Discussing Latest Developments of Inverters & Battery Storage, The Brains And Mitochondria Of Today’s Solar Systems

Often referred to as the brain of solar PV installations, inverters, and what could be the mitochondria of such systems, batteries have never been as significant as they are now. Like solar cells and modules, these have also undergone significant technological advancements and upgrades, albeit usually not so much in the limelight. 

What brings them the spotlight increasingly is the growing importance of a digitalized energy system of the future. While inverters’ role is growing in the scheme of things as stability and grid forming in an electricity system becomes key in advanced solar markets, batteries will assume a greater significance too with their ability to help shave peaks and provide further services to the grid, such as frequency and voltage control, reactive power support or black start capabilities. 

TaiyangNews’ 1st Virtual Conference on Inverters & Battery Storage on November 19, 2024, delved into the technology and application trends for the brain and mitochondria of the latest solar power systems.  

TaiyangNews Managing Director Michael Schmela opened the conference, explaining the role of these 2 technologies in ensuring how solar PV can grow intelligently to ensure a 24x7 renewable power supply. Pointing to the record levels of negative power prices observed in Europe, he said that the value of solar, the so-called solar capture rate, is decreasing due to grid congestion. The need of the hour hence is more electrification, more grid investments, and flexibility to lower energy costs, which is where the focus comes to the inverters and battery storage technologies.     

In his keynote address, the Purchasing Team Leader of BayWa r.e. Frank Mu discussed the impact of procurement on inverter and battery energy storage system (BESS) selection.  

An incorrect inverter, for instance, could lead to reduced electricity generation and negate cost savings while compromising safety. Not all products perform as well as suppliers claim, as inverters are difficult to test in the lab. This leads to surprise troubles in the field since most of the problems are actually unknown, pointed out Mu. 

Similarly for BESS, it is not an add-on, but an additional expense for a PV system. It needs to be backed by independent financial planning and is a different revenue stream. For a lot of companies, including BayWa, this is a new field with unique challenges of its own.  

Right now, he explained, the battery prices are down due to an oversupply of cells and stagnating demand from the electric vehicles (EV) business. However, it is important for the procurement team to not get distracted by this and make the correct decision as getting the cheapest option doesn’t always work.  

One learning for the team is to include price adjustment clauses in the procurement contract. So, if a €3 million battery system drops in market value by €2 million during project execution, its financial viability will be obviously at risk.  

This decision needs to be based on understanding the business case and technical integration. The team should also be knowledgeable about different battery chemistries; for instance, what lithium iron phosphate (LFP) offers that sodium-ion doesn’t and vice-versa, and their long-term potential.  

For BayWa, Mu added, supplier relationships are important since working with a small group of experienced suppliers with local service teams can mitigate risks during project execution.  

He also pointed out that the procurement team must keep abreast of the changing regulatory environment to reshape their strategies. In Europe, for instance, the thrust on local manufacturing under the European Union’s (EU) Net Zero Industry Act means the team should build relationships with local European manufacturers to align with potential trade restrictions or incentives in the future, which is already the case in other markets, like India or the US.   

Product Manager of Jinko ESS, Eathin Xu, presented the key features of the company’s advanced commercial and industrial energy storage systems (ESS). A subsidiary of Chinese solar PV manufacturer JinkoSolar, Jinko ESS has an annual production capacity of 10 GWh/year for ESS and 5 GW/year for cells, equipped with power conversion systems (PCS) and energy management systems (EMS). 

The current products in Jinko ESS’ portfolio are various generations of SunGiga ESS for the C&I segment comprising G1 — a 215 kWh/100 kW all-in-one system with an on-grid PCS solution. G1-2 is SunGiga 215kwh DC Battery Cabinet with an integrated PCS cabinet which is for microgrid Scenario. G1-3 is SunGiga 344 kWh DC Battery Cabinet which is tailored specifically for North America market. The New Generation product is a 261/125 kWh All-in-one product which could support use in both on and off-grid scenario. All of these cater to various geographical regions, added Xu.   

He shared that all of Jinko ESS’ products have 5-layer protection — at the cell level, pack level, system level, module level and rack level for a 3-dimensional safety strategy related to structural, electrical, and fire safety. 

Talking about the company’s new generation All-in-one 261 kWh system, Xu said it offers high throughput with a system cycle life of up to 8,000 cycles, an integrated system and intelligent unit management that can support 12 units parallelly, both on and off the grid.  

The 2 main features of SunGiga Liquid Cooled on-grid C&I ESS solution products are reliability and flexibility. These come with remote monitoring capabilities to monitor temperature and energy throughput that simplify operation and maintenance. 

Xu added that the company’s C&I products are used in diverse applications and can be paired with PV systems and integrated with diesel generators as well as EV chargers.   

The next presentation was from Hopewind, a Shenzhen-based supplier of inverters, ESS PCS and converters to the solar and wind industry with over 150 GW of renewable product shipments. Hopewind’s Utility Technical Support Director Alvaro Zanón discussed the power of digitalization in utility PV inverters and storage, for which the company also uses some of its learnings from the wind energy segment.  

Sharing the company’s product portfolio in the inverter and storage space, Zanón called the HSHV320~385K-G02 the most powerful string inverter in the industry with 385 kW up to 40°C, 8 MPPT/32 strings, compatible with both 182mm and 210 mm modules. Hopewind uses silicon carbide (SiC) for its inverters as these have better behavior for higher temperatures, higher efficiency and longer lifecycle.  

Hopewind offers three different transformer stations HPMVS-3000/6000/9000 specifically designed for its HSHV320~385K-G02 string inverters. It integrates all the necessary systems and components that work as a plug-and-play system.  

Zanón’s presentation focused on the increased use of digitalization within the company’s offerings. He specifically talked about intelligent DC switches, DC & AC terminals temperature detection, Arc-Fault Circuit Interrupter (AFCI), Smart Air Cooling, PID Recovery and Anti-PID, Smart I-V Curve Diagnosis, and High-Speed Power Line Communications (HPCI) features.  

The intelligent DC switch, for instance, automatically detects and isolates faults to ensure uninterrupted operation of unaffected circuits. Its temperature sensors monitor the difference on both DC and AC terminals, triggering protections in case of any anomaly.  

Similarly, the AFCI protects against fire and short circuit risks with 100% detection accuracy, said Zanón. The Smart Air Cooling feature supports the maximum capacity of 385kW up to 40°C and extends the components’ lifetime by lowering the operating temperature. 

The I-V Curve tool can check 100% PV strings in a few minutes, while automatically generating diagnosis and O&M reports. It can detect over 10 types of faults and also provides solutions, thereby reducing labor costs.  

According to Zanón, high-speed PLC communications allow simultaneous power and data transmission without the need to lay any additional communication cables.  

Talking about the growing presence of hybrid renewable energy power plants, SMA Solar Product Manager Isabella Caschetto said these are the solutions to future energy challenges such as surplus energy during peak hours leading to negative pricing and inefficiencies. This directly impacts project economics.   

China is an example of this where curtailments are regular since the grid cannot always consume all the solar energy produced. Hence, the need for flexibility that the hybrids offer – a topic Europe is facing increasingly too. 

Hybrids are more complex energy systems than plain vanilla solar or wind power projects. She defined these as the combination of a renewable energy generation technology like solar or wind with flexibility, which in the current environment means BESS, but can also mean adding flexible loads like electrolyzers.  

These also have 2 approaches, one where these various technologies are co-located with batteries, but these work independently using shared infrastructure. 

The other approach of full hybrids has batteries and renewable energy assets fully integrated with grid connections and dispatching strategies.   

Caschetto explained that hybrid power systems allow the use of energy on a when and where basis. Digitalization enables the effective operation of hybrid energy assets efficiently with the use of accurate data, forecasting and advanced optimization algorithms.  

She also touched upon the revenue stacking option where energy assets can participate in multiple markets to earn their revenues. With flexibility, it is possible to attempt this for better profitability. For instance, Caschetto said assets can participate in frequency response markets – spot trading in the UK, while a hybrid plant in Germany can buy energy during negative price hours, storing it and selling it at higher prices at a later date. This strategy, however, needs to be adapted on a daily basis with the help of optimized schedules including input data, technical parameters, contractual situations, and live operational data. This is required since various energy markets work differently.   

SMA has started a subsidiary called Camopo, which has built an optimization software that can work together with a full-scope EMS in a hybrid plant to participate actively in energy markets. Offering SMA’s Sunnyside Flex Platform as an example of modular and flexible technology, Caschetto stressed that such systems allow asset owners to support various components including solar PV, hybrids, hydrogen, etc., thus adapting to various market demands. In this context, SMA introduced its new Sunny Central Flex at The smarter E / Intersolar Europe event in the summer. It is a SiC-based central hybrid inverter including a DC-DC converter that can connect BESS both on the DC and AC side. 

Moving from centralized to distributed generation, Enphase Energy’s Policy & Government Affairs Manager Alexander Krenek brought in the perspective of safety and grid-friendly operation of rooftop and plug-in solar systems with the company’s microinverters. Based out of Silicon Valley in the US, Enphase is currently responsible for the manufacturing of around 80% of global microinverters, he claimed.  

Using silicon for its microinverters till now, Enphase is now transitioning to next-gen Gallium Nitride (GaN) high-voltage transistors which will make the future generations of the company’s products much smaller, more efficient and cheaper with lower BOM.  

A single microinverter per panel can operate with low-voltage AC, thus lowering high-voltage DC risks. This also ensures that there is no single point of failure, he emphasized. These systems are fully modular and can be scaled over time. These are also enhanced for fire safety for rooftop solar applications.  

The future, however, he added, belongs to solar+storage systems where batteries support simultaneous charging and discharging, thus enabling grid participation.  

Krenek listed the benefits of microinverters in promoting the democratization of energy use. Balcony PV systems, as plug-in systems are called in Germany, are mushrooming in the hands of the prosumers of Europe’s largest PV market while lowering grid stress. Such simplified systems with up to 2 kW DC / 0.8 kW AC can be plugged into the household socket without the need for certified installers or permitting, enabling customers to reduce their energy bill by around 10% and a payback of 2-4 years. 

Moreover, renters and lower-income households also get access to compact products such as portable solar systems that can be disconnected, moved and even used off-grid. Specific standards in this space can boost this segment further.  

Panel discussion 

Moderated by TaiyangNews’ Michael Schmela, the panel discussion revolved around how inverters, battery storage and digitalization can really smarten solar PV systems in the future. Both the panelists from Enphase and SMA stressed the importance of policy stability and certainty in the markets, along with the need for cybersecurity measures to ensure the safety and sustainability of an increasingly digitalized energy system of the future. 

SMA Solar’s Isabella Caschetto believes there are customers who are ready to invest in renewable energy systems, but the problem exists at the regulatory level. Each country has its own regulations, not to miss permitting timelines and also grid congestion issues that take a toll on the investor plans. Governments need to understand the business case for the investors.  

Grid congestion and unavailability make for another aspect that needs troubleshooting if hybrid projects, which are key to energy transition, are to succeed.  

Enphase Energy’s Alexander Krenek agreed, saying the need of the hour is for governments to provide clarity and future direction. He offered the example of the Netherlands where uncertainty regarding net metering has finally been resolved after so many years. But then any policy change must be followed for consumers to understand where to go from here, which is not the case and is also why the market has collapsed over the course of 2024 (see Netherlands Set To Abolish Net Metering Scheme From 2027).

Krenek also stressed on customer education and awareness to be able to use their various energy assets optimally. Referring to the opportunities that the revenue stacking option brings to the prosumers, Krenek said most users are unaware of its potential and how to exercise it.  

The videos of the presenters can be watched on our website.

TaiyangNews will end the year 2024 with its flagship High Efficiency Solar Technologies 2024 Virtual Conference where leading names from the global solar PV industry and experts will discuss better and lower-cost solar cells and modules with high-efficiency solar technologies like TOPCon, HJT, XBC and even tandems. TOPCon part I and HJT will be discussed on December 2 and 3, respectively. On December 10, we will pick up the thread on TOPCon part II, followed by back contact and next-generation technologies on December 11. Registrations for the event are already on here.