ESS QUALITY ASSURANCE Quality assurance methods for energy storage systems
Renewable energy depends on safe, reliable, and efficient energy storage systems (ESSs) to provide buffering between supply and demand. However, proving that an ESS is fit for purpose while complying with all relevant legislation is not a straightforward task. This article looks at the issues involved, and possible solutions.
Renewable energy makes up an ever-increasing proportion of the world’s energy supplies; a trend that will receive continued impetus from strategies like the EU’s plans to be carbon-neutral by 2050. However, one aspect of renewable energy sources like wind turbines or photovoltaic cells (PVs) is that they are intermittent, and cannot be relied on to produce energy on demand. Accordingly, energy storage systems (ESSs) become essential components of any renewable energy scheme, as they are buffers that can store energy when it is created and release it when it is needed.
While renewable energy generation is growing fast in developed countries – by 2019, it comprised 47.3 % of net electricity generation in Germany for example – it is also expected to pay a significant role, especially using PVs, in rural electrification in developing nations. This will eliminate the demand for costly infrastructure investment, and dependency on diesel generators and the fuel they use.Although these ESS scenarios are diverse, they share a need to attract finance for their construction, commissioning, and operation. Therefore, they must both demonstrate high quality, safe and reliable technical credentials, not only to protect the environment, provide reliable service and assure the safety of on-site personnel, but also to give confidence to potential investors. Quality assurance is understood as the wide range of measures required to provide these credentials.
However, there is no single standard, or set of standards, that provide a simple route to compliance. This is partly because ESS systems are complex installations that need many components and services, all with their own standards applicable, to function safely, efficiently, and reliably, and also because different regulations apply in different regions of the world. Additionally, due to the pace of the technology’s emergence, appropriate codes, standards, and regulations (CSRs) tend to lag behind some of the requirements of some technologies or systems being installed, especially in developing countries, where pressure on resources, finances, and difficult environments are the norm.
Daniel Hannemann, CEO of ESS provider Tesvolt, has first-hand experience of this: he comments that gaining certification across diverse regions remains the biggest challenge in forming strategy today – especially as the company delivers to over 30 countries. Activities should be compliant with applicable local CSRs as well as guideline documents developed by relevant international organisations. If local CSRs do not yet exist, the authorities having jurisdiction (AHJ) and/or project developers may adopt international CSRs that have been reviewed and adapted for local conditions as needed.
North American ANSI/CAN/UL 9540 Standard
Yet there is legislation available to help operators or developers take a holistic view, and evaluate their ESS as a complete system. For example, the North American standard for energy storage systems and equipment is ANSI/CAN/UL 9540. The standard covers energy storage systems that are intended to receive and store energy in some form and then provide electrical energy to loads or to the local/area electric power system (EPS) when needed.
UL describes 9540 as a system standard, where an energy storage system consists of an energy storage mechanism, power conversion equipment and balance of plant equipment. Individual parts (e.g., power conversion system, battery system, etc.) of an energy storage system are not considered an energy storage system on their own. The standard evaluates the compatibility and safety of these various components integrated into a system.
9540 covers systems implemented according to installation codes and standards including the International Fire Code, International Residential Code, and the National Fire Protection Association NFPA 1 Fire Code. These codes’ 2018 edition first introduced requirements aimed specifically at modern ESS applications, with a focus on lithium-ion battery installations. Requirements were further refined in the 2021 editions of those model codes, and in the 2020 edition of NFPA 855, the Standard for the Installation of Stationary Energy Storage Systems.
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These ESS installation codes contain size and separation requirements designed to prevent a fire originating in one ESS unit from propagating to adjacent ESS units or adjacent battery room walls and exposures. The size requirements limit the maximum electrical storage capacity of non-residential individual ESS units to 50 KWh while the spacing requirements define the minimum separation between adjacent ESS units and adjacent walls as at least three feet.
Exceptions in the codes allow the code authority to approve installations with larger energy capacities and smaller separation distances based on large-scale fire testing conducted in accordance with UL 9540A, the Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems Standard.
IEC TC 120
The International Electrotechnical Commission (IEC) also offers a systems approach to electrical energy storage systems, in the form of standard TC 120: this provides standardization in the field of grid integrated ESS systems. ‘TC’ refers to ‘Technical Committee’, which is an IEC working group. Each country has its own technical advisory group (TAG) associated with a TC. TC 120 focuses on systems aspects rather than energy storage devices. It also covers the interaction between ESS systems and electric power systems (EPSs). The standard relates to transmission and distribution grids in commercial, industrial, residential, municipal, military, and other applications.
TC 120 works in liaison with other IEC TCs, covering aspects including :
- TC8: Systems aspects for electrical energy supply
- TC21: Secondary cells and batteries
- SC21A : Secondary cells & batteries containing alkaline or other non-acid electrolytes
- TC22: Power electronic systems and equipment
- TC57: Power systems management & associated information exchange
- TC 82: Solar photovoltaic energy systems
- TC 88: Wind turbines
- TC 105: Fuel cell technologies
- TC 117: Solar thermal electric plants
Third party testing and certification
Operators who wish to ensure that their systems are safe, reliable, and efficient can turn to third party organizations who can perform testing and certification to international standards - and design evaluation programs to individual requirements. The process can include document review, standards-based testing, test reporting, factory inspection, and certification and awarding of test marks. It can cover all ESS components, including batteries, management systems, inverters, and interfaces. Other aspects, such as vibration, shock, environmental, IP protection, EMC and electrical safety can also be added.