From almost nothing in 2010, the Indian solar sector has come a long way, with total installed capacities well above 2500 MW by end of Jul 2014. Sure, that’s a blip on the global solar radar screen that is clocking 150+ GW (1,50,000 MW), but that also shows the kind of potential that the Indian solar sector has.

ReGen Powertech is a well-known name in the wind power sector, being a leading OEM for wind turbines. ReGen also has the distinction of being the first wind turbine OEM to have an almost dedicated focus on the emerging wind IPP (independent power producer) sector. As a result of this focus, the company has an impressive 1600 MW of wind power installed for the IPP sector in under 6 years from its start.

From such an impressive performance in the wind power sector, ReGen started its efforts for the solar power sector in 2012 when it started surveying the Indian solar market for MW scale solar inverters.

In August 2014, ReGen launched its MW scale central solar inverter series for India, with the highlight being the 2 MW, water cooled solar inverter.

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EAI had been associated with ReGen on their efforts into the solar inverters right from the inception, when they asked our consulting team to do a thorough market study of the solar inverters in 2012. It was hence a pleasure for us to see the formal launch of the inverter.

It was also the right time for me to sit down with Anirudh Khemka, Head of ReGen’s Renewables & Special Initiatives division, and get all the details of the newest MW scale central solar inverter in the Indian market.

Me: Anirudh, good to meet you after the launch. How has the market received the new inverter so far?

Anirudh: It is too early to say, but we already have some serious prospects in the pipeline and are hoping to make quick inroads.

Me: Let me ask you a simple question. If I were a solar utility scale power plant developer, why should I consider going for ReGen’s solar inverter over other well-known names in the market today?

Anirudh: The short, elevator-pitch type of answer would be:

1. ReGen’s  inverters are of a superior German design, manufactured in India and best tailored to Indian and other tropical conditions
2. We have the most comprehensive O&M network among all solar inverter companies in India

Me: Now, let me take up each of those elevator-pitch points. Firstly, how do you say that yours is the inverter best tailored to Indian conditions? Couldn’t other inverter companies say that too?

Anirudh: There are specific highlights for our inverters that are unique and hence can make the claim.

• First, while the core technology is German, we will be assembling these inverters in India. This will enable us to make the necessary technological advances and modifications that can make them work better in Indian conditions.
• Second, ReGen inverters in partnership with Vensys are a derivative of our wind power converters, of which we have about 1600 MW already running in Indian Subcontinent. So, in that context, we are not exactly new to the country and the basic technology has been operating for a more demanding sector such as wind for almost seven years now.
• Third, unlike most other solar inverters in the market, ours is a unique water-cooled inverter.  For a hot, humid and dusty country like India, water cooled inverters result in more robust cooling, resulting in much higher efficiencies and much lower maintenance costs.

Me: During the launch as well, you spent some time on explaining the water cooling aspect of your inverter. It will be wonderful if you could explain the clear benefits of a water cooled inverter over an air cooled one

The solar inverters available in India currently from our competitors are air-cooled ones. Water cooled inverter have the following advantages in Indian conditions

• ReGen’s is the only water cooled mainstream inverter in the market. While a select few competitors might have other liquid-based cooling systems, they are way more expensive than ReGen’s and require more frequent and complex maintenance, thus making them unaffordable and unsuitable for the Indian market.
• If air cooling is used, the possibility of dust entering the inverter is high. Water cooled inverters completely avoid this problem and thus are ideal for Indian conditions where you can expect significant dust in the air around solar power plants. The water cooling system is completely sealed and closed system with no requirement of any sort of water replacement or change, resulting in much higher efficiencies and very low maintenance.
• Water cooling presents another equally important advantage for Indian conditions that are much hotter than those in many European countries. Water cooling allows higher temperature without de-rating the inverter’s output .  At 50°C, most of the competition will have the efficiency drop to much lower levels  but ReGen’s inverter will maintain efficiency over 97% even at temperatures above 50°C.
• ReGen’s inverters come in two options, an inverter suitable for conditions upto 50°C and a superior version for performance above 50°C.  Most inverters in the market begin de-rating at 45 °C.

Me: Your second elevator pitch point was about leveraging your O&M network for the 1600 MW wind farm operations you have currently in the country. Can you elaborate on what competitive advantages such a position gives you?

Anirudh: As you will know, ReGen has been a pioneer in the wind power segment, as we were one of the first to start targeting the wind IPP (independent power producer) sector with dedicated and customised solutions. As a result, we today have over 1,600 MW of wind farms, across the Indian subcontinent, with ReGen turbines powered by Vensys technology. Of the 1,600 MW of installed wind capacity, majority are under 20-year O&M contract with ReGen.

To provide O&M services to this vast network of farms, we already have a team of over 250 trained maintenance engineers and experts, and this will be increased to 300 by end of the year. This is one of the largest O&M networks available in India for wind power.

This is one of our best assets today, in addition to the proven Vensys wind converter technology, that can be directly employed to ensure that our solar inverter customers get excellent support services, with quick turnaround times and highest inverter availability.

It also helps that the states that have good potential for solar power are the same states that have excellent potential for wind power. This enables us to use and leverage our excellent O&M network in a more optimal manner.

What are the other highlights of ReGen’s solar inverters?

• Output Voltage – Inverter output is at 620 V, while most competing products provide at 320 V.  A higher output voltage is useful because 320 V transformers are much more expensive than 620 V, and in addition, transmission losses are lower for a higher voltage.
• The other differentiator is the customisation options – We have both Indoor and Containerised models for the inverter. The containerised model, where the inverter comes with its own casing, provides two multiple options to the user: One option is a “balance of systems in a package” where the user gets both the inverter and transformer packed in one package; the other option is where the user can buy the containerised option with just the inverter. Outside of these two, should the user desire, he can purchase the indoor version (this is not containerised, and the user has to make provisions for the room etc)
• Better performance in high temperatures – Most inverters derate at 45 degrees C, but for our inverters, derating could be delayed to temperatures above 50°C. This can be a significant advantage when you consider solar power plants in really hot regions such as Rajasthan.

Does your inverter come only with a 2 MW capacity?

No, the ReGen inverters come in three capacities – 1 MW, 1.5 MW and 2 MW

From our side, the recommended capacity would be the 2 MW version for solar power plants with capacities of 2 MW and above.  The solar inverter market is now moving towards large capacity central inverters in multi-megawatt sizes.

You also mentioned customizability of your inverter based on containerised and indoor models. Can you provide more details on this?

ReGen’s solar inverters can be offered as an Indoor model or as a Containerised model. The highlights of each of these are as follows:

Containerised Model

• Prebuilt, ready to go
• Can be kept outside, no room required.
• Containerised model requires no construction, just needs to be unloaded at the required location on site
• Uses standard 20’, 40’ containers – easy transportation
• Container has inbuilt cooling
• This model is also available with a transformer included, should the user want it

Indoor Model

In this case, the user needs to build a room. Building a room and using the indoor model might seem cheaper, but it should be remembered that it is difficult to get labour and other resources to build the room in various remote parts of India where solar projects usually come up.  The outdoor/containerized solutions are a great advantage as civil works can be avoided.

The indoor model does not have the option of having a transformer as part of the package

As you can observe, the Containerised Model is a fairly unique offering providing some really distinct benefits to a solar power plant developer.

Are there any installations for your inverter?

While this inverter is new to the Indian market, Vensys has about 40 MW of solar inverter installations running in Germany and other parts of Europe for this inverter.

In India too, we have several qualified prospects in the pipeline, amounting to about 90 MW.

How would you compare your inverters against string inverters which appear to have some advantages over central inverters, especially in the context of redundancy?

Central inverters are much superior to string inverters when it comes to efficiencies. While the former can boast efficiencies upwards of 97%, string inverters typically have efficiencies in the 85-90% range. That can mean a very significant difference in output between string and central inverters leading to reduced revenues.

On the redundancy aspect too, our inverter can compete with string inverters. For instance, our 2 MW inverter is configured with 5 IGBTs. Thus in the unlikely event of the failure of one IGBT, the load can be taken up by other IGBTs, and thus there is no downtime at all. Even the servicing of any malfunctioning IGBTs will be a quick affair as the IGBTs used in the solar inverters are the same as those used in our wind power converters.  Hence, there is enough skillsets available to take care of any troubleshooting needs and there are no longer any significant advantages offered by string inverters.

During the launch of this inverter, it was also mentioned that ReGen will be bringing out a unique inverter for the solar-wind hybrid power plants. Given the current interest in collocating solar and wind power plants, such a hybrid inverter could be of significant interest to the market. When can we expect ReGen to bring this hybrid inverter to the market?

Yes, this is one of the exciting projects we have been working on. In alliance with Vensys, we will be launching perhaps the world’s first solar/wind hybrid inverter that has an integrated power electronics for both wind and solar power conversion. The prototype solar-wind hybrid inverter is under development, and we estimate we should be able to bring this to the market by early 2015.

While we are confident of overcoming the technological challenges associated with solar/wind hybrid inverters, especially for MW scales, the regulatory challenges still remain as there are no policies and regulations for a combined solar/wind blended power in India. While we have submitted these concerns to the regulators, in the meantime, we are also trying to work on initiating pilots in some regions for this pioneering technology.

Thanks Anirudh, for taking time off and talking to us!

Should any of you be interested in knowing more about the inverter for your solar power projects, you of course can get in touch with ReGen, or send a note to narsi[at]eai.in and I will forward it to the right guys at ReGen. Thanks!