Understanding Solar Battery Storage Systems

Technology Trends

Renewable energy deployment in the electricity sector is catalysing efforts to modernise the electricity grid, including the increased implementation of battery storage.


Driven by policy and technological progress, renewable energy has been installed at unprecedented rates in recent years. This is particularly true of variable renewable energy like wind and solar PV. In 2006-12, solar PV and wind energy experienced an annual capacity growth rate worldwide of 190% and 40% respectively.


The battery is only one part of a larger battery storage system, displayed and described below. A battery storage system contains several primary components, including the battery, monitoring and control systems, and a power conversion system. 


Cell based batteries consist of individual cells connected into modules and then into packs. Flow batteries consist of external tanks filled with an electrolyte which flows through a reaction stack. Monitoring and control systems, referred to as the battery management system, ensure safety and maximise performance. The battery management system prevents individual cells from overcharging, and controls charge and discharge of the battery. This is important for safety and performance. Battery cells and component monitoring may vary to some degree, in that different types require emphasis on particular issues. 



For instance, lithium-ion battery packs must emphasise thermal monitoring and controls, given a tendency to overheat. In many of the new devices that are entering on the market, the storage system is also coupled to an inverter to provide one integrated product. In addition, the system may need to incorporate power electronics to communicate with the area utility and adhere to local grid interconnection requirements. For example, while the majority of conventional electric systems run on alternating current (AC), batteries deliver electricity as direct current (DC). This means a power conversion system is required, which contains bi-directional inverters. The power conversion system in this case converts DC power from the battery to AC power for grid use or site demand. With the use of a rectifier, AC flows back to the battery for charging after conversion to DC power. 


Battery management systems are increasingly complex and expensive for larger battery solutions. For example, one new development is the integration of software technologies and tools to allow for remote tracking, control and management of battery storage systems. With up to date information about wind and sun forecasts, the charging level, expected electricity demand and information about the state of charge of other battery systems, it will become possible to optimise and create intelligent demand and supply assets to manage load. For example, Panasonic has developed the so-called LiEDO platform to remote control distributed li-ion batteries deployed in solar-equipped buildings. Furthermore, Panasonic is working on the integration of artificial intelligence into control systems to optimise their services (Katsufumi, 2014). At the same time, significant advances have been made over the last six years. For example, in 2008 a 22-foot containers with li-ion battery storage systems provided 500 kW, while the same container in 2014 can provide up to 2 MW of capacity.