TWAICE Availability metrics: Track warranties and improve performance

General Description

Availability is one of the key indicators of system performance and directly impacts revenue generation. Next to that, it is included in almost all warranty or guarantee discussions in the industry and hence an important contractual indicator.

TWAICE offers different availability metrics

TWAICE looks at the system from different angles and calculates different availability metrics. All of these metrics are configurable in the Warranty Tracker feature. Most of the times, not all of them are part of warranty contracts, but they are all relevant from a performance management perspective and give valuable insights into the state of the system. We offer the following availability metrics:

1. Component Availability assesses the share of components which are "operational" (= not offline or disconnected):

   1. String Availability is calculated based on the number of disconnected strings

   2. PCS Module Availability is calculated based on the number of disconnected PCS modules

2. Power Availability assesses whether the system can deliver and actually delivers the power it is supposed to:

   1. Guaranteed Power Availability compares the available power with the guaranteed power

   2. Requested Power Availability compares the requested power with the delivered power

Component Availability assesses the share of components which are "operational" (= not offline or disconnected):

Power Availability assesses whether the system can deliver and actually delivers the power it is supposed to:

How TWAICE Calculates Availability

Component Availability

Component availability answers the question, how much components of a respective level in the hierarchy are technically available. For a 15 min interval, each component is classified as either "available" or "not available" (0 or 1). How this is detected for String and PCS module availability is described in the following.

String Availability

TWAICE calculates string availability by analyzing the operational status of individual components within a BESS. A disconnected string is a specific string within a BESS that has not been actively contributing to the system's energy throughput.

A string is classified as disconnected if:

• It is performing less than 5% in EFC per 15 minute interval compared to the string with the highest EFC count within the same DC Combiner on the same day.

• The parent PCS module is identified as disconnected.

The string availability on the system level is calculated by the average of all strings within the system.

The 15 min intervals are averaged over a day to calculate the string availability for individual strings and the entire system for the whole day.

Example: if a PCS is connected for 12 h and disconnected for 12 h, than the resulting availability is 50%.

PCS Module Availability

A PCS module is classified as disconnected when it is electrically disconnected from the DC combiner. This typically happens when the switch between the PCS and the DC combiner is open. For each 15 minute interval, a PCS module is considered to be disconnected and not available if the DC voltage is either:

• Close to 0 V, or

• Shows a voltage difference to the DC Combiner more than 50 V.

Aggregation to days and to the system level happens analogous to the string availability.

⚠️ Note: To ensure reliable detection at 15-minute resolution, periods with near-zero current where the string is still reported as operating or idle are treated as unreliable. In these cases, the most recent valid Operation State is used to maintain continuity. The resulting 15-minute disconnection status is then aggregated to a daily level to assess full-day availability and recoverable energy impact.

⚠️ Note: TWAICE flags "missing data" and "Idle" states within the platform. Missing data implicates no data is available for that component in that time range. In such a period the component is considered as available because we don't have the data to detect whether it is disconnected. Idle implicates the system or component is not charging or discharging, just in resting state. Check out this article for further information: What do “Disconnected,” “Idle,” and “Missing Data” mean in TWAICE platform?

Power Availability

TWAICE Power Availability KPIs take a different perspective and compare different power values, which are provided by the system, with each other.

Guaranteed Power Availability

Guaranteed power availability answers the question whether the system is theoretically capable to charge or discharge at least with the same power that was guaranteed. For every 15 min interval, we compare the available power (as reported by the EMS) with the guaranteed power (as defined in the nameplate power in the TWAICE system) according to:

guaranteed power availability = mean available power (15 min) / guaranteed power

Requested Power Availability

Requested power availability answers the question, whether the system actually could deliver the power that was requested. For every 15 min interval, we compare the delivered power with the requested power according to:

requested power availability = mean delivered power (15 min) / mean requested power (15 min)

In case of a reduced availability, we quantify how much energy could not be delivered (missed requested energy) by:

missed requested energy = delivered energy (15 min) - requested energy (15 min)

⚠️ Note: Per default, we calculate power availability KPIs based on 15 minute intervals. If 5 minute or 60 minute intervals are relevant to your system, please get in touch with us.

⚠️ Note: To be able to calculate power availability KPIs, we need available charge & discharge power, requested power, and active power sensors to be onboarded to the TWAICE platform (on PCS module, AC combiner and/ or system level). See Sensor Requirements and Guide to TWAICE KPIs for more details.

The Advantages of TWAICE Availability Calculation

Transparency

TWAICE provides a clear and transparent view of system availability with daily granularity and the option to dive deeper into the 15 min base windows. The calculation is done based on our industry knowledge and merges the TWAICE understanding of the most common guiding principles concerning the availability topic into one easy-to-understand indicator. The indicator serves all parties in the BESS value chain to align on system performance.

Actionable Insights

Leveraging the analytics, non-operational components are automatically identified and displayed as alerts in the "TWAICE System Monitoring" solution. This facilitates the operation of systems and highlights the components that require attention. At the same time, the impact of these issues is translated into the system-level performance, making it clear if these alerts significantly impact the overall system performance.

What You Can Do with TWAICE Availability

Proactive Maintenance with Hierarchy Diagram and Smart Alerts

By monitoring availability trends, potential issues can be identified proactively and maintenance can be scheduled upfront to prevent downtime. Instead of long delay time between availability reporting and active maintenance work performed, the TWAICE Availability indicator is based on the latest available information from the system and is updated daily.

Leveraging these advantages, maintenance jobs can be informed with the latest information and planned accordingly. Understanding how individual components can contribute to the overall system availability makes the severity of the issues easier to understand.

👉🏻 Disconnected String alerts can be tracked in Hierarchy Diagram and direct you to Smart Alerts for details.

👉🏻 Disconnected Strings are flagged in Smart Alerts as minor breach. You can see the data in 15 min resolution and monitor the breach history of the component in details panel.

Head over to Smart Alerts or Hierarchy Diagram to identify disconnected strings

which are causing low availability on the system level.

👉🏻 PCS Availability can be tracked in Hierarchy Diagram, flagged as yellow if the availability is below 90%.

Track Performance with Warranty Tracker

Monitor the current availability of your BESS system and identify any anomalies. Based on data directly collected by the system, the technical component performance can be linked to the system availability and issues can be identified quickly.

Compare the availability of different BESS systems within your portfolio. The lack of a general industry-wide availability KPI which is based on component performance makes it impossible to compare the technical storage performance against each other.

Leveraging the TWAICE Availability Indicator, a true comparison between different systems can be performed to understand the impact of system integrator, battery cell type, or market on the system availability.

Leverage the TWAICE Warranty Tracker to track availability and compare the availability of different systems across your portfolio.