Posting in Design
Microinverters -- a new techie spin on the traditional solar inverter -- are popping up with increasingly regularity and have been embraced by some powerful industry players including SunPower Corp.
OK, maybe it's not quite an invasion. But microinverters -- a new techie spin on the traditional solar inverter that converts direct current into alternating current for the grid -- are popping up with increasingly regularity and have been embraced by some powerful industry players including SunPower.
Solar installations typically have a large central inverter that takes the direct current generated by a group of panels and converts it into AC for the electrical grid. Microinverters function essentially the same way but are placed on each solar panel (see photo), which has some distinct advantages over central inverters. Microinverters make a rooftop or large commercial installation more efficient. They also make it easier to monitor power generation of each panel and quickly pinpoint a failure in the system. The idea is the added expense of the microinverter is offset by the savings created by increased efficiency and lower maintenance costs.
The number of microinverter solar products and partnerships that have been unveiled in recent weeks indicates the industry is paying attention and beginning to invest in technological innovation beyond the panel itself.
A few of recent microinverter developments
SunPower announced Monday that it was launching a series of AC solar panels. The microinverters, made by startup SolarBridge, are embedded into the panel at the factory. Microinverter leader Enphase Energy , which takes a different approach by selling their units directly to solar installers and system manufacturers, recently partnered with Hanwha Solar One, which will add the microinverter to its modules.
Earlier this month, Upsolar unveiled an AC module that features Enphase's microinverter and uses a mounting and grounding system from Zep Solar. The logical next step of this arrangement -- a microninverter designed to be compatible with any Zep Solar mounting and grounding system -- was announced today at the Solar Power International conference currently underway in Dallas.
Photo: Enphase Energy
Oct 18, 2011
solareye must be working for SolarEdge or some competitor. I am an Electronic engineer and find his comments show an anti-micro inverter bias. I don't work for a solar company. 1 and 6. These inverters are not in any more hostile environment than a wall-mounted inverter that is in full sun exposure. In fact, these micros are shaded under the panels, and are fairly free from water due to the panel above, and careful sealing. Mounted correctly, they get airflow top and bottom, from roof air convection and wind. Not the hostile environment described, unless the panel is not given sufficient clearance as recommended. 4 to 6 inches from panel to roof gives sufficient airflow. Micros produce very little heat, a 6x6" box and a few watts, mounted with space under a panel do not dramatically increase heat- a few degrees maximum. Remember, its only a few % of the panel's output, not a few% of 30 or 40 panel's output that is waste heat in each micro. 2 and 7. Lower efficiency rating- give me a break! This is nit-picking. He quotes SolarEdge at 98.3% peak, EnerPhase claims 96.3%. What he does not say is that the individual MPPT trackers in EVERY micro gives up to 50% more power in some conditions of shading than a single inverter system does. He is missing the big picture- 50% energy not getting to the inverter in a series string is a tad more loss than a couple % of nearly unobtainable "peak" efficiency. Series string panels limit total energy due to shading, way more than micro inverter systems. Each Micro has its own individual MPPT control, adjusting for conditions on its single panel, not one MPPT adjustment for a dozen or more panels! Talk about nonsense! Electronic professionals (not salesmen like this guy) have been watching this trend for years and have given it accolades due too the redundant low-power approach, that encourages reliability. No single part failure to shut down the whole system, as is likely in the highly-stressed multi-kilowatt typical inverter. If a inverter or panel fails, it disconnects, and does nothing. Yes, the Enerphase M215 limits power to around 215-220 Watts output. You can expect a long time continuous power with 240-275 Watt panels before panel degradation happens, or you can get the minimal panel power and save a dollar or two. Reality is, a 250 watt panel rarely gives peak power output, due to sun angle mismatch, dirt, temperature, wire loss, etc. so oversizing ("rightsizing") panels rarely cause power limiting! OTOH, series strings are limited by the weakest panel in the string. Too bad. A typical 250Watt panel generate around 220 Watts in typical non-tracking configurations. solareye knows his technology "is on the way out" so he attacks micros. 3, 4, and 5. Far more expensive? the only difference is the inverter. Panel prices are market-driven. The M215 (the current production model) is around $148.00 each. The supposed "$400 to $500 per microinverter replacement" is a flat out "exaggeration." You can buy packages of panels and microinverters for about $1.80 to $2/Watt (less hardware, mounts, wiring). Difficulty of installation!? panels mount like panels. Plug in to the ac bus cable, the panel, and wire the bus to the to the service. How long does it take to plug in a plug!? If a failure occurs, you don't have do anything. Power output drops according to the failed inverter or panel. 1/32 power loss in a 32 panel system. When you feel like it, you call someone to replace the failed inverter. No emergency, no weekend calls. In a series system, when the inverter fails, the whole system goes down. Think about how much a 7kW inverter failing will "wipe out a micro inverter system owner's return on investment" as he claims? A $148.00 inverter and an hour of time vs an expensive 7Kw inverter and several hours of time (and total power shutdown). This guy is selling you a line. He clearly likes SolarEdge, which is an excellent product, BUT is not being unbiased as he tries to imply. His bias is clearly showing. From an electronic standpoint, the smaller inverters are more likely to last many years, due to the lowered component stress achievable. Go on their website- they have dozens of helpful articles and whitepapers addressing the many false attacks they receive from the entrenched single-inverter competitors. Don't listen to someone with this kind of bias!!!
1. Poorer reliability and shorter life: Micro inverters are mounted in the most hostile location possible. On your hot roof underneath your solar panels where there is limited airflow. This environment dramatically increases the stress to micro inverter components resulted in shorter lfe expectencies. 2. Poorer productivity: Micro inverters typically offer lower efficiency ratings or lower power ratings resulting in poorer energy harvest. 3. Difficulty of installation: Micro inverters involve far more expensive, complex, cabling and connection points resulting in far more time on the roof.. 4. Flexibility: Micro inverters score one point. Micro inverters can be installed in multiple orientations but SolarEdge offers this same flexibilty while offering much higher performance. 5. Increase in lifecycle costs: All inverters fail, micro inverters do not employ some sort of magic technology that makes them more reliable. Micro inverters won't all fail at the same time which will result dozens of service calls over the life of a typical micro inverter system. The micro inverter warranty does not pay for the labor of removing and replacing micro inverters so the customer will bear this expense. At $400 to $500 per micro inverter replacement, this will wipe out a micro inverter system owner's return on investment. 6. Increased heat underneath your solar panels: Micro inverters generate heat due to their lower efficiency. This heat will not only shorten the life of the micro inverter itself but may also decrease your solar panel's energy production due to the solar panel's temperature coefficient. Solar panels produce power from light not heat. In fact the hotter a solar panels gets, the poorer the solar panel will perform. 7. Loss of power output: Enphase's limited 215 watt rating can only output a maximum of 215 watts. So 250 watts in and only 215 watts out. Talk about wasted power. A much better solution than a micro inverter is SolarEdge which offers the highest efficiency rating on the market at 98.3 % peak, better shade mitigation, a high power rating, built in cabling at no addtional cost, built in Internet portal at no additional cost, built in arc fault protection and individual solar panel monitoring at a much lower price than a typical micro inverter system. Micro inverters are yesterday's technology and are on their way out.
Solar panels are inherently susceptible to shading because they are set up in series. What micro inverters do is isolate each panel from each other in the array. By doing this the micro inverters can use Maximum Power Point Tracking (MPPT) to improve the conversion efficiency and at the same time minimize the effects of shading. This is a great system, and the tracker shown in the picture (Sentinel Solar) is also a great unit. Many people use this micro inverter/tracker combination here in Ontario. Thanks to Ontario's microFIT program solar is not only feasible it is profitable. Solar Trader http://www.solartrader.ca
The process of inverting DC to AC has relative standard loss of efficiency per KWH converted, but there is also an inherent system unit loss of efficiency per inverter. Otherwise the micro-inverter technology would have to be inherently more efficient. As you say the technology is the same between micro and macro inverters. Assuming micro-inversion technology is equally efficient as standard macro-inverters - multiplying the inversion process with numerous micro-inverters and each's systemic inefficiencies - would logically and cumulatively increase the efficiency loss per micro converter used - making the micro-inversion process significantly less efficient than a single inverter's single system loss. So unless you have a significant economic advantage to micro-inverters - which isn't supported by limited details of the article, micro-inverters make no efficiency sense at all.
Now they need to be more consumer friendly and establish standard connectors and panel ratings for modular installations. That way panels from different manufacturers that are rated the same can be chained together making system expansion simple and affordable. The high upfront cost of solar makes affordable expansion attractive. Consumers could start with a system that decreases their grid power use in year 1, but with budgeted annual expansions they could be off the grid in a few years.
When talking solar power, efficiency and cost-effectiveness should be one of the top priorities. These are the two most frequently cited reasons why people don't "like" solar power. "It's doesn't generate that much energy and it's expensive!" Well, not anymore, there are so many solar companies sprouting recently. It only took so many crises to force us to switch to greener, cleaner options. Are there any other recent innovations that increase the cost-effectiveness and efficiency of panels that you know of? Juan Miguel Ruiz (Going Green) http://www.GreenJoyment.com
I have a business model to make all the monthly financed payments for the buyer of solar systems(alternative energy). Just in the process of searching for a partner to help me bring to fruition. Thomas firstname.lastname@example.org