The intermittent nature of renewable energy makes it imperative to store energy to maintain an uninterrupted supply of power. KEHUA, one of the leading energy solutions providers, has come up with a direct current (DC-DC) bidirectional converter, which has been in use in southern India.

The primary function of battery storage is to store photovoltaic (PV) energy in the battery and inject the power into the grid on time. Compared to AC-side energy storage, DC-side energy storage has more advantages and is more efficient. So, it is vital for DC-DC bidirectional converters, which are the most critical power conversion centers for energy storage, to adapt to various types of batteries.

Types of Batteries

• Lithium-ion Battery: Currently, the most common battery in use is the lithium battery, which has high power density and long cycle life. With the continuous growth of electric vehicles (EVs), the cost of lithium batteries has come down drastically, and the cost per watt of lithium-ion batteries is ~$0.15 (~₹11.14). Lithium-ion batteries are widely in use for energy storage at power stations. But one thing that goes against lithium-ion batteries is the safety of these batteries, and it requires strict monitoring of power devices. The DC-DC converter has an adjustable bidirectional voltage with gradual onset, and it communicates with the battery management system (BMS) of batteries to protect the batteries.
• Flow Battery: The flow battery is now being called the ‘best match’ battery for energy storage in the PV system. The factors that set it apart from other batteries are high reliability, long service life, high residual value, and ease of maintenance. All these factors make it a perfect choice for solar power stations that can generate electricity for 25 years. But there are also some flaws in flow battery like low density and low conversion efficiency, which make flow battery projects as pilot demonstration projects. Notably, the DC-DC bidirectional energy storage converter can be compatible with the flow battery.
• Echelon Battery: The third type of battery that is also known as the ‘secondary battery’ is the Echelon battery. With the growing demand for electric vehicles, the need for Echelon batteries has also increased. But the fact remains that the consistency of the Echelon battery is weak, and to match the Echelon battery, the DC-DC converter is supposed to have two-stage topology to solve the consistency problem.

Speaking to Mercom, Jon Zhang, Senior Marketing Manager at KEHUA, said, “Almost every energy storage solution (ESS) application is customized, because of different demands, battery type, and grid requirements. KEHUA converters are based on a deep understanding of the development trend of energy storage. They have many functions as the application of maximum power point tracking (MPPT) mode and constant power mode, which can increase efficiency and reduce cost. Our independent energy management system (EMS) and intelligent online monitoring system make the systems smarter.”

Various Functions of DC-DC Converter   

• Application of Constant Power Mode: At present, the standard application mode of a DC-DC converter is mainly constant power mode, that is, DC-DC converter connects the battery with the DC bus. In this application, the DC-DC bidirectional converter is supposed to accept the scheduling of EMS and charge and discharge under certain circumstances.
• Application of MPPT Mode: In some areas with high demand for frequency modulation, DC-DC converter has an innovative application, which helps to track the maximum power points of solar panels to achieve high-power generation.

In April this year, the International Renewable Energy Agency (IRENA) published a report showing how electricity storage technologies can be used for several applications in the power sector, ranging from e-mobility and behind-the-meter applications to utility-scale.  According to the study, utility-scale batteries can enable a greater feed-in of renewables into the grid by firming renewable energy output.

According to Mercom Capital Group’s 1H and Q2 2020 Funding and M&A report for Battery Storage, Smart Grid, and Efficiency, in 1H 2020, Battery Storage companies raised $536 million in 14 deals.

Image credit: KEHUA