Solar Central Grid Tie Inverters vs Microinverters – Advantages and Disadvantages

Solar Microinverters have opened an entire new category in the traditional Solar Inverter Industry threatening the business model of the incumbent companies which have seen spectacular growth in recent years.Solar Inverter Manufacturers have enjoyed enviable growth of more than 50% CAGR to become a $5 billion industry in 2010.However this industry faces competition from a host of new tiny competitors led by Enphase Energy who claim to reduce costs,increase reliability and add monitory plus flexibility as compared to String Inverters.The threat is the most in residential and commercial solar installations where the advantages of solar micro inverters are more pronounced than in utility applications.Solar EPC Companies in the USA have started adopting this new product though the growing size of the Solar Inverter Industry has managed to temporarily lower the thread.SMA Solar,the biggest solar inverter company in the world recently bought a couple of firms like OKE Services to increase its presence in distributed electronics for the solar panel industry.Here is a list of advantages and disadvantages of Central Inverters and Microinverters.

Pros of Microinverters compared to String Inverters

1. Reliability and Longer Life  – Micoinverters are more Reliable as the failure of a single piece affects only that solar panel and not the whole solar array of solar panels in case of Solar Inverters.Also the Mean Life of Solar Inverters are much more than the life of the Solar Panels compared to the 5-10 year life of String Inverters which have to be replaced.
2. Productivity – Microinverters claim to have 5-25% more power production from solar panels as they manage to maximixe the power production from each solar panel (MPTT) compared to string inverters which MPTT the whole solar array.Microinverters give more accuracy  If a single panel is operating at a different point, a string inverter can only see the overall change, and will move the MPPT point to match. Shading of as little as 9% of the entire surface array of a PV system can, in some circumstances, lead to a system-wide power loss of as much as 54%
3. Ease of Installation – Installing Solar Panels with Microinverters is easier and faster and leads to lower costs compared to Solar Inverters though there is still some dispute on this.
4. Flexibility – Another benefit of the distributed microinverter design is the potential for installations to be expanded over time. An initial set of solar modules can be installed and additional modules added as needs and budgets grow without requiring the replacement of a large centralized inverter.
5. Reduction in Lifecycle Costs – Installers are no longer limited by string design, marginal designs, co-planarity, and matched modules. Microinverters  reduce wiring time, and remove the need for DC switching points.
6. Space and Heat of String Inverters – String Inverters occupy more space (though not a big problem) and generate a lot of heat which has to be cooled by used fans.
7. Higher Power Inverters have to be used – Because of the limited range of power rated inverters availabe,solar panels have to generally use power inverters of greater size for eg. 800 W of Solar Panels will have to use 1 KW solar inverters wasting the 200 W

Disadvantages of Microinverters compared to String Inverters

1) Cost – Traditional Inverters cost between 35-50c/watt depending on the size,technology,brand etc. while microinverters typciall cost between 75-90c/watt again depending on brand,market etc.This is the biggest disadvantage of microinverter compared to solar inverters

2) Placement of Microinverters – Microinverters are place on the rack below the solar modules.This is said to cause problems as it is placed on the hottest part of the solar system and could lead to problems in case of high insolation areas

3) Not useful in utility solar power plants – Solar Power Plants of more than 1 MW in size have not used microinverters as microinverters are more useful in power plants of smaller size where maximum power is needed and where there are problems of shading,debris etc.Also monitoring of small power plants is difficult.