BMS & ESS Design Challenges - Meeting Europe’s Renewable Energy Goals

Author : Ros Kruger, TTI Europe

04 January 2024

The ambitious target set out by the European Union (EU) to generate 45% of its energy from renewable sources by 2030, and the UK Government’s intention to do the same with its Renewable Energy Roadmap, will lead to a dramatic reshaping of the energy landscape.

As countries across the continent seek to reduce their reliance on fossil fuels and transition to cleaner forms of energy, the development of advanced battery management system (BMS) and energy storage system (ESS) solutions will be critical. This article explores the design obstacles that are currently presented and the engineering innovations required to address them.

Growing demand for energy storage
Batteries have emerged as a pivotal technology in the quest for a more sustainable, renewable-oriented energy future. They play a multifaceted role in the energy ecosystem - from supporting large-scale solar and wind farms, right through to enhancing energy efficiency at the household level. Each of these aspects will now be looked at in turn.
  •  Household-level energy independence - In traditional domestic solar set-ups without storage, excess energy is often exported to the grid when it is not needed. Then, conversely, households have to buy electricity from the grid when the sun is not shining. As the costs associated with large-scale batteries decreases, there will be the prospect of any excess energy being stored locally, thereby lowering dependency on the grid and bringing electricity bills down. This can increase self-consumption rates from around 30% (in non-storage systems) to beyond 70%. Batteries also provide greater energy resilience during grid outages. In the event of a cut to the mains power supply, a home with a solar panel and an accompanying battery reserve can still continue to operate principal systems (like central heating and lighting) and key appliances, thus ensuring comfort and safety for the occupants.
  •  Storing renewable energy - Solar and wind energy sources are inherently intermittent, being dependent on weather conditions and daylight hours. Batteries provide a crucial solution by ‘time-shifting’ energy production and consumption. During periods of peak renewable energy generation (such as a sunny afternoon or a windy night), the excess energy being built up can be stored in banks of batteries. This stored energy may then be released back to the grid during periods of peak demand, so that a constant and reliable energy supply is maintained. By offering ancillary services like voltage control and frequency regulation, batteries will be able enhance the overall stability of the grid. This is especially critical as the proportion of intermittent renewable energy sources in the grid mix continues to grow (and the more stable output fossil fuel driven power plants further diminish).

The crucial role of battery management
At the heart of any battery-based energy storage system lies the BMS. This core technology is responsible for monitoring, controlling and optimising the performance of the individual constituent battery cells within a larger battery pack, and ensuring the longevity and safety of battery packs.

One of the foremost concerns with batteries is the risk of thermal runaway occurring - a potentially catastrophic event where a battery overheats and can catch fire (or worse still, possibly explode). To mitigate this risk, the integration of gas sensors is crucial, in order for early warning detection to be enabled. These sensors can identify the various gases emitted as the battery pack heats up. With the help of temperature sensing devices and various control mechanisms, any temperature fluctuations within the battery pack can be managed to make certain that it remains within the safe operation area (SOA).

Optimising the efficiency and lifespan of batteries requires accurate monitoring of both state-of-charge (SoC) and state-of-health (SoH). Applying advanced algorithms to the data gathered from current sensors helps to determine the battery’s remaining capacity more accurately. Residual current detection is essential for identifying potential faults or short circuits within the battery system. Here, current sensors also have an important part to play in monitoring and addressing such potential safety issues promptly.

With 5G connectivity and high-end antennas, wireless battery management in the field is becoming an increasingly viable option. Within the home environment, wireless modules for widely adopted protocols (such as Wi-Fi or Bluetooth) are available fully tested and pre-certified, thereby enabling a faster route to market. This wireless connectivity allows real-time monitoring and control of battery systems without the need for implementation of physical connections, resulting in benefits like greater flexibility and scalability.

Connectivity and modularity
Effective, adaptable and modular connectivity components are becoming increasingly common in batteries and their associated management systems. Batteries are expensive to make, and cell interconnect designs are becoming more complex. As battery production scales up, the development of efficient manufacturing processes is going to be paramount. At the same time, optimising the flow of electricity within the battery pack, reducing the energy losses witnessed and improving overall system efficiency are all high priority design requirements. Here, custom flex circuit technology can help speed up assembly. Alternatively, the modularity and customisability of busbars allow for easy scaling, maintenance and replacement of individual components, hence reducing downtime and the costs that this will entail. 

High-reliability power connectors are called for to deliver efficient energy transfer between batteries and their connected systems. These need to withstand high currents and cause only very minimal energy losses. Printed circuit board (PCB) interconnect components can prove themselves very effective in connecting various components within the BMS. High-reliability connectors enable secure and efficient connections, meaning that the risk of failure is reduced.

Compliance, safety and reliability
In many applications, batteries are used for both charging and discharging. Efficiently managing bi-directional power flow is a complex task. The ability to switch between charging and discharging modes seamlessly while maximising energy efficiency is a key design consideration.
Also, where fast and reliable emergency disconnection of high DC voltages is required, high-voltage contactors are critical. Depending on the type, they can switch off high continuous DC currents and DC voltages within a 30ms timeframe (or possibly less), adhering to strict safety standards and regulations. Contactors are now coming onto the market that have bi-directional arrangements. The upshot of this is reduced design complexity and system expense.

Managing larger-scale energy storage systems requires sophisticated control and monitoring of energy flows to maximise efficiency and grid stability. Bi-directional power supplies and configurable power supplies are vital components of such systems, because they allow for precise control over energy transfer and adaptation to the characteristics of the particular energy storage technology in use. These features enable ESS implementations to contribute to grid stability, support renewable energy integration, and provide back-up power during outages, while still maintaining high efficiency and reliability. For metering, particularly in systems that involve bi-directional power flow, compliance with the EU’s Measuring Instruments Directive (MID) will be advisable. This translates into accurate measurement of energy sent back to the grid and detailed billing of electricity usage.

The conception and subsequent implementation of battery management and energy storage solutions are major steps in Europe’s transition to more sustainable energy generation. From thermal runaway detection to high-voltage contactors, each component in ESS and BMS installations must contribute to overall system safety, efficiency and reliability. Meeting the design challenges involved head-on will not only drive technological advancements, but also contribute to a cleaner, greener and more efficient energy ecosystem. TTI Europe, with its broad product portfolio of sensors, connectors, passives, antennas, circuit protection and power supplies, can offer technical support and guidance for best-fit BMS and ESS solutions.

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