Battery Inverter Webinar with Kaco: Your questions answered

Kaco New Energy presented its 50-kilowatt battery inverter in a pv magazine webinar, which not only can provide flexibility but, in the opinion of Matthias Haag, CTO of Kaco New Energy, is also extremely flexible in use.

Haag refers to the possibility of connecting several inverters to one battery, which allows for easy scaling and open software interface. This not only allows the device to be controlled in a very flexible way, but also integrators can contribute their own expertise here and enable a USP.

This is the end point of a development that Kaco has already begun with a  residential district storage project in Weinsberg, Germany more than four years ago. There, solar power supplies energy to a new housing estate, and is stored centrally.

Here you can view the webinar with initiative partner Kaco and download the presentations.

Here, Matthias Haag and Martin Ammon, Head of Energy Management at EuPD Research, will answer some of the important questions asked by the webinar participants, which the experts did not have time to get to.

How do you see advanced lead acid products like lead carbon competing with Lithium-ion?

Martin Ammon: Today I see a strong focus on the lithium-ion technology. Depending on price development and availability of lead carbon, there will be a market for advanced lead acid. Because of the fact that storage solutions from the automotive sector are going to dominate the whole storage segment, lithium-ion is dominant today.

Are growing battery storage projects helping battery prices to decrease, especially Li-ion, and when should the market begin to really notice these price reductions?

Large scale storage projects are important for the price development today, because one large project (50 MWh) uses the net capacity of over 8,000 standard small residential storage systems. The main impact factor for future price reductions will come from the electric mobility sector. There are 2 reasons: 1. Growth rate of electric cars will be much larger than for storage solutions. 2. In the near future all storage projects will use second hand storage from electric mobility. The development of the electric mobility industry will dominate the price development for storage applications.

Is there a trend in Europe for sodium nickel chloride batteries? Or do you expect there to be one soon?

I heard about some interesting approaches regarding sodium nickel chloride batteries. It could be an interesting alternative technology, if the availability of lithium becomes a problem. Today I can’t see a trend, but in mid to long term perspective there are opportunities for new technologies such as sodium nickel chloride batteries.

Are you planning to offer emergency power for the blueplanet gridsave in the future? Can KACO storage inverters operate in off-grid condition?

Matthias Haag: The blueplanet gridsave 50.0 TL3-S is not off-grid capable. The coming I-version, which we are already working on, will be.

Will Kaco focus on Virtual power plants (VPPs) and microgrid applications in future?

Kaco new energy remains focused on providing our customers and partners with reliable inverters of the highest quality. The open communication gives our partners and system integrators a high degree of flexibility. This also includes the possibility of coupling the blueplanet gridsave 50.0 TL3-S into virtual power plants.

How does this invertor differentiate itself from other models on the market at the moment? What features does it provide?

There are different market companions with different functionalities of the applicable battery inverters: AC/DC coupling, DC voltage ranges, with or without transformer, power classes, and so on. The focus of our product development is very high flexibility of use and the simplest manageability for our customers – complemented with highest quality at market-driven prices.

The high flexibility is achieved through open communication interfaces and, above all, the possibility of DC parallel connection. This makes it possible to operate battery systems between 30 and 200 kWh efficiently as “one energy cell”. Further scaling of these energy cells will quickly reach the MWh range.

Due to the decentralized, modular “energy cells”, high system availability can then be achieved in the MWh class – coupled with a high efficiency, even in the partial load range. So, one positive effect leads to another.

Which battery voltage is suitable for the inverter: 24/48/96V?

Our battery inverter has a DC voltage window between 665V – 910V. This is a suitable voltage window for most high voltage storage applications.

What are the types of battery it supports?

Our customers have 100 percent freedom in the choice of battery technology. We have developed the blueplanet gridsave 50.0 TL3-S so that it is compatible with all common storage technologies and manufacturers. The batteries need only correspond to the DC operating range of the battery inverter, and must be intrinsically safe.

Can you name BMS', where the communication has already been tested?

The communication to the BMS (Battery Management System) is in the scope of the EMS (Energy Management System). The communication between our battery inverter and EMS has been qualified by various system integrators. These are battery system providers as well as energy system providers that are both using their own EMS.

For a 50 – 100 MWh sized project, will the 50 TL3-S work? If yes, can it be competitive with centralized systems of 2 MW offered by competitors?

It will work here due to the fact that you can connect the inverter in parallel on the AC side. This makes it scalable to fit even this kind of large-scale battery storage system. We are positive that the decentralized design will be competitive with centralized systems. Since we are distributing the blueplanet gridsave 50.0 TL3-S as a component to system integrators, a detailed calculation should be discussed with them, however.

How do you manage the DC voltage of the batteries if you are compatible with all of them?

The batteries as well as the system stability (such as DC voltage, or SOC management) in general are controlled through the EMS. As long as the DC-voltage is within the given DC-voltage range, the blueplanet gridsave 50.0 TL3-S can charge or discharge the battery as per the command received from the EMS. The integrator of the system is responsible for the overall function of the system, dependent on the battery technology they are using.

Does the system integrator have to test the communication with the BMS?

The communication to the BMS (Battery Management System) is scope of the EMS (Energy Management System). Generally, the integrators have their own EMS and are responsible for the overall function of the EMS. KACO new energy works closely with all of its partners in order to ensure that we bring reliable and efficient solutions to the market.

Do two inverters operate together from light loads or sequential on 2*bg50 parallel operation condition?

The battery inverter is flexible and supports both cases: Depending on the application it might be required that two blueplanet gridsave 50.0 TL3-S share even small loads (for instance, when full power must be available within a very short time). The Energy Management strategy can be programmed in the EMS.

In order to spare the inverters unnecessary operation time when there are light loads, the Energy Management System can in this case control them to work sequentially because of the DC parallel connection.

What is the output connection voltage for the BP 50 TL3-S?

It is 400 V / 230 V.