Holtec International and Eos Energy Storage (Eos), the developer of the Znyth® Direct Current (DC) Battery Energy Storage System, have formed HI-POWER, LLC, a multi-gigawatt manufacturing joint venture to mass produce state-of-the-art aqueous zinc batteries for industrial-scale energy storage. The principal manufacturing plant for making the batteries is located in Pittsburgh, Pennsylvania, adjacent to Holtec’s 700,000 square feet heavy manufacturing facility known as the Holtec Manufacturing Division, which builds nuclear power plant equipment.
Znyth® Direct Current Battery Energy Storage
The core of the Battery Energy Storage System is the Znyth® (zinc hybrid cathode) battery technology, which employs a unique zinc-halide oxidation/reduction cycle to generate output current and to recharge with minimal degradation. Eos’s simple battery design includes three key components: bipolar electrodes (titanium current collector and carbon felt), injection-molded plastic frames and an aqueous, non-flammable electrolyte. The battery is sealed, static, and tolerant to temperature extremes and abusive conditions. The Zynth® technology does not require precious metal catalysts, nor does it employ rare earth metals. There are no tanks, plumbing or electrolyte outside the battery case, no pumps or high-pressure seals and no membrane to foul or damage.
Once filled with the non-flammable electrolyte, the batteries are integrated into a containerized Energy BlockTM that provides 150 kW of nominal system power (DC) and a maximum energy output of 600 kWh. The innovative Energy BlockTM packaging enables flexible options for system installation while significantly lowering the installation cost, and accelerating permitting and installation time.
The Energy Block is shipped with batteries and all DC electrical equipment integrated into a standard 20 ft ISO shipping container for drop and play convenience. The scope of supply for each sub-system includes pre-integrated strings of the Znyth® batteries with DC wiring, DC system protection, racking, enclosure and Battery Management System (BMS). With no HVAC system and no fire suppression requirements, simple fans built into the enclosure ensure consistent air temperature, greatly reducing upfront capital cost, maintenance costs and auxiliary loads. The Energy Block container is equipped with outside opening doors for easy access to all electrical components for maintenance operations and safety. The system is fully recyclable, reducing the cost of system decommissioning/removal and minimizing environmental impact.
Data from cell, battery and system testing shows that a Round Trip Efficiency (RTE) of 70-78% is achieved across -20 to 45°C ambient temperature, whereas Lithium Ion (Li-Ion) batteries have a strict operating range between 15 to 25°C. Efficiency losses under extreme temperatures are temporary for the Zynth® battery and performance recovers quickly with abuse cycles tested for up to 93°C and recovery cycles operating near optimal RTE at 31°C. The Zynth® battery can achieve an even larger range of operating temperatures, from -40 to 50C, with added packages that expand its applicability to extreme temperature environments.
The allowable depth of discharge (DoD) of a battery directly correlates to the percent of usable energy available within the battery relative to its nameplate ratings. The life span of lead-acid, Li-Ion and many other types of batteries depends heavily upon the number of charge/discharge cycles they undergo and the DoD for each cycle. Typically, the higher the DoD per cycle, the shorter the life span as measured by the number of cycles the battery can withstand while still providing acceptable performance to the Customer.
Although specific batteries can vary widely, it is a general characteristic of Li-Ion systems that the usable energy capacity is less than 100% of the theoretical capacity, with the standard being around 70% (although some Li-Ion companies claim 100% utilization). In addition, Li-Ion batteries become unstable if they are fully discharged, which could result in damage to the cell.
In contrast, Znyth® batteries allow for 100% DoD, with no restrictions affecting battery life span or performance. With a full 4 hours of discharge capability, the batteries are designed for a 100% DoD daily duty cycle. Compared to Zynth®, most Li-Ion batteries will require greater up-front capital investment to accommodate an extra 30% of theoretical battery capacity that will never be used.
The Znyth® Battery Energy Storage System is undergoing certification by a Nationally Recognized Testing Laboratory against the following standards with targeted completion in 4Q2020: UL 1973, UL 9540 Safety for Energy Storage Systems, and UL 9540A. The system is currently accredited to CE Marking for European Conformity and CSA/cUL.
- Peak-shaving and Demand Management
- Solar / Wind Integration, Shifting
- Frequency Regulation
Further technical information regarding the Znyth® Battery Energy Storage System can be found at Holtec’s technology partner’s webpage https://eosenergystorage.com/.