Maximizing output is the goal of any utility-scale renewable energy asset with a capacity commitment, and battery energy storage system (BESS) augmentation can increase available energy capacity to counter energy losses due to battery degradation.
Augmentation is the addition of new storage capacity, usually as additional battery enclosures, during a project’s design life. While it is not the only energy maintenance option, BESS augmentation is a viable solution for managing desired energy capacity and an important consideration for asset owners and operators.
Formulating a strategy to address inevitable battery degradation in the initial design process can ensure a smooth, cost-efficient transition to next-generation BESS technology.
Storage strategy
Storage capacity can be increased by adding new battery enclosures paired with existing power conversion infrastructure, or by combining new battery enclosures with additional power conversion skids (PCS).
Similar to utility-scale solar PCS systems, BESS power conversion products include bidirectional inverters to accommodate battery charge and discharge cycles. PCS are a combination of a medium-voltage transformer (also known as an inverter step-up unit) and an inverter via low-voltage connections that are integrated on a concrete pad. Utility-scale systems convert power to a 34.5 kV alternating-current (AC) medium-voltage collection level. Because the market for these products is limited by system protection nuances and supply chain availability, new generations of PCS products provide marginal increases in energy density.
Improvements in internal battery cell chemistry, cooling systems, and energy management via onboard control systems, by contrast, have driven big improvements in performance by industry-standard 20-foot battery containers. Leading manufacturers have boosted the nameplate energy density of mass-produced products by nearly 20% in recent years and some are touting future systems that see no degradation for the first several years of operation.
The unpredictability around future battery technology suggests that it is unwise to overdesign BESS sites for products that could rapidly change, but it is equally shortsighted to ignore augmentation planning. With more advanced products on the horizon, it is advisable to plan for augmentation via new AC blocks including the latest battery and PCS products.
Future flexibility
Flexible intelligence is the key to future-proofing BESS augmentation. It is wise to plan BESS augmentation based on all current market data related to energy storage, while leaving space down the road for new products and integration strategies.
For every project there is a unique opportunity to develop a flexible strategy to accommodate future technology. When augmentation is needed, it may be more economical to bring in newer and more efficient technology, even if the initially installed equipment is still available. It is reasonable to assume that spacing requirements for equipment and construction will tend to remain equal or improve over time as the energy density of these products increases. Designing with this approach offers peace of mind to utility owners. Even in the worst-case scenario where new-generation products are not available, it is still feasible to install more of the same product within the existing site boundaries.
A forward-looking approach to augmentation planning can be useful to optimize the footprint of additional battery and PCS units on land-constrained sites. Locating site staging and laydown areas near the entrance of an energy storage facility is often a consideration for optimal equipment handling and delivery. Future augmentation work at the same site can be optimized by using the area committed for laydown during initial construction as the footprint of future energy storage equipment. This approach improves ease of access and mitigates disturbance to the existing BESS installation. Energy density improvements of future products can optimize land-constrained sites even further.
Choose wisely
BESS augmentation relies on battery degradation simulations, also known as state of health (SOH) models, combined with diligent testing data. On the financial side, future cashflows can incorporate battery pricing forecasts along with investment or production tax credits. Technical data on SOH is key to informing financial forecasts of project performance and augmentation needs. State of health information is based on empirical data, which grows daily as new BESS facilities are constructed globally.
An integrated engineering, procurement, and construction (EPC) services and operations and maintenance (O&M) partner with extensive expertise in the field can provide utilities and asset owners with performance data from several years of operations. As a result, both parties can benefit from accurate guarantees, as opposed to relying solely on generalized warranties from manufacturers based on simulation data alone.
Finally, selecting the right partner to develop a facility’s energy management system (EMS) and plant controls is crucial for long-term success. Though battery containers have internal battery management systems, they all answer to a centralized EMS, which is integrated with a broader supervisory control and data-acquisition system for both standalone storage and solar-plus-storage sites. Working with a proprietary EMS supplier can make integrating future battery and inverter technology a challenge. A flexible and experienced EMS provider can open the door to the best technology available for future augmentation, regardless of the technology selected for initial installation.
About the author: Jordan Perrone is senior project development engineer at US-based EPC service provider Depcom Power, which is part of the Koch family of companies. He has designed, optimized, and developed hundreds of PV plants and is experienced in financial optimization analyses for clients. With 10 GW of utility-scale experience, Depcom Power integrates EPC and O&M capabilities for solar, standalone BESS projects, distributed generation and storage, and hybrid plants.
The views and opinions expressed in this article are the author’s own, and do not necessarily reflect those held by pv magazine.
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