MPPT and energy storage key PV inverter features

IMS Research conducted the survey, PV Inverter Customer Opinions & Requirements Survey – World – 2012, in the fourth quarter of 2011, as many inverter suppliers were realising they could no longer rely on high end-demand, a good product and acceptable prices to ensure a successful business: they needed to better understand how to fulfil their customers’ requirements in a slowing market. It posed a number of questions to over 400 buyers and users of photovoltaic inverters across the globe.

Brand

Unsurprisingly, SMA Solar Technology, the global market inverter leader, was found to have the strongest brand in all the countries studied. Its brand strength varied considerably by country, however, and the survey found a clear preference towards local vendors in many markets, such as the U.S. and Italy.

Power One ranked second in the participants’ list of preferred inverter brands, followed by Fronius, Kaco, Danfoss, SolarMax, Schneider Electric, Diehl Ako, Kostal and Refusol.

Generally, it was discovered that most customers prefer to use three inverter brands. Even when analysed by different customer types, for example, small installers versus large EPCs, this preference did not vary greatly. However, in less-developed markets, such as the U.S. and China, there was a very strong trend for customers to use five brands or more.

Moreover, while nearly three-quarters of all respondents admitted to having a preferred inverter brand, only 17 percent currently use this brand exclusively. Most customers instead prefer to have the design flexibility offered when using multiple inverter brands, with nearly 20 percent being concerned about the risk involved from a single-source supply.

When selecting an inverter supplier, customers overwhelmingly indicated that the inverter quality and price competitiveness were the two most critical factors. This broadly remained the case across most countries and customer types.

In terms of Chinese inverter products, around 70 percent of respondents thought that they did not offer acceptable levels of quality, with this figure increasing to 90 percent in Germany. Italian customers, however, appeared more accepting, with more than 40 percent suggesting that they provided acceptable quality.

Improvements

The on-going trend of building large installations using three-phase string inverters was evident from the survey, and more than 70 percent of respondents indicated that they would consider using a string inverter in photovoltaic systems over 750 kilowatts in size. More than 30 percent additionally said they would use string inverters to build megawatt-sized projects.

The survey provided some insight into desired technical improvements of inverters. For example, more than half of customers questioned would pay an extra five percent for the inverter in order to have a one percent efficiency gain. However, respondents appeared less concerned about overall energy yields or failures, and were less inclined to pay for extra uptime compared to efficiency gains.

Product features

Around 30 percent of string customers indicated that having several Multiple Power Point Trackers (MPPTs) was the most important product feature for photovoltaic inverters. The same was true for string inverters.

One product feature proving to be very important was the monitoring and diagnostics capabilities of inverters. The survey found that maximising uptime and early detection of issues and/or faults are key reasons why customers are demanding improved monitoring and diagnostic systems in today’s highly competitive environment.

The survey also found that the majority of customers prefer wireless protocols for communication with the inverter and photovoltaic array.

Energy storage

The survey also examined customers’ opinions on energy storage in photovoltaic systems. Roughly one-sixth of customers questioned expected the majority of their photovoltaic systems to incorporate energy storage in the next two years.

There were three common factors given for driving the adoption of energy storage: the reduction of battery prices; technical improvements; and the implementation of government policy and legislation.

Inverter pricing

In the main, customers expect inverter prices to steadily decrease over time. Over the next 12 months, nearly half of customers believe that prices will fall by up to 10 percent. However, one-third of respondents did not expect to see inverter prices fall at all. The surveyed customers also most commonly indicated that they expect inverter prices to fall by 20 to 30 percent over the next three years.

Microinverters and power optimizers

Although it was found that customers were more likely to use microinverters in the next 12 to 24 months, the main reason why 40 percent of respondents do not use them is the higher costs associated.

Those that did use microinverters, or wanted to in future, stated that the main reasons were to combat shading and also for the better monitoring they provide.

It was further found that more customers used power optimizers than microinverters, with 16 percent of respondents offering them. In the next 12 to 24 months this percentage is set to increase slightly. However, it must be noted that there is great uncertainty whether the technology will be used or not in the next 12 to 24 months, due to the lack of knowledge of the technology and its benefits, and the additional cost associated.

Written by survey analysts Cormac Gilligan and Ash Sharma; edited by Becky Stuart.

More details on the report will be published in the next edition of pv magazine, due out on February 1. Solarpraxis will also be holding its "Inverter and PV System Technology Forum – USA 2012" conference from February 27 to 28 in San Francisco, the U.S.

Over the two days, the conference will address such topics as photovoltaic system design and performance optimization, grid integration and infrastructure, and next generation inverters.