Keeping Your BESS Online: 4 Critical Practices for Energy Storage Performance and Availability
Maintaining high availability and optimizing performance in Battery Energy Storage Systems ensures grid stability, return on investment and brings us closer to a sustainable energy future.
Battery Energy Storage Systems (BESS) are becoming increasingly critical in the energy landscape as they support the integration of renewable energy sources like solar and wind. These systems provide essential functions, including the storage of electricity and grid firming, that are vital for a sustainable energy system.
System availability, defined as the time the system is operational and capable of delivering the intended energy output, relative to the total time it is expected to function, is an essential requirement for any BESS. System availability ensures that energy storage projects contribute effectively to grid stability and meet operational expectations, as outlined in contracts and required by independent system operators (ISOs) or regional transmission organizations (RTOs).
Ensuring system availability, reliability, and performance depends on deep expertise across multiple functions, including BESS design, project sizing, equipment quality evaluations, thorough commissioning, and power plant software design. This blog post aims to delve into the factors that influence BESS availability and performance, offering insights into best practices for managing and optimizing these systems.
Factors that Determine System Availability
System availability is critical due to the growing size and proliferation of BESS. As energy storage takes a greater share of the electricity mix, maintaining BESS as a reliable electricity source becomes crucial to ensuring grid stability.
Furthermore, contractual agreements often specify vital requirement periods when the system must be operational to meet peak demand from the utility. For example, during summer months in the lower half of the United States, projects must operate at full availability to meet the increased demand for electricity that arises from the use of air conditioning during hot weather and especially during heat waves.
These contractual requirements will shift maintenance schedules and operational strategies to ensure that BESS projects remain online during these important seasonal times. Taking care of maintenance items before equipment breaks will help ensure the system remains available, and preventive maintenance will be scheduled around these periods of high demand.
Corrective maintenance will be addressed during peak periods if it is essential but will otherwise be deferred to post-critical operational windows, if possible. This type of pragmatic scheduling helps in maintaining system functionality and optimizing performance during high-revenue periods for energy storage projects.
Performance Metrics and Evaluation
Performance metrics are essential to gauge the effectiveness of energy storage systems. Availability percentages (i.e., achieving 97%, 98% or even 99% uptime) and meeting performance specifications are critical indicators of system reliability. These metrics are not just contractual obligations but also reflect the system's ability to perform as expected under various conditions, contributing to overall grid stability.
Performance metrics can include
- BESS or Inverter Power = meeting or exceeding specified MW reading at the point of measurement (POM)
- Energy Capacity = ensuring system provides the required amount of MWh within a specific time
- Ramp Rate = ensuring the system can change power output either quickly enough (power output to change by some MW within a number of seconds) or slow enough (power output not to exceed a defined number of MW change within a number of seconds)
- Response to market rules and grid stabilization needs: for example, in markets where fast frequency response (FFR) operation is required, the BESS must receive a command, process it, and change the output of the site to a defined MW output within a defined duration (typically measured in milliseconds).
- Round trip efficiency = a ratio between the amount of MWh that have been charged into the system and the MWh discharged from it. Achieving the highest possible round-trip efficiency is beneficial for projects because it ensures the least amount of system loss and the maximum amount of energy available for discharge when commanded by the ISO or RTO.
The performance of energy storage systems has a direct impact on grid stability. If a system fails to meet its performance specifications — such as delivering the required megawatts when needed — the result can be grid instability. Ensuring that systems can consistently perform at their specified capacity is therefore crucial for maintaining the reliability of the grid and supporting the transition to a sustainable energy future.
Short-Term Reponses vs. Long-Term Planning
In the short term, quick responses to system issues are essential. Having a responsive and integrated maintenance team that can promptly address any operational problem ensures minimal downtime. This involves addressing immediate concerns and troubleshooting to get the system back online quickly, thereby meeting customer expectations and maintaining system reliability.
Long-term planning, however, is essential for minimizing the risks of system issues. Important considerations include designing systems with adequate capacity and planning for future maintenance needs. Overbuilding systems beyond the mandated capacity helps accommodate battery degradation and adds spare capacity when maintenance is required.
Predictive maintenance using data insights, along with routine maintenance, and having the right collection of spare parts on site are all crucial strategies for ensuring that systems continue to perform over their entire lifespan, which can be up to 20 years.
4 Best Practices for Ensuring High System Availability and Performance
- Design and Sizing — Effective system design involves balancing the need for extra capacity with cost considerations. Overbuilding systems ensures that they can handle capacity degradation for a predictable number of years without compromising financial returns for a project. Quality assurance in selecting reliable components and adhering to rigorous testing standards are also vital for maintaining high system performance.
- Commissioning testing is critical for validating that systems function as intended before they are placed in full operation. This involves testing corner cases and troubleshooting performance issues to identify and rectify any shortfalls or unexpected behavior of equipment. Addressing component failures, especially during the initial operational phase, ensures that the system is fully functional when it begins commercial operation.
- Monitoring and Data Utilization — Continuous monitoring and data collection are essential for maintaining system performance. By leveraging data analytics, IHI Terrasun can predict potential issues before they become critical problems. Continuous monitoring is also essential for long-term success. This predictive approach allows for preventive maintenance and ensures that energy storage systems remain reliable and perform optimally over time.
- Integration and Team Coordination — Integrating the engineering teams and field teams enhances responsiveness and efficiency. Effective coordination ensures that any issues identified on-site are quickly addressed by the appropriate teams. As demonstrated by IHI Terrasun’s success in project execution, this seamless integration contributes to maintaining high availability and performance.
Battery energy storage systems play a crucial role as the third pillar of a sustainable energy grid, alongside solar and wind power. These systems are essential for managing intermittency, peak shifting, and energy dispatch, all functions that are key to ensuring a stable and reliable grid. Maintaining high system availability and performance is therefore essential for ensuring BESS reliability. And to achieve this, project developers need to focus on effective design, strategic maintenance, continuous monitoring and a seamless integration of engineering and field teams.