BESS consists mainly of shipping containers and step-up transformers, and the different systems all look very similar on the surface. Careful consideration of the differences ensures that BESS projects achieve good integration, high performance, and cost-effectiveness. Listed below are ten key design considerations encountered in a battery energy storage system design.
1. High energy density and conductors
Energy density, especially for batteries in the most popular lithium-ion battery energy density, is very high within the relatively small BESS footprint. This means there will be multiple sets of very thick conductors connected somewhere on site – most likely underground, often in pipes.
Therefore, techniques that minimize the total conductor cross-sectional area must be identified and implemented to reduce installation costs while creating a design such that the necessary number of penetrations can actually be intercepted within the designated floor access openings.
This task can be particularly challenging for floor access openings that appear to be arbitrarily small in size, making it difficult to fit large turning radius conductors within the small square of this access opening.
2. Maximum String Voltage and Centralized Converter
The maximum string voltage allowed by this technology often cannot be economically matched to the DC input voltage of a large centralized converter, and a DC/DC converter is required. In these cases, it is important to determine whether the DC/DC converter is packaged in individual containers or is a separate large device for use in multiple containers.
Likewise, it is necessary to determine if the DC/AC converters are packaged within a container or if they are separate, larger devices for use in multiple containers.
Depending on the number of building blocks in the system architecture, the number of large parallel cable runs may need to be doubled, with the consequent doubling and tripling of the number of cable glands to be connected and bolts to be secured.
3. Auxiliary load
When it comes to auxiliary loads to minimize project costs, there are several factors to consider. First, is the auxiliary power to the BESS for the HVAC system for cooling and heating a separate feed loop from the utility so that HVAC can be provided even when the utility recloser is open?
Second, it should be determined whether the auxiliary power loads are clearly defined, or whether they appear to be oversized and overly cautious, requiring expensive oversized equipment. In addition, it needs to be determined which of the large list of auxiliary loads actually require external power from the auxiliary distribution cabinet within the power station and which are actually internally fed auxiliary loads that can be ignored.
Battery designers often do not distinguish between internal and external power supplies because they often lump them into the general category of auxiliary loads.
4. Communications and Cabling
A common BESS design challenge is that communications diagrams often do not indicate what type of wiring should be used between points. For bidirectional power flow, it is necessary to determine the maximum full load current in each direction based on the number of battery racks at a specific location for a given operating current.
5. Determining Applicable Codes
There are sometimes conflicts between NEC Article 480, UL 1788, UL 1973, UL 9540, NFPA 101, NFPA 855, NFPA 5000, IFC Chapter 12, NFPA 1 Chapter 52, and locally adopted codes in determining the applicable code. , gap or more stringent requirements.
If a project involves hybrid BESS and solar power PV installations, it will be critical to understand how many code rules have changed. Finding a one-stop expert within the jurisdiction of the project site who can give clear answers on which codes apply will also go a long way in ensuring that the project is executed as efficiently and economically as possible.
6. One-page Brochures, Design Guides and Installation Manuals
BESS design evolves so rapidly that one-page brochures, design guides, and installation manuals often contain outdated, conflicting, or missing information. Multiple rounds of RFIs (requests for information) and document revisions may not clarify the issue.
It would be a fortunate, but now rare, situation if the answer provided a pragmatic, experience-based judgment on the information, providing extensive explanatory notes on the design elements to provide clarity and not add to the level of confusion.
7. The Gray Area of NEC Standards
NEC spent much of its development dealing with less complex, non-automated equipment that did not have onboard computer type processing capabilities. Therefore, there are several sets of gray areas that the NEC standards do not properly address.
For example, assume that a BESS is well designed, has multiple levels of fail-safe protection against overcurrent, and is also exhaustively UL tested and certified. Will the owner’s engineer or other third-party standards reviewer require that a 3,000-amp external fuse be installed within the 60-week lead time?
In these gray areas, the industry is probably at least two NEC standard revision cycles away from any language version. Here are about balcony energy storage.
8. Ambiguous Terminology
Due to the rapid development and continued technological innovation of BESS, there remains considerable confusion, misunderstanding, and lack of agreement on specific terminology.Â
The container over there only has batteries in it and only needs to be connected to the DC power output cable, while the same-looking container next to it contains a energy storage inverter with half the number of battery clusters, so it has AC power cables. They put the AC power cable in Is there any particular reason that the container for the power output conductors is placed furthest from the step-up transformer and utility interconnection point?
9. Adding Underground Pipes and Risers
There will be a lot of large electrical conduits underground at BESS, but those conduits are starting to have some non-electrical companies as well. Many energy storage container have risers installed at each end so firefighters can connect hoses and fill the container with water if needed.
Depending on the intensity of the fire, there may not be many volunteers stepping up to connect the hoses, so the BESS installation manual began to recommend making riser connections some distance away from the container. As a result, not only has the number of large underground pipes increased dramatically, but water pipes also run beneath and above electrical conduits.
10. Lack of Necessary Terminal Blocks
Assuming you install a BESS product with excellent documentation and labeled terminals, problems may still arise at a later stage. Don’t be surprised if the lead electrician prepares to connect the main controller to the BESS system main ground and discovers that it appears the design does not provide a terminal for it. Here are more information about bess manufacturers.
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