Micro-Inverter Is Rapidly Taking Share from String Inverters

According to IMS Research, more than 21 GW of solar photovoltaic capacity will be installed in 2011. This is a huge market opportunity for micro-inverters, which at present have a market share of just a few percent. Micro-inverters are rapidly taking share from string inverters and there is no longer any commercial or technical reason for people to install string inverters in residential and commercial rooftop applications. Louis-Philippe Lalonde, VP of Worldwide Marketing and Product Management at Enecsys, talks about why he believes micro-inverters are not just for niche applications, but for the mainstream market.

Reported by Jeanny H. Lim (swied@infothe.com)

Could you tell us about the status of the micro-inverter market?

The micro-inverter market has only taken off in North America in the last 3 years, and in Europe during the last 18 months since the introduction of Enecsys micro-inverters in the U.K., Germany and other northern European markets. Recently, Enecsys micro-inverters have also become the first to receive approvals for installation in Italy and Spain. We estimate that across all markets, close to 1 million micro-inverters will have been shipped by the end of 2011, so the technology is now taking significant share from traditional string inverters. It’s now a mainstream technology, not one that’s just for niche applications.

The new breed of high reliability micro-inverters offers a very simple proposition to customers─up to 20% lower cost of energy over the lifetime of the system. The specific benefits include the elimination of problems caused by shadowing or buildup of debris on solar modules, greater energy harvesting because Maximum Power Point Tracking (MPPT) can be applied to each individual module, simpler system planning and installation, and safer systems because there is no high voltage DC present, as is the case with PV strings used in conventional systems. The absence of high voltage DC makes the systems safer, reduces fire risk and reduces the risk to fire fighters in the event of a fire. It also means that no specialist skills are needed to do the installation work―most electricians can do it, and micro-inverters are also well suited to self-installation by homeowners. There’s one further big advantage. You can monitor solar PV systems based on micro-inverters right down to the level of individual modules, so system operation can be optimized throughout its lifetime and faults are very easy to pinpoint, reducing maintenance costs. Monitoring can be carried out at the installation site, or from any online location if the monitoring system is fitted with an Internet gateway.

Another challenge has been to bring the cost of micro-inverters down to that of string inverters. Even with all the benefits they offer, some people will not pay the small up-front additional cost for micro-inverters. We’ve overcome that with the Enecsys Duo. This accepts input from two solar modules, maintaining independent MPPT for both. The Duo halves the number of micro-inverters in a given system and brings the total power conversion cost for the system to a level comparable with string inverters. Under these circumstances, there is no reason why anyone would now want to use string inverters.

What do you think is the major challenge that micro-inverter players are facing in the market and what are the potential solutions?

The biggest challenge to-date has been to make micro-inverters reliable in the very demanding environment found behind solar modules on rooftops. Ambient temperatures can range from -40 degrees C to +85 degrees C in some locations, with huge variations in humidity levels and air quality. Convincing installers and end customers that micro-inverters will withstand these conditions has been a challenge. Enecsys has approached this by eliminating the limited-life components found in string inverters and other micro-inverters, particularly electrolytic capacitors and opto-couplers. The removal of these components from our patented design has enabled us to create the first micro-inverter with a service life of over 25 years, matching that of solar modules. The Enecsys micro-inverter is also the only one to be warranted for 20 years over an ambient temperature range of -40 degrees C to +85 degrees C. Some micro-inverter manufacturers limit their warranties to an upper ambient temperature of +65 degrees C. We view this as woefully inadequate for products that need to operate in real-world conditions on rooftops. Enecsys also provides its customers with detailed reliability data from accelerated life tests, something that not all manufacturers of micro-inverters seem prepared to do. It’s this conservative and responsible approach to the specification of our products that has overcome the doubts that many people had about the reliability of micro-inverters.

What is your perspective on the micro-inverter demand and market in 2012?

There are so many conflicting forecasts for the solar inverter market in 2012 that nobody can be very confident about the total market size, or rate of growth. However, according to IMS Research, more than 21 GW of solar photovoltaic capacity will be installed in 2011, so this is a huge market opportunity for micro-inverters, which at present have a market share of just a few percent. As I mentioned earlier, we are rapidly taking share from string inverters and there is no longer any commercial or technical reason for people to install string inverters in residential and commercial rooftop applications, so we see micro-inverter demand growing strongly throughout 2012 as more and more people come to understand the benefits.

There’s another major factor that will drive demand for micro-inverters in 2012─ the launch of AC modules by the module manufacturers. The major module makers are planning to integrate micro-inverters into their modules to produce products that are even easier for customers to install. There will be a step-by-step process of integration but we expect this market opportunity to accelerate in 2012.

What do future inverters look like?

The short answer is smaller, cheaper and more efficient. Improvements in efficiency will be incremental and our latest products already achieve 96% peak efficiency. Component technologies are improving all the time, and we are evolving our product design to take advantage of these. Our next generation of products will be based on proprietary ASIC (application-specific integrated circuit) technology. This will reduce the number of components in each micro-inverter by almost 100, reducing costs and increasing reliability and service life even further.

How long have you been involved in the solar industry? Why did you choose to enter the solar market?

Enecsys was founded in 2003 to commercialize a patented solar PV micro-inverter technology that was originally developed at Cambridge University. The solar PV market was attractive to us because of the known shortcomings of traditional string inverters. These are usually only warranted for 5 or 10 years and have a service life less than half that of solar modules, so these expensive units have to be replaced at least once or twice during the life of a PV installation. We knew we had a technology that would eliminate the need for string inverters and that would enable inverters to match the service life of solar modules. That’s a major breakthrough for system owners and one that we’ve demonstrably achieved.

Who is your target customer?

Enecsys targets commercial and residential rooftop solar PV installations in Europe and North America. There is no reason why micro-inverters should not be used with individual solar PV modules or in MW scale installations, but typical 3kWp to 7kWp installations on rooftops are where the benefits are most relevant.

What is your strength that your competitors can’t imitate?

Enecsys micro-inverters are based on a patented technology originally developed at Cambridge University in the U.K. The removal of life limiting components, particularly electrolytic capacitors, which we replaced with long-life film capacitors, means that we have been able to produce micro-inverters that deliver full performance and efficiency in ambient temperatures up to +85 degrees C. To my knowledge, we are the only micro-inverter company to have achieved this. It’s important because the ability to withstand high temperatures is directly related to an electronic product’s reliability at all temperatures. We believe that we are producing the world’s most reliable micro-inverter today.

Do you have an expected lifespan for your inverters? Are you planning to give a specific warranty for your product like for the panels?

Based on the predictions from industry-standard test methodologies, Enecsys micro-inverters will have a service life of over 25 years, matching that of solar modules. Uniquely, we warrant them for 20 years at up to +85 degrees C ambient and, as they will never experience this high temperature on a continuous basis, their service life will be greater than 25 years.

What solar market do you wish to focus on? Asia? Europe?

We are currently certified to supply products into Europe and North America, where our marketing efforts are focused today. We do not rule out expansion into other geographies at the appropriate time.

Jeanny H. Lim is Editor-in-Chief of InterPV. Send your comments to swied@infothe.com.

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