Batteries are becoming more and more part of our daily life, with an average 20 battery powered devices present in every single house. In our daily life their application is no longer limited to portable devices, but it is becoming massive with the introduction of residential energy storage systems and electric vehicles, essential for supporting the decarbonization path.
On the other hand, for data center professional batteries are not new, as they have been present since their introduction, connected to the UPS system to grant operations without service outages.
The battery system provides instantaneous power continuity to support power drawn down from the grid. Batteries are usually designed to take up the short-term needs and maintain the power for five to 10 minutes in most Western areas, while it can be substantially longer in other areas where power cut or power shading are more frequent or even regularly planned. Beyond that time and when longer support is needed, a generator or other means of power generation like fuel cells starts and continues to power the site.
Battery technology options
For years lead batteries have been basically the only option available in the market offering the requested features. Their design has evolved thorough the years, improving the energy density and reducing the service needs with the introduction of VRLA technology.
Over the past 10 years, lithium solutions have been developed as alternative to lead. Lithium offers several advantages, like lower weight, better cycle life and reduced carbon footprint in some design. But, it comes with its drawbacks, mainly linked to the inherent instability of lithium which needs proper control and management to remain within safe operational limits.
For this reason, all lithium-based batteries include a Battery Management System (BMS) which is designed to protect the battery, provide alarms and disconnect it from the load in case the controlled parameters get outside the safety window.
Battery design criteria
When selecting, designing, and sizing a battery system several factors shall be taken in account. As any other component or device battery may fail. Therefore, the system must be fault tolerant by design. Commonly this is achieved by selecting multiple battery strings in n+1 configuration in conjunction with n+1 UPS design, specifically in case of UPSs connected to common battery system.
Redundancy comes with its issues in terms of space, weight and cost linked to the additional devices. The level of redundancy is therefore selected in accordance with the level of availability requested by the system.
Battery sizing criteria
Once the system configuration has been selected, the battery is sized in order to grant the requested back up time. As battery performances are not linear, but depend on discharge rate and operating temperature, manufacturer recommendations should be followed.
To support this activity the most prominent manufacturers have made available online tools in which key functioning parameters, like back up time and operating temperature, are input in order to get the right battery solution.
Moreover, battery performances are decreasing during operational life. International standards state that battery end of life is reached when capacity falls below 80 percent of its nominal value. This should be taken in consideration when sizing battery, which will be oversized if the requested back up time is expected at the end of the battery life.
In the case of lithium, performance degradation during operations can be considered linear, while lead battery performances are quite stable, with performance degradation next to end of life. For this reason, we recommend lead battery to be replaced when reaching 80 percent of design life in order to limit initial oversizing factor.
Battery installation criteria
Whilst most batteries are often referred to as “sealed”, this is not technically correct given all batteries are equipped with a safety valve. In the case of lead, this valve operates during normal charging conditions releasing hydrogen.
In order to avoid hydrogen concentration reaching critical levels, ventilation cabinet and room ventilation shall be granted as specified by IEC 62485 -2. In the same standard, prescription for the correct battery installation is specified.
Lithium batteries do not release flammable or toxic gases under normal operating conditions but may do so under failure conditions, such as thermal runaways, therefore, proper ventilation must also be granted.
Batteries end of life management
All Fiamm batteries are 99 percent recyclable with residual value due to their lead-based construction.
Recently approved European Battery Regulations impose 85 percent of recycled lead to be used for any new batteries introduced in the EU market by 2031, with Fiamm using to date an average 80 percent of recycled lead. The same target given for lithium is six percent in 2031 and 12 percent in 2036, demonstrating the economic and technical challenges in recovering it from spent batteries.
Designing a cost-effective solution
Energy costs are a major expense and concern for data center operators. Cooling systems in particular use large amounts of energy adding significant operating costs.
Fiamm Energy Technology has developed the FHB range that reduces these costs by introducing a product designed to operate at higher ambient temperatures.
A recent cost study calculated that the operator could adjust cooling temperatures in a data center and make a significant saving on cooling energy costs. The study revealed that an advanced lead acid system designed to operate at elevated temperatures has a lower cost of almost 30 percent than the equivalent lithium system.
The data center industry is crucial for the development of our society and economy because the demand for data storage will grow to more than 180 zettabytes up to 2025. At the same time, there is a need to reduce the overall environmental impact by reducing the costs and energy required to maintain and recover materials granting more efficiency and less effort.
Fiamm Energy Technology is constantly working with customers to develop ever more advanced lead-acid batteries to meet these challenges and support with dedicated case studies their choice.
Whilst initial battery cost is a major deciding factor in selecting the right batteries, there are other elements that data center operators must consider. Data center technical and purchasing teams evaluate a menu of criteria which finally sum up to a total cost of ownership. As well as product performance, delivery, safety, quality, new factors now need to include environmental and legislative requirements.
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