CEA began growing vitality storage companies in 2015, at a comparatively early stage within the storage trade. The corporate foresaw the expansion potential of stationary vitality storage as a vital enabler of the renewable vitality transition and a helpful asset for grid operators.
Within the final eight years we’ve seen battery cells scaling from under 100 Ah to at this time’s 300-plus Ah; techniques reworking from 12-meter, walk-in containers to at this time’s extremely built-in, energy-dense modular cupboards; and the appearance of liquid-cooled techniques necessitated by large cells.
Battery suppliers have created specialised cell codecs and chemistries for the stationary BESS sector, versus utilizing electrical car cells in grid storage techniques, as within the early days. We have now additionally witnessed the transition of BESS’ from a nickel, cobalt, and manganese (NCM) battery cell chemistry – primarily equipped by South Korean and Japanese producers – to lithium ferrous phosphate (LFP) units, completely equipped by Chinese language producers. Different storage applied sciences, akin to circulation batteries, have but to make a breakthrough and take a slice of the market from lithium-ion batteries (LIBs).
Speedy change
Total, the trade could be very completely different from a number of years in the past. This has introduced important challenges, exacerbated by a excessive progress charge. LIB chemistries have inherent limitations and violating them can result in extreme degradation that just about invariably leads to uncontrolled thermal runaway.
Manufacturing defects, in addition to electrical, thermal, or mechanical abuses, can push battery cells into thermal runaway. Within the best-case state of affairs, security techniques will stop propagation of a hearth, resulting in the incapacitation of solely a part of a system. A worst-case state of affairs might see a number of containers burn, leading to prolonged system downtime. Furthermore, the complexity present in numerous subsystems creates extra factors of failure that may result in cell abuse and thermal runaway. A battery hearth is the nightmare state of affairs that any BESS proprietor or operator needs to keep away from in any respect prices, because it results in important reputational and monetary injury and prolonged operational disruption.
CEA has been specializing in effectively figuring out the manufacturing dangers related to all ranges of an vitality storage system, by way of our high quality assurance companies. This work contains figuring out dangers throughout cell, module, rack, and containerized techniques.
High quality in numbers
Since 2018, CEA’s crew of engineers has been conducting high quality assurance inspections throughout greater than 26 GWh of lithium-ion vitality storage initiatives deployed worldwide. Our high quality assurance inspections are carried out earlier than manufacturing, at pre-production manufacturing unit audits; throughout manufacturing, by way of in-line manufacturing monitoring; and after manufacturing by way of pre-shipment inspection and manufacturing unit acceptance testing. Greater than 1,300 findings have been recognized throughout CEA’s oversight at 52 factories globally. On this context, a discovering is a matter recognized throughout inspection that signifies deviation from customary greatest apply, course of deviations, or product specs.
Most trade newcomers overly concentrate on cell high quality and don’t pay shut sufficient consideration to integration points as cells are packaged into modules, racks, and containers. System degree points account for 47% of these recognized, in comparison with 30% on the cell degree and 23% on the module degree. A battery cell’s advanced manufacturing course of, and high-performance sensitivity with respect to the robustness of the standard management system, make it the single-most risk-prone element inside a BESS. However there are such a lot of different parts included in a containerized system that the majority dangers come from the non-cell parts of the BESS. The big variety of system-level findings is because of insufficient high quality management of extremely guide integration processes, the advanced nature of vitality storage techniques, and system vulnerability to underlying issues originating from upstream parts akin to balance-of-plant (BOP) objects and batteries. Because the final step of the BESS manufacturing course of, system integration can amplify underlying points at sub-system ranges and is susceptible to extra high quality and efficiency dangers on the interfaces between sub-systems.
System-level issues
In integration factories, vitality storage techniques are constructed with many shifting components, a reality mirrored by the massive variety of CEA findings on system enclosures – amounting to 45% of the whole system-level findings (see chart to the left). Nevertheless, the bulk (84%) of the enclosure findings are minor and pose comparatively low threat to system efficiency and security. Enclosure inspection includes visible inspection of look, power and rigidity, wiring and cabling, grounding mechanism, and ingress efficiency.
The supporting parts and system that kind the BOP for a BESS consists of a hearth detection and suppression system, an influence distribution set-up and a thermal administration system. A BESS is inherently susceptible to defects originating from all upstream parts and that is attested by the massive variety of direct findings within the BOP. The findings in sub-systems are usually attributable to sub-component defects and dangerous apply throughout system integration. Consultant findings embrace liquid coolant leakage on account of deformed flange plates, malfunctioning fuel sensors, air flow failure on account of incorrect set up, and reside conductor publicity inside AC/DC distribution.
Efficiency check findings contribute solely 4% to the whole variety of system-level findings as capability and round-trip effectivity (RTE) assessments are procedurally easy and have express cross and fail standards. Within the worst instances, the place a system fails each capability and RTE assessments, solely two findings will likely be recorded. Nevertheless, efficiency check findings point out excessive threat as they’re instantly linked to system efficiency ensures, and the foundation causes of any failed check often level to a bigger and deeper downside upstream.
Baseline efficiency assessments are essential to figuring out system deficiencies, confirming contractually-promised metrics, and providing one final alternative to rectify high quality and efficiency points. Between the 2 efficiency assessments, a better share of main and significant points are discovered in the course of the RTE check, which measures DC system biking effectivity, excluding auxiliary hundreds. That is probably the most difficult check that reveals how effectively batteries have been assembled electrically. Capability assessments are at a extra basic degree and the chance of capability shortfalls are often hedged by an implicit rule in battery cell design – that’s, to oversize capability by round 5% on the cell degree.
Underachieving system effectivity and capability is usually on account of both batteries or BOP techniques. The extra frequent findings embrace underachieving capability and RTE, ensuing from abnormally massive temperature and voltage variations amongst cells inside a battery module; charging or discharging failure on account of wiring points in a battery rack’s excessive voltage bins; and thermal runaway initiated in one of many battery modules by inner brief circuiting.
Cells and modules
Battery-related findings are recognized at cell and module factories in the course of the manufacturing and integration processes of the respective parts.
The cell is the place the electrochemical reactions happen at a nanoscale. Rigorous course of management is required to keep away from inner brief circuiting attributable to high quality points. The prolonged manufacturing course of and excessive sensitivity to the storage, packaging, and delivery circumstances of battery cells results in a bigger variety of findings, in contrast with battery modules.
The general cell manufacturing course of may be divided into three levels: electrode manufacturing, cell meeting, and cell ending. Cell meeting processes comprise a bigger variety of findings with greater severity on account of their shut causal relationship with inner brief circuiting. As battery cells evolve to 300 Ah, and even greater capability ranges, it’s anticipated the related dangers will likely be aggravated on account of greater necessities for burr dimension and international particle management in the course of the cell meeting processes.
Much like the system integration course of, battery modules contain extremely guide manufacturing processes together with cell set up, interconnection welding, enclosing, and finish of line testing. Cell set up and interconnection welding are liable for 86% of all battery module-related findings.
Battery cell set up begins with polarity verification, with the cells then positioned into brackets which have thermal insulation layers utilized in between. Interconnection welding connects cells electrically into the designed configuration. The big variety of findings in these two areas is principally on account of imprecision in materials dealing with and welding high quality management. Relating to the interconnection welding course of, the vast majority of such findings are main and are attributable to poorly outlined welding procedures and sloppy operations.
Lowering threat
The fast tempo of battery expertise development means new dangers are being launched throughout the provision chain. Accordingly, a multi-stage high quality management strategy ought to begin from threat evaluation on the early levels of the procurement course of.
The evaluation ought to establish particular dangers related to mission design and use instances, which ought to inform battery necessities. Throughout manufacturing, high quality assurance must be executed beneath shut scrutiny to make sure all beforehand recognized dangers are coated.
One key takeaway from our 26-plus GWh high quality assurance observe file is that typically even excellent system check outcomes can not assure ongoing efficiency and reliability as soon as techniques are put into operation. Any given vitality storage system is simply pretty much as good because the cross standards outlined within the provider’s high quality management guidelines. We have now seen efficiency check failures on account of testing gear limitations, round-trip effectivity targets which might be set too low and don’t conform to efficiency ensures, temperature and voltage variations that aren’t monitored and analyzed, untested battery administration system management capabilities, and extra. A few of these issues may be addressed within the early procurement stage by conducting a spot evaluation of a provider’s high quality assurance and testing protocols.
Making certain the reliability and efficiency of BESS’ requires a continuing technique of reassessment. There must be frequent updates to quality-inspection greatest apply, threat monitoring, and prioritization and growth of mitigation approaches. The prize for patrons adhering to a multi-stage high quality assurance strategy is a protected battery system that performs as anticipated.
In regards to the authors: George Touloupas is the senior director of expertise and high quality for photo voltaic and storage at CEA. He has greater than 12 years’ expertise in technical consulting for PV manufacturing, mission growth, and photo voltaic and vitality storage initiatives.
Chi Zhang is a senior engineer at CEA. His analysis focuses on vitality storage and inexperienced hydrogen.
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