Delta Energy Systems Australia manager of regional business Matti Dinkelmeyer talks about the advantages of string inverters in utility-scale solar and what the company has planned for storage and vehicle charging in Australia.


What’s your role at Delta?

Whenever new Delta product lines are launched in Australia I take care of the product management and certification and generate the first leads. From then the product lines are spun off into their own freestanding departments. Delta is a massive company with a huge product portfolio. We started in Australia with one product line: PV inverters. Since then we’ve set up product lines for UPS [uninterruptable power supply] and industrial automation.

How would you summarise Delta’s approach to the electricity market?

Over the years power supplies have shrunk in size, with higher and higher power densities, and that’s basically Delta’s core business; understanding the miniaturisation of components in power supplies and power conversion. That goes hand in hand with thermal management. The more you shrink the size of power components the more important thermal management becomes.

Which part of the renewable energy market in Australia is most interesting for you?

Large-scale solar installations, or “solar farms” as they’re commonly known. They are very well established already in many countries, especially in Europe and the US. We’ve participated in many large-scale projects.

Where are you concentrating your efforts?

Traditionally, in large-scale megawatt-sized PV solar farms they have been predominantly using central inverters, in 1MW blocks or even larger. At Delta we believe string inverters definitely have a very cost-effective and technological advantage over central inverters. Our largest string inverter is 88kW with two MPPT [maximum power point trackers] and we are working on a 100kW string inverter. These are self-contained units that can be installed underneath the PV array – they are IP66-rated – and thereby you reduce cabling costs.

Because you have many distributed string inverters you reduce your risk of large-scale failure. If your central inverter goes down you lose a large chunk of your capacity, whereas with string inverters you only lose a fraction of the generating capacity. And it’s easier to find an electrician comfortable with installing a string inverter than it is to find an expert capable of working on a central inverter, which often have complex pressurised liquid cooling.

How can string inverters improve the efficiency of a solar plant?

Each string inverter comes with two MPPT trackers, so if there are shading issues, maybe some degradation of individual panels or dust or contamination on the panels, this doesn’t affect the entire array but only specific parts of the strings. The individual MPPTs can cater for variations much better than bringing down an entire array as you would expect with a central inverter.

Are you keeping an eye on the commercial and industrial market in Australia?

Yes. Currently we have 15kW, 20kW, 30kW and 50kW three-phase string inverter models on offer and we’re hoping later this year to launch our 88kW or 100kW models, depending on interest of large-scale solar projects. It will be an interesting year for us.

You also provide battery storage technology. Have you shown any interest in the South Australian and Victorian tenders?

Yes, all of the above. We’ve put forward our string inverter solution and bundled them with our battery storage. This is a relatively new division of Delta; a couple of years ago Delta acquired 100% of Mitsubishi Heavy Industries’ lithium-ion production facility. We are making our own cell, based on nickel-manganese-cobalt chemistry with a graphite anode. The main features of the chemistry are the high charge and discharge rates, which makes it ideally suited towards peak shaving and grid stabilisation operation where you lots of charge and discharge cycles a day.

Have you heard anything back after submitting your expressions of interest?

The response must have been quite overwhelming [for the state governments]. They would have had reams and reams of proposals. It is very attractive. We would really like to get involved in this sector.

Any other products you may be considering for entry into this market?

A relatively new product line in Australia is electric vehicle charging stations, a very young market. Delta offers AC and DC chargers. When you are talking about deploying DC chargers of 50kW or 150kW, these are fairly significant power requirements. Grid connection is not always up to the emerging demands. If you want to deploy DC fast chargers near transport corridors, very seldom will you find spare capacity in the transformer that would support deployment of large electric vehicle charging infrastructure.

Delta has come up with a new approach to combine DC fast charging with energy storage and renewable power. We are trialling an installation in Holland, near Amsterdam. If you pair the DC charger with energy storage your requirement on the grid connection is vastly reduced. And depending on the power draw of the charger, the battery will be able to smooth out the hit on the grid and stabilise the grid in that area. You don’t want the lights to dim when people charge their cars.