these larger, they would have been larger.

[Siwastaja]

If you had a professional installer, two guys can place an entire installation in like 3 hours.
Its really not big of a deal.

This is true, that's why I'm saying current situation is good enough so that competing against it will be tough.

Current systems are not ideal from reasons nctnico points out but popularity and competition has wed out inefficient install companies and forced those who want to remain in the market to invent efficient processes and deal with the details. Professionals can do two domestic install sites per day, so 10 install a week. Maybe installs could be made 5% faster and 50% simpler to learn but simplicity does not matter to professionals who do this and only this every day, and 5% faster is still the same 10 installs a week.

[nctnico]

If you had a professional installer, two guys can place an entire installation in like 3 hours.
Its really not big of a deal.

This is true, that's why I'm saying current situation is good enough so that competing against it will be tough.

Current systems are not ideal from reasons nctnico points out but popularity and competition has wed out inefficient install companies and forced those who want to remain in the market to invent efficient processes and deal with the details. Professionals can do two domestic install sites per day, so 10 install a week. Maybe installs could be made 5% faster and 50% simpler to learn but simplicity does not matter to professionals who do this and only this every day, and 5% faster is still the same 10 installs a week.

No. You are overlooking that the majority of the installers who do 10 installs a week do not adhere to work safety regulations at all. If you want to see acrobats without a safety net, go watch solar panel installers. Evel Knievel wouldn't do such crap if he where still alive. Needless to say this is not viable a long term  situation either through fines or Darwin awards. The proper installers either use safety harnesses or use scaffolding (which is more convenient). But they won't be doing 2 installs are day because dealing with the scaffolding alone takes a couple of hours by itself. IOW: if you want to make a more competitive solar panel solution, a good long term strategy is to create a system which is also safer to install.

[Siwastaja]

No. You are overlooking that the majority of the installers who do 10 installs a week do not adhere to work safety regulations at all. If you want to see acrobats without a safety net, go watch solar panel installers. Evel Knievel wouldn't do such crap if he where still alive. Needless to say this is not viable a long term  situation either through fines or Darwin awards. The proper installers either use safety harnesses or use scaffolding (which is more convenient). But they won't be doing 2 installs are day because dealing with the scaffolding alone takes a couple of hours by itself. IOW: if you want to make a more competitive solar panel solution, a good long term strategy is to create a system which is also safer to install.

I would want to agree with you, but it seems the current system is working, from the fact this has been going on for years and years. So it's probably more sustainable than you think. Just like it's a compromise on every other respect, it's also a compromise on worker safety. Clearly laws and regulations are ignored. Yet surprisingly few people actually die doing that. Go figure.

[nctnico]

True, but it leaves room for a manufacturer to create a demand for safer to install solar panels by swaying public opinion. In the NL the government is actively going after solar panel installers who work unsafe BTW as there are several lethal accidents each year and many more accidents with serious injuries. IMHO just leaving the situation as-is because only a few people die (or get seriously injured) is NOT acceptable. Especially if it is just to make a few bucks extra.

[Siwastaja]

Well, that's also one reason why I believe alternatives will have a chance. But they need to hit the nail in many respects simultaneously. Not introduce new problems; solve enough of the old. And bootstrap the market from scratch with massive investments so they can be affordable from day one to buy. Not an easy task.

Microinverters are crap because they introduce more new problems than they solve:
* More DC-to-DC connector interfaces
* Having to do both AC and DC connection
* Having to mount and wire up 20 inverters instead of 1
* Track record of reliability issues due to placement of inverters
* Worse production under some conditions, due to
  * Worse efficiency
  * Clipping of peak production power because of slow response to the market increasing panel power
* Higher idle consumption
* Possibly a dangerous product which does not have the mandated grid isolation relays due to cost optimization done in desperation by dying manufacturer

What problems do they solve?
* Increase in production under some other conditions
* Per-panel data for troubleshooting
* Wiring on the roof is AC instead of DC