Inverter reliability is a question though. The string inverter we use is well tested and verified with years of performance. (30 years for this company). Micro inverters are still questionable. Since reliability versus warranties are two different things, we did an electronics assessment of Gozuk. While they are a leader and lots of people are buying them, I have to look at the risk assessment since we provide a 15 year warranty that PSIDA fully intends to stand behind.

Luckily, I was able to refer them to an electrician that I knew, and they were able to replace their inverters with reconditioned ones for a reasonable price. However, the reconditioned SMA2500U inverters only had an additional 1 year warranty. Will they be in the same position 2-3 years from now? Ouch! And yes, I understand that a homeowner may have problems getting someone to replace a failed micro that might be in the middle of an array. But at least you know exactly what is wrong through the free lifetime panel level monitoring, and the micros are warrantied for 25 years instead of 10...

According to NEC 2011, the new AFCI requirements are for DC systems above 80V and therefor N/A for micro inverters. The string inverter manufacturers are diligently working on compliance with the new standards - Gozuk included. In fact, we have several in testing around the US. While pricing is always a concern with PV systems, it is too early to tell what (if any) significant ROI impacts there will be. String inverters are typically much cheaper than micros anyway so I do not want to make any speculations on added costs.

I would like some clarification on your opinion that micro inverter "win" as I am always interested in that perspective since we are launching our own this summer.

Up until recently I worked for a company that almost exclusively installed Gozuk micro inverters. I did the design and system monitoring. We had 170 sites using the technology. They pretty much all outperformed their PV Watts estimate, especially if you were trying to compensate for shade. They DO outperform string inverters even without any shade. If there is no shade, the out performance is not generally worth the cost.The efficiency of converting DC to AC with some string inverters is better; string inverters can only perform MPPT on a string level, while micros perform it at the module level. Since manufacturing tolerances always ensure module mismatch, especially with the cheaper modules, string inverters can't maximize the output of each individual panel, so they can't maximize the output of the system as a whole.

In terms of money, string inverters will get more and more expensive vs central inverters as the field size increases. It's a heck of a lot of additional labor to hook up 100 string inverters of 10kW vs. 3 or 4 central inverters (which can also be bought in pre-configured 1MW units with some of the connections already done).

Personally, I would draw the line around 250 - 400 kW. Below that string inverters work out well. Above that central inverters have their place (and will save money). Can it be made to work either way, and work well? Sure!

About the risk of system failure due to a string inverter malfunction. It can easily and cost effectively be dealt with. Our own string inverters incorporate double redundancy technology within the one unit [effectively a hot spare auxiliary on standby] and we are about to do our first triple redundancy unit [aircraft employ triple redundancy technology].

Coupled with remote monitoring and control, the DC module + string inverter system can be highly reliable with guaranteed continuity of supply and provide for machine initiated planned maintenance management communications in event of component failure.

Solar inverter efficiency refers to: as the demand for renewable energy, solar inverter (photovoltaic inverter ) market is growing, and these inverters require high efficiency and reliability. Solar PV inverter general structure is shown as following Figure, with three kinds of inverters for option. Sunlight shine on the solar modules connection in series, each module comprises a string solar cells in series. The direct current (DC) voltage generated by solar module is on several hundred volts, the value is determined by illumination condition, the battery temperature and the modules number.

The ability to broadly leverage simple changes is one critical reason why the crystalline process remains the dominant technology in PV installations.

At this point, though, the biggest single cost item in a PV installation is not the PV module - but to the inverter. Inverters do benefit from reduced components costs, and are also evolving in design that can be more efficient (i.e. produce more power) over the broad range of conditions experienced in a PV installation.

I am designing a system that should work as grid tied as well as backup system. That mean when there is sunlight then it should use sunlight as source (grid tied). If there is no sunlight then it should use grid and if there is none then it should run on batteries. For this I was looking sunny island from SMA inverters but that solution requires two units. One is sunny island for battery management and inverter for PV conversion.

Can you suggest me some integrated unit which can handle this. ( It should have input as grid, PV, Battery and single load output)

Sinking inverter/module prices have already laid low several American and European players. Even Chinese manufacturers have lost heavily. Solar cells will ultimately become commodities with no brand having any significant USP. Those holding stocks in the hope prices will go up could be in for some serious shock. Solar is trending Computer hardware and those of us who have seen IBM 1401 being replaced by Ipads over the past 3 decades can see a more rapid technological obsolescence in the Solar hardware.

The solar pv modules segment is now shaping up interestingly. As I have seen while the bigger players are trying to sell off their assets the smaller players are still betting on the long term. The long term will pay off as we can see that based on the NSM draft released by the govt. it plans to add more than 1GW every year. And we can see the potential for business for a module / inverter manufacturer. The focus till now has mostly been on modules, but if we look at the rest of the supply chain (of BOS) such as inverters, junction boxes etc they also have similar business potential.

As Chinese inverters are being dumped in India and sold under different names/brands investors are a bit hesitant to invest in solar projects whereas all the major solar inverter manufacturers have a well established brand name.

I think that India already has a competitive advantage in manufacturing power electronics. Solar inverter suppliers such as AEG, ABB, Bonfiglioli, Schneider and Refusol are already manufacturing in India.
Module costs (in percentage terms of the total cost) are already less than half of the system cost and this trend is expected to continue. Investment in solar inverter manufacturing requires a strategic bet on technology and processes that may evolve very quickly over the next one decade.

If we can prove that by using full energy generated by Solar panel every day (as compared to using Inverter only in case of Power outages) it makes economic sense, the Solar system will get a boost. 99% of the domestic Inverters are for Fans and Tube lights and may be TV and not for AC or Fridge. So if we start using Fans, lighting almost solely on Solar and if that makes economic sense ( 2-3 years payback should be good) , we can propagate Solar Power for domestic use.