The Micro inverter Is New Technology. Should You Buy It?
The micro inverter is a hot new trend in solar power modules. Some day, they will probably be used in most PV systems, and be the norm rather than the exception. But as of right now, they are high risk and unreliable. They work like this. Every PF panel is fitted with its own micro inverter, the output of the panel is AC, just like your household power and that of the electrical grid. Therefore the amount of these mini inverters is equal to the total number of PV panels.
Each of these mini-mites delivers its very own AC power, and all the micro inverters in the panels must match each other in wave form and wavelength to work properly. This is a super difficult arrangement electrically, and a special electrical box needs to be added very close to the PV panels. The AC power from the inverter channels through this collector box where it is combined into one channel and routed in a more traditional manner to your main power meter or fuse box.
That is the hard part, but the good thing about micro-inverters is their simpler design. They also need no complex calculations to hook up, and there is no DC to AC transfer to deal with. Also, panel types can easily be switched out and mixed. One really odd side-effect that is positive; shade does not affect the overall PF system as harshly.
When one panel is shaded, it’s no big deal since the other micro inverters are producing at full power. So if your project is going to deal with lots of shade, the inverter is the way you want to configure your system. And if one panel dies, quits, or is damaged, you only lose that panel, not the whole system.
Having said that, the technology is day-old-new. That means waiting a while to get more results and input as every new purchaser is basically a solar guinea pig at this point. And like all new technology, micro-inverters are expensive right now. You will spend about $0.40 more per watt of energy production, and in a common 4,000 watt system, that means $1,600. However, in a really shady application, you could have that back in a year or two.
Some specifications to keep in mind:
CEC Rated Power output – this number is the max wattage output you can get, and is variable according to operating temperature.
Maximum Power Point Tracking (MPPT) range – these circuits allow the micro inverter to maximize their efficiency, and produce the highest amount of power possible in a 24 hour period.
Maximum recommended PV input power – this is never to be exceeded, and is the number for all the panels combined. If this number is surpassed by all the panels in combination, inefficiency reigns, and you have a “clipped” circuit. Basically, micro inverters must be married to each panel correctly, and you can ensure proper model structure by comparing PV watts of your inverter in comparison with the array you are building.
PV Start Voltage – This is the PV level that needs to be reached to start your system. As soon as the first ray of light hits any panel, it begins to output power, but an inverter needs a certain level to be reached before they will start transferring power out. Obviously, you want your system outputting power to your grid as soon as possible, and to run all day.
Overall, if you had to judge an inverter by one characteristic, it would be efficiency. Manufacturers only report numbers of peak efficiency when the system is running perfectly. Before you choose, look at the efficiency range over a wide spectrum of diverse conditions, and judge output load, temperature range, input power and other rigrid traits. This will ensure you get the best micro inverter overall.