Solar and hybrid inverters: Greater variety, lower costs

9/14/18, 11:00 AM -

Photovoltaics is moving into new applications. These days, units need to also integrate storage batteries, charge points for EVs, heating elements, additional generators or monitoring. Configurations that fit most precisely result in one thing: expanding product ranges.

Award winning string inverter PVS 175TL of ABB Solar at the Intersolar Europe in Munich.

Following a few years of consolidation, the global growth in the PV segment is now actually affecting the manufacturers of inverters. Until some years ago, the only job on inverters used to be transforming DC solar power into alternate current suitable for the grid in as inexpensive and efficient a manner as possible.

These days, they have turned into multitalented machines: In addition to transforming the electricity, they analyse and manage the solar strings and batteries as well as power-2-heat or smart home solutions. They have interfaces for digital communication and are linked to energy management systems that also integrate electric vehicles.

Solar PV and digitalisation

All these added functionalities for inverters are mostly the result of digitalisation and have led to an increase in the inverters sold in 2017 of about another 23 percent compared to the year before – to 98 gigawatts’ worth, according to an analysis by GTM Research.

Along with raising the efficiency (which is currently just shy of 99-percent), inverters are having to fulfil a whole lot of new functions – such as e-mobility. In Munich, Fronius and Solaredge were demonstrating how simple integrating EV charge points via an inverter ca be. Through the integrated charging function it is possible to charge EVs up to two and a half times faster than with conventional charge controllers. And that also reduces the cost of installation because additional wiring and fuses are not necessary.

Intersolar Award for ABB

Giovanni Frassineti is the chief product manager at ABB Solar. “Top efficiency alone are no longer deciding factors,” he says. “Inexpensive solutions to meet the requirements and expectations of the customers are much more important.” Thus it can be seen that all manufacturers of inverters are expanding their product ranges. On the other hand, string inverters for grid-connected large-scale installations are having their range of functionalities reduced.

Since their take-over of Power One, ABB Solar has seen two-figure annual growth rates. As with SMA, Kaco or Sungrow, the larger string inverters were boosted up to 1,500 volts DC. The higher voltage from the panel array results in lower currents. This in turn means lower costs for wiring and cooling.

Surprisingly compact unit

ABB’s new model PVS 175 TL that was presented in Munich a surprisingly compact solar inverter (power density: 1.3 kilowatts per kilogram) that has an output of up to 185 kilowatts (at 800 volts AC). A number of units can be combined to achieve higher outputs, in order to also be able to equip larger installations. Its operational temperature ranges from minus 20 to 60 degrees Celsius.

Because the DC disconnectors are integrated, these inverters do not require a separate DC disconnector or AC combiner at low voltages. Up to 24 solar strings can be connected.

The AC wiring has an optional disconnector, resulting in a 65-percent reduction in the cost for the power electronics. All of the inverters of a solar park can be configured into a cluster within 20 minutes.

Delta: New 125-kilowatt unit

In Munich, Delta Energy also presented an innovative and high-power density inverter able to accept 1,500 volts from the panel array. After introducing the 88-kilowatt M88 last year, they now show a unit with 125 kilowatts. “It will be available in early 2019,” according to Andreas Schmidt, head of marketing at Delta. “It will be able to accept 20 strings and the DC circuit breakers are integrated.”

The MPP tracker and the monitoring of the string(s) are also integrated. The initial installation is carried out via an app and by WiFi. This inverter does not have any form of screen, because these days no one walks up to the actual box to check the operational data. Only the state of operation is shown by an LED, monitoring and control happen at a distance.

This inverter only weighs 78 kilograms, and its power density is 1.6 kilowatts per kilogram. It also can tolerate outside temperatures of up to 60 degrees Celsius without powering down. As was the case with ABB’s 175 model, the ventilation units can be easily exchanged, which significantly lowers maintenance costs. The electronics are enclosed in a dust free IP55 housing.

Hybrid unit including emergency power

Delta also presented their storage solution Hybrid E5. “It is available for shipping as of now is able to integrate a DC battery with up to six kilowatt hours of capacity,” Andreas Schmidt explains. “And with a second battery pack, the system can be extended to 12 kilowatt hours.”

As most manufacturers of hybrid or battery inverters, Delta have equipped their E5 with an emergency power outlet. This is useful to keep crucial consumers under power in case of manual switching. A variety of operational modes can be set, and monitoring is integrated. So far, however, the E5 can only manage the batteries by Panasonic that Delta have as part of their product range.

Kostal is rolling out their Plenticore

Kostal also had good news to report: The new Plenticore plus is now available between 4.2 and ten kilowatt hours. This three-phase hybrid inverter allows the connection of solar strings and one storage battery. “In the first quarter of 2019, the Plenticore will be equipped with AC coupling, specifically to suit our commercial customers,” head of marketing, Markus Vetter, predicts. “That will make it possible to connect DC batteries to all of the MPP inputs.”

It does not take a prophet to see that this will make the installing companies very happy. After all, that gives them total freedom to hook up any combination of panel strings or DC high-voltage batteries to the inverter.

In Munich, Kostal presented their new Piko MP plus, the variant of their single-phase inverter optimised for storage. It can now be installed as an outdoor unit. And the small hybrid inverter with outputs of three, 3.6 and 4.6 kilowatts is also supposed to be available from the first quarter of 2019.

Fronius: Fully roof-based solar

The integration of storage batteries through high voltages at the DC circuit of the hybrid inverter is also a top priority for Fronius. To date Fronius has sold around 1.65 million inverters worldwide. This corresponds to about 12.5 gigawatts' worth of inverter power. This figure is all the more astonishing when you consider that their largest inverter, the Agilo, only produces 100 kilowatts.

Fronius is focussing on solar end customers as well as commercial enterprises. As with Kostal, the string inverters can be used to easily build up larger solar generators.

Every day, 1,300 solar installations are set up using power electronics by Fronius. So far, they have 28,000 battery systems out there. The solar energy harvested through Fronius inverters adds up to about 17 terawatt hours per year. As a comparison, all of Austria’s nuclear power plants together generate about 13 terawatt hours per year.

Inverter with integrated charging point

A few years ago, Fronius introduced the first inverters that allowed the direct integration of specific consumers. For instance, the Snap inverters now come off the shelf with the capability to control a heat pump – via an external relay. But it can also be used to control a charging point or a wall box.

As of very recently, the units are equipped with a manual switch for fast charging. For dynamic charging, Keba or E-Charge wall boxes can be integrated, and Fronius inverters already come with an energy management system.

Battery is charged even if the grid fails

Fronius’ Symo Hybrid is now able to manage storage batteries by LG Chem, BYD and Solarwatt. Not only can it now supply electric consumers with emergency power, but it can also charge the battery even if the grid fails: In such a case, the roof-mounted solar array is connected to the battery and the emergency consumers as in an off-grid system.

Worldwide, Fronius cooperates with about 4,000 installing company partners. When it comes to customer service, Fronius have announced an innovation: What used to be ‘service partners’ will from now on become ‘system partners’. For example, these will be able to take advantage of a flexible tariff that they can then offer to their customers to allow these in turn to close the electricity gap. In Germany, this tariff will be available starting from the third quarter of 2018. (HS)

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