Thinking Big to Transform the Inverter

In the world of photovoltaics, inverters are the gateway through which the energy of the sun is delivered into a usable format. Discrete, unobtrusive and often fairly non-descript boxes, inverters may be low key, but ultimately their efforts are what make a project economically viable.

Indeed, a new report from French industry analysis firm Yole Developpement confirms that the rapid growth of the solar PV power industry in recent years has created a multi-billion euro market for inverter manufacturers. The company’s market analyst, Brice Le Gouic, suggests that the PV inverter market is set to more than double over the coming years, growing to an estimated €5.91 billion ($8.1 billion) in 2014.

There is certainly a growing market to aim for if the trends evidently emerging from both the latest 24th European Photovoltaic Solar Energy Conference and Exhibition (EU PV-SEC) event in Hamburg and the Solar Power International event in California late last year are anything to go by. The shift towards larger installations and the growing interest of T&D technology companies more typically associated with the conventional power industry are key developments.

According to Yole, there are more than 40 inverter manufacturers currently, most of them established and specialized in solar inverters. But they also identify an evolving supply chain and the growing number of new entrants. With the manufacture of large-scale inverters as their core activity, these new entrants are moving into the sector as solar plant sizes typically increase from, say, 200 kW to megawatt-plus scale installations.

While such players, such as Siemens and ABB, have announced new solar inverter products of late, they remain focused on larger, grid-connected installations, and given this emerging trend, it is likely other major transmission and distribution and utility services companies will follow suit. And there is evidence to support this theory in the market. For example, in a move which may be perhaps seen as an early signpost to the growing interest in the solar PV inverter market, in late September 2008 Schneider Electric, a global specialist in energy management, announced the acquisition of Xantrex, a top three global player in the solar and wind inverter market. Schneider said it expected to realize significant synergies with Xantrex’s technology and distribution channels combined with its own global sales, service and supply chain capabilities.

Even so, the current market leader, Germany-based SMA with a 34% share according to Yole, has seen its revenues grow. In its latest figures to 30 September 2009, SMA reports total sales increased to €560 million ($767 million) in the first nine months while sold inverter output rose from 0.2 GW in the first quarter to 1.2 GW in the third. Specific price was reduced to a claimed €0.25/W in the third quarter of 2009, the company said and as a result of these improved figures, the group estimates it has increased its market share to between 45% and 50% during the year.

Currently, the company has an annual production capacity of 5 GW, but in December 2009 it announced that in the medium term SMA is planning to develop additional production facilities at Sandershaeuser Berg near Niestetal in Germany. The company went on to say that against the ‘background of the current high demand for solar inverters, a further extension of the maximum yearly production capacity to 9–10 GW can be achieved stepwise through interim solutions over the next six months, provided the demand remains at a high level.’

‘The solar sector is a highly dynamic market characterized by strong volatility. Therefore, a lot of flexibility is required in order to quickly adapt to the different market developments’, explained CEO Günther Cramer. SMA is also planning to open an additional 1 GW of manufacturing capacity in the US at Denver, Colorado, for its Sunny Boy, Sunny Central and Sunny Island product lines. ‘In the medium term, we expect the US market to become the largest solar market globally’, noted Cramer.

Certainly, inverters are getting bigger and a centralized architecture is also emerging as a key trend, but there is also the emergence of potentially disruptive technologies, such as micro-inverters, to consider. Micro-inverters are particularly well suited for use in small systems of 1 kWp or less but in larger installations which use string inverters, individual module shading can significantly lower energy output of the entire system, an impact which may be avoided by using individual micro-inverters on each module, (see panel on page 58).

Perhaps recognizing the implications, SMA has also been acquisitive and in September 2009, the group, which is based in Niestetal and employs more than 3000 people, announced the acquisition of a micro-inverter technology platform from the Dutch company OKE-Services. In the coming years, SMA says, it intends to continue to develop the technology and launch its own product range. The acquisition makes it the only manufacturer in the world with a product portfolio which includes all existing inverter technologies for operating PV systems of any size and with optimal technical system configuration, says the company. Both parties have agreed to keep the exact purchase price confidential.

In terms of the inverter market, Yole names Austria’s Fronius as the next largest player in Europe, with 10.1% of market share, closely followed by Kaco with about 9.9%, while Siemens is already one of the top 10 suppliers with close to 2% of market share. The impact from the more recent entry of major companies such as ABB, with its global reach in terms of industrial-scale power, has yet to be realized, but clearly signals the development of a far more competitive market in the near future.

One overriding consideration in inverter design is baseline efficiency, given that any losses within are sliced from the output of the entire array. In a potential nod to the next generation of inverters, the Fraunhofer Institute for Solar Energy Systems (ISE) claimed a new world record in the summer of 2009 with a PV inverter of 99.03% efficiency based on junction field-effect SiC transistors, which the Institute says are significantly better than the conventional silicon Insulated Gate Bipolar Transistor (IGBT) architecture currently in common use.

Alongside the push for ever greater efficiency and lowest cost of operation, another significant trend in inverter technology has been engendered by a tightening of the rules for grid connection in the EU. Under current directives, systems intending to connect to the grid must become progressively more sophisticated with the capability of supplying reactive power to support grid stability. In addition, the rules dictate that grid-connected inverters above a certain capacity must support remote operation from the transmission system operator. Starting in January 2009, this remote-controlled reduction in output has been required by both the Renewable Energy Act in Germany as well as the new guidelines for the connection and parallel operation of generation plants issued by Germany’s Federal Association of Energy Suppliers and Water Utilities (Bundesverband der Energie-und Wasserwirschaft).

SputnkStakes are Raised in the US and Europe

When in October 2009, Mitsubishi Electric announced that it is to introduce two large-scale transformerless photovoltaic inverters to the North American market – a 100 kW model scheduled for launch in October 2010 and a 250 kW model scheduled in April 2011 – the news topped off a remarkable period of activity in the global PV inverter sector. With the development apparently making Mitsubishi the first Japanese manufacturer to enter the North American inverter sector, the company is already facing stiff competition from a host other European and US players vying for US market share.

Mitsubishi says its move has been prompted by policy change in the US, noting that a recent increase in government subsidies has witnessed the development of numerous large PV plants, built mainly for the purpose of receiving returns on investments. These large industrial PV systems of 100 kW and more cover approximately 70% of demand, Mitsubishi says, with the market expected to expand further with the Green New Deal and other federal incentives.

This trend towards larger, centralised systems, though perhaps less marked, has apparently repeated itself in Europe. And, among a swathe of announcements over the latter months of 2009, a series of large-scale transformerless inverter models were revealed by a number of established PV inverter manufacturers. Among them, a new central or grid-tied inverter was unveiled by Switzerland-based Sputnik Engineering, for example. Open land in Hemau, in the district of Regensburg, saw the commissioning of the first 1 MW installation using its new SolarMax 330C-SV. The device has a rated capacity of 330 kW and as many as three SolarMax 330C-SVs can be combined to create effectively a 1 MW station which, as in this case, can then be directly fed into the medium-voltage grid. The company says the use of transformerless technology in the new design has enabled it to cut both the size and the weight of the system by half compared with the previous models. At the same time, the company claims to have boosted efficiency by 1.5% to 98%.

With the growing demands of the regulatory environment influencing the inverter’s design, the system is monitored remotely using a proprietary internet-based data logger and is designed to automatically respond to grid operator requests for a reduction in output to support grid stability.

Kaco New Energy also continues to develop its product range and in 2009 launched its new transformerless large-scale inverter, the Powador XP350-HV TL, with a 350 kW rating and 97.8% maximum efficiency. It can also be supplied in a triple configuration as a megawatt unit.

Matthias Haag, Kaco’s technical director commented: ‘The Powador XP350-HV TL is also specifically designed for large-scale ground-mounted and roof-mounted PV systems. Large-scale PV systems are playing an increasingly important role in Germany and in particular, Italy’.

Similarly, there were several other examples of transformerless product launches in the small to medium commercial scale, for instance LTi REEnergy GmbH unveiled its new PVmaster Outdoor large-scale inverter. Available with 68 kW and 100 kW outputs, the system has a maximum efficiency of 97%. And transformerless technology has expanded its footprint on the domestic scale too, with the first transformerless inverter from Fronius presented at the 2009 Intersolar. The Fronius IG TL is expected to be available in early 2010, after the completion of final testing. Meanwhile, the new Conergy IPG transformerless string inverter system was unveiled in 2009, which, the company says, offers an efficiency level of up to 96.7%. Both ranges support an output of up to 5 kW.

Mainstream Players Catch the Inverter Bug

Looking towards the larger scale and the entry of companies more closely associated with the mainstream transmission and distribution (T&D) and industrial sector we see players such as Converteam, which launched its so-called ProSolar inverter in 2009, offered for power ranges of between 500 kW and several megawatts. Based on IGBT technology and with possible input voltages of more than 1000 V, efficiency of up to 98% is claimed. The system can also immediately communicate unexpected as well as pre-defined events via the internet or SMS and the inverters meet with the grid requirements laid down in the latest directives, the company says. The move marks the company’s entry to the solar sector, having previously been a significant supplier of electrical equipment to the wind industry, among other sectors.

Outside of Europe, US-firm Advanced Energy Industries, Inc. (AE) also introduced its new transformerless, grid-tied PV inverter, the Solaron 250, at Solar Power International. The company says that with a 250 kW capacity, the device is ideal for applications such as commercial rooftop installations and it joins its stable of previously released 333 kW and 500 kW Solaron inverters.

Simultaneously, the company also announced a number of new tie-ins, marking another emerging trend that is seeing inverter and module manufacturers form closer ties to optimize design. For example, the group secured a strategic alliance with Shanghai Guangdian Electric Group (SGEG), which will market AE’s inverters in China, and Advanced Energy also entered into a multi-year agreement with major crystalline-silicon PV module manufacturer Suntech Power Holdings Co Ltd. As a part of this agreement, a statement from the company says, AE will contribute to the development of a simplified, integrated platform for designing and building utility-scale PV plants.

And in a further notable development, September 2009 saw the company launch a European version of its 500 kW inverter, claiming a rated efficiency of 97.5% CEC-weighted or 98.1% European-weighted.

ABB chose the EU PVSEC event to launch its first foray into the solar inverter sector. Aimed at system integrators and end users which require inverters for large PV plants and industrial and commercial buildings, they are available in a range from 100 kW to 500 kW. Developed from its established industrial drives technology, among other features the transformerless inverter offers power factor compensation.

The inverters are optimized for cost-efficient, multi-megawatt solar power plants, ABB says, adding that its PVS800 inverter is modular, compact and fully integrated into the company’s global service network. ABB adds that, initially, it will start the marketing and sales of its new solar inverter series in the German, Italian and Spanish markets.

‘The path ABB is taking now was mapped out long ago’, said Dirk Leinweber, responsible for sales and marketing of PV products at ABB Automation Products in Germany. He added: ‘The company has much experience in the field of converter technology, and has been an acknowledged supplier to leading producers for many years. We are now drawing on this experience to enter the market ourselves.’ Leinweber concluded: ‘The positive feedback from our strong and well-established partners in the solar market puts us in a confident mood.’

Industrial powerhouse Siemens, meanwhile, says its newly launched Sinvert PVM range is ideally suited for large to medium-sized photovoltaic systems and solar power plants of up to 2 MW and is aimed squarely at both PV plant engineers and end users operating in the commercial segment. Using master/slave combinations, PV plant from 60 kVA to 2 MVA can be supplied, the company says, while the use of IGBT technology gives an efficiency of up to 98%. The new inverter family is also fully integrated into the Sinvert webmonitor tool which can be used for worldwide access and analysis of inverter and PV plant data.

Sinvert PVM inverters will initially be available in 10 kW, 13 kW, and 17 kW, while a 20 kW addition is in the pipeline and Siemens now offers PV inverters with a range of over 20 different power ratings up to 2 MW.

According to the company, its strategy is backed by a recent IMS Research study which concluded that the PV plant market is expected to grow by at least 30% annually until 2013, with the expectation that the growth rate will be disproportionately high in the commercial and power plant segment. Karlheinz Kaul, CEO of Siemens Systems Engineering Business Unit explained: ‘To address this growth market we are extending our product portfolio to include the new powerful Sinvert PVM inverter for medium-sized commercial plants.’ Initially, the company says, the devices will be available in Belgium, the Czech Republic, France, Germany, Greece, Italy and Spain.

SputnikCompetition, Co-operation and Consolidation

Higher efficiency, better communications and more sophisticated management systems, improved reliability, lower costs and a reduction in materials, all these factors map out a clear direction within the PV inverter sector that leads, inevitably, to the lowest cost of ownership. Certainly, as with the rest of the PV manufacturing sector, inverter companies are striving for grid parity and as a vital part in the PV value chain it is essential that they continue to do so. An equally strong market driver comes from the flood of interest in larger PV installations in Europe, the US, and elsewhere which has seen the rapid emergence of a new breed of player with large-scale manufacturing and commercial expertise. Evidently a more competitive inverter market will emerge in the coming years and potentially a wave of consolidation and industrial alliances as inverter companies forge stronger links with module manufacturers and system integrators in order to squeeze every last usable morsel from the sun’s harvest. In any event, advances in inverter technologies, architecture and manufacture signal a cost benefit to the consumer, and, ultimately, a far greater benefit to the environment.

David Appleyard is associate editor of Renewable Energy World. e-mail. rew@pennwell.com

For additional analysis on microinverters, check out “Solar Power Optimizers Gaining Market Share” by RenewableEnergyWorld.com’s News Editor, Graham Jesmer.

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