Microinverters Are Changing How Grid-Tie Solar Systems Work
Single points of failure can plague a home solar system with a central inverter.
Think of a centralized solar system as a string of Christmas lights run in series. If one bulb goes out, the rest go with it. Even shading a portion of one panel in an array can drag the entire array’s energy harvest down. Enphase Energy has laid claim to being the first to produce a microinverter system available for commercial or residential applications. According to a friend of mine in the solar industry, “[Enphase Microinverter systems] are taking the solar world by storm.”
Microinverters reduce the bulk, space and noise of traditional inverters. A microinverter mounts below each PV panel, converts that panel’s DC current to AC and then ties directly into the existing wiring and power panel of the house. This saves the expense of heavy gauge copper wire, as well as the task of running it to your garage (or other centralized location) from the PV array. At a few dollars per foot, that wire amounts to a lot of money in labor and material.
According to the Enphase Energy website, their microinverter can boost performance of PV panels by 5%-25%. The benefit of one inverter per PV panel is the continued production of individual panels, even if one panel of the array is shaded or damaged. In traditional arrays where all the panels are tied together, the least efficient panel drags the rest to its level.
Microinverters reduce the chances of total system failure significantly by isolating the system’s components. Enphase also claims that if a single inverter goes out, repairs can wait until routine maintenance is necessary, which saves the homeowner a lot of pulled hair in the end.
Detractors say that the inverter is the most likely piece of equipment to fail (next to batteries if you are thinking of an off-grid application). They argue that increasing the number of inverters could lead to increased expenses in system maintenance for a homeowner. To help limit premature failure, check if the product you are thinking of purchasing has met Highly Accelerated Life Testing (HALT) and Highly Accelerated Stress Screening (HASS) testing standards. Enphase’s microinverter has passed this testing.
Watch the Enphase presentation about their microinverter system.
Or you can come back here. There will be more said about this exciting new development of the solar world in coming blogs.
Posted on October 7th in Solar Electric by Craig.
October 9th, 2009 at 10:36 am
Wow…..I loved reading this. I am passionate about solar power and this development sounds fantastic.
If the micro inverter can boost the performance of a photovoltaic panel by up to 25% as claimed, surely this has the potential to bring down the price of mid sized domestic units – This has to be a good thing if it encourages more people to install the technology.
February 16th, 2010 at 5:45 pm
Read the claims carefully. 25% improvement if one of the panels of a string is shaded. No shade during prime solar hours, then little need for micro-inverters.
Second issue is changing these out when they reach end of life. Dismantling the array one panel at a time will be very costly.
real solution is to build the inverter function into the panels directly.
February 20th, 2010 at 12:31 pm
Those are good points Solar Installer. It is always good to do a lot more research than buying when it comes to major investments like going solar. I wonder if there is any way for the micro inverter to be mounted in a more accessible area other than the back side of the panel? That would solve that particular issue. Maybe in the future this will be one of the bugs that gets ironed out of this new technology.
Thanks for your (and everyone’s) input. We love to know you’re reading. Even more than that, we love to learn from you.
April 25th, 2010 at 8:46 pm
Home Depot has started offering “solar in a Box Systems” in DFW. These are dual solar panels with the micro-inverters built-in from SunPhase.
August 8th, 2010 at 7:45 pm
Very misleading introduction to this article. Today’s top pv modules have a by-pass diode that will drop a panel from the string’s production once that panel’s output drops below a manufacturer’s programmed percentage. If only one cell in the panel is shaded the ouput of the string is reduced very minimally. If an effective shade analysis is applied to the layout then the shade should be only occuring temporarily during sun hours and will have a minimal impact on the total daily kwh. If there is long-term shading on a panel, even with a micro-inverter, where’s the beneficial R.O.I. justification? If the system doesn’t have multiple strings (central inverters can handle up to 12-14 panels on one string) then the effect of a shaded panel is even less.
With regard to wiring; ac wiring still has to be ran from the combiner box on the roof to the service panel and a larger gauge wire allows less line loss because the electricity travels on the outside of the wire so the larger surface provides more efficiency. The wire must still be protected by EMT conduit same as the dc wiring.
With regard to noise from a central inverter; have yet to experience this from SMA, Fronius or PV Powered inverters.
What’s curious to me is that all of the aforementioned inverter manufacturers are in the inverter business, have the engineers, have the distribution network…why haven’t they introduced a line of micro-inverters if these are truly the “way of the future”? And, why would anyone in solar keep buying central inverters if the micro-inverter is the “silver bullet” for kwh output?
I’m a proponent of new and improving technology, but there is a risk to deploying hundreds of these or any other until they have sufficient “in the field” exposure.