Solar Power World Q&A with Power Factors on Large-Scale Battery O&M Considerations
The Q&A below features Solar Power World’s editor-in-chief, Kelly Pickerel, and Robert Johnson, Global VP of Sales Solutions at Power Factors, on the topic of O&M on utility-scale energy storage projects. An abridged version of this article originally appeared in Solar Power World on April 15, 2024.
The operations and maintenance (O&M) of a utility-scale solar project is largely obvious — keep solar panels clean, monitor inverter health, maintain the grounds, and check tracker mechanisms for wear. Maintaining large-scale lithium battery energy storage system (BESS) installations takes a different skill set, although they’re largely hands-off and don’t require any weather-related upkeep. But that doesn’t mean there isn’t anything to monitor, since BESS projects actually generate an enormous amount of data. Asset managers can help portfolio owners sift through the mountains of data to ensure batteries are working at their full ability.
Software company Power Factors optimizes its customers’ project portfolios through data-driven products. The company’s Unity Asset Performance Management product helps BESS project owners and operators with O&M tasks, improving uptime and yield. Solar Power World talked with Robert Johnson, Global VP of Sales Solutions at Power Factors, about the asset manager’s work in the BESS space.
SPW: What kind of maintenance is regularly performed or monitored on large-scale lithium BESS?
Maintenance activities fall under two broad categories: corrective maintenance, which is fixing something that’s already broken, and preventive maintenance, which is proactively taking care of something to reduce the probability it will break at some point in the future.
Corrective maintenance involves activities like replacing faulty BESS modules (the components that encompass a set of cells), BESS racks (the components that encompass a set of modules), inverters or inverter components, balance of system (BOS) components like HVAC systems and distribution panel breakers, or fire and safety-related components.
Preventative maintenance involves activities like replacing filters, refilling liquid-cooling systems, calibrating sensors, replacing modules that indicate excessive degradation, checking fire suppressant systems, recalibrating SOC estimations, and much more.
But the ability to perform these activities effectively rests on having a solid operations and maintenance (O&M) strategy and the underlying data and tools to execute on the strategy.
What are some recommendations you have for O&M strategies for these systems?
Acquiring the data is key, and it’s not always easy. BESS systems involve a lot of data, and in some cases can represent a step change in the volume of data from more familiar asset classes like solar and wind. And often integrators and OEMs are reluctant to share it, or they may limit what’s shared. It’s critical for owners, operators, and O&M providers to understand the importance of this data and to develop a strategy for securing access to it up front. That means understanding your network capacity for continuously transmitting it, having the right communication gateways to collect it, and the right upstream systems to process, store, and retrieve it. Power Factors helps with all of that.
In addition to a strategy for managing BESS data, it’s equally important to understand the division of responsibilities, incentives, and contractual obligations among a long list of stakeholders: Owners, Operators, O&M providers (including boots on the ground), BESS Integrators, OEMs, Qualified Scheduling Entities (QSE), Independent System Operators (ISO), Bid Optimizers, Transmission Operators (TO), Analytics Providers, and others. It can be quite challenging to tease apart the complex interactions and overlapping responsibilities among these stakeholders, and these relationships and responsibilities can change across different operating models and contexts.
Once you have your data under control and have established a clear division of responsibilities, the next best strategy is to develop a capacity to foresee system failures to proactively address them before they occur. This helps avoid costly truck rolls and downtime incidents, which reduce revenues and may incur liquidated damages depending on the underlying contractual agreements.
Key to foreseeing system failures is predictive alerting. Along these lines, Power Factors provides a growing library of early fault detection (EFD) alerts and events. For example, we detect imminent cooling system failures, which allow operators to intervene well in advance of significant degradation or damage.
On a recent occasion, one of our customers dispatched a field technician after receiving a cooling failure EFD event. When they arrived on site, they discovered that the liquid-cooling system had not been returned to service after a recent maintenance activity. Luckily, they were able to return the system to service before any damage was done and avoid the expensive headache of having to litigate who was responsible for the mishap.
What data is important for executing an operations and maintenance strategy for large-scale BESS?
Some background on Power Factors and our customers might be helpful to start. Our customers are typically owners, operators, and service providers of portfolios of renewable energy assets. These portfolios are often growing rapidly and usually include some mix of utility-scale solar, storage, wind, hydro, and soon hydrogen.
Power Factors helps our customers scale operations of these assets through a family of domain-specific products built upon our Unity technology platform. These products span the domains of asset management, performance & reliability engineering, remote and real-time operations, financial & compliance management and oversight, field service management and oversight, and market operations. We provide a common data backbone for these interrelated functions. That backbone includes a common asset model, metadata, signal naming, and APIs for interoperability between applications.
There are many BESS OEMs and integrators out there, each with their own ways of presenting and modeling data. With our Unity Asset Performance Management (APM) product, we take an OEM-agnostic approach and normalize and contextualize this heterogeneous data so our users can make apples-to-apples comparisons across their portfolio of assets. The resulting simplification helps them optimize their operations and maintenance strategies, which improves uptime and yield, reduces operating expenses, and ultimately increases revenues and profits.
Power Factors’ customers have around 5 GWh of BESS assets operating globally on our platforms today with another 7 GWh in construction or late-stage development.
How does Power Factors acquire the data needed to support these strategies?
Our process starts with acquiring the data. We get data from the Battery Management System (BMS) provided by the BESS integrators, as well as from Power Plant Controllers (PPC) and Supervisory Control and Data Acquisition (SCADA) Systems. We acquire data from systems using communication gateways, which are typically deployed onsite. However, we can also acquire data from sites remotely over a secured network. We can also acquire and exchange data with other central data aggregators via APIs.
In many cases, Power Factors is the provider of the PPC and SCADA, which greatly simplifies the data integration process. We have a family of solutions that include our Unity PPC, Unity SCADA, and Unity EMS products for solar, wind, and storage assets. And we have full turnkey services to support them, which includes engineering, panel fabrication, and EPC construction and commissioning support.
From BMS, we acquire string-level sensor measurements of temperature, voltage, and current, as well as any digital error and fault codes. We can also read this data directly from equipment like inverters, meters, and relays. We then use all this data to determine if systems are operating within their nominal parameters. If they are not, our Event Management system generates important information that helps to answer questions like:
- Which device is impacted?
- What is the severity level (how urgently do I need to act)?
- When did it start?
- What is the ongoing revenue impact?
- Am I nearing any compliance or warranty thresholds?
- What are the instructions, operating procedures, tools, and skillsets needed to resolve this issue?
- Who is responsible for fixing this issue?
- How much will the repairs cost?
- How often has this type of event occurred on this asset? On other assets like it at the site? Within my portfolio? Across other OEMs? Across other service providers?
- What did I have for lunch today?
Well, maybe not that last one…but at least you’re still reading.
It’s easy to see how important this type of information is. If you’re operating just one large BESS or if you have just a couple of sites with the same OEM, you can probably get by using the BMS or Energy Management System (EMS) for your monitoring needs. But as soon as you have a few systems or more, and especially if they involve different OEMs and integrators, managing the torrent of information is daunting, let alone trying to build and sustain a coherent operations and maintenance strategy.
Which data is most important for operations and maintenance and what do you do with that data?
Since we’ll talk a little bit about cooling systems later, let’s start there. Knowing the status and health of the cooling system is critical because temperature is such an important factor in a battery’s health. The more analog readings and digital codes we have related to temperature, the better.
Like cooling system health, cell imbalance is also particularly important due to its negative impact on system performance. These imbalances are generally the result of variations in manufacturing quality or temperature impacts from thermal management system design flaws, which lead to unbalanced power distribution on the shared DC bus and can quickly pull down the performance of adjacent strings. String-level sensor-based measurements from the BMS are necessary for these diagnostics.
State of charge (SOC) also warrants special mention. SOC indicates a battery’s capacity to discharge, and for Lithium-Iron Phosphate (LFP) chemistries, which are predominant today, they can be notoriously difficult to estimate. Power Factors provides advanced diagnostics that help operators understand the accuracy of the native BMS SOC estimations and we’re hoping to soon have the capability of providing SOC estimations that are more accurate than those provided by the BMS itself.
Other important system indicators include state of health (SOH), state of charge (SOC), round trip efficiency (RTE), cycle counts (how often the battery has charged and discharged), and depth of discharge (DOD – how deeply the battery has discharged).
When BESS is sited with solar, how do you ensure both are working at their full ability? For example, if a solar inverter is down, what can an asset manager do to ensure the battery is working as best it can in the interim?
Firstly, it’s helpful to have an integrated view of both solar and storage asset performance, which isn’t always the case. Recall the role of the BMS. The BMS is only “aware” of its scope, which is the BESS components. There still needs to be an aggregating system on top of both the BMS and Solar SCADA systems. Unity APM provides that aggregating layer above both and includes tools for trending data, KPIs, event management, dashboards, reports, and more.
How an operator or asset manager responds to a failure at a hybrid site, whether it’s a solar inverter, battery inverter, or DC-DC converter in the case of DC-coupled systems, will depend on their operating model and revenue objectives for the site. There are too many permutations to cover here, but you can find a great distillation of the topic in a white paper by one of Power Factors’ co-founders and industry veteran, Steve Hanawalt: A Single Pane of Glass: One Scalable, Future-Ready APM Platform for BESS.
Whichever the case, the operator will generally use the SCADA and/or PPC systems to compensate by using the other non-faulted inverters/converters until they can make repairs. Power Factors’ Unity PPCs are designed to automatically make this compensation for failed equipment while alerting operators of the issue. In some cases, the operator may have to use the local SCADA system to intervene by manually inputting inverter set points, which you can imagine is a challenging activity to sustain over time.
The goal in either case is to achieve the output targets set for the site, whether that is for ancillary service, day-ahead or intraday bids, or a combination of each.
How does O&M monitoring differ for BESS installed in New York vs. Arizona?
The most significant difference between operating a BESS in Arizona versus New York is probably their differing weather profiles. Arizona is generally hotter most of the year than New York, while New York sees a lot more snow and cold weather than Arizona.
For sites in Arizona, operators might focus more on failure signatures related to high-temperature conditions and then tune their alarming thresholds accordingly. They might have more liquid than air-cooled systems because they are more efficient, so they will have telemetry specific to those systems. And they may be more concerned with dust, so they may have a more frequent filter replacement regimen.
In New York, they’re likely planning for severe cold weather and perhaps even hurricane or flooding conditions. They may be especially interested in telemetry and forecasts from specialized weather data providers, which they can see in our UI via our integrations with these 3rd party data services.
It’s important to note here that many BESS have service obligations, such as reserve capacity agreements, that require them to support the grid precisely when these extreme weather events are happening, so owners and operators need to be especially prepared. This is also another reason why it’s so important to have confidence in your SOC levels per the SOC estimation challenges I mentioned earlier.
On top of that, most revenue for BESS assets come from just a fraction of the days in a year. It’s critical for an owner/operator to know which days those are likely to be and then plan maintenance accordingly. This will look different between Arizona and New York due to their contrasting market and weather dynamics.
Last thing I’ll say on this topic – from a maintenance perspective, the real work begins weeks and months beforehand by ensuring all the underlying system components are kept in good working order and that your teams are trained for each contingency that may occur. As Benjamin Franklin said, “By failing to prepare, you are preparing to fail.”
As BESS manufacturers upgrade from HVAC-supported containers to ones using liquid-cooling technology, how does that change O&M monitoring? What other battery technology developments may change O&M?
I don’t see any radical changes in O&M monitoring with the increased prevalence of liquid-cooling technologies, at least from a data perspective. However, some of the maintenance strategies might change, like the frequency of servicing specific components and the procedures and equipment needed to execute the work.
As for other battery technology developments that may change O&M monitoring, I think we’re going to see a rapid maturing of predictive capabilities leveraging big data, machine learning (ML), and AI techniques to enhance our understanding of BESS operations. For example, we will better understand the complex interplay between operating profiles (e.g. how often and deeply systems are cycled) and system degradation. Expert AI systems will quickly provide recommendations for what actions to take and when and who to notify.
Insights from these systems will lead not only to more profitable operating profiles but also to things like improved augmentation strategies (the process of replacing BESS modules and/or racks once they reach a certain level of degradation). Much of this same data will also help developers improve their BESS designs and determine more optimal locations to site their systems.
How is Power Factors using AI to enhance the operation of BESS?
We provide AI-based capabilities, such as our early fault detection events and enhanced SOC estimations, through our product called Unity AI Insights, which is a complementary add-on to Unity APM. We also see tremendous potential for AI in closing the loop between these insights and BESS controls.
Automated control actions can take the form of things like optimizing SOC recalibration, which we already provide to customers today; auto-resetting inverters under specific fault conditions; or executing charge/discharge profiles that have been optimized via a sophisticated understanding of the interactions between market signals (think LMP nodal prices), weather patterns, historic asset performance data; and more.
We believe owners who harness these capabilities will have a clear competitive advantage, but it’s still early days. Frankly, it feels a little bit like the solar industry about ten years ago when everyone was trying to figure out the best ways to model PV performance, but with a modern AI twist (and perhaps a slightly more dystopian scent in the air).
In any case, the market’s crowded with a lot of really smart people doing really smart things and we’re excited to be in the mix. This is one of the reasons why Power Factors has made significant investments in R&D and strategic technology acquisitions. We want to sit squarely at this intersection of big data, AI, and controls by providing the world’s best enterprise data and controls platform for renewables.
We’re helping to accelerate the great Energy Transition and we see the emergence of cost-competitive BESS technologies as one of the most important catalysts making this acceleration possible.
Robert Johnson is Power Factors’ Global VP of Sales Solutions. Robert has been with Power Factors since 2016 and oversees the development and execution of sales strategies. Follow him on LinkedIn!
Interested in learning more about how Power Factors’ Unity Asset Performance Management product helps BESS project owners and operators with O&M tasks, improving uptime and yield? Get in touch!