Microinverter vs Conventional Inverter for roof top installations

[Ram S]

Dear Members,

Would like to have views on the below:

Will microinverters completely replace or take major share in roof top segment when compared to conventional inverters in the future?

Micro inverters are becoming more efficient, smaller, cheaper and with very long operating life and warranty. Do you think they will continue this way until completely replacing the inverters we know today? Can we point out the pros and cons of these devices when compared to the conventional inverters we find nowadays? Expected dates for the microinverter's "boom" into market? 

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Regards,
Ram Shirhatti

[ankush goel]

Dear Ram,

 

One of the benefits of Micro inverters that I have learned is that it eliminates the possibility of loss/reduction in efficiency of the entire array/plant because of the inefficiency/malfunctioning of any one particular panel. It should be noted that in any Solar panel or a system of say 10 panels if any one cell in the panel or any one panel in the array fails or under performs because of any particular reason, it would reduce the overall performace of the entire system proportionately to its own. Micro inverters overcome this problem by making every panel independent of the other. Another advantage is that since each panel is independently feeding power into the system, the solar panel system can be spread out over different areas of the roof or property and be made of different types of panels.

 

Regards

 

Ankush

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Regards,
Ram Shirhatti

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Regards

Ankush Goel

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[Ram S]

Dear Ankush,

Thanks for your views mentioning the positive aspects of the microinverters.

Some of the drawbacks:

The cost and hardware for installing one Micro Inverter is very expensive when compared to string inverters. Is there any Indian firm who manufactures microinverter ?

When considering for roof top grid interactive system higher wattage modules is required which favors string inverters, especially those with high voltage input that deliver better efficiency and lower installed costs. What is the maximum wattage available in market of microinverter ?

Regards,

Ram Shirhatti

Regards,
Ram Shirhatti

[Gaurav N]

Dear Ram,

The most important advantage is that each panel has its own MPP tracking device. This allows considerable saving in losses which occur due to shading especially in urban installations. This allows flexibility also in the installation, such as different panels having different orientation, etc (provides high system flexibility).

These days, micro inverters are coming at a competitive price and the direction for PV inverters is going in this direction. A lot of major inverter companies such as SMA and Schneider electric are looking into these products. However special safety requirements depending on the country may increase system price.

Here is a list of manufacturers  http://www.psma.com/sites/default/files/uploads/tech-forums-packaging/minutes/list-micro-inverter-manufacturers-rev-2.pdf 

Best Regards,

--

Gaurav Durasamy Nandakumar

M.Sc. Sustainable Energy Technology '10,

TU Delft

Mobile: +31634421717

Skype: gauravn.88

Alternate Email: g.d.nan...@student.tudelft.nl

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“It is better to conquer yourself than to win a thousand battles. Then the victory is yours. It cannot be taken from you, not by angels or by demons, heaven or hell.” 

- Gautama Buddha

[Ram S]

Dear Gaurav,

Thanks for giving the list.

Does any Indian manufacture have entered in making these ? Also, how much is the cost/watt of microinverter and maximum wattage ?

Regards,

Ram Shirhatti

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Regards,
Ram Shirhatti

[Gaurav N]

Dear Ram,

Up to my knowledge, I am not aware of any Indian manufacturer. With regards to wattage rating, there are micro-inverters ranging between 200 - 400W (maximum) . 300W is most commonly used however (this very much depends on the PV panel rating). You also have micro-inverters with or without a high freq. transformer (so the costs depend on this as well).

Best regards 

Gaurav

Gaurav Durasamy Nandakumar

M.Sc. SET '10,

[Ram S]

Dear Gaurav,

Thanks for the information.

Regards,

Ram Shirhatti

[squar...@gmail.com]

You can also check microchip site. They are supporting manufacturers with micro inverter designs and I had opportunity to test it in Pune. It has mppt with grid interest active system

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From: Gaurav N <gaura...@gmail.com>

Sender: green...@googlegroups.com

Date: Tue, 3 Apr 2012 18:53:28 +0200

To: <green...@googlegroups.com>

ReplyTo: green...@googlegroups.com

Subject: Re: [Green-India] Microinverter vs Conventional Inverter for roof top installations

[Nagaraj Ramanna]

Dear Ram, Ankush,

We were approached by one of the leading chip manufacturers to design and test
their chip for the solar panel micro-inverters.

The technology is coming up now. It is cheaper and safe compare to Big inverter. Considering the wiring cost and repair and maintenance on the roof top. The power loss will be less when you use micro-inverters.

Based on the chip, the efficiency can be achieved by 95%. It is huge.

It will take some more time to commercialize these product.

Regards,
Nagaraj Ramanna
09341212081

[Ram S]

Dear Mr. Nagaraj,

Yes as per my research also seems microinverter will be a success in near future once rooftop kicks off in due time.

As per our experience in the individual rooftop system, customer are mainly worried of cost than technology so hope it comes to be cost effective product.

Regards,

Ram Shirhatti

+91-9971485301

[Nagaraj Ramanna]

Hi Ram,

There are some Good products it cannot sold at cheap.

If Customer looking for efficiency at 95%. It will not come cheap. The customer will get better realization for the same input. 

The R&D and Testing itself need minimum one year time. The components of these system are not like regular inverter. It  stays in Dust, Heat in sun for days, months & years.

Otherwise, Customer has traditional roof-top wiring with Maintenance model.

Regards,
Nagaraj Ramanna

[Ram S]

Hi Nagaraj,

I suppose then its viability comes for projects >100kw.

Regards,

Ram Shirhatti

[Inverters]

A much better choice than both micro inverters and conventional inverters is the use of power optimizers that are "tuned" to work with a high efficiency ground level inverter such as SolarEdge. SolarEdge offers a 98.3% peak efficiency rating, up to a 25% increase in energy harvest when compared to conventional string inverters, better shade protection, individual solar module monitoring via a built in Internet port, Built in cabling so there's no expensive specialized cable to buy, a 300 watt per module power rating and a lower price than a micro inverter system.

 

Regards

Ray Boggs

[Manu Sharma]

Note to members: 

Ray Boggs is affiliated with a company that has been installing and repairing solar inverters in US and elsewhere for several decades. He is NOT affiliated, to my knowledge, with SolarEdge, the company whose product he recommends below.  

Unfortunately SolarEdge does not appear to have a presence in India. The nearest distributor is in Sri Lanka. Perhaps an opportunity for the entrepreneurs on the list? 

Thanks,

Manu

___________

Manu Sharma

Moderator & Convener

Green-India

[squar...@gmail.com]

According to my information these Inverter are having 60Hz frequency and hence not useful for India

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From: Manu Sharma <orang...@gmail.com>

Sender: green...@googlegroups.com

Date: Sun, 27 May 2012 09:41:07 +0530

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Subject: Re: [Green-India] Re: Microinverter vs Conventional Inverter for roof top installations

[Manu Sharma]

The datasheet of both their single phase and three phase inverters mention AC frequency to be 50/60 Hz ± 5. 

[Manu Sharma]

I wrote:

The datasheet of both their single phase and three phase inverters mention AC frequency to be 50/60 Hz ± 5. 

Also, the Inverter Configuration Tool offered by SolarEdge allows one to configure the maximum and minimum grid frequency of the inverter (from the given range) as per the country / region where it is installed. 

Manu

[Gaurav N]

Hey all,

I have been using another power optimizer from Femto-grid (Netherlands) and have installed it for a 2kW rooftop project and it seems to give a very good performance, especially because all these these power optimizers have individual tracking of modules and especially in urban installations this can play an important role. 

The product is mentioned here  http://www.femtogrid.com/en/products/femtogrid-power-optimizer and it has an efficiency of 97.4%

However I am curious why Ray Boggs feels power optimizers are better than micro inverters other than a slight performance increase.. I know that these days micro inverters exist with efficiency of 96%..

Any ideas of cost comparison between power optimizers and microinverters? also, it would be interesting to have a study of system losses of two similar pv systems, one using a microinverter and another using a power optimizer coupled with inverter

Best,

Gaurav Durasamy

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[Manu Sharma]

On Mon, May 28, 2012 at 9:11 PM, Gaurav N <gaura...@gmail.com> wrote:

I have been using another power optimizer from Femto-grid (Netherlands) and have installed it for a 2kW rooftop project and it seems to give a very good performance [...] However I am curious why Ray Boggs feels power optimizers are better than micro inverters other than a slight performance increase...

Dear Gaurav,

SolarEdge website has a bunch of videos about their technology here on their website including "The Benefits of SolarEdge" - Part I, II and III.

In Part I video, at about 2 min 45 seconds, they talk about how SolarEdge's superior algorithm performs better than traditional MPTT trackers. 

Here's the direct link: http://youtu.be/lsa9rHpDVmQ?t=2m45s

Thanks,

Manu

[Gaurav N]

Dear Manu,

The comparisons made in the video of Solar Edge with regards to the advantages of individual MPPT tracking is referenced to conventional inverters such as central and string based MPPT tracking systems and not with Micro-inverters.

In Micro inverters (as well as power optimizers such as Solar Edge and Femtogrid), the MPPT tracking is done on the module level. The difference between the power optimizer and micro inverter is that in the power optimizer, the voltade is stepped up to the inverter operating voltage by boost converter and the inverter used is simplified. In micro inverter, the step-up of voltage and conversion of DC to AC is done by the single unit behind the panel.

Enphase Energy (http://enphase.com/products/microinverters/m215/) manufacture micro-inverters and claim stable averaged efficiency of 96% (almost the same as that of conventional string inverters).

So this led to my curiosity in comparison between "power optimizers" and "micro inverters" with regards to performance and costs... 

Best,

Gaurav

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Gaurav Durasamy 

[Avinash Deshmukh]

Dear Ram

 Does the solar micro inverters works when  power input is available from solar panel but grid is OFF.

Avinash Deshmukh