BATTERY X
BATTERY X (NMC)
Volterra Advantages
High Energy Density
Low production cost
Fast charging
High Power
High Thermal Stability
High Cycle life
Applications
Stationary Storage
Electric Vehicles
Airborne transportation
Waterbourne transportation
Hybrid battery storage
Electrical Appliances
BESS Technical
Application Families
BESS may serve several tasks in modern power grids, resulting in distinct BESS load patterns. Storage integration also involves variable stakeholders and value streams. Previous approaches for classification have analyzed in detail the potential involvement of storage systems to power grids and grouped e.g., among required storage system duration or potential impact to overlying grid levels As we limit our focus on LIB (Lithium Battery) based storage systems, a novel classification to four categories (application families) is suggested herein distinguishing Ancillary Service, Behind-the-Meter, Energy Trade and Investment Deferral and Local Grid Support applications. It is worth mentioning, that this classification is found suitable for analysis of LIB applications and may not match well for other ESS fulfilling different application tasks.
Ancillary Service
From a system perspective, it is necessary to keep the balance between power generation and load at all times within an interconnected grid. BESS is able to react to fluctuations in the power grid on a millisecond timescale, a task increasingly important due to the intermittent nature of variable RES and decreasing inertia in modern power grids. While different market systems exist in various regions worldwide, frequency control reserve demand is often tendered via an auctioning system supervised on the ISO level. In fact, especially for compensation of short-term (milliseconds to a few seconds) fluctuations often tendered as Primary Control Reserve (PCR), BESS have been shown to be technically mature and potentially economically superior to conventional power plant dispatch adaption. A detailed analysis of regulatory constraints (forcing e.g., minimum energy content of storage for continued power provision), market profit scheme, as well as storage system operation strategy, is a prerequisite for profitable BESS operation in this application.
Behind the Meter
In contrast to the aforementioned ancillary services, BESS can also serve various BTM applications. The combination of a local generation with battery storage for residential customers (i.e. PV-BESS application) is a hotly debated topic: PV-BESS may serve to increase the self-consumption of prosumer residential households and help the end user to save retail tariff cost. Adapted system control strategies for storage systems may allow for achieving additional grid-relieving effects. As enforced by regulatory constraints or incentivized in some regions, this aspect may draw more attention in the future. LIB has proven to be ideally suited for PV-BESS applications due to superior cycle and calendar life as well as high energy and power densities when compared to PbA storage systems. Nevertheless, techno-economic calculations reveal that only for regions with low PV feed-in remuneration and high retail electricity tariff, self-consumption increase via BESS integration is an economically viable option at present, when taking into account LIB storage investment and degradation costs. Industrial customers may significantly reduce their peak demand and consequently their electricity bill via the usage of BESS in Peak Shaving (PS).
Energy Trade
Variability of electricity demand and supply in a marketing region may cause fluctuations of wholesale electricity prices at exchange markets. Storage arbitrage trading aims to buy/sell electricity according to market price variations leading to charge-discharge cycles for the storage system. For several decades, the daily load fluctuations in conjunction with persistent strong power generation by base load or non-adaptable sources (e.g., nuclear, lignite) caused a clear arbitrage revenue pattern being highly attractive for pumped hydro storage. Power-to-energy ratios of about 1:8 were found adequate to supply during daytime and recharge overnight resulting in a daily storage cycling pattern. However, due to increased PV power feed-in during the daytime, an overall rise of intermittent generation and adaption of load patterns e.g., via demand side management, the earlier observed wholesale price variations have become less pronounced. In some cases, they are being replaced with new variation patterns which have other duration factors and may be harder to anticipate. As an example, a low market electricity price at mid-day on a sunny day due to the high share of PV installations followed by the striking rise of electricity cost in the evening hours, when electricity demand peaks for air conditioning. Such patterns may severely impact the profitability of arbitrage ESS, and faster reacting (non pumped-hydro) storage systems may be required. Recent work showed that arbitrage with short time fluctuations can in fact be economically viable for LIB based BESS and may become a larger profit opportunity in the future.
Investment
BESS may serve several tasks for (local) grid support and serve as a deferral or even alternative to traditional grid reinforcement measures: Power grids need control capabilities to adapt to power flow variations at demand and supply points occurring at all times. Furthermore, the layout of power grid utility (e.g., transformers) is often rated for peak power flows via the respective units. Upgrading power lines and transformers is the most straightforward measure to prevent from overloading of units in grids with increasing overall demand and/or rise of fluctuations. In detail, variation of RES generation as well as changes of residential and industrial loads cause voltage fluctuations due to non-zero resistance of power transmission cables. Integration and appropriate control of BESS by specific regulations often do not provide a direct reimbursement scheme for serving voltage support which hinders private enterprises to access this market. Instead, DSO obligated to stabilize local grids may consider storage integration if the investment cost for alternative measures exceeds BESS cost. Others have analyzed more generally the technical constraints and potential profitability of BESS for investment deferral in local power grids.
Other Applications
A prominent multi-use scenario is using BESS for support of a Micro-Grid (MG) or Island Grid: BESS linked to EMS control may serve simultaneously for control reserve (drop control, frequency regulation), voltage stabilization (active and reactive power control) and as a balancing unit in times of supply/demand mismatch. As such, BESS may significantly reduce fuel consumption of diesel generation (a direct applications’ profit) and lower local emissions.
In the context of increasing penetration of EVs and electric charging station infrastructure built-up, Vehicle-to-Grid concepts have been proposed frequently as briefly discussed in the previous Section. Combining the battery usage for the EV propulsion and for grid-connected V2G applications is also considered a variant of application stacking: Possible aggregation/pooling concepts for V2G storage have been studied in detail. Others analyzed the technical (e.g., simultaneity factors of vehicles at charge bays), operational (e.g., mixing applications and vehicle charging requirements) and regulatory (e.g., multiple stakeholder involvement) challenges of V2G concepts.